HP8920B power supply removal
The power supply in my 8920 has failed and I want to try to repair it but I cannot figure out how to remove from the instrument. I have successfully removed all the screws which bind it to the chassis. It is now possible to jiggle it around about 0.25 inches in all directions, but it remains firmly trapped by surrounding modules and frame pieces. It's not clear how to proceed, I could try dissembling the instrument bit by bit until the power supply assembly is free but I would prefer to be told the proper sequence of disassembly to avoid unnecessary work (and risk of damage).
Any help is appreciated,
Brian
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Re: 8642B displays A6A1 transient failure F3 when audio peaks at FM mod input
I was part of the design team on the 8642 but I¡¯m not sure I remember the FM modulation details well enough. Is the error truly transient? Is the deviation correct after the error message? ?
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From: [email protected] [mailto:[email protected]] On Behalf Of wilson2115@...
Sent: Sunday, November 04, 2018 11:29 AM
To: [email protected]
Subject: Re: [HP-Agilent-Keysight-equipment] 8642B displays A6A1 transient failure F3 when audio peaks at FM mod input ? 700 MHz -140dB Mod out 1.00VL at 10Hz in FM mod in AC coupled?
I am playing around with FM deviation, with test setup above 33khz is the threshold which it is about to throw an alarm, I can reduce the FM deviation to 1 kHz and below no problem, seems any fm deviation above 33 kHz deviation causes an alarm even to 1.5 MHz. Interesting
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Re: 8642B displays A6A1 transient failure F3 when audio peaks at FM mod input
700 MHz -140dB Mod out 1.00VL at 10Hz in FM mod in AC coupled?
I am playing around with FM deviation, with test setup above 33khz is the threshold which it is about to throw an alarm, I can reduce the FM deviation to 1 kHz and below no problem, seems any fm deviation above 33 kHz deviation causes an alarm even to 1.5 MHz. Interesting
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Re: 8642B displays A6A1 transient failure F3 when audio peaks at FM mod input
I am running my test with this setup
100Mhz -140dB RF output not used
mod output connected to fm mod input AC coupled?
mod output 1.00VL at 60 hz
FM deviation 70 kHz
if I drop FM deviation to 50kHz screen flashes transient failure A6A1, if I increase mod frequency to 65 hz it¡¯s right on the threshold of detecting alarm 70 hz is fine, I switch operating frequency to 700 MHz it is running fine, drop mod frequency back to 65 Hz still ok, 60 hz fine, drop to 20 hz fine, 13 hv is threshold, 10 he triggers transient failure. Interesting?
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Don,
Good idea. Thanks for the suggestion.
I removed the covers. There wasn't any corrosion but I noticed these were tabs holding the module i place. I removed the tabs and the module slid right out. While inspecting he module I noticed a sticker affixed to the front "SECURED WITH SIDE TABS. REFER TO MANUAL"
Back to my original problem. The sweep and attenuator controls seem to work but I don't see a signal on the display. The skirt of my REFERENCE LEVEL setting used to adjust the INPUT ATTEN broke off the knob and someone suggested checking the contacts on the REFERENCE LEVEL and FREQ SPAN switches. They look fine.
I'd like to try another module, a 8559A or 8558B. I'm located in central NJ. Would anyone in the vicinity have one? Anyone in the market for a 853A chassis?
Mike N2MS
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On November 3, 2018 at 4:08 PM "Don Bitters via Groups.Io" <donbitters@...> wrote:
What kind of conditions has the system been stored in? Any dampness? If so then the rail guides may have some aluminum alloy corrosion making the fit even tighter.
The probable solution is to remove the 853A case cover.
Don Bitters
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Re: 8560E New to Me: Some Issues & Questions
On Sun, Nov 4, 2018 at 09:31 AM, tmillermdems wrote:
where are you located?
Boston metro area
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Re: 8642B displays A6A1 transient failure F3 when audio peaks at FM mod input
The transient failure occurs when the phase deviation between the reference signal and the divided VCO signal exceeds the range of the loop phase detector. ?If you have the schematic you can look for the circuit which generates the out of lock indication. ?This might be a window comparator on the phase detector output or the loop integrator input. ?Since I don't have a schematic I am making assumptions here. ?Anyway, the modulating signal that is shown being applied to the input of the integrator is there to cancel the phase signal being generated by the phase detector. ?The FM signal applied directly to the VCO should ideally generate the modulation so the PLL doesn't have to do any correction via the PLL tune port on the VCO. ?If the signal wasn't applied at the integrator, the loop would see the modulation as an error and try to remove it. ?This would create a high-pass response to the modulation applied to the VCO with the corner frequency determined by the PLL bandwidth. ?Anyway, if the phase deviation at the phase detector exceeds the detector's range, the loop will lose lock on the phase deviation peaks. ?At low modulating frequencies the divided VCO frequency will differ from the reference frequency for longer periods causing more phase difference to build between them. ?
Here is something to try to see if this is what is going on. ?Go to 100MHz at 50kHz deviation and reduce the modulating frequency until the transient error just begins to occur. ?Then cut the deviation to 25kHz. ?The error should go away until you reach about half the mod frequency where the error started at 50kHz deviation. ?There is one thing that could upset this experiment. The 8642 can generate 100MHz by dividing or mixing down to the output frequency. ?If the firmware decides to change the method based on the deviation setting the actual FM loop deviation will change. ?You could avoid this by going to a main band output frequency like 700 MHz.
The VCO center frequency drift could cause problems if the loop integrator output is operating too close to its rails to compensate and if the loop is trying to correct for gain errors between the inside and outside loop BW modulation paths.
Jim
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On Nov 4, 2018, at 8:46 AM, wilson2115@... wrote: Thanks for the very informative reply, I did some additional testing and included some schematics of the A6A1 A6A2 module If I calibrate my sine wave generator (iPad) for an amplitude that is shown neither high or low on the 8642, in FM AC coupled at 50 kHz deviation at 100 MHz there is no issues at higher frequencies >= 100Hz, but when I start feeding lower and lower frequencies the issue seems to occur around <= 60 Hz when I get a transient failure. I have increased the deviation from 50 kHz to 500 kHz but there is no change in the symptoms. I tried setting the generator to 1 GHz and 700 Mhz but symptoms still appear the same. I am not to terribly concerned about this symptom but curious if its just a operational characteristic of this generator or perhaps the FM VCO has shifted off. But I find it strange if the FM VCO might be off shouldn't I get a transient failure at any other frequency I feed into the FM mod input at the same amplitude that causes the transient failure at 60 Hz or below? Thanks <A6A2.jpg><A6A1.jpg>
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8902A Relay A26K1 replacement part
Hi All,
I was overly optimistic when I thought it was a dry joint - Looks like the relay is sticking so I'm going to take it out and try cleaning it.
However, in case I bugger it up, I'm wondering if anyone knows what the replacement part is? According to the service manual it is a HP part 0490-0618 (Relay 2C 24VDC-Coil 5A 115VAC) - I've taken a look around and I can find a number of parts that could be replacements but I can't find one that has the same pin out.
Any suggestions?
Thanks,
TonyG
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Re: 8560E New to Me: Some Issues & Questions
?
Rick, where are you located? Maybe there is someone close to
you that can lend some help.
?
I have not had anything but good results with the Newscope
products, I have done at least six conversions that include the 85662/8566 SA,
8756A SNA, and the HP 70004A MMS displays.
?
The other great benefit is the shedding of many pounds of boat
anchor weight.
?
Regards?
----- Original Message -----
Sent: Sunday, November 04, 2018 12:01
PM
Subject: Re:
[HP-Agilent-Keysight-equipment] 8560E New to Me: Some Issues &
Questions
Go
for it !
Well ¡ I spent some time this AM
reading through the Newscope 6 (8560E kit) manual and found good news and bad
news there. The good news is that the end result is quite nice. The bad news
is that the install, with my limited recent experience in such matters, seems
in the same league as a heart transplant! It¡¯s the kind of thing where you¡¯d
much prefer the person doing the conversion had done it at least a few times
previously. So far, I have never seen an 8560E with the case off. Just getting
the anatomy understood will be a challenge. I¡¯d much rather commission an 8560
expert who has done this before to install this mod, preemptively replace
components which commonly fail, and do a calibration, etc. Short of this, I
may wait for a serious failure that leaves no choice but to open it up and
jump in. In the meantime, I will keep looking at the photos of the end result
for motivation.
OTTH, I recently tore into a Tek 495P SA (also had
never previously had the case off) which had problems and found and fixed the
problem without much difficulty. This was relatively easy however: sourcing a
replacement memory board on eBay, recapping, and programming the firmware
EPROMs. Maybe I can do this!
Thanks Shaun, for the link. This may tip
me over to go ahead.
RB
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Re: 8560E New to Me: Some Issues & Questions
Go for it !
Well ¡ I spent some time this AM reading through the Newscope 6 (8560E kit) manual and found good news and bad news there. The good news is that the end result is quite nice. The bad news is that the install, with my limited recent experience in such matters, seems in the same league as a heart transplant! It¡¯s the kind of thing where you¡¯d much prefer the person doing the conversion had done it at least a few times previously. So far, I have never seen an 8560E with the case off. Just getting the anatomy understood will be a challenge. I¡¯d much rather commission an 8560 expert who has done this before to install this mod, preemptively replace components which commonly fail, and do a calibration, etc. Short of this, I may wait for a serious failure that leaves no choice but to open it up and jump in. In the meantime, I will keep looking at the photos of the end result for motivation.
OTTH, I recently tore into a Tek 495P SA (also had never previously had the case off) which had problems and found and fixed the problem without much difficulty. This was relatively easy however: sourcing a replacement memory board on eBay, recapping, and programming the firmware EPROMs. Maybe I can do this!
Thanks Shaun, for the link. This may tip me over to go ahead.
RB
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Re: 8642B displays A6A1 transient failure F3 when audio peaks at FM mod input
Thanks for the very informative reply, I did some additional testing and included some schematics of the A6A1 A6A2 module If I calibrate my sine wave generator (iPad) for an amplitude that is shown neither high or low on the 8642, in FM AC coupled at 50 kHz deviation at 100 MHz there is no issues at higher frequencies >= 100Hz, but when I start feeding lower and lower frequencies the issue seems to occur around <= 60 Hz when I get a transient failure. I have increased the deviation from 50 kHz to 500 kHz but there is no change in the symptoms. I tried setting the generator to 1 GHz and 700 Mhz but symptoms still appear the same. I am not to terribly concerned about this symptom but curious if its just a operational characteristic of this generator or perhaps the FM VCO has shifted off. But I find it strange if the FM VCO might be off shouldn't I get a transient failure at any other frequency I feed into the FM mod input at the same amplitude that causes the transient failure at 60 Hz or below? Thanks  
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Re: 8642B displays A6A1 transient failure F3 when audio peaks at FM mod input
I think what you are seeing is that in AC mode, the FM PLL is being asked to generate too large of a phase deviation which knocks the loop out of lock causing the transient error. ?Switching to DC opens the PLL and just FMs the VCO. ?Since the peak phase deviation is equal to the peak frequency deviation divided by the modulating frequency, reducing the peak frequency deviation or increasing the modulating frequency should eliminate the transient error. If the specifications indicate you should be able to achieve the deviation you are setting at 20Hz in AC mode then perhaps the FM VCO center frequency has shifted.
Jim
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On Nov 3, 2018, at 8:12 PM, wilson2115@... wrote: I found that when I I feed a higher amplitude 20 hz sine wave into the FM mod input with the coupling mode set to AC, I get a warning message stating that A6A1 has a transient failure F3. I turn down the audio level and the message goes away after I clear it. At lower amplitudes this doesn't seem to be a problem but as I increase the amplitude again, that message appears every time. At first I thought I had a module failing but I found when I switched to DC coupling mode this problem goes away, instead of flashing A6A1 transient failure I get just a HI indicator at 20 HZ. Higher frequencies in AC coupled mode doesn't seem to reproduce this problem. Perhaps if anyone could reproduce this on a 8642B that happens to be sitting by.
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Re: 8560E New to Me: Some Issues & Questions
For additional motivation to go the Newscope route, consider that there is an RGB output option which allows you to send the screen output of the instrument to a VGA monitor. ?So now you can watch a large LCD screen while making measurements or working on a piece of gear. Put said LCD on a flexible mount and you can see it from anywhere you are working. ?I did this with a 3562A whose display was limping along and I am very happy with the results.
?
There is a YouTube video from Terry at D-lab in which he documents the CRT replacement process with a Newscope kit in a 3562A:?
Shaun M
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Re: 8560E New to Me: Some Issues & Questions
Go for it ! The old crt displays in these Analyzers are fading out fast. ? Bill Lauchlan ?
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From: [email protected] [mailto:[email protected]] On Behalf Of Rick Boswell
Sent: Sunday, November 04, 2018 8:14 AM
To: [email protected]
Subject: Re: [HP-Agilent-Keysight-equipment] 8560E New to Me: Some Issues & Questions? My recommendation is to get a replacement LCD display from Simcomm labs
Have been looking at this. Just need the courage! ?
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Re: 8560E New to Me: Some Issues & Questions
My recommendation is to get a replacement LCD display from Simcomm labs
Have been looking at this. Just need the courage! ?
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Re: 8560E New to Me: Some Issues & Questions
The biggest problem with this series of scope is cathode poisoning on the CRT. First symptom is the text gets soft
My recommendation is to get a replacement LCD display from Simcomm labs aka newscope kits are about $650 and take about 4H to install you also reduce weight by about 10 pounds. I They also sell through the well known auction site.
Since so many adjustments are dependent on X CRT divisions either in the X or Y dimensions a solid display system is a must. Also the LCD display adds value to the instrument as it makes it equivalent to a EC series of the same scope with the same multicolor display.
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Sierra 303B service manual
By any chance, does anyone have one lying about?
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8642B displays A6A1 transient failure F3 when audio peaks at FM mod input
I found that when I I feed a higher amplitude 20 hz sine wave into the FM mod input with the coupling mode set to AC, I get a warning message stating that A6A1 has a transient failure F3. I turn down the audio level and the message goes away after I clear it. At lower amplitudes this doesn't seem to be a problem but as I increase the amplitude again, that message appears every time. At first I thought I had a module failing but I found when I switched to DC coupling mode this problem goes away, instead of flashing A6A1 transient failure I get just a HI indicator at 20 HZ. Higher frequencies in AC coupled mode doesn't seem to reproduce this problem. Perhaps if anyone could reproduce this on a 8642B that happens to be sitting by.
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Re: 8902A Power Supply issue
Thanks for the help everyone ¨C I ended up tracing it to what appeared to be a dry solder joint on A26K1. It was running the fan but not providing the +15V switched to the rest of the power supply.
?
TonyG
?
Sent from for Windows 10
?
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Exactly what Peter said! Running out of headroom at low line, high load and high regulator¡¯s reference is a bit shameful, so in good designs one makes sure that with everything against them, they¡¯ll still work. Linear regulators waste
lots of power, and that¡¯s that. Personally, seeing something like LM7805 running from 8V unregulated at load is not something I¡¯d expect in a good design: it¡¯ll run out of headroom at 7.2V input, so the minimum unregulated instantaneous (not RMS!) voltage
must be above it in all conditions, with bulk capacitors aged for design lifetime of the power supply. That won¡¯t happen with only 8V RMS input, and even 9V will be too low. Sure, it ¡°will work¡± on the bench, in perfect conditions, but those don¡¯t always occur
in practice.
I don¡¯t know what regulators are in use in the subject instrument ¨C that¡¯s just an example.
Cheers, Kuba
> 3 nov. 2018 kl. 17:44 skrev Peter Gottlieb <hpnpilot@...>:
>
> Remember that the supply must have sufficient voltage pre-regulator at the lowest line voltage and the highest load the supply was designed for. Also it must be the lowest voltage of the ripple.
>
>
> Peter
>
>>> On Nov 3, 2018, at 5:41 PM, Harvey White <madyn@...> wrote:
>>>
>>> On Sat, 3 Nov 2018 15:41:06 -0400, you wrote:
>>>
>>> Those seem ok as the unregulated supplies.
>>
>> I'd think -20 volts and +8 volts might have been a better design. Just
>> being conservative without thinking of what they really did. Could
>> those voltages be a result of light loads on the bulk supplies?
>>
>> Harvey
>>
>>>
>>>
>>> Peter
>>>
>>>> On Nov 3, 2018, at 3:36 PM, Tony Goodhew <tony_goodhew@...> wrote:
>>>>
>>>> Hey All,
>>>>
>>>> My 8902A stopped powering up and I've just started looking at the power supply.
>>>>
>>>> I worked through the manual troubleshooting steps and it seems to leave the finger pointing at the regulators (basically no rail other than the +15 came up when I tried the steps and it doesn't appear to indicate a short in any other area).
>>>>
>>>> Looking at the unregulated -15V and +5V I'm seeing -23.5V and +10V. I understand they're not regulated but that seems a bit far away from the values on the schematic.
>>>>
>>>> Is this expected or should they be closer to -15V & +5V?
>>>>
>>>> Thanks,
>>>>
>>>> TonyG
>>>>
>>>
>>>
>>
>>
>>
>>
>
>
>
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Re: 8116A schematics for late model boards
We have a later scan of the 8116A available with an even later A3 board 08116-66535
The change section is up to change level 74
Not free, but not embarassingly expensive
Manual number 08116-90014
Dave
www.ArtekManuals.com
manuals@...
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On 11/3/2018 7:14 PM, tgerbic wrote: Folks,
A number of years have past with people looking for schematics for the later model 8116A.? All the manuals I have seen so far have the earlier schematics and depend on updating lots of places in the manuals.? I would assume HP sold a lot of the later model units and so would have shipped manuals that were more current, showing the newer schematics and the component layouts.?? Does anyone have a later manual that could scan the schematics and board layouts? What I am looking for is a manual that is at the 61 or higher change level, which could be identified by the newer nicad charging circuit on the 08116-066531 A3 board, as opposed to the diode/resistor one in all the older manuals.
If someone wants to loan one of the later manuals I would be happy to create a pdf and have it posted on at least Glen's site (HP Archive) where I have contributed about 100 others.? KO4BB would be another well known spot to post.
I am hoping HP did not just publish the same old manual with nothing but old schematics and depended only on the manual updates to document it.? As a plan B, if there is a newer version of the 8112A that is close, that could be substituted.
Let me know if you have a later version and can either loan it out, or at least can provice a scan of the more recent schematics and parts layouts.
Thanks
--
Dave
Manuals@...
www.ArtekManuals.com
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Shaun M