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Capacitor damaged on a VaxStation 3100

J

jplr

Experienced Member
Joined
Sep 3, 2022
Messages
149
Location
Brittany/France
Someone who damaged a capacitor near the power connector on the mainboard of their VaxStation 3100, asked me for a photo. Unfortunately, my photos do not reveal any text.
I wonder if someone knows where to find the main board schematics for the 3100?
I have included a photo of the damaged capacitor.

Thanks!

Jean-Pierre
 

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Bitly said:
What model 3100? The KA42 schematics are on bitsavers (here), but they don't match the component locations shown in your picture.

CW
Click to expand...
Many thanks, I asked my correspondent, but as on my VS there is a capacitor at the same place I would assume they have a VS 3100 model 38 VS42A
 
Hi,

The computer is VaxStation 3100 M38. I have recently acquired it. I think I managed to damage what looks like a capacitor with the screwdriver, so now I am afraid it will damage the mother board the moment I try to start it for the first time.
Thank you all!!!
 
Puzzling. The M38 should have a KA42 motherboard, but it doesn't match the component locations in the online documents. Perhaps it's a different board revision? It's also possible the motherboard was upgraded to a KA43 (M76) without re-badging the case, but that seems unlikely.

In any event, that is a capacitor, and unless there is visible cracking/breakage, it is unlikely to be damaged. If you wipe the top of the component with some alcohol cleaner on a Q-tip, you might be able to read the markings on top.

CW
 
The exact model is: 3100 M38 VS42A-BW. There seem to be no markings on the capacitor.
 
Last edited:
I looked at one of my 3100s, and I have the same board. On closer inspection, I believe the component is an old style tantalum capacitor based on the pin protruding from the positive end, but I don't have any idea of the value. Like yours, mine doesn't have any visible markings.

I think I have another 3100 with the old board. When I get time I'll take it apart and see if there is a similar component on it we can cross reference to the existing schematic.

CW
 
Bitly said:
I looked at one of my 3100s, and I have the same board. On closer inspection, I believe the component is an old style tantalum capacitor based on the pin protruding from the positive end, but I don't have any idea of the value. Like yours, mine doesn't have any visible markings.

I think I have another 3100 with the old board. When I get time I'll take it apart and see if there is a similar component on it we can cross reference to the existing schematic.

CW
Click to expand...
Thanks! And can you please measure the voltage at the capacitor? I do not have a working power supply at the moment. This way only the value of the capacitor will be missing.
Or I just take more than 12V which the maximum on the motherboard and that's it? For example 16 or 25.
 
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tonata said:
Thanks! And can you please measure the voltage at the capacitor?
Click to expand...

Unfortunately, I've already put them away. I'm in the process of painting, so everything is piled under tarps.

I did look at an older machine, and it matches the schematic on bitsavers. Page 65 shows the component placement, and C5 (just below the power connector) is a visual match. The parts list (Page 60) has
Code: 
10-24455-27 A 100 MFD 10V +/-10% CHI

I think it is a tantalum, but I'm not 100% positive. The only capacitors I've see with a pin marking the positive terminal are tantalums, but the part description doesn't say. Maybe someone else online can provide more information.

CW
 
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