HP 8903A Service Manual for SN 2336A
Hello all,
I¡¯m trying to repair an old HP 8903A and found there is a problem in the A6 board.
The thing is, my A6 board has 3 relays on it while all service manuals I found have a completely different A6 board with only 2 relays.
My A6 board is #08903-60105 and I have included a picture of it.
Does anyone have a SM with the correct layout and schematics for this 8903A / A6 board?
My 8903A has SN prefix 2336A.
Thank you!
Att.,
Bernardo Santos
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Hi all i have a hp54503A scope with a dead psu,has anyone subbed one of these with a pc atx psu ?,as they seem to have most of the voltages required,cheers Paul.?
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Re: HP 6286A power supply question
Thanks Michael,
I'll spin through the that again tomorrow and see what? can see.? I didn't come across anything on my first go round
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Re: HP 6286A power supply question
If the rear jumpers are correct, the first thing to do on these Harrison Labs designed bower supplies is to verify the right output voltages from the reference section.
Also, the filter cap that supplies the reference can cause a lot of wrong readings if it is open.
Rather than use 1% resistors, they used 5% along with 'Select In Test' or a trimmer resistor.
The rest of the power supply is a high current DC amplifier.
I have one of these, somewhere that needs repaired but I haven't looked at it. It is one of a large pile that need somee work.
On Sat, Nov 27, 2021 at 4:16 PM mill_glen_chevy via <brstpr= [email protected]> wrote: Good afternoon folks.?
On the bench today is a 6286A power supply.? I bought it with a broken power switch, which I replaced.? It powers up but makes no positive voltage.? At full power I get -24vdc to ground, but nothing on the positive side.? In following the troubleshooting guide, I found that there's no resistor at R604, which is listed as a selective resistor.? Frankly, it looks like there was never anything there, but I can't imagine that's the case.??
Do you know what resistance I would start at when running a decade resistor to choose the proper value???
Am I on the right track here?? I've been trying to follow the troubleshooting guide carefully and don't want to smoke it up.
Thanks
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Re: HP 6286A power supply question
Okay, I see your point with that.? I was going in the wrong direction.? I'm not too sure where to go from here.? Experience matters, and I have very little
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Re: HP 8640B - internal counter suddenly got crazy - SOLVED
Excellent deduction!? Well done.
?
Dave Wise
?
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Show quoted text
From: [email protected] [mailto:[email protected]]
On Behalf Of Emanuele Girlando via groups.io
Sent: Saturday, November 27, 2021 2:00 PM
To: [email protected]
Subject: Re: [HP-Agilent-Keysight-equipment] HP 8640B - internal counter suddenly got crazy - SOLVED
?
For posterity:
after noting that the counter is correct in the positions with band code A4, C4 and B4 and confirming that all the wipers in the A9 assembly are correctly in situ I suspected U8 ..
It looked like it was stuck with a preset value of: LHHL = binary 0110 = decimal 6 corresponding to division 4.
Next step has been to investigate if the U8 freeze in position 4 was due to a U8 fault OR by its input preset lines (coming directly from S2 wipers....) being stuck in a frozen code.
To check this I noticed that all the S2 positions corresponding to the working band codes (A4, C4 and B4) are the ONLY positions with no connection (see TIMEBASE schematic p. 8-67) . All other band code lines are +5V pulled-up with S2 bringing
them to GND as required by the underlying logic.
So I suspected that the GND connection to S2 was somewhere faulty. A quick continuity test CONFIRMED this: none of the bandcode lines went to ground moving S2 so innocent U8 only receives preset code 6 corresponding to band codes X4. Fault
explained.
I proceeded with the removal of the A9 assembly for further investigation, and ...
bingo!
As soon as I touched the outer wiper of S2 it immediately fell down on my bench.
So it was an extreme case: the wiper was in situ, on sight it looked perfect but it was indeed detached enough not to make any contact with the underlying GND PCB trace.
Applied cyanoacrylate to all wipers, put all stuff together and the rig is now working again.
Thank you all.
Emanuele.
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Re: HP 8640B - internal counter suddenly got crazy - SOLVED
For posterity:
after noting that the counter is correct in the positions with band code A4, C4 and B4 and confirming that all the wipers in the A9 assembly are correctly in situ I suspected U8 ..
It looked like it was stuck with a preset value of: LHHL = binary 0110 = decimal 6 corresponding to division 4.
Next step has been to investigate if the U8 freeze in position 4 was due to a U8 fault OR by its input preset lines (coming directly from S2 wipers....) being stuck in a frozen code.
To check this I noticed that all the S2 positions corresponding to the working band codes (A4, C4 and B4) are the ONLY positions with no connection (see TIMEBASE schematic p. 8-67) . All other band code lines are +5V pulled-up with S2 bringing them to GND as required by the underlying logic.
So I suspected that the GND connection to S2 was somewhere faulty. A quick continuity test CONFIRMED this: none of the bandcode lines went to ground moving S2 so innocent U8 only receives preset code 6 corresponding to band codes X4. Fault explained.
I proceeded with the removal of the A9 assembly for further investigation, and ...
bingo!
As soon as I touched the outer wiper of S2 it immediately fell down on my bench.
So it was an extreme case: the wiper was in situ, on sight it looked perfect but it was indeed detached enough not to make any contact with the underlying GND PCB trace.
Applied cyanoacrylate to all wipers, put all stuff together and the rig is now working again.
Thank you all.
Emanuele.
|
HP 6286A power supply question
>I found that there's no resistor at R604, which is listed as a selective resistor.?? >Frankly, it looks like there was never anything there, but I can't imagine that's the case.??
I think you are wrong.
Resistor R604 is selected by HP at check out to provide the correct voltage out from the? reference regulator.
If there is nothing there it simply meant that the voltage was correct without the resistor.
-----------
Best regards,
Goran Finnberg
The Mastering Room AB
Goteborg
Sweden
E-mail: mastering@...
Learn from the mistakes of others, you can never live long enough to
make them all yourself.??? -?? John Luther
(\__/)
(='.'=)
(")_(") Ranglet, Aron, VovVov, Nero & Smurfen:RIP
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Re: HP 6286A power supply question
Did you look in th front of th manual (not the parts list) for any selected components? One possibility is the value of the "missing" component was listed as from "R" to infinity.
Cheers!
Bruce
Quoting "mill_glen_chevy via groups.io" <brstpr@...>:
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Show quoted text
Good afternoon folks.
On the bench today is a 6286A power supply.? I bought it with a broken power switch, which I replaced.? It powers up but makes no positive voltage.? At full power I get -24vdc to ground, but nothing on the positive side.? In following the troubleshooting guide, I found that there's no resistor at R604, which is listed as a selective resistor.? Frankly, it looks like there was never anything there, but I can't imagine that's the case.
Do you know what resistance I would start at when running a decade resistor to choose the proper value?
Am I on the right track here?? I've been trying to follow the troubleshooting guide carefully and don't want to smoke it up.
Thanks
|
HP 6286A power supply question
Good afternoon folks.?
On the bench today is a 6286A power supply.? I bought it with a broken power switch, which I replaced.? It powers up but makes no positive voltage.? At full power I get -24vdc to ground, but nothing on the positive side.? In following the troubleshooting guide, I found that there's no resistor at R604, which is listed as a selective resistor.? Frankly, it looks like there was never anything there, but I can't imagine that's the case.??
Do you know what resistance I would start at when running a decade resistor to choose the proper value???
Am I on the right track here?? I've been trying to follow the troubleshooting guide carefully and don't want to smoke it up.
Thanks
|
Re: HP H424A 7-10 GHz Detector Diode.
Forgot to add, all the washers and springy things are present in the detector housing, just missing the detector element.?
Thanks again
Ian.?
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Re: HP H424A 7-10 GHz Detector Diode.
Hi Jeff ¨C ? Didn¡¯t those just use the 1N78 style diode in a DO-37 package? 73 ¨C Mike ? Mike B. Feher, N4FS 89 Arnold Blvd. Howell NJ 07731 848-245-9115 ?
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From: [email protected] < [email protected]> On Behalf Of Ian Smith via groups.io Sent: Saturday, November 27, 2021 2:38 PM To: [email protected]Subject: [HP-Agilent-Keysight-equipment] HP H424A 7-10 GHz Detector Diode. ? Hi,?
I found an HP H424A (7-10Ghz) waveguide to detector diode in a box of bits recently. Although in good condition, it is missing the detector diode.? I can only find an HP part number for this, can anyone name the original diode and possibly a supplier or a sensible modern plug ¡®n play equivalent.? Many Thanks
Ian?
UK
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I friend of mine just uses 3 primary 9V batteries and has mounted holders on the back. He disabled charging the charging feature and removes batteries when not in use.
Norman Eric Haskell, AG5XV
3709 Oakbriar Lane
Colleyville, TX? 76034 USA
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HP H424A 7-10 GHz Detector Diode.
Hi,?
I found an HP H424A (7-10Ghz) waveguide to detector diode in a box of bits recently. Although in good condition, it is missing the detector diode.?
I can only find an HP part number for this, can anyone name the original diode and possibly a supplier or a sensible modern plug ¡®n play equivalent.?
Many Thanks
Ian?
UK
|
E8257D enable all options please
Hello experts - is there anyone out there who has the secret to enabling the options on my E8257D sig gen.
Specifically I need the AM back and FM back - used to work but the options list does not show it anymore.
How it went missing is another challenge, but to re-install it would be a good start.
Thank you.
Alan?
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I've purchased 3 x 9V "PP3"? NiMh, should be fine.
From: Robin
Szemeti
Date: Fri, 26 Nov 2021 13:15:08 PST
The "charging circuit" is a 383 ohm resistor hung off the raw
DC ... Li Ion is much less sensitive to charging than previous
technologies. I'm sure it will be fine ... I was just interested
if anyone knew af a decent Li 24V pack that woudl fit in the case
...
Hi again.
You most deffinately do not want to continuously trickle charge
a Lithium cell/pack!?? That can eventually make them unstable in a
very bad and spectacular way!
Also, if you over discharge them, they go very high resistance
and won't recharge.? Well, not without "a lot" of delicate care
and monitoring over a prolonged time, and even then the cell
capacity is reduced.
There are some 24V packs about (portable tool batteries etc.)?
But they and their chargers are mainly engineered for fast
charging and high current discharge.?? Trouble is, the Battery
Monitoring System (BMS) is rarely built into the pack, but lives
in the matching charger.? (Hence the multiple connections between
them)
(or constant power)
How much current does the 415 draw from the battery??? It may
be viable to use two Lithium cells (easy to find
charging/management modules for two or three cells) and a flyback
converter to whistle up the needed 24V.? (With some extra
decoupling/filtering.)
I've done that trick with ex laptop cell's, and the common
el-cheapo eBay modules for BMS/charging, and a step-up converter
set to 15V for an old MFJ antenna "analyser".? It works OK.? (I
used one cell for that, easy charging from any USB power source.)
Hint...? "Expired" laptop battery packs, are a good source of
good quality high capacity Lithium cell's.? It's usually just one
cell that dies, but the internal BMS then shuts off the entire
pack on safety grounds.? (And profit margin for the makers no
doubt!)
Just be "VERY" careful how you crack open the casing.? You do
not want to accidentally puncture or short cct a cell!? See
YouTube for videos of punctured/shorted Li cell's for details!
And you do need to test each cell individually to find the best
ones to use.
The duff cell rarely jumps out at you, so some work needed
regarding charging and discharging an individual cell while
monitoring it.
Charging is easy with any of the common eBay modules.? If it
won't charge, it's a "lobster" (as in to lob, or throw away.)
Discharge using a constant current load while monitoring the
terminal voltage, and make sure not to over discharge them, or
you've another lobster on your hands.? LOTS of info about Lithium
cell characteristics and doing that on the Interweb.
You can either use GPIB controlled HPAK kit (just to get
vaguely back on topic) or any of the Arduino based battery testing
open source projects.?? As always...? Google is your friend...
All the best.
Dave G8KBV.
--
Created on and sent from a Unix like PC running and using free and open source software:
|
From: Robin
Szemeti
Date: Fri, 26 Nov 2021 13:15:08 PST
The "charging circuit" is a 383 ohm resistor hung off the raw
DC ... Li Ion is much less sensitive to charging than previous
technologies. I'm sure it will be fine ... I was just interested
if anyone knew af a decent Li 24V pack that woudl fit in the case
...
Hi again.
You most deffinately do not want to continuously trickle charge
a Lithium cell/pack!?? That can eventually make them unstable in a
very bad and spectacular way!
Also, if you over discharge them, they go very high resistance
and won't recharge.? Well, not without "a lot" of delicate care
and monitoring over a prolonged time, and even then the cell
capacity is reduced.
There are some 24V packs about (portable tool batteries etc.)?
But they and their chargers are mainly engineered for fast
charging and high current discharge.?? Trouble is, the Battery
Monitoring System (BMS) is rarely built into the pack, but lives
in the matching charger.? (Hence the multiple connections between
them)
(or constant power)
How much current does the 415 draw from the battery??? It may
be viable to use two Lithium cells (easy to find
charging/management modules for two or three cells) and a flyback
converter to whistle up the needed 24V.? (With some extra
decoupling/filtering.)
I've done that trick with ex laptop cell's, and the common
el-cheapo eBay modules for BMS/charging, and a step-up converter
set to 15V for an old MFJ antenna "analyser".? It works OK.? (I
used one cell for that, easy charging from any USB power source.)
Hint...? "Expired" laptop battery packs, are a good source of
good quality high capacity Lithium cell's.? It's usually just one
cell that dies, but the internal BMS then shuts off the entire
pack on safety grounds.? (And profit margin for the makers no
doubt!)
Just be "VERY" careful how you crack open the casing.? You do
not want to accidentally puncture or short cct a cell!? See
YouTube for videos of punctured/shorted Li cell's for details!
And you do need to test each cell individually to find the best
ones to use.
The duff cell rarely jumps out at you, so some work needed
regarding charging and discharging an individual cell while
monitoring it.
Charging is easy with any of the common eBay modules.? If it
won't charge, it's a "lobster" (as in to lob, or throw away.)
Discharge using a constant current load while monitoring the
terminal voltage, and make sure not to over discharge them, or
you've another lobster on your hands.? LOTS of info about Lithium
cell characteristics and doing that on the Interweb.
You can either use GPIB controlled HPAK kit (just to get
vaguely back on topic) or any of the Arduino based battery testing
open source projects.?? As always...? Google is your friend...
All the best.
Dave G8KBV.
--
Created on and sent from a Unix like PC running and using free and open source software:
|
Re: I'm old 70+, the 70K system is old; good or bad omen?
I'll be glad to Paul, should be able to get that done tomorrow before the end of the day.
Richard
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Show quoted text
Hi Richard
?
Pictures of the 70900 module extender outside and inside would be good
Could you please make them each smaller than 1 meg as I will put them on both HP sites
Regards Paul
?
PS I was hoping the line was going to say I have a spare module extender but alas not
?
?
I actually have both the service kits made for the 70K series, there are a LOT of cables and extender cables of one kind or the other.? I think that there are roughly 30+ extension cables for the series
and a module extender that isn't very user friendly.? If I remember correctly, there's one service kit for the 70900x and one kit for the series in general.? I can take some pictures if it would be helpful.
Hi Gene
?
Regarding assembly extension cables I have yet to find anyone with one and there is $100 waiting for one hear
I am actually collecting the parts to make such an item
The starter is a plug unit that has been pulled apart but it must have the all the connections in the rear connecter for it to be universal
The other thing is not to flex the fragile ribbon cable to the rear socket and just Mary up with the connecter that is on the ribbon
?
Best of Luck Paul
?
?
I' m poorly equipped, without assembly extension cables, to test powered which would be a plus. Has anyone tried to pipe 40 kHz to the 70900A PS board unloaded?
Sent from my T-Mobile 5G Device
Get
I believe that makes sense it what I'm seeing on measurements (Q, DF, ESR)? taken with my DE-5000 meter. I measured in circuit and couldn't get any readings above 1kHz, e.d. 10 and 100 kHz. Cutting them loose produced same readings so meter as advertised was
able to read in-circuit.?
As a comparison, I measured similar Al caps and was able to get 10 and in some cases 100 kHz believable values. Did this across various OEMs incuding USA, Japanese and PRC. As expected , the PRC caps showed worst of the lot with very few producing any readings
above 1kHz.
Panasonic FR caps will be ordered to replace the lot on the 70900A. As the condition of caps in the display, IF and RF are unknown, I need to composite a full list... just to cover my lower anatomy.?Did Dr. Frankenstein ever ponder the economics of his rejuvenation
efforts, I wonder.
Sent from my T-Mobile 5G Device
Get
From my experience, new aluminum electrolytic capacitors will often measure 10-20% low on capacitance.
Older caps that from nonuse need to be reformed will measure higher due to thinner dielectric.
When the capacitors start to dry out due to electrolyte loss, the ESR will increase by 10X or more before the capacitance falls off.
?
On Thu, Nov 25, 2021 at 2:34 PM Chuck Harris <cfharris@...> wrote:
Perhaps, it is a cult, but I don't think so.? Cult-ship
usually implies a blind following of a personality.
ESR meter users are just happy that the instruments
cut a lot of time and effort out of repairs.? Failed
capacitors usually have very obvious ESR signatures: 10 to
1000x the expected ESR.
If you are looking at 1.5 ohm measured ESR vs 1.25 ohm,
expected ESR, as a sign of a failed capacitor, you are
using the ESR meter wrongly.
Capacitors have to get really bad before the circuitry
will fail, in most cases.
The dissipation factor is very useful for designing a
power supply, but a bit awkward to use for repair purposes.
Most meters that read DF need the capacitor out of circuit
to give any sort of useful reading.? ESR meters measure
at such a low voltage that the semiconductor part of the
circuit is not activated.
The other thing I notice is the ESR meters generally work
at 50KHz, but bridges that measure DF are mostly 1KHz.
50KHz measurements usually mean a lot more to me when I am
repairing switching power supplies, than does 1KHz.
-Chuck Harris
On Wed, 24 Nov 2021 18:44:14 -0500 "Dave McGuire"
<mcguire@...> wrote:
> On 11/24/21 6:40 PM, Richard Knoppow wrote:
> >? ?? It may prove more useful to use dissipation factor rather than
> > ESR even though both are a measure of the same thing. Since DF is a
> > ratio of reactance to resistance it varies with frequency and may
> > be more indicative of capacitor quality than plain ESR.
> >? ?? There is a good, short article on DF at:
> > <>?
>
>? ? You know, I keep telling people that, and people keep telling me
> I'm crazy.? All converting DF to ESR does is introduce a frequency
> dependency that gets in the way of deciding "good capacitor" or "bad
> capacitor".? There's almost a "cult of ESR" these days, it seems.
>
>? ? ? ? ? ? ? -Dave
>
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Re: I'm old 70+, the 70K system is old; good or bad omen?
Have you got the complete set of drawings yet ? As I believe they will answer all your questions If not available for the A version suggest you get a set for the B version ? From memory the biggest change between the A and the B is the CPU ? Paul ?
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Show quoted text
From: [email protected] [mailto:[email protected]] On Behalf Of Gene Silvernail
Sent: 27 November 2021 00:00
To: [email protected]
Subject: Re: [HP-Agilent-Keysight-equipment] I'm old 70+, the 70K system is old; good or bad omen?? Thanks Paul¡. ? Waiting for a ship to come in that isn¡¯t afloat is time otherwise spent, like maybe if these boards could be powered externally with a proper 40 kHz source¡ my reservation is what is the expected loading and if unloaded would the design misbehave destructively.? ? ³¢²¹³Ù±ð°ù¡ ? Hi Gene ? Regarding assembly extension cables I have yet to find anyone with one and there is $100 waiting for one hear I am actually collecting the parts to make such an item The starter is a plug unit that has been pulled apart but it must have the all the connections in the rear connecter for it to be universal The other thing is not to flex the fragile ribbon cable to the rear socket and just Mary up with the connecter that is on the ribbon ? Best of Luck Paul ? ? I' m poorly equipped, without assembly extension cables, to test powered which would be a plus. Has anyone tried to pipe 40 kHz to the 70900A PS board unloaded? Sent from my T-Mobile 5G Device
Get
I believe that makes sense it what I'm seeing on measurements (Q, DF, ESR)? taken with my DE-5000 meter. I measured in circuit and couldn't get any readings above 1kHz, e.d. 10 and 100 kHz. Cutting them loose produced same readings so meter as advertised was able to read in-circuit.? As a comparison, I measured similar Al caps and was able to get 10 and in some cases 100 kHz believable values. Did this across various OEMs incuding USA, Japanese and PRC. As expected , the PRC caps showed worst of the lot with very few producing any readings above 1kHz. Panasonic FR caps will be ordered to replace the lot on the 70900A. As the condition of caps in the display, IF and RF are unknown, I need to composite a full list... just to cover my lower anatomy.?Did Dr. Frankenstein ever ponder the economics of his rejuvenation efforts, I wonder. Sent from my T-Mobile 5G Device
Get
From my experience, new aluminum electrolytic capacitors will often measure 10-20% low on capacitance. Older caps that from nonuse need to be reformed will measure higher due to thinner dielectric. When the capacitors start to dry out due to electrolyte loss, the ESR will increase by 10X or more before the capacitance falls off. ? On Thu, Nov 25, 2021 at 2:34 PM Chuck Harris <cfharris@...> wrote: Perhaps, it is a cult, but I don't think so.? Cult-ship
usually implies a blind following of a personality.
ESR meter users are just happy that the instruments
cut a lot of time and effort out of repairs.? Failed
capacitors usually have very obvious ESR signatures: 10 to
1000x the expected ESR.
If you are looking at 1.5 ohm measured ESR vs 1.25 ohm,
expected ESR, as a sign of a failed capacitor, you are
using the ESR meter wrongly.
Capacitors have to get really bad before the circuitry
will fail, in most cases.
The dissipation factor is very useful for designing a
power supply, but a bit awkward to use for repair purposes.
Most meters that read DF need the capacitor out of circuit
to give any sort of useful reading.? ESR meters measure
at such a low voltage that the semiconductor part of the
circuit is not activated.
The other thing I notice is the ESR meters generally work
at 50KHz, but bridges that measure DF are mostly 1KHz.
50KHz measurements usually mean a lot more to me when I am
repairing switching power supplies, than does 1KHz.
-Chuck Harris
On Wed, 24 Nov 2021 18:44:14 -0500 "Dave McGuire"
<mcguire@...> wrote:
> On 11/24/21 6:40 PM, Richard Knoppow wrote:
> >? ?? It may prove more useful to use dissipation factor rather than
> > ESR even though both are a measure of the same thing. Since DF is a
> > ratio of reactance to resistance it varies with frequency and may
> > be more indicative of capacitor quality than plain ESR.
> >? ?? There is a good, short article on DF at:
> > <>?
>
>? ? You know, I keep telling people that, and people keep telling me
> I'm crazy.? All converting DF to ESR does is introduce a frequency
> dependency that gets in the way of deciding "good capacitor" or "bad
> capacitor".? There's almost a "cult of ESR" these days, it seems.
>
>? ? ? ? ? ? ? -Dave
>
|
Hi Robin:
If you can provide a small adjustable forward bias to the Schottky diode you can greatly improve it's performance.
PS A lead acid battery inside any electronic equipment where there's any heat can lead to acid etching of PCB traces. Guess how I know this.
--
Have Fun,
Brooke Clarke
axioms:
1. The extent to which you can fix or improve something will be limited by how well you understand how it works.
2. Everybody, with no exceptions, holds false beliefs.
|
Michael A. Terrell
Emanuele Girlando
Eric Haskell [KC4YOE]
Paul Bicknell