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leiy
May 21st, 2015, 09:33 PM
88-2 SIO board, damaged capacitor, need some help.

Can I just remove the damaged capacitor? If I remove the damaged capacitor, the 88-2 SIO board can still working?????

The damaged capacitor labeled JM 16V Y5S, what the specification about this capacitor? If I have to replace the capacitor.

note: the capacitor is mechanically damaged in transition process.

Thank you.
Leiy.

http://www.vintage-computer.net/bbsupload/sn221148a/88-2sio/1.jpg

http://www.vintage-computer.net/bbsupload/sn221148a/88-2sio/2.jpg

http://www.vintage-computer.net/bbsupload/sn221148a/88-2sio/4.jpg

http://www.vintage-computer.net/bbsupload/sn221148a/88-2sio/3.jpg

Chuck(G)
May 21st, 2015, 10:16 PM
That's a plain old 0.1 uF 16V disc ceramic cap. You can either find one to match it (if you care about looks) or just use any old 0.1 uF (or something in that range) to replace it. It's a bypass cap, so the rating isn't super critical. Modern caps for this purpose tend to be ultra-tiny MLCs, so technology marches on.

I suspect that it would work just fine without the cap, so you don't have to be in a hurry to replace it. Modern caps tend to marked with the code "104" to signify this value.

g4ugm
May 22nd, 2015, 12:36 AM
Some of the others look a bit odd, pretty sure I can see part of the metal disk exposed on a couple of others. If you get intermittent issues it might be worth replacing all of these.

Armageddon
May 22nd, 2015, 04:59 AM
That's a plain old 0.1 uF 16V disc ceramic cap. You can either find one to match it (if you care about looks) or just use any old 0.1 uF (or something in that range) to replace it. It's a bypass cap, so the rating isn't super critical. Modern caps for this purpose tend to be ultra-tiny MLCs, so technology marches on.

I suspect that it would work just fine without the cap, so you don't have to be in a hurry to replace it. Modern caps tend to marked with the code "104" to signify this value.

Exactly, it is a 100nF ceramic capacitor. It is not critical, but better if you replace it. You can try searching another similar at some ancient board, for example.

@Chuck(G): I'm new here, I need to ask you a private question. Please, could you send me a message? Thank you! :)

Chuck(G)
May 22nd, 2015, 09:38 AM
If you want to replace them all with disc ceramics (like with like), you can hardly find a cheaper capacitor (http://www.ebay.com/itm/Durable-100pcs-bag-Ceramic-Disc-Capacitors-50V-100nF-0-1uF-104pF-CA-FM-/291335151105?pt=LH_DefaultDomain_2&hash=item43d4ed9e01)

Personally, I'd probably replace them all with monolithic axial-leded ceramics (http://www.ebay.com/itm/QTY-100-1uf-100V-Z5U-AXIAL-CERAMIC-MLCC-CAPACITORS-C420C104Z1U5CA-KEMET-/111078545502?pt=LH_DefaultDomain_0&hash=item19dccc185e). They just look neater and aren't likely to get damaged.

Capacitor technology has come a long way in 30 years.

Corey986
May 22nd, 2015, 06:19 PM
I'll take a look later and see if I have a spare matching capacitor. I have a box of NOS green ones floating around.

leiy
May 22nd, 2015, 10:18 PM
Thanks for all the value helps.

I'm decide to replace them, when ready.

after some short circuit checks, I mounted this 88-2 sio board to Altair 8800 computer, no smoke happen, the temperature of VRM is at normal range, seems it will work ok.


Thanks.
Leiy.

http://www.vintage-computer.net/bbsupload/sn221148a/88-2sio/88-2-sio-1.jpg

http://www.vintage-computer.net/bbsupload/sn221148a/88-2sio/88-2-sio-2.jpg

leiy
May 22nd, 2015, 10:21 PM
I'll take a look later and see if I have a spare matching capacitor. I have a box of NOS green ones floating around.

That's perfect, if the board can replace with original vintage one. Thank you.

leiy
May 22nd, 2015, 11:32 PM
UPDATE

Chuck(G) is right, the damaged capacitor is nothing affect the operation of this 88-2-SIO board.

I run keyboard echo program(code from tkc8800.com) on front panel, the the 88-2-SIO board function perfectly!!!!!!

Keyboard echo program code from tkc8800.com




000: 076 003 323 020 076 021 323 020
010: 333 020 017 322 010 000 333 021
020: 323 021 303 010 000

http://www.vintage-computer.net/bbsupload/sn221148a/88-2sio/88-2-sio-test-ok.png


The light status when keyboard echo program are running.

http://www.vintage-computer.net/bbsupload/sn221148a/88-2sio/882sioechoprogram-running.jpg



Thank you.
Leiy

Chuck(G)
May 23rd, 2015, 08:39 AM
As far as the "chipped" disc ceramics go, it's not as bad as it looks. Manufacturers of precision disc ceramics start with a complete device, then saw a notch in them until the capacitance reaches the desired value. I wouldn't worry about some surface damange.

Corey986
May 24th, 2015, 02:29 AM
Ok I checked I don't have exact match to that cap. I have the same brand and size electronically, but the ones I have a physically large in green with the same MFR.

Sorry,
Cheers,
Corey

daver2
May 24th, 2015, 03:32 AM
I think the 'JM' marking you are referring to is actually '.1M'.

According to the 88-2SIO construction manual - these are 0.1 microfarad 10V ceramic disc decoupling capacitors - although your 16V marking implies 16 Volts rather than the parts list in the assembly manual stating 10 Volts.

Any 0.1 microfarad 10 Volts (or higher) ceramic disc decoupling capacitor should work just fine.

The card will technically work without the decoupling capacitor(s) - but they are there to prevent transients on the power rails due to very brief switching currents induced by the integrated circuits. Good logic design requires one decoupling capacitor per integrated circuit. Over time - the capacitors will become damaged. I would suggest replacing them with modern parts to ensure continued reliable operation.

Dave

leiy
May 24th, 2015, 03:45 AM
Ok I checked I don't have exact match to that cap. I have the same brand and size electronically, but the ones I have a physically large in green with the same MFR.

Sorry,
Cheers,
Corey

That's all right.

Since the 88-2 SIO can working, relife me a lot.

Thank you.
Leiy.

leiy
May 24th, 2015, 03:58 AM
I think the 'JM' marking you are referring to is actually '.1M'.

According to the 88-2SIO construction manual - these are 0.1 microfarad 10V ceramic disc decoupling capacitors - although your 16V marking implies 16 Volts rather than the parts list in the assembly manual stating 10 Volts.

Any 0.1 microfarad 10 Volts (or higher) ceramic disc decoupling capacitor should work just fine.

The card will technically work without the decoupling capacitor(s) - but they are there to prevent transients on the power rails due to very brief switching currents induced by the integrated circuits. Good logic design requires one decoupling capacitor per integrated circuit. Over time - the capacitors will become damaged. I would suggest replacing them with modern parts to ensure continued reliable operation.

Dave



Thank you for the valuable suggestions.

Leiy.