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Old 03-14-2019, 07:14 PM   #1
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Default Apple ][+ Astec power supply

bought a used apple ][ plus for a reasonably amount, I had it on a total of 3-4 min, while i was on i started to hear a soft sizzle noise and turned it off immediately, good news was it was still displaying digdug on the TV while I was turning it off.

I haven't taken it apart yet but i suspect bad RIFA caps and I was wondering how to select replacments. I would imagine its the same as other mobo caps where you can go higher but not lower. anyways I'll take some pics after I get it apart, I had it powered on at my place of work and it really stunk up the place
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Old 03-14-2019, 08:51 PM   #2
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Default Re: Apple ][+ Astec power supply

Apple II power supply Astec AA11040 or AA11040-B schematic etc. https://ia801002.us.archive.org/1/it...lies_Aug82.pdf
Have to look inside to see what part is failing.
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Old 03-14-2019, 10:10 PM   #3
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Default Re: Apple ][+ Astec power supply

panasonic sell suitable PolyPropylene caps that are cheap.
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Old 03-15-2019, 09:33 AM   #4
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Default Re: Apple ][+ Astec power supply

allrighty got it open indeed the rifa blew but doesn't look like it made to big a mess its a 0.1uf cap 250v i think. I found this site https://www.reactivemicro.com/produc...-power-supply/

thought that would be a good replacement. any thoughts?
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Old 03-15-2019, 10:21 AM   #5
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Default Re: Apple ][+ Astec power supply

Quote:
Originally Posted by stj View Post
panasonic sell suitable PolyPropylene caps that are cheap.
I found these would they be suitable? https://www.ebay.com/itm/5pcs-1uF-0-...d/122034179568
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Old 03-15-2019, 01:29 PM   #6
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Default Re: Apple ][+ Astec power supply

that's good, but way overpriced.

you should be paying around 25c each!!
https://uk.rs-online.com/web/p/polye...itors/8697466/
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Old 03-15-2019, 05:26 PM   #7
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Default Re: Apple ][+ Astec power supply

OMG, hilarious! I'd guess the vintage is ca. 1982, and I'm chuckling at the switch transistor with the part number removed. Astec used NEC TV horizontal flyback transistors.

That's a discontinuous flyback design. If you actually load it to full output power (43W?) those axial rectifiers and the transformer core will get REALLY hot. Guess how I know all this.

So those output caps are excellent quality parts, for the era, but they are ~35 years old. Once you fix the immediate problem, I'd suggest checking the ripple at 50%-75% load. If it's OK, leave well enough alone. If it's not, you have to use the least excellent low impedance caps (e.g. Nichicon RS series) and hope those aren't "too good".
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Old 03-15-2019, 06:10 PM   #8
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Default Re: Apple ][+ Astec power supply

Quote:
Originally Posted by PeteS in CA View Post
OMG, hilarious! I'd guess the vintage is ca. 1982, and I'm chuckling at the switch transistor with the part number removed.
Where? All I saw, except for the caps, what looks like diodes on the PCB, what look like heatsinked diodes or resistors and what looks like a round magnet with a thin heatsink around it. Was it that wide round one on the PCB?

The round one with the thin heatsink, is a package format that makes me get lost, even when I starting learning about more stuff related to PSUs... It reminds me of my early badcaps.net days, when I didn't even know what a MOSFET was, LOL

I saw a round device like that before in a later-1980s' Simplex 4001 FACP. Is that a choke?
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Old 03-15-2019, 07:22 PM   #9
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Default Re: Apple ][+ Astec power supply

Quote:
Originally Posted by stj View Post
that's good, but way overpriced.

you should be paying around 25c each!!
https://uk.rs-online.com/web/p/polye...itors/8697466/
I agree but using mouser or any of the other ones shipping is outragous so 6.75 for 5 with free shipping isn't too bad. I did order them!

Power supply has a 1980 copyright inside but the computer is a 1982 based on the logic board stamp of 5082 so week 50 of 82 i guess.
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Old 03-16-2019, 01:43 AM   #10
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Default Re: Apple ][+ Astec power supply

the "magnet" is a power transistor.
and as peteS said, it's usually a bu208 < very reliable btw.
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Old 03-16-2019, 07:24 PM   #11
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Default Re: Apple ][+ Astec power supply

Quote:
Originally Posted by stj View Post
the "magnet" is a power transistor.
and as peteS said, it's usually a bu208 < very reliable btw.
It's an Astec PSU. They generally use very reliable parts... save for those RIFA film caps.
But once you get those taken care of (and maybe the output caps too, as PeteS mentioned)... the PSU should be as good as new. Astec PSUs are near damn indestructible.

Quote:
Originally Posted by PeteS in CA View Post
That's a discontinuous flyback design. If you actually load it to full output power (43W?) those axial rectifiers and the transformer core will get REALLY hot. Guess how I know all this.
Probably worked on a similar (if not same) PSU design many years ago in a former job?
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Old 03-18-2019, 06:27 PM   #12
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Default Re: Apple ][+ Astec power supply

Quote:
Originally Posted by momaka View Post
It's an Astec PSU. They generally use very reliable parts... save for those RIFA film caps.
But once you get those taken care of (and maybe the output caps too, as PeteS mentioned)... the PSU should be as good as new. Astec PSUs are near damn indestructible.


Probably worked on a similar (if not same) PSU design many years ago in a former job?
Ca. 1981 when I worked for Boschert we got ahold of an Apple ][+ P/S and I figured out the schematic (by staring at the PCB) and tested its performance. Astec hadn't done a very good job of removing the switch transistor part number, so I was able to make it out. It was a (2S)C (the "2S" was omitted, common practice) part. The package is commonly called TO-3, but it's actually TO-204. That stamped and bent black sheet metal device under it is a heatsink.

The Astec design was very similar to Boschert's OL25 series design and the XL50-XL165 family then in development.

Rifa PME271 series caps have gotten, IMO, a bad rap. The failures I've seen referenced here tend to be P/Ss that are 30+ years old, where the X Caps have taken lots of line surges. I seriously doubt MKP or MKT would have done much better. Rifa was very popular back then because they were the ones out marketing their product in the US and Asia. Roederstein, Wima, and Plessy (Westlake) were late to pursue markets outside of Europe, so Rifa PME271 parts got into a lot of product.

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Old 03-18-2019, 09:13 PM   #13
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Default Re: Apple ][+ Astec power supply

Quote:
Originally Posted by stj View Post
the "magnet" is a power transistor.
Is that package rare now? Looks like it was possibly much more the usual back in the 1980s.

And for the group home FACP, I honestly thought that it was possibly the trouble buzzer, for when a trouble is reported. (Usually just a loss of utility AC and running on battery, most likely 2 12-volt batteries in series.)

(But when the fire alarm system was tested once with just the batteries, I think they were laughably weak! The electromechanical DC horns were low in volume!)

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Old Yesterday, 01:48 AM   #14
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Default Re: Apple ][+ Astec power supply

TO3 package is not rare,
it's used for stuff that has to transfer a lot of heat - like 2n3055's
very common in psu's and audo amps.
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Old Yesterday, 12:27 PM   #15
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Default Re: Apple ][+ Astec power supply

TO-3/TO-204 (why did they change the designation? Or is it it because of the flat flange vs textured, aluminum vs steel, or low profile vs full height?) is "rare" now in modern design because they're expensive to make and assembled compared to plastic parts like TO-247/TO-3P. However the metal case was very typical in the past.

- Metal cap does not contribute much to thermal dissipation due to thickness
- Don't need to weld the metal top cap on during part manufacturing
- Only one screw needed to assemble in end product in the TO-247/TO-3P
- TO-3/TO-204 has more capacitance on the case terminal which is a major drawback for high speed design.
- only advantage of TO-3/TO-204 is that it's got slightly lower thermal resistance and has more thermal mass if run with only a small heatsink. But today's designs, we shouldn't be making heaters in the first place

The "shield" that the TO-3/TO-204 provides seems like a benefit, but it's not because it's one of the terminals. It would have been nice if the heatsink was emitter (BJT) or source (FET) but it's never the case (pun intended). Point is moot anyway because there will always be situations that the lower impedance point will be opposite what you want. For linear power supplies and audio frequency applications it may not matter too much. In this case Astec/Apple is running that transistor likely around or just outside the audio frequency range where a few pf doesn't matter that much.
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Old Yesterday, 12:29 PM   #16
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Default Re: Apple ][+ Astec power supply

allrighty shes up and running again, the panasonic part fit perfect and flush since the board had a second set of closer spaced holes for the smaller part.
I probably gamed on it an hour loading games through the cassette in jack using the appleiionlinegameserever.
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Old Yesterday, 12:50 PM   #17
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Default Re: Apple ][+ Astec power supply

The main difference I've seen between a TO-3 and a TO-204 is that the former has a rounded top on the dome/cap. They were/are good for heat dissipation and better at mounting flush to a surface than a TO-220. TO-247//TO-3P have similar junction-case thermal resistance to a TO-204. TO-247//TO-3P are less expensive to make and are more space efficient and flexible.

That is one french-fried X Cap! Dual mounting holes was not uncommon, allowing the use of vendors with different lead spacing and package size.
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Old Yesterday, 04:09 PM   #18
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Default Re: Apple ][+ Astec power supply

Anyone got pictures of a french fried or bloated X/Y cap (certified by UL or whatever safety agency in your locale) that's not a Rifa?

I have yet to see one, and still feel convinced the old Rifas are Replace On Sight... which I'm failing to do because I know I have Rifas in my old Tek scopes, and probably other stuff...

And a picture of a bunch of ???
2N3055 Si-NPN "TO-3"
BUW44 Si-NPN "TO-204"
D1879 Si-NPN TO-247 isolated
2N1136A Ge-PNP "TO-204"
466 103-9 Ge-PNP "??"
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Old Yesterday, 04:42 PM   #19
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Default Re: Apple ][+ Astec power supply

Quote:
Originally Posted by eccerr0r View Post
Anyone got pictures of a french fried or bloated X/Y cap (certified by UL or whatever safety agency in your locale) that's not a Rifa?

I have yet to see one, and still feel convinced the old Rifas are Replace On Sight... which I'm failing to do because I know I have Rifas in my old Tek scopes, and probably other stuff...

And a picture of a bunch of ???
2N3055 Si-NPN "TO-3"
BUW44 Si-NPN "TO-204"
D1879 Si-NPN TO-247 isolated
2N1136A Ge-PNP "TO-204"
466 103-9 Ge-PNP "??"
Yes! Those round ones are what I were thinking about! The one on the upper right 2012? (Or is that just another way of saying that it's the third year of a previous decade, such as 1992 or 1982?)

(And if in the international-year-of-manufacturing-format, it would mean 2010 or the first year of a previous decade, such as 1990 or 1980, for example, I would think.)

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Old Yesterday, 05:29 PM   #20
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Default Re: Apple ][+ Astec power supply

Hah... None of these TO-3/TO-204s were made this century!

As far as I know of the pictured transistors:
BUW44: made in 1980
2N3055: made in 1976
2N1136A: made in 1973 (as far as I can guess)
466 103-9: made in 1972 (same deal)
2SD1879: no clue, not looking it up, but likely 1990s.
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