Apple IIe: list of capacitors

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Apple IIe: list of capacitors

II bought my Apple IIe P.A.L.. made in Ireland - 820-0073-B, in the early 1980s.  Some years later, faced with the option of buying a Mac or an “IBM compatible”, I opted for the latter. Now I’d like to get the Apple working again.

My first step was to order a new power supply from Reactive Micro.  I installed it and checked the DC voltages which were all OK. I connected the PSU to the motherboard, removed the boards from all the slots and switched on. The power light on the keyboard lit up but there was no beep and the power light on the motherboard didn’t light up.  Soon after there was a smell and a small pillar of smoke rose from the capacitor at C17. 

II guess that my next step should be to replace the capacitors one by one.  I’ve spent hours searching the internet and downloading documents but have been unable to find a list of the capacitors, matching location to specification.  I live in Accra, Ghana and might have to choose from a limited range of available capacitors, so I’d like to know what alternative specs would work. Looking at the motherboard, I see C9, C12, C17, C15, L1 and L2 above the DC power socket and L4, L5 and L6 below it. They are tightly packed so matching size is important.

I’d be grateful for advice.

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Hello

Hello

C9, C12, C17 & C15 are all 10µF. You can replace them using radial capacitors rated at 16V.

You will find useful information in the Sams Computer Facts Apple IIe

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Apple IIe: list of capacitors

TLDR, if you have an Apple IIe board that does not start up (i.e. Power LED does not turn on), try replacing C12 and C15 with new 10µF/16V or 20V capacitors

Now for the longer version…

For reference, I have a PAL: Apple IIe board (820-0073A) that would not start up (no beep, no power LED, but ticking sound emanating from the power supply).

A friend helped me to find out that there was a short circuit on the 12V circuit by measuring resistance between ground and 12V at the pins on the motherboard where the power supply is usually connected.  

Seeing as capacitors are often the cause of problems on older equipment, I visually inspected all the caps on the board but could not spot anything out of the ordinary. When I searched around online, I found this forum and the reference to caps C9, C12, C17 and C15. Using the multimeter again, I measured the resistance over these caps. As the previous poster mentioned they are all 10µF caps. However, two of them are 20V ones and two are 6.3V - I hence concluded that the two 20V ones were relevant to the short circuit on the 12V circuit (C12 and C15). Measuring resistance over these - it turned out that there was hardly any resistance on C12, so I desoldered and replaced this part. C15 looked OK.

I was able to find replacement axial capacitors (Nichicon, as I heard they have a good reputation; manufacturer part number TVX1C100MAD, ordered from Digi-Key (their part number 493-14809-ND). Note the original part is rated to 20V and this part is to 16V, but I figured if it relates to the 12V circuit it would be OK.

Once I had completed the replacement and powered up, the power LED briefly flashed and then the same symptoms appeared (i.e. ticking power supply etc).  At a whim I measured C15 again, and it also now had no resistance. Quickly replaced C15 as well with the same part, and the board sprang to life!

Unfortunately, the system still only displayed vertical bars on screen. I swapped out the RAM with known good RAM, but it made no difference.

After leaving the system on for about 5 minutes I checked the ICs for any unusual heat – one was very hot. It was a SN74LS245N in position B11 (LS245) on the board. Luckily all the ICs on this board are socketed, and I could swap this IC with one taken from an original Apple IIe 80Col/64k Memory expansion card. Once I had done this – machine fired up normally.

 

 

 

 

 

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