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HP 9825 power supply crowbar mod could have saved disaster
#HP9825
Maybe of interest for German (any maybe other European) users: finally I received the thyristors and can now offer five remaining sets of Rik's pcb board with parts for 12€ each, plus shipping costs.
Maybe of interest for German (any maybe other European) users: finally I received the thyristors and can now offer five remaining sets of Rik's pcb board with parts for 12€ each, plus shipping costs.
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By
Martin Hepperle
· #5651
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HP 9825 power supply crowbar mod could have saved disaster
#HP9825
Hi Martin, did you receive my e-mail some days ago? Cheers Chris
Hi Martin, did you receive my e-mail some days ago? Cheers Chris
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By
ChrisBeee
· #5648
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HP 9825 power supply crowbar mod could have saved disaster
#HP9825
I built up one of my earlier revision boards today with an added-on capacitor. I also uploaded the current revision of the board (with cap included) to Oshpark, shared as "HP 9825/35 Crowbar". Oshpark
I built up one of my earlier revision boards today with an added-on capacitor. I also uploaded the current revision of the board (with cap included) to Oshpark, shared as "HP 9825/35 Crowbar". Oshpark
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By
Jack Rubin
· #5575
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Edited
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HP 9825 power supply crowbar mod could have saved disaster
#HP9825
Hi Martin, as a nice coincidence, I am living in Germany too (in the Ammersee region, likely not tooooo far away from you). It would be awesome if you put me on the list for two boards, I will contact
Hi Martin, as a nice coincidence, I am living in Germany too (in the Ammersee region, likely not tooooo far away from you). It would be awesome if you put me on the list for two boards, I will contact
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By
ChrisBeee
· #5574
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HP 9825 power supply crowbar mod could have saved disaster
#HP9825
In order to upgrade my 9825s I had 10 PCBs manufactured (minimum order), but I only need 3-4. So I have 5 boards avaialable, but currently unpopulated. I have most of the parts and am currently waitin
In order to upgrade my 9825s I had 10 PCBs manufactured (minimum order), but I only need 3-4. So I have 5 boards avaialable, but currently unpopulated. I have most of the parts and am currently waitin
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By
Martin Hepperle
· #5567
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HP 9825 power supply crowbar mod could have saved disaster
#HP9825
Hi Chris, No, I'm sorry but all boards are used or spoken for. -Rik -Rik
Hi Chris, No, I'm sorry but all boards are used or spoken for. -Rik -Rik
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By
Rik Bos
· #5566
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HP 9825 power supply crowbar mod could have saved disaster
#HP9825
Hi Rik, are there any of your crow bar PCBs available? A 9825A will arrive in my lab tomorrow and I'd love to see it being well protected before I fire it up the first time! Cheers Chris
Hi Rik, are there any of your crow bar PCBs available? A 9825A will arrive in my lab tomorrow and I'd love to see it being well protected before I fire it up the first time! Cheers Chris
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By
ChrisBeee
· #5565
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9825A Troubleshooting
#HP9825
#VintageHPComputers
Thanks Rik, This is my first time ordering a PCB from a file (pretty non-commercial if I'd say so). I'm having some trouble finding the size of the board/number of layers etc from the file. Any help w
Thanks Rik, This is my first time ordering a PCB from a file (pretty non-commercial if I'd say so). I'm having some trouble finding the size of the board/number of layers etc from the file. Any help w
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By
Rhys Lowry
· #5430
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9825A Troubleshooting
#HP9825
#VintageHPComputers
Rhys, I uploaded a slightly optimized gerber, you’re free to use it non-commercial 😉 -Rik Van: VintHPcom@groups.io <VintHPcom@groups.io> Namens Rhys Lowry Verzonden: donderdag 4 maart 2021 19:15 Aan:
Rhys, I uploaded a slightly optimized gerber, you’re free to use it non-commercial 😉 -Rik Van: VintHPcom@groups.io <VintHPcom@groups.io> Namens Rhys Lowry Verzonden: donderdag 4 maart 2021 19:15 Aan:
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By
Rik Bos
· #5412
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9825A Troubleshooting
#HP9825
#VintageHPComputers
I just ordered new filter caps as well as a new 2N4398. I'll let you know if that fixes things or if I need any more help. I'll make sure to test it safely this time. Rik, is your crowbar circuit avai
I just ordered new filter caps as well as a new 2N4398. I'll let you know if that fixes things or if I need any more help. I'll make sure to test it safely this time. Rik, is your crowbar circuit avai
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By
Rhys Lowry
· #5408
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9825A Troubleshooting
#HP9825
#VintageHPComputers
The 2N4398 is the pass transistor for the +5V supply if it failed short (mine did too) it will put +20V in places it really should not be. I am afraid the damaged trace would suggest the fuse did not
The 2N4398 is the pass transistor for the +5V supply if it failed short (mine did too) it will put +20V in places it really should not be. I am afraid the damaged trace would suggest the fuse did not
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By
Paul Berger
· #5379
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9825A Troubleshooting
#HP9825
#VintageHPComputers
The trace that burned some of the solder mask off is the leg of the transformer feeding the +20 unregulated. I am surprised it did not blow the fuse before doing that damage, maybe there is a nail in
The trace that burned some of the solder mask off is the leg of the transformer feeding the +20 unregulated. I am surprised it did not blow the fuse before doing that damage, maybe there is a nail in
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By
Paul Berger
· #5377
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9825A Troubleshooting
#HP9825
#VintageHPComputers
By head I say it's the AC return line to the transformer. So it seems your very lucky. -Rik
By head I say it's the AC return line to the transformer. So it seems your very lucky. -Rik
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By
Rik Bos
· #5374
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9825A Troubleshooting
#HP9825
#VintageHPComputers
If you haven't already, download a copy of the service manual: http://www.hpmuseum.net/document.php?hwfile=1808 Also two sets of schematics are available, one are the hand drawn ones by Tony Duell: ht
If you haven't already, download a copy of the service manual: http://www.hpmuseum.net/document.php?hwfile=1808 Also two sets of schematics are available, one are the hand drawn ones by Tony Duell: ht
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By
Craig Ruff
· #5370
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9825A Troubleshooting
#HP9825
#VintageHPComputers
I was measuring the 12V rail when it happened and was confused as to why it wasn’t changing the voltage when I turned the pot. As for dead components, the 2N4398 is shorted and it looks like some sold
I was measuring the 12V rail when it happened and was confused as to why it wasn’t changing the voltage when I turned the pot. As for dead components, the 2N4398 is shorted and it looks like some sold
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By
Rhys Lowry
· #5368
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9825A Troubleshooting
#HP9825
#VintageHPComputers
12.43 V was within the spec and probably didn't need adjustment immediately. Did you look at the schematic before you turned the potentiometer? Doing so without understanding what you were adjusting o
12.43 V was within the spec and probably didn't need adjustment immediately. Did you look at the schematic before you turned the potentiometer? Doing so without understanding what you were adjusting o
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By
Craig Ruff
· #5356
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9825A Troubleshooting
#HP9825
#VintageHPComputers
Hi all, I'm a newish vintage electronics repair enthusiast having recapped and done basic troubleshooting and the such in the past. No expert, although I aspire to be. After picking up this HP 9825A l
Hi all, I'm a newish vintage electronics repair enthusiast having recapped and done basic troubleshooting and the such in the past. No expert, although I aspire to be. After picking up this HP 9825A l
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By
Rhys Lowry
· #5349
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HP 9825 power supply crowbar mod could have saved disaster
#HP9825
I don't think the exact SCR used is that critical but it will need to withstand a pretty heavy current pulse when it trips. Blowing the fuse will be nothing for it, but it will effectively short the b
I don't think the exact SCR used is that critical but it will need to withstand a pretty heavy current pulse when it trips. Blowing the fuse will be nothing for it, but it will effectively short the b
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By
Paul Berger
· #4980
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HP 9825 power supply crowbar mod could have saved disaster
#HP9825
The choice of brexit is pure nonsense, but at least in the UK they have a true democracy that respects the choices of the people, which is not the case in all countries including France.... Don't worr
The choice of brexit is pure nonsense, but at least in the UK they have a true democracy that respects the choices of the people, which is not the case in all countries including France.... Don't worr
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By
jbemond
· #4973
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HP 9825 power supply crowbar mod could have saved disaster
#HP9825
I've all the parts except the thyristors RS is moving it's stock from GB to Germany ( they told me) and that seems to take some time. So I'm waiting for those. The stupid thing is most of the time I h
I've all the parts except the thyristors RS is moving it's stock from GB to Germany ( they told me) and that seems to take some time. So I'm waiting for those. The stupid thing is most of the time I h
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By
Rik Bos
· #4969
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