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Date
Re: HP 3455a DVM repair

 

Like most DVM's, there is a relay between the terminals on the
front panel, and the internal circuitry. If that relay is not
closing... for whatever reason... you would have behavior like
you are describing.

I have found lots of relay failures on the sorts of reed relays
that are used in the 3456 and 3455. I would suggest looking
there.

-Chuck Harris

Bob Albert via groups.io wrote:

How do I know if the tests fail?? It just presents the test number and that changes each time I press TEST.
My level of hope has been raised.? I think this is repairable.? Yes, Inguard to Ourguard communication seems to be the clue.? When I put a signal in it does not change ranges.? The Auto range takes it to the lowest range every time, regardless.
Bob On Wednesday, April 1, 2020, 11:18:39 AM PDT, Orin Eman <orin.eman@...> wrote:

Figure 8-H-1 in my manual shows where the assemblies and test points are.
Do all the tests 11 down to 0 fail?
I'd do the cal constant tests (Section 8-B-11), monitoring A10 TP4 () to see if the right voltages are getting to the AtoD.? Table 8-B-5 has the voltages to look for.? The procedure is a little tricky, but you are looking to see if A10 TP4 gets different voltages as you step through the constants at this stage.
If these voltages look reasonable, I'd look at the inguard to outguard communication - there are test points on A3 in the outguard section.

On Wed, Apr 1, 2020 at 10:36 AM Bob Albert via groups.io <bob91343@...> wrote:

Well Chuck, I don't know what to do next with this beast.? It acts as though it works but the display gives nothing useful.? Yet the display electronics seem to be working okay.
If I put a signal in, it ignores it.? Open or short on Ohms, voltage or no on volts, gives zeros and no autorange activity.? So perhaps it's an input circuit issue.? In Test I get error 11.? I press test repeatedly and it gives error numbers 10, 9, etc down to 0.
The manual sucks.? It tells me to look on module such and such but nowhere does it seem to show me which module is where.
Bob
On Wednesday, April 1, 2020, 10:22:56 AM PDT, Chuck Harris <cfharris@...> wrote:

Hi Bob,

I don't see how you can come to that conclusion.

The 3455A is highly reparable, and should be well
within your abilities.? Lots of people have fixed
their own successfully.

What you won't be able to do is send its calibration
module out for calibration.? You will have to do that
yourself.? But, it is not any more difficult to
calibrate than the 3456A.

It is not my meter of choice, as I greatly prefer
the 3456A, but for many, it is a useful addition to
their labs.

-Chuck Harris

Bob Albert via groups.io wrote:
? I don't see a whole lot of encouragement here regarding the possibility of getting my 3455A working.? Maybe I will just put it aside and wait for a scrap unit to swap out boards or parts.? My 3456A still works so I am grateful for that.
Bob
? ? On Wednesday, April 1, 2020, 06:40:17 AM PDT, Chuck Harris <cfharris@...> wrote:

? The 3455A was a dinosaur when it was first released.

The 3455A and 3456A were sold side by side, with the
3455A being about twice as expensive as the much more
capable 3456A.? The 3455A's interesting feature was
it was supposed to be cheap to calibrate.? All you
had to do to do a complete calibration was to unplug
the module in the back panel, and replace it with a
recently calibrated module.? The idea was you could
order up a calibration by mail, and return your old
calibration module as a core... never having to send
the full meter in for calibration.

Interesting idea, but surely not worth twice the price
of a 3456A.

I say it was a dinosaur, because it used all small
scale logic rather than large highly capable hybrid
circuitry, like the 3456A.? It should be much easier
to repair, but it should also be much less reliable.

And, that is my experience with the two units.

-Chuck Harris

paul swedberg wrote:
With respect to the 3455 and 3456 the difference is night and day. I have
numbers of 3456s and was given a seriously troubled 3455. Quite a
interesting meter.
Replaced at least 11 actually malfunctioning chips on the logic board. The
logics simple so easy to verify the chips were bad. No shot gunning
involved. Never really did get it working but ended up with a different
3455 that needed help and the AC board and it is in fine shape. With
respect to the old 3455 it has both a logic and voltmeter issue. The 3455
uses an unusual processor and teh DVM uses the same proc and a masked eprom
that is known to go bad. It acts as a state machine.
The 3456s are losing there eproms and copies can be found on the net. Thank
heavens.
Regards
Paul
WB8TSL
Re: HP 3455a DVM repair

 

Its been years since I've repaired one of these, but it sounds like the opto coupler may be a problem.
Quoting Orin Eman <orin.eman@...>:

The test number is the test that failed. If you press test, it goes onto
the next test - so all the numbers it displays are failures.

It does sound like it's getting all zeros from the inguard. A10 TP4 will
tell if anything is getting close to the AtoD.

On Wed, Apr 1, 2020 at 11:34 AM Bob Albert via groups.io <bob91343=
[email protected]> wrote:

How do I know if the tests fail? It just presents the test number and
that changes each time I press TEST.

My level of hope has been raised. I think this is repairable. Yes,
Inguard to Ourguard communication seems to be the clue. When I put a
signal in it does not change ranges. The Auto range takes it to the lowest
range every time, regardless.

Bob
On Wednesday, April 1, 2020, 11:18:39 AM PDT, Orin Eman <
orin.eman@...> wrote:


Figure 8-H-1 in my manual shows where the assemblies and test points are.

Do all the tests 11 down to 0 fail?

I'd do the cal constant tests (Section 8-B-11), monitoring A10 TP4 () to
see if the right voltages are getting to the AtoD. Table 8-B-5 has the
voltages to look for. The procedure is a little tricky, but you are
looking to see if A10 TP4 gets different voltages as you step through the
constants at this stage.

If these voltages look reasonable, I'd look at the inguard to outguard
communication - there are test points on A3 in the outguard section.


On Wed, Apr 1, 2020 at 10:36 AM Bob Albert via groups.io <bob91343=
[email protected]> wrote:

Well Chuck, I don't know what to do next with this beast. It acts as
though it works but the display gives nothing useful. Yet the display
electronics seem to be working okay.

If I put a signal in, it ignores it. Open or short on Ohms, voltage or no
on volts, gives zeros and no autorange activity. So perhaps it's an input
circuit issue. In Test I get error 11. I press test repeatedly and it
gives error numbers 10, 9, etc down to 0.

The manual sucks. It tells me to look on module such and such but nowhere
does it seem to show me which module is where.

Bob

On Wednesday, April 1, 2020, 10:22:56 AM PDT, Chuck Harris <
cfharris@...> wrote:


Hi Bob,

I don't see how you can come to that conclusion.

The 3455A is highly reparable, and should be well
within your abilities. Lots of people have fixed
their own successfully.

What you won't be able to do is send its calibration
module out for calibration. You will have to do that
yourself. But, it is not any more difficult to
calibrate than the 3456A.

It is not my meter of choice, as I greatly prefer
the 3456A, but for many, it is a useful addition to
their labs.

-Chuck Harris

Bob Albert via groups.io wrote:
I don't see a whole lot of encouragement here regarding the possibility
of getting my 3455A working. Maybe I will just put it aside and wait for a
scrap unit to swap out boards or parts. My 3456A still works so I am
grateful for that.
Bob
On Wednesday, April 1, 2020, 06:40:17 AM PDT, Chuck Harris <
cfharris@...> wrote:

The 3455A was a dinosaur when it was first released.

The 3455A and 3456A were sold side by side, with the
3455A being about twice as expensive as the much more
capable 3456A. The 3455A's interesting feature was
it was supposed to be cheap to calibrate. All you
had to do to do a complete calibration was to unplug
the module in the back panel, and replace it with a
recently calibrated module. The idea was you could
order up a calibration by mail, and return your old
calibration module as a core... never having to send
the full meter in for calibration.

Interesting idea, but surely not worth twice the price
of a 3456A.

I say it was a dinosaur, because it used all small
scale logic rather than large highly capable hybrid
circuitry, like the 3456A. It should be much easier
to repair, but it should also be much less reliable.

And, that is my experience with the two units.

-Chuck Harris

paul swedberg wrote:
With respect to the 3455 and 3456 the difference is night and day. I
have
numbers of 3456s and was given a seriously troubled 3455. Quite a
interesting meter.
Replaced at least 11 actually malfunctioning chips on the logic board.
The
logics simple so easy to verify the chips were bad. No shot gunning
involved. Never really did get it working but ended up with a different
3455 that needed help and the AC board and it is in fine shape. With
respect to the old 3455 it has both a logic and voltmeter issue. The
3455
uses an unusual processor and teh DVM uses the same proc and a masked
eprom
that is known to go bad. It acts as a state machine.
The 3456s are losing there eproms and copies can be found on the net.
Thank
heavens.
Regards
Paul
WB8TSL
Re: HP 3455a DVM repair

 

The test number is the test that failed.? If you press test, it goes onto the next test - so all the numbers it displays are failures.

It does sound like it's getting all zeros from the inguard.? A10 TP4 will tell if anything is getting close to the AtoD.

On Wed, Apr 1, 2020 at 11:34 AM Bob Albert via <bob91343=[email protected]> wrote:
How do I know if the tests fail?? It just presents the test number and that changes each time I press TEST.

My level of hope has been raised.? I think this is repairable.? Yes, Inguard to Ourguard communication seems to be the clue.? When I put a signal in it does not change ranges.? The Auto range takes it to the lowest range every time, regardless.

Bob
On Wednesday, April 1, 2020, 11:18:39 AM PDT, Orin Eman <orin.eman@...> wrote:


Figure 8-H-1 in my manual shows where the assemblies and test points are.

Do all the tests 11 down to 0 fail?

I'd do the cal constant tests (Section 8-B-11), monitoring A10 TP4 () to see if the right voltages are getting to the AtoD.? Table 8-B-5 has the voltages to look for.? The procedure is a little tricky, but you are looking to see if A10 TP4 gets different voltages as you step through the constants at this stage.

If these voltages look reasonable, I'd look at the inguard to outguard communication - there are test points on A3 in the outguard section.


On Wed, Apr 1, 2020 at 10:36 AM Bob Albert via <bob91343=[email protected]> wrote:
Well Chuck, I don't know what to do next with this beast.? It acts as though it works but the display gives nothing useful.? Yet the display electronics seem to be working okay.

If I put a signal in, it ignores it.? Open or short on Ohms, voltage or no on volts, gives zeros and no autorange activity.? So perhaps it's an input circuit issue.? In Test I get error 11.? I press test repeatedly and it gives error numbers 10, 9, etc down to 0.

The manual sucks.? It tells me to look on module such and such but nowhere does it seem to show me which module is where.

Bob

On Wednesday, April 1, 2020, 10:22:56 AM PDT, Chuck Harris <cfharris@...> wrote:


Hi Bob,

I don't see how you can come to that conclusion.

The 3455A is highly reparable, and should be well
within your abilities.? Lots of people have fixed
their own successfully.

What you won't be able to do is send its calibration
module out for calibration.? You will have to do that
yourself.? But, it is not any more difficult to
calibrate than the 3456A.

It is not my meter of choice, as I greatly prefer
the 3456A, but for many, it is a useful addition to
their labs.

-Chuck Harris

Bob Albert via wrote:
>? I don't see a whole lot of encouragement here regarding the possibility of getting my 3455A working.? Maybe I will just put it aside and wait for a scrap unit to swap out boards or parts.? My 3456A still works so I am grateful for that.
> Bob
>? ? On Wednesday, April 1, 2020, 06:40:17 AM PDT, Chuck Harris <cfharris@...> wrote:
>
>? The 3455A was a dinosaur when it was first released.
>
> The 3455A and 3456A were sold side by side, with the
> 3455A being about twice as expensive as the much more
> capable 3456A.? The 3455A's interesting feature was
> it was supposed to be cheap to calibrate.? All you
> had to do to do a complete calibration was to unplug
> the module in the back panel, and replace it with a
> recently calibrated module.? The idea was you could
> order up a calibration by mail, and return your old
> calibration module as a core... never having to send
> the full meter in for calibration.
>
> Interesting idea, but surely not worth twice the price
> of a 3456A.
>
> I say it was a dinosaur, because it used all small
> scale logic rather than large highly capable hybrid
> circuitry, like the 3456A.? It should be much easier
> to repair, but it should also be much less reliable.
>
> And, that is my experience with the two units.
>
> -Chuck Harris
>
> paul swedberg wrote:
>> With respect to the 3455 and 3456 the difference is night and day. I have
>> numbers of 3456s and was given a seriously troubled 3455. Quite a
>> interesting meter.
>> Replaced at least 11 actually malfunctioning chips on the logic board. The
>> logics simple so easy to verify the chips were bad. No shot gunning
>> involved. Never really did get it working but ended up with a different
>> 3455 that needed help and the AC board and it is in fine shape. With
>> respect to the old 3455 it has both a logic and voltmeter issue. The 3455
>> uses an unusual processor and teh DVM uses the same proc and a masked eprom
>> that is known to go bad. It acts as a state machine.
>> The 3456s are losing there eproms and copies can be found on the net. Thank
>> heavens.
>> Regards
>> Paul
>> WB8TSL
>>
>>
>>
>>
>
>
>
>
>
>
>
>
Re: HP 3455a DVM repair

Bob Albert
 

How do I know if the tests fail?? It just presents the test number and that changes each time I press TEST.

My level of hope has been raised.? I think this is repairable.? Yes, Inguard to Ourguard communication seems to be the clue.? When I put a signal in it does not change ranges.? The Auto range takes it to the lowest range every time, regardless.

Bob
On Wednesday, April 1, 2020, 11:18:39 AM PDT, Orin Eman <orin.eman@...> wrote:


Figure 8-H-1 in my manual shows where the assemblies and test points are.

Do all the tests 11 down to 0 fail?

I'd do the cal constant tests (Section 8-B-11), monitoring A10 TP4 () to see if the right voltages are getting to the AtoD.? Table 8-B-5 has the voltages to look for.? The procedure is a little tricky, but you are looking to see if A10 TP4 gets different voltages as you step through the constants at this stage.

If these voltages look reasonable, I'd look at the inguard to outguard communication - there are test points on A3 in the outguard section.


On Wed, Apr 1, 2020 at 10:36 AM Bob Albert via <bob91343=[email protected]> wrote:
Well Chuck, I don't know what to do next with this beast.? It acts as though it works but the display gives nothing useful.? Yet the display electronics seem to be working okay.

If I put a signal in, it ignores it.? Open or short on Ohms, voltage or no on volts, gives zeros and no autorange activity.? So perhaps it's an input circuit issue.? In Test I get error 11.? I press test repeatedly and it gives error numbers 10, 9, etc down to 0.

The manual sucks.? It tells me to look on module such and such but nowhere does it seem to show me which module is where.

Bob

On Wednesday, April 1, 2020, 10:22:56 AM PDT, Chuck Harris <cfharris@...> wrote:


Hi Bob,

I don't see how you can come to that conclusion.

The 3455A is highly reparable, and should be well
within your abilities.? Lots of people have fixed
their own successfully.

What you won't be able to do is send its calibration
module out for calibration.? You will have to do that
yourself.? But, it is not any more difficult to
calibrate than the 3456A.

It is not my meter of choice, as I greatly prefer
the 3456A, but for many, it is a useful addition to
their labs.

-Chuck Harris

Bob Albert via wrote:
>? I don't see a whole lot of encouragement here regarding the possibility of getting my 3455A working.? Maybe I will just put it aside and wait for a scrap unit to swap out boards or parts.? My 3456A still works so I am grateful for that.
> Bob
>? ? On Wednesday, April 1, 2020, 06:40:17 AM PDT, Chuck Harris <cfharris@...> wrote:
>
>? The 3455A was a dinosaur when it was first released.
>
> The 3455A and 3456A were sold side by side, with the
> 3455A being about twice as expensive as the much more
> capable 3456A.? The 3455A's interesting feature was
> it was supposed to be cheap to calibrate.? All you
> had to do to do a complete calibration was to unplug
> the module in the back panel, and replace it with a
> recently calibrated module.? The idea was you could
> order up a calibration by mail, and return your old
> calibration module as a core... never having to send
> the full meter in for calibration.
>
> Interesting idea, but surely not worth twice the price
> of a 3456A.
>
> I say it was a dinosaur, because it used all small
> scale logic rather than large highly capable hybrid
> circuitry, like the 3456A.? It should be much easier
> to repair, but it should also be much less reliable.
>
> And, that is my experience with the two units.
>
> -Chuck Harris
>
> paul swedberg wrote:
>> With respect to the 3455 and 3456 the difference is night and day. I have
>> numbers of 3456s and was given a seriously troubled 3455. Quite a
>> interesting meter.
>> Replaced at least 11 actually malfunctioning chips on the logic board. The
>> logics simple so easy to verify the chips were bad. No shot gunning
>> involved. Never really did get it working but ended up with a different
>> 3455 that needed help and the AC board and it is in fine shape. With
>> respect to the old 3455 it has both a logic and voltmeter issue. The 3455
>> uses an unusual processor and teh DVM uses the same proc and a masked eprom
>> that is known to go bad. It acts as a state machine.
>> The 3456s are losing there eproms and copies can be found on the net. Thank
>> heavens.
>> Regards
>> Paul
>> WB8TSL
>>
>>
>>
>>
>
>
>
>
>
>
>
>
HP 209A

 

¿ªÔÆÌåÓý

Hello, Glenn--
You wrote...

"Has anyone seen abnormalities at 60, 120 and 180 Hz sine wave output?
Specifically AM modulation or changing amplitude."

The oscillator design is a Wien bridge, and I dimly recall reading something
about the sensitivity of the bridge circuit at the dialed-in frequency. Specifically, at a 60 Hz
frequency setting, any stray 60 Hz pickup will interact? with the 60 Hz oscillation frequency
setting and exhibit "pulling" or modulation of the desired 60 Hz output. I've seen this
effect many years ago with an older tubed HP oscillator (a HP 200CD).

The 120 Hz and 180 Hz frequencies are harmonics of 60 Hz and may be exhibiting
the same "beat" with stray 60 Hz fields.

So, I'm not sure if the effect is a "feature" or a "bug", but I'd check the 209A's power supply
for ripple, and if there are screws that connect the PC boards' ground planes to the
chassis, make sure that they're tightened.

Perhaps someone in the group can offer further insights?

73--

Brad? AA1IP

*??? *?? *
For some April 1st fun, go to...

..
Re: HP 3455a DVM repair

 

Figure 8-H-1 in my manual shows where the assemblies and test points are.

Do all the tests 11 down to 0 fail?

I'd do the cal constant tests (Section 8-B-11), monitoring A10 TP4 () to see if the right voltages are getting to the AtoD.? Table 8-B-5 has the voltages to look for.? The procedure is a little tricky, but you are looking to see if A10 TP4 gets different voltages as you step through the constants at this stage.

If these voltages look reasonable, I'd look at the inguard to outguard communication - there are test points on A3 in the outguard section.


On Wed, Apr 1, 2020 at 10:36 AM Bob Albert via <bob91343=[email protected]> wrote:
Well Chuck, I don't know what to do next with this beast.? It acts as though it works but the display gives nothing useful.? Yet the display electronics seem to be working okay.

If I put a signal in, it ignores it.? Open or short on Ohms, voltage or no on volts, gives zeros and no autorange activity.? So perhaps it's an input circuit issue.? In Test I get error 11.? I press test repeatedly and it gives error numbers 10, 9, etc down to 0.

The manual sucks.? It tells me to look on module such and such but nowhere does it seem to show me which module is where.

Bob

On Wednesday, April 1, 2020, 10:22:56 AM PDT, Chuck Harris <cfharris@...> wrote:


Hi Bob,

I don't see how you can come to that conclusion.

The 3455A is highly reparable, and should be well
within your abilities.? Lots of people have fixed
their own successfully.

What you won't be able to do is send its calibration
module out for calibration.? You will have to do that
yourself.? But, it is not any more difficult to
calibrate than the 3456A.

It is not my meter of choice, as I greatly prefer
the 3456A, but for many, it is a useful addition to
their labs.

-Chuck Harris

Bob Albert via wrote:
>? I don't see a whole lot of encouragement here regarding the possibility of getting my 3455A working.? Maybe I will just put it aside and wait for a scrap unit to swap out boards or parts.? My 3456A still works so I am grateful for that.
> Bob
>? ? On Wednesday, April 1, 2020, 06:40:17 AM PDT, Chuck Harris <cfharris@...> wrote:
>
>? The 3455A was a dinosaur when it was first released.
>
> The 3455A and 3456A were sold side by side, with the
> 3455A being about twice as expensive as the much more
> capable 3456A.? The 3455A's interesting feature was
> it was supposed to be cheap to calibrate.? All you
> had to do to do a complete calibration was to unplug
> the module in the back panel, and replace it with a
> recently calibrated module.? The idea was you could
> order up a calibration by mail, and return your old
> calibration module as a core... never having to send
> the full meter in for calibration.
>
> Interesting idea, but surely not worth twice the price
> of a 3456A.
>
> I say it was a dinosaur, because it used all small
> scale logic rather than large highly capable hybrid
> circuitry, like the 3456A.? It should be much easier
> to repair, but it should also be much less reliable.
>
> And, that is my experience with the two units.
>
> -Chuck Harris
>
> paul swedberg wrote:
>> With respect to the 3455 and 3456 the difference is night and day. I have
>> numbers of 3456s and was given a seriously troubled 3455. Quite a
>> interesting meter.
>> Replaced at least 11 actually malfunctioning chips on the logic board. The
>> logics simple so easy to verify the chips were bad. No shot gunning
>> involved. Never really did get it working but ended up with a different
>> 3455 that needed help and the AC board and it is in fine shape. With
>> respect to the old 3455 it has both a logic and voltmeter issue. The 3455
>> uses an unusual processor and teh DVM uses the same proc and a masked eprom
>> that is known to go bad. It acts as a state machine.
>> The 3456s are losing there eproms and copies can be found on the net. Thank
>> heavens.
>> Regards
>> Paul
>> WB8TSL
>>
>>
>>
>>
>
>
>
>
>
>
>
>
Re: HP 209A issues

 

On 4/1/20 1:45 PM, Glenn Little wrote:
Has anyone seen abnormalities at 60, 120 and 180 Hz sine wave output?
Specifically AM modulation or changing amplitude.
Hmm, suspicious! Heterodyning with AC ripple from dried-out filter
capacitors in the power supply?

-Dave

--
Dave McGuire, AK4HZ
New Kensington, PA
HP 209A issues

 

Has anyone seen abnormalities at 60, 120 and 180 Hz sine wave output?
Specifically AM modulation or changing amplitude.

Glenn

--
-----------------------------------------------------------------------
Glenn Little ARRL Technical Specialist QCWA LM 28417
Amateur Callsign: WB4UIV wb4uiv@... AMSAT LM 2178
QTH: Goose Creek, SC USA (EM92xx) USSVI LM NRA LM SBE ARRL TAPR
"It is not the class of license that the Amateur holds but the class
of the Amateur that holds the license"
Re: HP 3455a DVM repair

Bob Albert
 

I just made an interesting test.? In Ohms it does put out a test current to the front panel terminals.? So it's trying to make a measurement.? It appears to be a voltmeter issue, at the input to the machine, since it ignores the input.? It even puts out a current in the 4-terminal Ohms mode (from the other pair of terminals).

Bob

On Wednesday, April 1, 2020, 10:36:17 AM PDT, Bob Albert via groups.io <bob91343@...> wrote:


Well Chuck, I don't know what to do next with this beast.? It acts as though it works but the display gives nothing useful.? Yet the display electronics seem to be working okay.

If I put a signal in, it ignores it.? Open or short on Ohms, voltage or no on volts, gives zeros and no autorange activity.? So perhaps it's an input circuit issue.? In Test I get error 11.? I press test repeatedly and it gives error numbers 10, 9, etc down to 0.

The manual sucks.? It tells me to look on module such and such but nowhere does it seem to show me which module is where.

Bob

On Wednesday, April 1, 2020, 10:22:56 AM PDT, Chuck Harris <cfharris@...> wrote:


Hi Bob,

I don't see how you can come to that conclusion.

The 3455A is highly reparable, and should be well
within your abilities.? Lots of people have fixed
their own successfully.

What you won't be able to do is send its calibration
module out for calibration.? You will have to do that
yourself.? But, it is not any more difficult to
calibrate than the 3456A.

It is not my meter of choice, as I greatly prefer
the 3456A, but for many, it is a useful addition to
their labs.

-Chuck Harris

Bob Albert via groups.io wrote:
>? I don't see a whole lot of encouragement here regarding the possibility of getting my 3455A working.? Maybe I will just put it aside and wait for a scrap unit to swap out boards or parts.? My 3456A still works so I am grateful for that.
> Bob
>? ? On Wednesday, April 1, 2020, 06:40:17 AM PDT, Chuck Harris <cfharris@...> wrote:
>
>? The 3455A was a dinosaur when it was first released.
>
> The 3455A and 3456A were sold side by side, with the
> 3455A being about twice as expensive as the much more
> capable 3456A.? The 3455A's interesting feature was
> it was supposed to be cheap to calibrate.? All you
> had to do to do a complete calibration was to unplug
> the module in the back panel, and replace it with a
> recently calibrated module.? The idea was you could
> order up a calibration by mail, and return your old
> calibration module as a core... never having to send
> the full meter in for calibration.
>
> Interesting idea, but surely not worth twice the price
> of a 3456A.
>
> I say it was a dinosaur, because it used all small
> scale logic rather than large highly capable hybrid
> circuitry, like the 3456A.? It should be much easier
> to repair, but it should also be much less reliable.
>
> And, that is my experience with the two units.
>
> -Chuck Harris
>
> paul swedberg wrote:
>> With respect to the 3455 and 3456 the difference is night and day. I have
>> numbers of 3456s and was given a seriously troubled 3455. Quite a
>> interesting meter.
>> Replaced at least 11 actually malfunctioning chips on the logic board. The
>> logics simple so easy to verify the chips were bad. No shot gunning
>> involved. Never really did get it working but ended up with a different
>> 3455 that needed help and the AC board and it is in fine shape. With
>> respect to the old 3455 it has both a logic and voltmeter issue. The 3455
>> uses an unusual processor and teh DVM uses the same proc and a masked eprom
>> that is known to go bad. It acts as a state machine.
>> The 3456s are losing there eproms and copies can be found on the net. Thank
>> heavens.
>> Regards
>> Paul
>> WB8TSL
>>
>>
>>
>>
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Re: HP 3455a DVM repair

Bob Albert
 

Well Chuck, I don't know what to do next with this beast.? It acts as though it works but the display gives nothing useful.? Yet the display electronics seem to be working okay.

If I put a signal in, it ignores it.? Open or short on Ohms, voltage or no on volts, gives zeros and no autorange activity.? So perhaps it's an input circuit issue.? In Test I get error 11.? I press test repeatedly and it gives error numbers 10, 9, etc down to 0.

The manual sucks.? It tells me to look on module such and such but nowhere does it seem to show me which module is where.

Bob

On Wednesday, April 1, 2020, 10:22:56 AM PDT, Chuck Harris <cfharris@...> wrote:


Hi Bob,

I don't see how you can come to that conclusion.

The 3455A is highly reparable, and should be well
within your abilities.? Lots of people have fixed
their own successfully.

What you won't be able to do is send its calibration
module out for calibration.? You will have to do that
yourself.? But, it is not any more difficult to
calibrate than the 3456A.

It is not my meter of choice, as I greatly prefer
the 3456A, but for many, it is a useful addition to
their labs.

-Chuck Harris

Bob Albert via groups.io wrote:
>? I don't see a whole lot of encouragement here regarding the possibility of getting my 3455A working.? Maybe I will just put it aside and wait for a scrap unit to swap out boards or parts.? My 3456A still works so I am grateful for that.
> Bob
>? ? On Wednesday, April 1, 2020, 06:40:17 AM PDT, Chuck Harris <cfharris@...> wrote:
>
>? The 3455A was a dinosaur when it was first released.
>
> The 3455A and 3456A were sold side by side, with the
> 3455A being about twice as expensive as the much more
> capable 3456A.? The 3455A's interesting feature was
> it was supposed to be cheap to calibrate.? All you
> had to do to do a complete calibration was to unplug
> the module in the back panel, and replace it with a
> recently calibrated module.? The idea was you could
> order up a calibration by mail, and return your old
> calibration module as a core... never having to send
> the full meter in for calibration.
>
> Interesting idea, but surely not worth twice the price
> of a 3456A.
>
> I say it was a dinosaur, because it used all small
> scale logic rather than large highly capable hybrid
> circuitry, like the 3456A.? It should be much easier
> to repair, but it should also be much less reliable.
>
> And, that is my experience with the two units.
>
> -Chuck Harris
>
> paul swedberg wrote:
>> With respect to the 3455 and 3456 the difference is night and day. I have
>> numbers of 3456s and was given a seriously troubled 3455. Quite a
>> interesting meter.
>> Replaced at least 11 actually malfunctioning chips on the logic board. The
>> logics simple so easy to verify the chips were bad. No shot gunning
>> involved. Never really did get it working but ended up with a different
>> 3455 that needed help and the AC board and it is in fine shape. With
>> respect to the old 3455 it has both a logic and voltmeter issue. The 3455
>> uses an unusual processor and teh DVM uses the same proc and a masked eprom
>> that is known to go bad. It acts as a state machine.
>> The 3456s are losing there eproms and copies can be found on the net. Thank
>> heavens.
>> Regards
>> Paul
>> WB8TSL
>>
>>
>>
>>
>
>
>
>
>
>
>
>
Re: HP 3455a DVM repair

 

Hi Bob,

I don't see how you can come to that conclusion.

The 3455A is highly reparable, and should be well
within your abilities. Lots of people have fixed
their own successfully.

What you won't be able to do is send its calibration
module out for calibration. You will have to do that
yourself. But, it is not any more difficult to
calibrate than the 3456A.

It is not my meter of choice, as I greatly prefer
the 3456A, but for many, it is a useful addition to
their labs.

-Chuck Harris

Bob Albert via groups.io wrote:

I don't see a whole lot of encouragement here regarding the possibility of getting my 3455A working.? Maybe I will just put it aside and wait for a scrap unit to swap out boards or parts.? My 3456A still works so I am grateful for that.
Bob
On Wednesday, April 1, 2020, 06:40:17 AM PDT, Chuck Harris <cfharris@...> wrote:

The 3455A was a dinosaur when it was first released.

The 3455A and 3456A were sold side by side, with the
3455A being about twice as expensive as the much more
capable 3456A.? The 3455A's interesting feature was
it was supposed to be cheap to calibrate.? All you
had to do to do a complete calibration was to unplug
the module in the back panel, and replace it with a
recently calibrated module.? The idea was you could
order up a calibration by mail, and return your old
calibration module as a core... never having to send
the full meter in for calibration.

Interesting idea, but surely not worth twice the price
of a 3456A.

I say it was a dinosaur, because it used all small
scale logic rather than large highly capable hybrid
circuitry, like the 3456A.? It should be much easier
to repair, but it should also be much less reliable.

And, that is my experience with the two units.

-Chuck Harris

paul swedberg wrote:
With respect to the 3455 and 3456 the difference is night and day. I have
numbers of 3456s and was given a seriously troubled 3455. Quite a
interesting meter.
Replaced at least 11 actually malfunctioning chips on the logic board. The
logics simple so easy to verify the chips were bad. No shot gunning
involved. Never really did get it working but ended up with a different
3455 that needed help and the AC board and it is in fine shape. With
respect to the old 3455 it has both a logic and voltmeter issue. The 3455
uses an unusual processor and teh DVM uses the same proc and a masked eprom
that is known to go bad. It acts as a state machine.
The 3456s are losing there eproms and copies can be found on the net. Thank
heavens.
Regards
Paul
WB8TSL
Re: HP 3455a DVM repair

Bob Albert
 

I don't see a whole lot of encouragement here regarding the possibility of getting my 3455A working.? Maybe I will just put it aside and wait for a scrap unit to swap out boards or parts.? My 3456A still works so I am grateful for that.

Bob

On Wednesday, April 1, 2020, 06:40:17 AM PDT, Chuck Harris <cfharris@...> wrote:


The 3455A was a dinosaur when it was first released.

The 3455A and 3456A were sold side by side, with the
3455A being about twice as expensive as the much more
capable 3456A.? The 3455A's interesting feature was
it was supposed to be cheap to calibrate.? All you
had to do to do a complete calibration was to unplug
the module in the back panel, and replace it with a
recently calibrated module.? The idea was you could
order up a calibration by mail, and return your old
calibration module as a core... never having to send
the full meter in for calibration.

Interesting idea, but surely not worth twice the price
of a 3456A.

I say it was a dinosaur, because it used all small
scale logic rather than large highly capable hybrid
circuitry, like the 3456A.? It should be much easier
to repair, but it should also be much less reliable.

And, that is my experience with the two units.

-Chuck Harris

paul swedberg wrote:
> With respect to the 3455 and 3456 the difference is night and day. I have
> numbers of 3456s and was given a seriously troubled 3455. Quite a
> interesting meter.
> Replaced at least 11 actually malfunctioning chips on the logic board. The
> logics simple so easy to verify the chips were bad. No shot gunning
> involved. Never really did get it working but ended up with a different
> 3455 that needed help and the AC board and it is in fine shape. With
> respect to the old 3455 it has both a logic and voltmeter issue. The 3455
> uses an unusual processor and teh DVM uses the same proc and a masked eprom
> that is known to go bad. It acts as a state machine.
> The 3456s are losing there eproms and copies can be found on the net. Thank
> heavens.
> Regards
> Paul
> WB8TSL
>
>
>
>



Re: Where to connect the efc input on a 10544A?

 

It's up to you. How close do you want to be abl to set it?

A +-5V supply an 10 Turn pot is not too hard to do. Personlly I've used a isolated 12V output DC-DC converter with lots of filtering, a 10V reference IC? a 1:1 resistive divider connected to the EFC common, and a 10k 10 tun pot.

Robert G8RPI
Re: Fixing a sick 4332A LCR meter

 

Hi Joel,

I might have meant R36. All I have to go on right now is the awful manual scan that Keysight hosts. It's very hard to read, and some of the key diagrams are illegible. I suppose I should see if Artek has a scan, or try to find a manual on ebay.

I may contact you as I continue to troubleshoot; thanks for the tips.

Sean


On Wed, Apr 1, 2020 at 06:05 AM, Joel Setton wrote:
Hello,

I also have a 4332A and the manual, too. I looked at the A4 schematic and found that R35 on A4 is a 9.09K resistor, not 100 ohms. I don't see how a 9.09K resistor could burn, you'd need something like 60V or more to burn it. There's no high-voltage source in the 4332A so I don't understand how R35 could overheat.

I would first suggest disconnecting the four input signal leads to A4: the HIGH and LOW leads, and the orange wire and the white-red-green wire. Then you can test the various voltages which are shown on the A4 schematic to look for a failed part.
And please let me know, I'm happy to help. The 4332A is quite a neat instrument !
Joel Setton
Re: HP 3455a DVM repair

 

The 3455A was a dinosaur when it was first released.

The 3455A and 3456A were sold side by side, with the
3455A being about twice as expensive as the much more
capable 3456A. The 3455A's interesting feature was
it was supposed to be cheap to calibrate. All you
had to do to do a complete calibration was to unplug
the module in the back panel, and replace it with a
recently calibrated module. The idea was you could
order up a calibration by mail, and return your old
calibration module as a core... never having to send
the full meter in for calibration.

Interesting idea, but surely not worth twice the price
of a 3456A.

I say it was a dinosaur, because it used all small
scale logic rather than large highly capable hybrid
circuitry, like the 3456A. It should be much easier
to repair, but it should also be much less reliable.

And, that is my experience with the two units.

-Chuck Harris

paul swedberg wrote:

With respect to the 3455 and 3456 the difference is night and day. I have
numbers of 3456s and was given a seriously troubled 3455. Quite a
interesting meter.
Replaced at least 11 actually malfunctioning chips on the logic board. The
logics simple so easy to verify the chips were bad. No shot gunning
involved. Never really did get it working but ended up with a different
3455 that needed help and the AC board and it is in fine shape. With
respect to the old 3455 it has both a logic and voltmeter issue. The 3455
uses an unusual processor and teh DVM uses the same proc and a masked eprom
that is known to go bad. It acts as a state machine.
The 3456s are losing there eproms and copies can be found on the net. Thank
heavens.
Regards
Paul
WB8TSL
Re: HP 3455a DVM repair

 

With respect to the 3455 and 3456 the difference is night and day. I have numbers of 3456s and was given a seriously troubled 3455. Quite a interesting meter.
Replaced at least 11 actually malfunctioning chips on the logic board. The logics simple so easy to verify the chips were bad. No shot gunning involved. Never really did get it working but ended up with a different 3455 that needed help and the AC board?and it is in fine shape. With respect to the old 3455 it has both a logic and voltmeter issue. The 3455 uses an unusual?processor and teh DVM uses the same proc and a masked eprom that is known to go bad. It acts as a state machine.
The 3456s are losing there eproms and copies can be found on the net. Thank heavens.
Regards
Paul
WB8TSL
Re: Fixing a sick 4332A LCR meter

 

Hello,

I also have a 4332A and the manual, too. I looked at the A4 schematic and found that R35 on A4 is a 9.09K resistor, not 100 ohms. I don't see how a 9.09K resistor could burn, you'd need something like 60V or more to burn it. There's no high-voltage source in the 4332A so I don't understand how R35 could overheat.

I would first suggest disconnecting the four input signal leads to A4: the HIGH and LOW leads, and the orange wire and the white-red-green wire. Then you can test the various voltages which are shown on the A4 schematic to look for a failed part.
And please let me know, I'm happy to help. The 4332A is quite a neat instrument !
Joel Setton
Where to connect the efc input on a 10544A?

 

Hi,

So while we are stuck at home and have nothing to do but play with all
the instruments I started a project to build a distribution amplifier
for 10MHz reference. I do have a GPSDO, but that is cumbersome to use
as I don't have a good view of the sky from my room. So Instead I
decided that I build a two-in-one distribution amplifier + OCXO
reference, as I have a spare, well aged 10544A laying around. (I'll
share the design if it ever gets done.) That would be plenty of enough
precision for what I do, the GPSDO could be used to calibrate it once
in a while. That should be plenty of enough for me, as I would be
driving signal and function generators from it, nothing extreme
time-nuttery.
So my question is: Is it worth to connect the EFC input of the OCXO?
The datasheet says it has about 1 Hz range, but then I would need to
provide the -5/+5V supply for it, preferably with some good quality
reference. I know that this input is not connected in the 5335A for
example, only the "coarse" adjustment is used.
I guess it is is good for the 5335A then it should be good for me, but
on the other hand, why not make some overly complicated thing when we
finally have time for it :-)
So basically, my question is would you recommend to simply short the
EFC input and only have the coarse adjustment or should I take the
extra effort to have this fine adjustment? Would it have any drawbacks
if I do?

Thanks.

Szabolcs
Re: HP 3325A - with a short in board A14 negative 15V supply

 

This issue is almost always a shorted tantalum capacitor on the A14 board. Other suspects include the -15V zener diode or the Opto-couplers (4-pin DIPs) on the A14.

This can be an issue with the A3, A14 of A21 boards. You can verify that the A14 is the issue by temporarily disconnecting the ribbon cable supplying the A14. If the unit boots (with errors), then something on the A14 is shorted.

Perform a visual inspection of the A14 tantalums. The bad part is usually discolored from heat damage.

It's best to use a thermal IR camera to see which part is glowing, but lacking such, you can de-solder and lift one end of each tantalum capacitors along the -15V rail on the A14, then measure the resistance on the lifted diode, and on the -15V rail. The shorted part will eventually show itself using this method.

Hope that helps!

Joe, KN5U
Re: HP 3325A/B Option 002 HV output kit - who wants one?

 

¿ªÔÆÌåÓý


I would like two boards, please.


Tom Dawson

On 3/27/2020 11:19 AM, Jared Cabot via Groups.Io wrote:

Ok, let's make this the official thread for the 3325A/B Option 002 HV Output kit thread.

I'll get a batch of the latest boards spun up and finalise the documentation etc. once I have a full head count. Maybe I'll give it a week for people to get in on this first batch before I place the order.

?

The PCB is almost identical to the original board, just updated slightly for currently available parts. It will be gold plated with no top solder mask or silk screen like the original (It seems to not like sticking to the gold for whatever reason), so it'll end up as close a replica as can be.
Also, the dual transistor on the input will be replaced with two somewhat matched discreet transistors, as the cross referenced part from the original design is a little expensive.

I'll offer bare boards complete with all documentation, or a full kit including all parts minus the RF shield as I don't have the means to make them in any quantity unfortunately. I will provide the template so you can make your own from a scrap of thin aluminium though.
I will also provide some thin coax and right angle RCA jacks to build your own interconnects too.


Postage will be a flat fee worldwide and included in the total cost. I am still finalising the final cost, but I'm practically certain that it will be no more than US$50 all inclusive for the kit. The bare PCB will cost about $7 plus post (once I work out what a registered envelope costs to send...)

Here's the eevblog thread that needs to be updated. I'll do that once I get the latest boards back and have one assembled and tested to be 100% sure no bodge wires are needed. :)


So, sound off who wants one. :)
The following people have expressed interest so far, please confirm or correct as needed:


Mac Perkins: Board or Kit
Tom WA3PZI: Kit
JL Trantham: Kit x2
Bruce at westcut: Kit
Daun Yeagley: Board
Dave Wright: Kit
Joe KN5U: Board or Kit
Kerry Burns: Kit


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