#78410

as this is my first posting in this group i hope doing right...

I want to ask for some advice solving the following problem:
After some weeks of storage, the readout of the centre bay (right vertical module) makes problems: first the text itself was not OK (-> "4", "40m", "3S" (!), ...), then there was no text anymore. A few weeks in the past, everything was OK.
Changing the vertical modules did not move the problem, therefore the modules must be OK. As there were changes in readout when changing the scale factor, connection to the readout board A13 (early version without ROM) seems to be OK ?.?
Readout of the left vertical module and the timebase is OK.

I have not found a proper starting point in the schematics to begin searching. Hints and advices are highly appreciated.

Thanks a lot,
Max

Albert

#78414

Hi Max,

Did you read the other readout problems thread, concerning a R7903? Very informative and you might have a similar contact problem.
First of all put a dual channel vertical amplifier (like 7A18, 7A26) in the right vertical bay and find out whether the problem is restricted to just one of the channels. If so, you might also have that bad contact in the main interface (backplane) connector. If the problem is the same for both channels then one or more of the Time Slot contacts could be bad. Each TS pulse (TS-1, TS-2, ...) uses its own plugin contact, common for CH1 and CH2.
The ReadOut display is "compiled" from the results of several TS pulses. Hence a change in readout as response to turning V/div is not a guarantee that *all* connections from plugin to readout board are intact.

Albert

Show quoted text

--- In TekScopes@..., "max_3289" <max_3289@...> wrote:

as this is my first posting in this group i hope doing right...

I want to ask for some advice solving the following problem:
After some weeks of storage, the readout of the centre bay (right vertical module) makes problems: first the text itself was not OK (-> "4", "40m", "3S" (!), ...), then there was no text anymore. A few weeks in the past, everything was OK.
Changing the vertical modules did not move the problem, therefore the modules must be OK. As there were changes in readout when changing the scale factor, connection to the readout board A13 (early version without ROM) seems to be OK ?.?
Readout of the left vertical module and the timebase is OK.

I have not found a proper starting point in the schematics to begin searching. Hints and advices are highly appreciated.

Thanks a lot,
Max

#78418

Hi Albert,

thanks a lot; just tested the following:

I have 2 pcs. 7A22, 1 pc 7A26, 1 pc 7B53A, 1 pc 7B85.

The 7A26 in left position shows both channels ok, in centre position only CH2 (bottom middle position readout) ok, CH1 (top middle position) no readout.
7B53A and 7B85 timebases show no difference (except additional 7B85 readout bottom right).

It seems to be the problem of the backplane-connector you mentioned.

Did you read the other readout problems thread, concerning a R7903?not yet; have not known it yet.

Max.

--- In TekScopes@..., "Albert" <aodiversen@...> wrote:

Hi Max,

Did you read the other readout problems thread, concerning a R7903? Very informative and you might have a similar contact problem.
First of all put a dual channel vertical amplifier (like 7A18, 7A26) in the right vertical bay and find out whether the problem is restricted to just one of the channels. If so, you might also have that bad contact in the main interface (backplane) connector. If the problem is the same for both channels then one or more of the Time Slot contacts could be bad. Each TS pulse (TS-1, TS-2, ...) uses its own plugin contact, common for CH1 and CH2.
The ReadOut display is "compiled" from the results of several TS pulses. Hence a change in readout as response to turning V/div is not a guarantee that *all* connections from plugin to readout board are intact.

Albert

--- In TekScopes@..., "max_3289" <max_3289@> wrote:

as this is my first posting in this group i hope doing right...

I want to ask for some advice solving the following problem:
After some weeks of storage, the readout of the centre bay (right vertical module) makes problems: first the text itself was not OK (-> "4", "40m", "3S" (!), ...), then there was no text anymore. A few weeks in the past, everything was OK.
Changing the vertical modules did not move the problem, therefore the modules must be OK. As there were changes in readout when changing the scale factor, connection to the readout board A13 (early version without ROM) seems to be OK ?.?
Readout of the left vertical module and the timebase is OK.

I have not found a proper starting point in the schematics to begin searching. Hints and advices are highly appreciated.

Thanks a lot,
Max

Albert

#78421

Hi Max,
This makes contacts A37 and B37 suspect.
Remember this is a first check. The fault could also be in a readout board channel selector IC for instance.
Albert

Show quoted text

Hi Albert,

thanks a lot; just tested the following:

I have 2 pcs. 7A22, 1 pc 7A26, 1 pc 7B53A, 1 pc 7B85.

The 7A26 in left position shows both channels ok, in centre position only CH2 (bottom middle position readout) ok, CH1 (top middle position) no readout.
7B53A and 7B85 timebases show no difference (except additional 7B85 readout bottom right).

It seems to be the problem of the backplane-connector you mentioned.

Did you read the other readout problems thread, concerning a R7903?not yet; have not known it yet.

Max.

#78438

Hello Albert,

backplaneboard A1, J2 contact A37 to readout board A13, U2190 pin 12 -> low ohmic
backplaneboard A1, J2 contact A38 to readout board A13, U2190 pin 11 -> low ohmic

backplaneboard A1, J2 contact B37 to readout board A13, U2180 pin 12 -> low ohmic
backplaneboard A1, J2 contact B38 to readout board A13, U2180 pin 11 -> low ohmic

aAll the diodes on the protection circuit board of A13 are ok.

Connections are ok, connectors are all clean.

After cooling down over night, there were seen some false characters again for some time.

Any ideas?
Max.

Show quoted text

--- In TekScopes@..., "Albert" <aodiversen@...> wrote:

Hi Max,
This makes contacts A37 and B37 suspect.
Remember this is a first check. The fault could also be in a readout board channel selector IC for instance.
Albert

Hi Albert,

thanks a lot; just tested the following:

I have 2 pcs. 7A22, 1 pc 7A26, 1 pc 7B53A, 1 pc 7B85.

The 7A26 in left position shows both channels ok, in centre position only CH2 (bottom middle position readout) ok, CH1 (top middle position) no readout.
7B53A and 7B85 timebases show no difference (except additional 7B85 readout bottom right).

It seems to be the problem of the backplane-connector you mentioned.

Did you read the other readout problems thread, concerning a R7903?not yet; have not known it yet.

Max.

Albert

#78441

Hi Max,

It seems that U2180 or U2190 is faulty. It is often suggested to reseat ICs, did you try? If you get different readout (though still not good) after swapping U2180 and U2190 then you can feel more sure that one of these if defective.
In theory the format generator could be faulty and move one of the readout positions to outside the visible screen.

An even more thorough check on continuity would be as follows. I looked at the cables/plugs. Diagram <1> shows plugs P65 for J1 and J2 and plug P66 for J3. If it's physically possible you might pull P65 and move P66 to locations 6 to 10 of where P65 was (P66-1 to P65-6). Then the readouts of J2 will flow via P66. These should be OK but will appear in the rightmost screen position (normally the time base readout). The other readouts (of J1 an J3) simply will be missing.

Albert

Show quoted text

Hello Albert,

backplaneboard A1, J2 contact A37 to readout board A13, U2190 pin 12 -> low ohmic
backplaneboard A1, J2 contact A38 to readout board A13, U2190 pin 11 -> low ohmic

backplaneboard A1, J2 contact B37 to readout board A13, U2180 pin 12 -> low ohmic
backplaneboard A1, J2 contact B38 to readout board A13, U2180 pin 11 -> low ohmic

aAll the diodes on the protection circuit board of A13 are ok.

Connections are ok, connectors are all clean.

After cooling down over night, there were seen some false characters again for some time.

Any ideas?
Max.

#78443

Hi,

There are 3 power test points on the readout board. Make sure all 3 voltages(+/-15V and 5V) are ripple free and stable with the 5V reading 4.8V or better.

Jerry Massengale

Show quoted text

-----Original Message-----
From: max_3289
To: TekScopes
Sent: Sun, Jul 22, 2012 12:14 pm
Subject: [TekScopes] Re: 7633 readout problem, advice or hints needed

Hello Albert,

backplaneboard A1, J2 contact A37 to readout board A13, U2190 pin 12 -> low ohmic
backplaneboard A1, J2 contact A38 to readout board A13, U2190 pin 11 -> low ohmic

backplaneboard A1, J2 contact B37 to readout board A13, U2180 pin 12 -> low ohmic
backplaneboard A1, J2 contact B38 to readout board A13, U2180 pin 11 -> low ohmic

aAll the diodes on the protection circuit board of A13 are ok.

Connections are ok, connectors are all clean.

After cooling down over night, there were seen some false characters again for some time.

Any ideas?
Max.

--- In TekScopes@..., "Albert" wrote:
>
> Hi Max,
> This makes contacts A37 and B37 suspect.
> Remember this is a first check. The fault could also be in a readout board channel selector IC for instance.
> Albert
>
> > Hi Albert,
> >
> > thanks a lot; just tested the following:
> >
> > I have 2 pcs. 7A22, 1 pc 7A26, 1 pc 7B53A, 1 pc 7B85.
> >
> > The 7A26 in left position shows both channels ok, in centre position only CH2 (bottom middle position readout) ok, CH1 (top middle position) no readout.
> > 7B53A and 7B85 timebases show no difference (except additional 7B85 readout bottom right).
> >
> > It seems to be the problem of the backplane-connector you mentioned.
> >
> > >Did you read the other readout problems thread, concerning a R7903?
> > not yet; have not known it yet.
> >
> > Max.
>

#78455

Hi Albert, Jerry,

first i measured:

TP2119: -14,94 VDC with 3,75 mVAC ripple
TP2117: 4,96 VDC with 3,45 mVAC ripple
TP2115: 15,05 VDC with 9,94 mVAC ripple

-> ok.

Then, while thinking how to change the connections for Albert's proposal, i saw the characters all correct!
Obviously i touched some device while measuring the voltages (i have moved out and in all socketed transistors long before without success...), perhaps a bad soldering somewhere.
I will observe for the next days, by good luck the problem was gone and no IC affected.
Thanks a lot for your help!
Max.


BTW: is it possible to get email notification only for dedicated topics?

Show quoted text

--- In TekScopes@..., jerry massengale <j_massengale@...> wrote:

Hi,

There are 3 power test points on the readout board. Make sure all 3 voltages(+/-15V and 5V) are ripple free and stable with the 5V reading 4.8V or better.

Jerry Massengale

-----Original Message-----
From: max_3289 <max_3289@...>
To: TekScopes <TekScopes@...>
Sent: Sun, Jul 22, 2012 12:14 pm
Subject: [TekScopes] Re: 7633 readout problem, advice or hints needed

Hello Albert,

backplaneboard A1, J2 contact A37 to readout board A13, U2190 pin 12 -> low ohmic
backplaneboard A1, J2 contact A38 to readout board A13, U2190 pin 11 -> low ohmic

backplaneboard A1, J2 contact B37 to readout board A13, U2180 pin 12 -> low ohmic
backplaneboard A1, J2 contact B38 to readout board A13, U2180 pin 11 -> low ohmic

aAll the diodes on the protection circuit board of A13 are ok.

Connections are ok, connectors are all clean.

After cooling down over night, there were seen some false characters again for some time.

Any ideas?
Max.

--- In TekScopes@..., "Albert" <aodiversen@> wrote:

Hi Max,
This makes contacts A37 and B37 suspect.
Remember this is a first check. The fault could also be in a readout board channel selector IC for instance.
Albert

Hi Albert,

thanks a lot; just tested the following:

I have 2 pcs. 7A22, 1 pc 7A26, 1 pc 7B53A, 1 pc 7B85.

The 7A26 in left position shows both channels ok, in centre position only CH2 (bottom middle position readout) ok, CH1 (top middle position) no readout.
7B53A and 7B85 timebases show no difference (except additional 7B85 readout bottom right).

It seems to be the problem of the backplane-connector you mentioned.

Did you read the other readout problems thread, concerning a R7903?not yet; have not known it yet.

Max.

#78456

-> not stable, case closed and a few times off/on -> first "m" for mV disappeared while "?" was ok, then "V" changed to "S", then again "4", "500V", ... appeared.
I consider, resoldering all solderings on the board, but big effort as brute force method.
Max

Show quoted text

--- In TekScopes@..., "max_3289" <max_3289@...> wrote:

Hi Albert, Jerry,

first i measured:

TP2119: -14,94 VDC with 3,75 mVAC ripple
TP2117: 4,96 VDC with 3,45 mVAC ripple
TP2115: 15,05 VDC with 9,94 mVAC ripple

-> ok.

Then, while thinking how to change the connections for Albert's proposal, i saw the characters all correct!
Obviously i touched some device while measuring the voltages (i have moved out and in all socketed transistors long before without success...), perhaps a bad soldering somewhere.
I will observe for the next days, by good luck the problem was gone and no IC affected.
Thanks a lot for your help!
Max.

BTW: is it possible to get email notification only for dedicated topics?

--- In TekScopes@..., jerry massengale <j_massengale@> wrote:

Hi,

There are 3 power test points on the readout board. Make sure all 3 voltages(+/-15V and 5V) are ripple free and stable with the 5V reading 4.8V or better.

Jerry Massengale

-----Original Message-----
From: max_3289 <max_3289@>
To: TekScopes <TekScopes@...>
Sent: Sun, Jul 22, 2012 12:14 pm
Subject: [TekScopes] Re: 7633 readout problem, advice or hints needed

Hello Albert,

backplaneboard A1, J2 contact A37 to readout board A13, U2190 pin 12 -> low ohmic
backplaneboard A1, J2 contact A38 to readout board A13, U2190 pin 11 -> low ohmic

backplaneboard A1, J2 contact B37 to readout board A13, U2180 pin 12 -> low ohmic
backplaneboard A1, J2 contact B38 to readout board A13, U2180 pin 11 -> low ohmic

aAll the diodes on the protection circuit board of A13 are ok.

Connections are ok, connectors are all clean.

After cooling down over night, there were seen some false characters again for some time.

Any ideas?
Max.

--- In TekScopes@..., "Albert" <aodiversen@> wrote:

Hi Max,
This makes contacts A37 and B37 suspect.
Remember this is a first check. The fault could also be in a readout board channel selector IC for instance.
Albert

Hi Albert,

thanks a lot; just tested the following:

I have 2 pcs. 7A22, 1 pc 7A26, 1 pc 7B53A, 1 pc 7B85.

The 7A26 in left position shows both channels ok, in centre position only CH2 (bottom middle position readout) ok, CH1 (top middle position) no readout.
7B53A and 7B85 timebases show no difference (except additional 7B85 readout bottom right).

It seems to be the problem of the backplane-connector you mentioned.

Did you read the other readout problems thread, concerning a R7903?not yet; have not known it yet.

Max.

#78457

Max,

The readout board is a hybrid of analog and digital that defies explanation even with a long precise circuit description. I have worked on them many times and fixed boards for others but still mutter 'Oh Crap' when I see a problem. The IC sockets suck, the cables are long. The timer chip(-21) is a frequent problem. The outputs sometimes do not get a good low level. For some reason, the transistors near the top of the board are frequently bent over just enough to be unreliable and the old TI chips have black leads from silver oxide. Good luck.

Jerry Massengale

Show quoted text

-----Original Message-----
From: max_3289
To: TekScopes
Sent: Sun, Jul 22, 2012 2:28 pm
Subject: [TekScopes] Re: 7633 readout problem, advice or hints needed

Hi Albert, Jerry,

first i measured:

TP2119: -14,94 VDC with 3,75 mVAC ripple
TP2117: 4,96 VDC with 3,45 mVAC ripple
TP2115: 15,05 VDC with 9,94 mVAC ripple

-> ok.

Then, while thinking how to change the connections for Albert's proposal, i saw the characters all correct!
Obviously i touched some device while measuring the voltages (i have moved out and in all socketed transistors long before without success...), perhaps a bad soldering somewhere.
I will observe for the next days, by good luck the problem was gone and no IC affected.
Thanks a lot for your help!
Max.

BTW: is it possible to get email notification only for dedicated topics?

--- In TekScopes@..., jerry massengale wrote:
>
> Hi,
>
> There are 3 power test points on the readout board. Make sure all 3 voltages(+/-15V and 5V) are ripple free and stable with the 5V reading 4.8V or better.
>
>
> Jerry Massengale
>
>
>
>
>
> -----Original Message-----
> From: max_3289
> To: TekScopes <TekScopes@...>
> Sent: Sun, Jul 22, 2012 12:14 pm
> Subject: [TekScopes] Re: 7633 readout problem, advice or hints needed
>
>
>
>
>
> Hello Albert,
>
> backplaneboard A1, J2 contact A37 to readout board A13, U2190 pin 12 -> low ohmic
> backplaneboard A1, J2 contact A38 to readout board A13, U2190 pin 11 -> low ohmic
>
> backplaneboard A1, J2 contact B37 to readout board A13, U2180 pin 12 -> low ohmic
> backplaneboard A1, J2 contact B38 to readout board A13, U2180 pin 11 -> low ohmic
>
> aAll the diodes on the protection circuit board of A13 are ok.
>
> Connections are ok, connectors are all clean.
>
> After cooling down over night, there were seen some false characters again for some time.
>
> Any ideas?
> Max.
>
> --- In TekScopes@..., "Albert" wrote:
> >
> > Hi Max,
> > This makes contacts A37 and B37 suspect.
> > Remember this is a first check. The fault could also be in a readout board channel selector IC for instance.
> > Albert
> >
> > > Hi Albert,
> > >
> > > thanks a lot; just tested the following:
> > >
> > > I have 2 pcs. 7A22, 1 pc 7A26, 1 pc 7B53A, 1 pc 7B85.
> > >
> > > The 7A26 in left position shows both channels ok, in centre position only CH2 (bottom middle position readout) ok, CH1 (top middle position) no readout.
> > > 7B53A and 7B85 timebases show no difference (except additional 7B85 readout bottom right).
> > >
> > > It seems to be the problem of the backplane-connector you mentioned.
> > >
> > > >Did you read the other readout problems thread, concerning a R7903?
> > > not yet; have not known it yet.
> > >
> > > Max.
> >
>

Brad Thompson

#78459

On 7/22/2012 4:18 PM, jerry massengale wrote:
Max,

The readout board is a hybrid of analog and digital that defies
explanation even with a long precise circuit description. I have worked
on them many times and fixed boards for others but still mutter 'Oh
Crap' when I see a problem. The IC sockets suck, the cables are long.
The timer chip(-21) is a frequent problem. The outputs sometimes do not
get a good low level. For some reason, the transistors near the top of
the board are frequently bent over just enough to be unreliable and the
old TI chips have black leads from silver oxide. Good luck.Hello, Jerry and the group--

IIRC, the black substance on those IC pins is silver sulfide.
Silver oxide is conductive, but again IIRC silver sulfide isn't
a very good conductor. Hydrogen sulfide in the
atmosphere reacts with silver to form a black film on the pins.

Again IIRC, kraft corrugated cardboard (the familiar brown material
used for shipping cartons) contains sulfur compounds which can
form hydrogen sulfate given time, heat and moisture.

I'm not a chemist and my recall may be faulty, so don't hesitate
to offer a correction if i'm offbase.

73--

Brad  AA1IP

#78461

That is less brute force than I use.  Twice now I have replaced all of
the TI sockets with machined pin collet sockets.

Once was with my now working 7D15 where the problem might not have
been the sockets and another time was with my now working SG503.  In
the that case, I positively verified which socket was bad but changed
them all.

On Sun, 22 Jul 2012 19:38:57 -0000, "max_3289" <max_3289@...>
wrote:

-> not stable, case closed and a few times off/on -> first "m" for mV disappeared while "?" was ok, then "V" changed to "S", then again "4", "500V", ... appeared.
I consider, resoldering all solderings on the board, but big effort as brute force method.
Max

--- In TekScopes@..., "max_3289" <max_3289@...> wrote:

Hi Albert, Jerry,

first i measured:

TP2119: -14,94 VDC with 3,75 mVAC ripple
TP2117: 4,96 VDC with 3,45 mVAC ripple
TP2115: 15,05 VDC with 9,94 mVAC ripple

-> ok.

Then, while thinking how to change the connections for Albert's proposal, i saw the characters all correct!
Obviously i touched some device while measuring the voltages (i have moved out and in all socketed transistors long before without success...), perhaps a bad soldering somewhere.
I will observe for the next days, by good luck the problem was gone and no IC affected.
Thanks a lot for your help!
Max.

BTW: is it possible to get email notification only for dedicated topics?

--- In TekScopes@..., jerry massengale <j_massengale@> wrote:

Hi,

There are 3 power test points on the readout board. Make sure all 3 voltages(+/-15V and 5V) are ripple free and stable with the 5V reading 4.8V or better.

Jerry Massengale

-----Original Message-----
From: max_3289 <max_3289@>
To: TekScopes <TekScopes@...>
Sent: Sun, Jul 22, 2012 12:14 pm
Subject: [TekScopes] Re: 7633 readout problem, advice or hints needed

Hello Albert,

backplaneboard A1, J2 contact A37 to readout board A13, U2190 pin 12 -> low ohmic
backplaneboard A1, J2 contact A38 to readout board A13, U2190 pin 11 -> low ohmic

backplaneboard A1, J2 contact B37 to readout board A13, U2180 pin 12 -> low ohmic
backplaneboard A1, J2 contact B38 to readout board A13, U2180 pin 11 -> low ohmic

aAll the diodes on the protection circuit board of A13 are ok.

Connections are ok, connectors are all clean.

After cooling down over night, there were seen some false characters again for some time.

Any ideas?
Max.

--- In TekScopes@..., "Albert" <aodiversen@> wrote:

Hi Max,
This makes contacts A37 and B37 suspect.
Remember this is a first check. The fault could also be in a readout board channel selector IC for instance.
Albert

Hi Albert,

thanks a lot; just tested the following:

I have 2 pcs. 7A22, 1 pc 7A26, 1 pc 7B53A, 1 pc 7B85.

The 7A26 in left position shows both channels ok, in centre position only CH2 (bottom middle position readout) ok, CH1 (top middle position) no readout.
7B53A and 7B85 timebases show no difference (except additional 7B85 readout bottom right).

It seems to be the problem of the backplane-connector you mentioned.

Did you read the other readout problems thread, concerning a R7903?not yet; have not known it yet.

Max.

Albert

#78463

Hi Max,

The changes you mention are all due to a slight decrease in column current. So input wiring to U2190, or U2190 itself is suspect. If you interchange U2180 and U2190 then you can decide which problem it is.
Very speculative: it might be that a slight adjustment of R2214 Column Match cures the J2-top problem while not introducing new problems in the other readouts.

Albert

Show quoted text

---
-> not stable, case closed and a few times off/on -> first "m" for mV disappeared while "?" was ok, then "V" changed to "S", then again "4", "500V", ... appeared.
I consider, resoldering all solderings on the board, but big effort as brute force method.
Max

Don Black

#78489

开云体育

I'm not familiar with these boards but if the silver leads are black oxidized (indicating they are silver) it's likely that silver has migrated between the leads across the plastic. It can usually be seen as a rainbow bloom on the surface of the plastic. You can usually scrape it off the plastic (while unpowered of course) to restore operation.

Don Black.

On 23-Jul-12 6:18 AM, jerry massengale wrote:

Show quoted text

Max,

The readout board is a hybrid of analog and digital that defies explanation even with a long precise circuit description. I have worked on them many times and fixed boards for others but still mutter 'Oh Crap' when I see a problem. The IC sockets suck, the cables are long. The timer chip(-21) is a frequent problem. The outputs sometimes do not get a good low level. For some reason, the transistors near the top of the board are frequently bent over just enough to be unreliable and the old TI chips have black leads from silver oxide. Good luck.

Jerry Massengale

-----Original Message-----
From: max_3289
To: TekScopes
Sent: Sun, Jul 22, 2012 2:28 pm
Subject: [TekScopes] Re: 7633 readout problem, advice or hints needed

?

Hi Albert, Jerry,

first i measured:

TP2119: -14,94 VDC with 3,75 mVAC ripple
TP2117: 4,96 VDC with 3,45 mVAC ripple
TP2115: 15,05 VDC with 9,94 mVAC ripple

-> ok.

Then, while thinking how to change the connections for Albert's proposal, i saw the characters all correct!
Obviously i touched some device while measuring the voltages (i have moved out and in all socketed transistors long before without success...), perhaps a bad soldering somewhere.
I will observe for the next days, by good luck the problem was gone and no IC affected.
Thanks a lot for your help!
Max.

BTW: is it possible to get email notification only for dedicated topics?

--- In TekScopes@..., jerry massengale wrote:
>
> Hi,
>
> There are 3 power test points on the readout board. Make sure all 3 voltages(+/-15V and 5V) are ripple free and stable with the 5V reading 4.8V or better.
>
>
> Jerry Massengale
>
>
>
>
>
> -----Original Message-----
> From: max_3289
> To: TekScopes <TekScopes@...>
> Sent: Sun, Jul 22, 2012 12:14 pm
> Subject: [TekScopes] Re: 7633 readout problem, advice or hints needed
>
>
>
>
>
> Hello Albert,
>
> backplaneboard A1, J2 contact A37 to readout board A13, U2190 pin 12 -> low ohmic
> backplaneboard A1, J2 contact A38 to readout board A13, U2190 pin 11 -> low ohmic
>
> backplaneboard A1, J2 contact B37 to readout board A13, U2180 pin 12 -> low ohmic
> backplaneboard A1, J2 contact B38 to readout board A13, U2180 pin 11 -> low ohmic
>
> aAll the diodes on the protection circuit board of A13 are ok.
>
> Connections are ok, connectors are all clean.
>
> After cooling down over night, there were seen some false characters again for some time.
>
> Any ideas?
> Max.
>
> --- In TekScopes@..., "Albert" wrote:
> >
> > Hi Max,
> > This makes contacts A37 and B37 suspect.
> > Remember this is a first check. The fault could also be in a readout board channel selector IC for instance.
> > Albert
> >
> > > Hi Albert,
> > >
> > > thanks a lot; just tested the following:
> > >
> > > I have 2 pcs. 7A22, 1 pc 7A26, 1 pc 7B53A, 1 pc 7B85.
> > >
> > > The 7A26 in left position shows both channels ok, in centre position only CH2 (bottom middle position readout) ok, CH1 (top middle position) no readout.
> > > 7B53A and 7B85 timebases show no difference (except additional 7B85 readout bottom right).
> > >
> > > It seems to be the problem of the backplane-connector you mentioned.
> > >
> > > >Did you read the other readout problems thread, concerning a R7903?
> > > not yet; have not known it yet.
> > >
> > > Max.
> >
>

#78490

I suspect the voltages are too low for silver migration but the edge
wipe design IC sockets made by Texas Instruments that Tektronix used
during this era are notoriously unreliable.  If they are the problem,
then reseating the ICs should temporarily fix it.

I think twice now I have heard from individuals have had readout
boards where a trace was open.  They installed a jumper from the pin
connector to the IC pin to fix it.

On Mon, 23 Jul 2012 15:38:46 +1000, Don Black <jeans@...>
wrote:

I'm not familiar with these boards but if the silver leads are black
oxidized (indicating they are silver) it's likely that silver has
migrated between the leads across the plastic. It can usually be seen as
a rainbow bloom on the surface of the plastic. You can usually scrape it
off the plastic (while unpowered of course) to restore operation.

Don Black.

#78492

Erratic readout in one slot of my 7633, much like what you describe, was due to bad PCB tracks inside the main interface. Everything you touch flexes the MI, so it's easy to be misled when symptoms change.

mike

Show quoted text

--- In TekScopes@..., "max_3289" <max_3289@...> wrote:

After some weeks of storage, the readout of the centre bay (right vertical module) makes problems: first the text itself was not OK (-> "4", "40m", "3S" (!), ...), then there was no text anymore. A few weeks in the past, everything was OK.
Changing the vertical modules did not move the problem, therefore the modules must be OK.

#78495

Now i have reseated *all* reseatable parts except cables on the board (ICs, Qs) and deadjusted/readjusted all pots. Also i interchanged U2180 and U2190.
All contacs were clean.

I installed a 7A22 (to get the "?" character also) and switched from position to position and got out the following:

0S (instead of 10V)
4S (5V)
1S (2V)
0S (1V)
50S (500mV)
10S (200mV)
00S then 00V then 100V then 100mV (100mV)
 -> the "m" appeared slowly in weird way, here i started
    from beginning:

1V (10V)
5V (5V)
2V (2V)
1V (1V)
500V (500mV) "m" not here again
200V (200mV)
100V (100mV)

 -> gave a 3rd beginning:

10V
5V
...
everything OK down to 10?V, "m" correct now for some hours.

Lets see later with another cold start.
Max.

Show quoted text

--- In TekScopes@..., "max_3289" <max_3289@...> wrote:

Hi Albert, Jerry,

first i measured:

TP2119: -14,94 VDC with 3,75 mVAC ripple
TP2117: 4,96 VDC with 3,45 mVAC ripple
TP2115: 15,05 VDC with 9,94 mVAC ripple

-> ok.

Then, while thinking how to change the connections for Albert's proposal, i saw the characters all correct!
Obviously i touched some device while measuring the voltages (i have moved out and in all socketed transistors long before without success...), perhaps a bad soldering somewhere.
I will observe for the next days, by good luck the problem was gone and no IC affected.
Thanks a lot for your help!
Max.

BTW: is it possible to get email notification only for dedicated topics?

--- In TekScopes@..., jerry massengale <j_massengale@> wrote:

Hi,

There are 3 power test points on the readout board. Make sure all 3 voltages(+/-15V and 5V) are ripple free and stable with the 5V reading 4.8V or better.

Jerry Massengale

-----Original Message-----
From: max_3289 <max_3289@>
To: TekScopes <TekScopes@...>
Sent: Sun, Jul 22, 2012 12:14 pm
Subject: [TekScopes] Re: 7633 readout problem, advice or hints needed

Hello Albert,

backplaneboard A1, J2 contact A37 to readout board A13, U2190 pin 12 -> low ohmic
backplaneboard A1, J2 contact A38 to readout board A13, U2190 pin 11 -> low ohmic

backplaneboard A1, J2 contact B37 to readout board A13, U2180 pin 12 -> low ohmic
backplaneboard A1, J2 contact B38 to readout board A13, U2180 pin 11 -> low ohmic

aAll the diodes on the protection circuit board of A13 are ok.

Connections are ok, connectors are all clean.

After cooling down over night, there were seen some false characters again for some time.

Any ideas?
Max.

--- In TekScopes@..., "Albert" <aodiversen@> wrote:

Hi Max,
This makes contacts A37 and B37 suspect.
Remember this is a first check. The fault could also be in a readout board channel selector IC for instance.
Albert

Hi Albert,

thanks a lot; just tested the following:

I have 2 pcs. 7A22, 1 pc 7A26, 1 pc 7B53A, 1 pc 7B85.

The 7A26 in left position shows both channels ok, in centre position only CH2 (bottom middle position readout) ok, CH1 (top middle position) no readout.
7B53A and 7B85 timebases show no difference (except additional 7B85 readout bottom right).

It seems to be the problem of the backplane-connector you mentioned.

Did you read the other readout problems thread, concerning a R7903?not yet; have not known it yet.

Max.

raymonddompfrank

#78496

I haven't followed this thread so forgive me if old news:

The other day I washed my recently acquired flexible plugin extender. It was working ok but looking awful, smoke and coffee stains and that sort of thing...
I took everything apart (not PCB sockets for fear of breaking the brittle plastic), carefully washed the rigid parts and cable with washing up liquid and rinsed thoroughly. Afterwards, i  dried everything, using compressed air, a hot air blower sparingly and a soft towel.
Although I had been careful, obviously some water ended up where it didn't dry away immediately.
This resulted in strange characters and sequences showing up in the readout.
After a few hours of further drying, everything was ok again.

Just tells me that high-impedance leaks are enough to cause strange/false displays, so be prepared.

Raymond

Show quoted text

--- In TekScopes@..., "max_3289" <max_3289@...> wrote:

as this is my first posting in this group i hope doing right...

I want to ask for some advice solving the following problem:
After some weeks of storage, the readout of the centre bay (right vertical module) makes problems: first the text itself was not OK (-> "4", "40m", "3S" (!), ...), then there was no text anymore. A few weeks in the past, everything was OK.
Changing the vertical modules did not move the problem, therefore the modules must be OK. As there were changes in readout when changing the scale factor, connection to the readout board A13 (early version without ROM) seems to be OK ?.?
Readout of the left vertical module and the timebase is OK.

I have not found a proper starting point in the schematics to begin searching. Hints and advices are highly appreciated.

Thanks a lot,
Max

#78497

I haven't followed this thread so forgive me if old news:latest info is actually at Message #79395, i am waiting for a new cold start now.

The board PCB is very clean, also no dust and it is not smokey;
Leakage: you mean, cooling down makes some condensed humidity on high ohmic traces? I have a PCB-cleaner here ("Kontakt LR"), i can give a try next time the problem occurs again.
Max



--- In TekScopes@..., "raymonddompfrank" <r.domp.frank@...> wrote:

I haven't followed this thread so forgive me if old news:

The other day I washed my recently acquired flexible plugin extender. It was working ok but looking awful, smoke and coffee stains and that sort of thing...
I took everything apart (not PCB sockets for fear of breaking the brittle plastic), carefully washed the rigid parts and cable with washing up liquid and rinsed thoroughly. Afterwards, i  dried everything, using compressed air, a hot air blower sparingly and a soft towel.
Although I had been careful, obviously some water ended up where it didn't dry away immediately.
This resulted in strange characters and sequences showing up in the readout.
After a few hours of further drying, everything was ok again.

Just tells me that high-impedance leaks are enough to cause strange/false displays, so be prepared.

Raymond

--- In TekScopes@..., "max_3289" <max_3289@> wrote:

as this is my first posting in this group i hope doing right...

I want to ask for some advice solving the following problem:
After some weeks of storage, the readout of the centre bay (right vertical module) makes problems: first the text itself was not OK (-> "4", "40m", "3S" (!), ...), then there was no text anymore. A few weeks in the past, everything was OK.
Changing the vertical modules did not move the problem, therefore the modules must be OK. As there were changes in readout when changing the scale factor, connection to the readout board A13 (early version without ROM) seems to be OK ?.?
Readout of the left vertical module and the timebase is OK.

I have not found a proper starting point in the schematics to begin searching. Hints and advices are highly appreciated.

Thanks a lot, 
Max

raymonddompfrank

#78498

I am talking about humidity left between conductors after initial drying, no condensation, just incomplete drying. The high impedance water is enough to make phantom characters appear.
Kontakt LR seems an appropriate PCB cleaner. It's important that it doesn't leave an oily "protective" residue.
Raymond

Show quoted text

--- In TekScopes@..., "max_3289" <max_3289@...> wrote:


I haven't followed this thread so forgive me if old news:latest info is actually at Message #79395, i am waiting for a new cold start now.

The board PCB is very clean, also no dust and it is not smokey;
Leakage: you mean, cooling down makes some condensed humidity on high ohmic traces? I have a PCB-cleaner here ("Kontakt LR"), i can give a try next time the problem occurs again.
Max



--- In TekScopes@..., "raymonddompfrank" <r.domp.frank@> wrote:

I haven't followed this thread so forgive me if old news:

The other day I washed my recently acquired flexible plugin extender. It was working ok but looking awful, smoke and coffee stains and that sort of thing...
I took everything apart (not PCB sockets for fear of breaking the brittle plastic), carefully washed the rigid parts and cable with washing up liquid and rinsed thoroughly. Afterwards, i  dried everything, using compressed air, a hot air blower sparingly and a soft towel.
Although I had been careful, obviously some water ended up where it didn't dry away immediately.
This resulted in strange characters and sequences showing up in the readout.
After a few hours of further drying, everything was ok again.

Just tells me that high-impedance leaks are enough to cause strange/false displays, so be prepared.

Raymond

--- In TekScopes@..., "max_3289" <max_3289@> wrote:

as this is my first posting in this group i hope doing right...

I want to ask for some advice solving the following problem:
After some weeks of storage, the readout of the centre bay (right vertical module) makes problems: first the text itself was not OK (-> "4", "40m", "3S" (!), ...), then there was no text anymore. A few weeks in the past, everything was OK.
Changing the vertical modules did not move the problem, therefore the modules must be OK. As there were changes in readout when changing the scale factor, connection to the readout board A13 (early version without ROM) seems to be OK ?.?
Readout of the left vertical module and the timebase is OK.

I have not found a proper starting point in the schematics to begin searching. Hints and advices are highly appreciated.

Thanks a lot,
Max