Re: HP 140A and 141A oscilloscope power supply issues
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Re: HP 140A and 141A oscilloscope power supply issues
Thanks for the docs, Christopher. The LV supplies in both my 141A and the 140A have problems.? My 141A LV supply mostly works but has a strange instability in the -12.6V section.? In my 140A, the -100V section is faulty, which creates issues for other sections of the supply. The LV circuit boards in my two units are similar to one another, and appear to be closer to the schematic you supplied in the 140B manual than anything I have on-hand.? In my 141A, the HV board looks fairly close to the schematic you supplied with the 140T manual.? Not exact, but close.? Again, what you sent is closer than anything I have. For reference, the individual boards in my systems are:
In my 140A:
?
????????????? LV board PN is 00140-66510 RevA
????????????? HV board PN is 00140-66505 OR
?
In my 141A:
?
????????????? LV board PN is 00140-66508 RevA
????????????? HV board PN is 00141-66512 RevA
Best Regards,
Neil
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Re: HP 140A and 141A oscilloscope power supply issues
My notes on this:
141T_Manual_Change.pdf and HP 141T_changes.pdf from BAMA.
Same file just renamed.
Printed 8 January 1981.
For 00141-90914 printed June 1976.
Updating for 1850A, 2020A, and 2101A.
2101A is new power supply using 9V zener instead of ZZ1000 gas regulator.
Note: Change 3, the 2101A update, contains errors.
1. On page 6, the Table 6-2 entry for A2R25 is a Change, not an Add.
2. On page 6, the Table 6-2 entry for VR7 should be A2VR7.
Dave Wise
It’s a lot of work to implement this change on the old board; consider instead photo album “141 T Reference Replacement”, photo “Proposed Replacement Using TL431”. Proposed by Ed Breya.
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From: [email protected] < [email protected]> On Behalf Of Gary Appel via groups.io
Sent: Wednesday, February 02, 2022 10:13 AM
To: ' [email protected]' < [email protected]>
Subject: Re: [HP-Agilent-Keysight-equipment] HP 140A and 141A oscilloscope power supply issues
I have a 141 without the infamous "neon bulb" voltage regulator. I don't believe I have never seen a schematic for this supply. I too would like to find a schematic for this power supply.
Gary Appel
-----------------------------------------
From: "Neil Barlow"
To: mailto: [email protected]
Cc:
Sent: Wednesday February 2 2022 6:51:13AM
Subject: [HP-Agilent-Keysight-equipment] HP 140A and 141A oscilloscope power supply issues
Hi folks,
I'm in the process of attempting to repair two older oscilloscopes - one is an HP 140A and the other is an HP 141A (its storage tube "brother" version). My 140A frame has serial prefix 546 and my 141A frame's serial prefix is 844. Both are experiencing power supply problems and it would appear that HP went through MANY power supply design changes (both in the HV and LV sections) with this product line over the course of time. One result is that the service manuals that I've been able to find do not correspond well at all with my scopes in the power supply areas. I think the manuals are at least close enough in most other areas.
Is there someone kind soul here who might be able to help?
Thanks,
Neil
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Re: HP 140A and 141A oscilloscope power supply issues
I have a 141 without the infamous "neon bulb" voltage regulator. I don't believe I have never seen a schematic for this supply. I too would like to find a schematic for this power supply.
Gary Appel ----------------------------------------- From: "Neil Barlow" To: [email protected]Cc: Sent: Wednesday February 2 2022 6:51:13AM Subject: [HP-Agilent-Keysight-equipment] HP 140A and 141A oscilloscope power supply issues
Hi folks,
I'm in the process of attempting to repair two older oscilloscopes
- one is an HP 140A and the other is an HP 141A (its storage tube
"brother" version). My 140A frame has serial prefix 546 and my 141A
frame's serial prefix is 844. Both are experiencing power supply
problems and it would appear that HP went through MANY power supply
design changes (both in the HV and LV sections) with this product
line over the course of time. One result is that the service
manuals that I've been able to find do not correspond well at all
with my scopes in the power supply areas. I think the manuals are
at least close enough in most other areas.
Is there someone kind soul here who might be able to help?
Thanks,
Neil
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Re: HP 5090B Droitwich receiver documentation wanted
Dear Donald,
The contract for teleswitching that helps keep Droitwich going is said to be extended to 2023.
BBC management would probably quite like to close Droitwich to save money, as the licence fee is frozen by the UK government.
Thus, this is a project that should be completed sooner rather than later.
I have an ex-broadcast (198kHz) Droitwich-locked standard and it seems that Droitwich is GPS-locked these days, though I have no confirmation of this beyond my own measurements.
Do let us know, if you manage to get the schematics for the 5090B.
Regards,
Alwyn
_____________________________________________________
Alwyn Seeds, Director
SynOptika Ltd.,
114 Beaufort Street,
London,
SW3 6BU,
England.
SynOptika Ltd., Registered in England and Wales: No. 04606737
Registered Office: 114 Beaufort Street, London, SW3 6BU, United Kingdom. _____________________________________________________
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Re: HP 140A and 141A oscilloscope power supply issues
I believe the power supplies are referenced from the -100v so fix that first.
On Wed, Feb 2, 2022 at 11:51 AM Neil Barlow < nbarlow@...> wrote: Hi folks,
I'm in the process of attempting to repair two older oscilloscopes - one is an HP 140A and the other is an HP 141A (its storage tube "brother" version). My 140A frame has serial prefix 546 and my 141A frame's serial prefix is 844. Both are experiencing power supply problems and it would appear that HP went through MANY power supply design changes (both in the HV and LV sections) with this product line over the course of time. One result is that the service manuals that I've been able to find do not correspond well at all with my scopes in the power supply areas. I think the manuals are at least close enough in most other areas.
Is there someone kind soul here who might be able to help?
Thanks,
Neil
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Re: HP 140A and 141A oscilloscope power supply issues
As far as I know, the power supplies are identical for the 140S, 141S, 140T, and 141T - having repaired several. Between these and the 141A, the LV consist mainly of the transformer, four power transistors mounted on the aluminum 'L' brackets at the fan, and an amplifier board just at the back wall of the fan enclosure for all. There are differences in the HV section.
In almost all cases the LV supplies have been good except for the occasional transformer hum and all but one with fans needing replacement. It would be best to walk-through the power supply adjustment procedure (only measuring first), then as you become familiar with the ratio of voltages across the system - +100V, -100V, +250V, 6.3vac, -12.6V, -2350kV -? bring them into alignment according to the manual. I have sent along manuals for 140B, 141A, and 140T in an email outside of the group to help with reducing storage that should be able to help guide you.
Christopher
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Re: HP8753C Source Pretune after YIG replacement
It is hard to guess a person's?level of expertise but since you can measure?the 3.8GHz I think you know what you are doing. How and where are you measuring?the YIG output? Have you checked ALL the self tests.?The higher level ones have to be specifically called up and are not included in the normal boot up self test. Is the analog bus working? Does the tune voltage look normal? These are a few things that can make a YIG appear dead. I will send you some repair logs privately that might help.
On Tue, Feb 1, 2022 at 05:40 PM, peter bunge wrote:
Are you sure the YIG is dead? How do you know? I suggest you don't adjust anything until you know what the problem is.
My method of troubleshooting is to go through the adjustments procedure but WITHOUT ADJUSTING ANYTHING. Anything way off indicates the?problem area. Often a failure in a closed loop.
?
The voltages are OK but there is NO outut from the YIG. I see the 3.8 GHz signal (+10dbm) from the cavity oscillator but absolutely nothing from the YTO.? If it's no the YTO what else could it be?
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HP 140A and 141A oscilloscope power supply issues
Hi folks,
I'm in the process of attempting to repair two older oscilloscopes - one is an HP 140A and the other is an HP 141A (its storage tube "brother" version). My 140A frame has serial prefix 546 and my 141A frame's serial prefix is 844. Both are experiencing power supply problems and it would appear that HP went through MANY power supply design changes (both in the HV and LV sections) with this product line over the course of time. One result is that the service manuals that I've been able to find do not correspond well at all with my scopes in the power supply areas. I think the manuals are at least close enough in most other areas.
Is there someone kind soul here who might be able to help?
Thanks,
Neil
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Re: Defective YTO 5086-7906 HP-8561E
Thanks for your replies, I will look for a repair service.
Does anyone have a schematic for the small control board on top of the YTO assy ?
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Re: HP8753C Source Pretune after YIG replacement
On Wed, Feb 2, 2022 at 07:40 AM, Peter Hansen wrote:
yig is dead. The Yig in the 8753 part of the dreaded HP yigs that tend to fail. Find a new 5086-7934. Repair is only possible with a part that is not easy to source and you need a wirebonder
best regards Peter
Yes, my conclusion also (unfortuantely). I did find a replacement YIG (not cheap) but I still have the original question regarding the pretune constants setup when I replace it.
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Re: Convert monochrome 5454x scope to color
Depending on the display, you may be able to find a commercial
LED replacement.
Harvey
On 2/2/2022 10:34 AM, Glen Hoag wrote:
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That makes sense. I would assume that at least early LCD panels
used a CCFL lamp as a backlight. It may be possible to retrofit
LEDs on such a unit.?
?The display controller logic is completely
different, no pads for replacing the CRT stuff with the
components for the LCD. You could probably do a daughter board
to add the logic, but you're going to end up spending more
than you could get a C for. While we're on the subject, I've
been trying to figure out a replacement for the panel. The
model number of the panel shows up for sale by various
vendors, but the specs seem to differ between the vendors for
the same number. Not sure if that's just poor description, or
if there are variants with the same model number. Just want to
have a source for a replacement if my panel dies.
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HP 140A and 141A power supplies
Hi folks,
I'm in the process of attempting to repair two older oscilloscopes - one is an HP 140A and the other is an HP 141A (its storage tube "brother" version). My 140A frame has serial prefix 546 and my 141A frame's serial prefix is 844. Both are experiencing power supply problems and it would appear that HP went through MANY power supply design changes (both in the HV and LV sections) with this product line over the course of time. One result is that the service manuals that I've been able to find do not correspond well at all with my scopes in the power supply areas. I think the manuals are at least close enough in most other areas.
Is there someone kind soul here who might be able to help?
Thanks,
Neil
|
Re: HP8753C Source Pretune after YIG replacement
yig is dead. The Yig in the 8753 part of the dreaded HP yigs that tend to fail. Find a new 5086-7934. Repair is only possible with a part that is not easy to source and you need a wirebonder
best regards Peter
On Tue, Feb 1, 2022 at 05:40 PM, peter bunge wrote:
Are you sure the YIG is dead? How do you know? I suggest you don't adjust anything until you know what the problem is.
My method of troubleshooting is to go through the adjustments procedure but WITHOUT ADJUSTING ANYTHING. Anything way off indicates the?problem area. Often a failure in a closed loop.
?
The voltages are OK but there is NO outut from the YIG. I see the 3.8 GHz signal (+10dbm) from the cavity oscillator but absolutely nothing from the YTO.? If it's no the YTO what else could it be?
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Re: Convert monochrome 5454x scope to color
That makes sense. I would assume that at least early LCD panels used a CCFL lamp as a backlight. It may be possible to retrofit LEDs on such a unit.?
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On Feb 2, 2022, at 09:14, Bill E <solartron@...> wrote:
?The display controller logic is completely different, no pads for replacing the CRT stuff with the components for the LCD. You could probably do a daughter board to add the logic, but you're going to end up spending more than you could get a C for. While we're on the subject, I've been trying to figure out a replacement for the panel. The model number of the panel shows up for sale by various vendors, but the specs seem to differ between the vendors for the same number. Not sure if that's just poor description, or if there are variants with the same model number. Just want to have a source for a replacement if my panel dies.
_._,_._,_
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Re: Convert monochrome 5454x scope to color
The display controller logic is completely different, no pads for replacing the CRT stuff with the components for the LCD. You could probably do a daughter board to add the logic, but you're going to end up spending more than you could get a C for. While we're on the subject, I've been trying to figure out a replacement for the panel. The model number of the panel shows up for sale by various vendors, but the specs seem to differ between the vendors for the same number. Not sure if that's just poor description, or if there are variants with the same model number. Just want to have a source for a replacement if my panel dies.
|
Re: HP8753C Source Pretune after YIG replacement
On Tue, Feb 1, 2022 at 05:40 PM, peter bunge wrote:
Are you sure the YIG is dead? How do you know? I suggest you don't adjust anything until you know what the problem is.
My method of troubleshooting is to go through the adjustments procedure but WITHOUT ADJUSTING ANYTHING. Anything way off indicates the?problem area. Often a failure in a closed loop.
?
The voltages are OK but there is NO outut from the YIG. I see the 3.8 GHz signal (+10dbm) from the cavity oscillator but absolutely nothing from the YTO.? If it's no the YTO what else could it be?
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Re: Convert monochrome 5454x scope to color
Hello Glen,
??? Thanks for your suggestions. I google around since a while to try fixing this scope, and checked every element known to interfere with initialization. I replaced the battery by two AA alkaline as you did, and check carefully all the voltages and currents of the supply, which was in any case faulty. I even replaced it by another working one, but no issue.?
??? I am now convinced that it's a matter of an actuator some where, which is checked at boot, and does not return the right value, since the program is looping around a sequence which tests the input relays. The screen is not black, but scrambled, except if I press the blue key at start, then entering the sequence to activate the floppy for PROM update.
??? To fix this scope might be possible with the firmware source program (68020), but reverse engeneering of such a 8k piece of firm is out of my skill, even with a sophisticated logic analyzer (which I don't possess anayway). That's the reason for which I was asking Bill E if he was selling a motherboard.
???? Jean-claude
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Re: Convert monochrome 5454x scope to color
Jean-claude, Did you check the voltage on the Lithium battery at the rear of the main board?
A common problem with these oscilloscopes is that they will boot to a black screen when the battery is dead.?
I recently purchased a 54540A “for parts” and it’s main problem was the battery. I replaced it for testing with a pair of AA alkaline batteries and ordered a Lithium battery to replace it.?
It also had a number of leaky electrolytic capacitors in the power supply unit. I replaced all of the aluminum electrolytics for fresh units. It has helped; I don’t have screen distortion before warmup anymore.?
—Glen Hoag
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On Feb 2, 2022, at 06:50, JCB_SFR <jean-claude.bernengo@...> wrote:
?Hello Bill E, ?? I have a 54522 which has booting problems. It does not get out from initialisation, and i struggled a lot to to try fixing it, but without success. It's a CRT version, and the motherboards are the same for 522 or 542. Therefore one of your 542 would have been of great help, if shipping costs to France (and extra custom fees either) would not have been so expensive. May be a motherboard alone might be a solution to my problem, if you agreed to sell your scopes by parts. ??????? Jean-claude
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Re: Convert monochrome 5454x scope to color
I haven’t looked at the two boards side-by-side, but I don’t believe the differences are “significant”. They use the same ribbon cable to interface both the CRT in the A models as the LCD panel in the C models.?
I have an A model on which I just recapped the power supply. A significant number of the aluminum electrolytics were leaking.?
If I luck out and get hold of a C model, I’ll compare the boards.?
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On Feb 2, 2022, at 05:35, Bill E <solartron@...> wrote:
? I looked into this a while back. There are significant differences between the CRT and LCD versions, including different main pcbs. It seems the only practical path would be a hack that would convert the CRT scan signals to LCD usable, but you wouldn't have the color info.
I solved the problem by getting lucky, found a color 54542 on EPray for $199. "Not working". Apparently it wasn't working because the seller never plugged it in or some such, worked perfectly, all in spec. Now I need something to do with my 2 CRT 542s.
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Christopher Tucker
vk2bea
JCB_SFR