Apple IIe DynaComp

[sellmore]

So the magic smoke escaped from my Apple IIe and I am going to attempt to replace the caps. Before I do, I have two questions:

1) Does anyone have a list of modern substitutes to replace them with or know where I can find a rebuild kit?

2) can someone tell me what those 4 black things are between the orange caps on the DC side? They have heat shrink on them obscuring any kind of identification and I wanted to ask before I go cutting it off.

[PeteS in CA]

Re: Apple IIe DynaComp

Holy cow! That's an antique by personal computer standards. The date code on the bridge rectifier is 27th week of 1982. It's probably a discontinuous flyback design.

The components you asked about are what folks here like to call "Pi inductors". They're wire wound on ferrite rod cores and are on O/P lines between two electrolytic capacitors (draw out the schematic and it looks like the Greek letter Pi). They probably won't have any markings.

If you're planning to do a refurb, all of those electrolytic caps are over 30 years old. That alone makes them dubious. Replacing the general purpose caps should be no problem. They're probably rated for 85C, but I'd replace them with 105C general purpose parts.

It's the O/P caps that get interesting. The pix aren't clear, but they look like United Chemicon RX or RXA series, or maybe Marcon. For 1982, they were the lowest ESR parts around. Nowadays, well modern parts are so much better that they could cause stability problems. I'd suggest Nichicon PS or PM series, Rubycon YXF, or United Chemicon PJ series, in that approximate order of preference (maybe YXF before PM).

The I/P caps look like 100uF, 200V. Make sure you match the lead footprint. Even with 105C parts instead of what I suspect are 85C original parts, that could be an issue. Going with 150uF or even 220uF parts instead of 100uF (assuming my reading of the value is correct) should be OK.

[goontron]

Re: Apple IIe DynaComp

Be weary of those clear caps on the primary, they will go bad in short order. My apple plus and tectronics scope both had those fail.

[kc8adu]

Re: Apple IIe DynaComp

had one let go in a power one 12v 18a open frame.
helluva smoke show!
was funny to see smoke boiling out of an external speaker.
was on a cobra 2000.
i hid the psu in 1 speaker and an eb63 design amp in the other.
only cobra 2000 that did 150w pep!

Be weary of those clear caps on the primary, they will go bad in short order. My apple plus and tectronics scope both had those fail.

[kc8adu]

Re: Apple IIe DynaComp

to the op.
replace ALL lytics on this one.i used panasonic fc of the right voltage and similar can size on the output.
the machine runs a fancy sheetmetal fab line in a local shop.
it had been going non stop since 84!
all the caps were shot!

[Longbow]

Re: Apple IIe DynaComp

I'm sure that new caps are a good idea, however being the curious person that I am it would be interesting to know how the supply failed. The "black things" are your secondary chokes (inductors) and not likely to cause problems. Due to the age of the unit, I'll hazard a guess that the main switching device has blown due to a lack of filtering, no feedback and snubber network failure. At least the caps aren't leaking onto the pcb.

[sellmore]

Re: Apple IIe DynaComp

PeteS in CA - Wow back! Thanks for the quick response. You have an amazing eye my friend. I didn't even upload a good picture of the caps themselves. Here's a couple of better ones.

Longbow - I'm curious to find out too. None of them appear to be bulging or have any detectable leakage that I can see. Hopefully somone can see something I can't. Since I plan on replacing them I haven't desoldered any from the circuit to check them out yet.

Goontron - I'm a little worried about the clear rectangular ones as well. I've seen on various Apple forums that those have been know to ooze out some brown goo. From the attached image, I think I can see a little bit of spider webbing, so, not sure if that's the culprit or not.

I saw one guy replaced them with much smaller, efficient caps (heatshrinking the exposed leads). Just not sure if that's the way to go.

[goontron]

Re: Apple IIe DynaComp

Goontron - I'm a little worried about the clear rectangular ones as well. I've seen on various Apple forums that those have been know to ooze out some brown goo. From the attached image, I think I can see a little bit of spider webbing, so, not sure if that's the culprit or not.

Yep. Those caps have crazed... They are bad. That one closest to the big caps has gotten hot as well, you can see where the leads go up the package has darkened slightly.

[PeteS in CA]

Re: Apple IIe DynaComp

Rifa PME271 X and Y caps are a very old series (old, but good stuff). Their dielectric is impregnated paper rather than plastic film. They are a good series, but, like any type of X or Y cap, they get hit with voltage spikes and have momentary breakdowns. Those breakdowns are not destructive, but they are damage that accumulates over time. After many many many hits (and years, probably) that damage can lead to catastrophic destruction of the part.

This can happen with impregnated paper, it can happen with polyester, and it can happen with polypropylene. These parts are made with metallized (sprayed or sputtered fine metal particles) dielectric rather than with foil. Breakdowns clear the metal back from the breakdown site. BUT the dielectric - paper or film - leaves a carbon residue, which becomes a fairly high resistance leakage path. And when you get enough of those paths, the part gets hot and . (Long, long ago Wima had a white paper about this)

So this was a very verbose way of saying that those two Rifa PME271 X caps probably should be replaced.

As for the switch device being shorted, that would open the fuse (if I had to guess, it's probably a 2N654x series transistor). That Motorola SCR near the O/P caps is probably an OVP crow bar on the +5V.

RX (the RXA, and the large can RZ and RZA series, too) had that very recognizable orange sleeve. Nichicon's PA and PB series caps of the same era had green sleeves. I've been working with power supplies, ummm, for a while. I tested an Astec Apple II+ power supply at one point.

[sellmore]

Re: Apple IIe DynaComp

The I/P caps look like 100uF, 200V. Make sure you match the lead footprint. Even with 105C parts instead of what I suspect are 85C original parts, that could be an issue. Going with 150uF or even 220uF parts instead of 100uF (assuming my reading of the value is correct) should be OK.

I'm having a hard time finding caps for the I/P (AC) side. I found the clear(ish) Film Caps PME271M610MR30 on Mouser rated at 275volts AC, 0.1uF 20% LS 20.3mm. But I can't find ANY 200VAC (or 220 or 275) ranging from 100uf-220uf. Are the voltage on these blue caps on my board in AC or DC?

Other than that, here's a list of parts I came up with. Someone let me know if these look like they'll work, or if they'll wind up frying my board:

I/P Side:
Kemet - PME271M610MR30 275volts 0.1uF 20% LS 20.3mm (There's also a PME271M610MR300PS, that costs 3x as much @ $3.03, not sure what the difference is)

O/P Side: (These are all Nichicon)
UPS1A221MED 10volts 220uF 105c
UPS1C331MPD 16volts 330uF 8x11.5 20% 3.5LS
UPS1C681MPD 16volts 680uF 10x16 20% 5LS
UPS1C102MPD 16volts 1000uF 10x20 20% 5LS

[Agent24]

Re: Apple IIe DynaComp

I'm having a hard time finding caps for the I/P (AC) side. I found the clear(ish) Film Caps PME271M610MR30 on Mouser rated at 275volts AC, 0.1uF 20% LS 20.3mm. But I can't find ANY 200VAC (or 220 or 275) ranging from 100uf-220uf. Are the voltage on these blue caps on my board in AC or DC?

Blue capacitors? I see none.
Are you talking about the big black electrolytics 200v 100uF?
Like all the other electrolytics, they're polarised and only handle DC. If you're searching for ones with AC ratings you'll only find them with the left-handed screwdrivers

[goontron]

Re: Apple IIe DynaComp

Blue capacitors? I see none.
Are you talking about the big black electrolytics 200v 100uF?
Like all the other electrolytics, they're polarised and only handle DC. If you're searching for ones with AC ratings you'll only find them with the left-handed screwdrivers

Same isle as the blinker fluid!

[sellmore]

Re: Apple IIe DynaComp

Blue capacitors? I see none.
Are you talking about the big black electrolytics 200v 100uF?
Like all the other electrolytics, they're polarised and only handle DC. If you're searching for ones with AC ratings you'll only find them with the left-handed screwdrivers

Yeah, guess they are black. Been looking at caps all day, most of 'em were blue. As far as the A/C vs D/C thing, that's what I thought. However, someone ought to tell that to Mouser (see attached).

[sellmore]

Re: Apple IIe DynaComp

Same isle as the blinker fluid!

Thanks Goon. I'll be sure to install it with my metric crescent wrench.