T3 Transformer Specifications in Astec Apple IIe Power Supply

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T3 Transformer Specifications in Astec Apple IIe Power Supply

I have had an Apple IIe for several years now that I power up and play around with from time to time, but not on a regular basis.  I went to power it on one day recently and found it be completely dead.  I decide to open it up and check for power coming out of the main harness from the power supply, but get nothing on either the 12v and 5v rails. 

 

Tearing into the Power Supply I see no obvious signs of failure.  I check the fuse, it's still intact, not blown.  The electrolytics look pristine on the outside, so before I blindly replace them I wanted to get to the bottom of the failure, although I do start with replacing the RIFA capacitor(low effort to do so) near the mains input as they are well known components that fail in numerous electronics.  A new film capacitor made by TDK installed, no change in the output, still dead. 

I manage to pull the large Q2 transistor off the board to test it out of circuit.  No shorts there, all voltage flows in the correct directions (or doesn't) between Base, Emitter, and Collector.  

I test the resistance in the windings of the transformers.  The main, largest transformer, T2, checks out on all it's windings.  The smaller Transformer, labeled T3 however has a high resistance on what I can only assume are its primary windings.  I manage to remove it from the board and test it out of circuit.  The set of 4 pins are completely open it seems on both sets of the windings at those pins.  No continuity at all and no reading when checking Ohms.  I know this transformer has to do with the PWM control, which is likely why I am not getting any output from the main connector harness.

 

 

This problem seems to be similar to the situation described in this persons blog: https://www.jammarcade.net/tag/apple-iie/  Clearly, there is a break in the windings on this transformer, but I CANNOT see them visually on either of the pins, so they must be inside the windings, or somewhere I just can't see yet.  

 

Has anyone else encountered this problem and found a suitable replacement transformer?  Does anyone have a clue what it's specifications are?  I imagine this component is custom made by Astec many years ago.  Best I can find is a Vendor No. 852-10200680 from an Apple information PDF on these power supplies.  

 

If I have to determine what the number of windings on either side should be, I'll go down that route and try to report back here with my findings for the next guy.  

 

Thanks.

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Have you found a replacement transformer?

Hi, I also have a IIe where the psu AA11040B is not outputting any voltages.

I have replaced the capacitors, but not pulled the Q2 or transformers.

I just wanted to hear if you have managed to find a solution to your transformer?

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If that transformer is faulty

If that transformer is faulty you probably won't be able to find a new one.  Your only options are one from a donor power supply that has other problems, or having that one re-wound.  Those options are difficult and expensive.  Often easier and less expensive to look at other options like a ReativeMicro power supply rebuild kit, which is basically a new power supply board that fits inside a vintage Apple power supply chassis, but is made with all new components.  Looks original from the outside, but is all new inside.

 

 

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Those transformers are

Those transformers are unicorns.

 

Your best course of action at this point is to install a universal power supply from ReActive Micro.  It fits into the old case so it still looks stock.

https://www.reactivemicro.com/product/universal-psu-kit/

 

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Not yet, unfortunately. 
tolderlund wrote:

Hi, I also have a IIe where the psu AA11040B is not outputting any voltages.

I have replaced the capacitors, but not pulled the Q2 or transformers.

I just wanted to hear if you have managed to find a solution to your transformer?

Not yet, unfortunately.  Based on what everyone else is saying, it seems that the only reasonable solution with my time and skillset is to buy the replacement kit that fits in the casing of the original PSU.  Which is nice, since I am attempting to keep it stock looking as close as possible, and considering that other components in the PSU that are not generic may happen to fail down the road that would be the most ideal solution.

 

Still, I like my cheap inexpensive fixes that only cost me my time.  I am going to do my research on this transformer, see what can be done about using any generic replacment if possible at all.  All this will have to be in between everyday life so no timeframe or if I'll even be able to pull it off.  I'll try my damdest and report my findings back on this thread if I am ever successfull.  

 

Thanks for recommendations!

 

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If someone was dead set on

If someone was dead set on repairing one of these, you could try Heyboer Transformers. Antique radio guys use them to rewind old iron transformers all the time. If they can't rewind it (or even if they can), they might be able to disassemble it and at least figure out the specs for a suitable off the shelf replacement. 

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Kotomo wrote:Still, I like my
Kotomo wrote:

Still, I like my cheap inexpensive fixes that only cost me my time.  I am going to do my research on this transformer, see what can be done about using any generic replacment if possible at all.  All this will have to be in between everyday life so no timeframe or if I'll even be able to pull it off.  I'll try my damdest and report my findings back on this thread if I am ever successfull.

 

If I had the time I'd probably unwind the bobbins in that transformer, count the number of turns, size the wire, buy the respective magnet wire and re-wind it myself.

Problem is that magnet wire in small quantities is really expensive.

 

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I guess that depends on your

I guess that depends on your definition of really expensive is. You can get rolls of 2-8oz of wire for $10-$20 on Amazon. Just depends on diameter and how much you need. 2oz may not sound like much, but it actually is. I picked up 2oz of 30-something gauge last year to rewind an antique radio coil. Barely put a dent in the roll, if at all. Of course I used probably far less than needed for a power transformer. But I'm sure even 2oz you'll have plenty left over. 

 

Which speaking of, if you have an antique radio club near you, there is a good chance someone there is sitting on a lot of magnet wire and could probably sell you some cheaper. You'll need a micrometer to check the gauge though.

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nick3092 wrote:Which speaking
nick3092 wrote:

Which speaking of, if you have an antique radio club near you, there is a good chance someone there is sitting on a lot of magnet wire and could probably sell you some cheaper. You'll need a micrometer to check the gauge though.

 

And you need to measure the gauge without the varnish.  The way I measure it is to burn it off with a small blowtorch then clean it with a cotton cloth and then measure it with a micrometer.

 

 

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Well, I managed to get the

Well, I managed to get the power supply working again, but the cultript was NOT this T3 transformer. BTW, my Astec PSU is model AA11040-B.

 

I appreciate the replies and the advice on seeking out help with transformer repair. It’s confidence boosting if I ever need to actually undertake such a task.

 

I was looking at the pinout on the left side (according to the image) completely wrong. In the included image, I have circled the pins that are the real windings for this side. So there are two seperate windings on this side of the transformer and continuity testing across the each of the circled pairs of pins checks out OK. Admittedly I had noticed this before, but was sure of my original thinking that this had failed, but clearly I am wrong. It appears to be two windings, one wound over the other.

 

 

With that in mind, I re-install it and then attempt a complete electrolytic capacitor replacement anyway, since even if they are not the point of failure, it couldn’t hurt to try. Still no luck after replacing all of them.

 

I realize I should start testing individual components and break into categories of resistors, diodes, transistors, etc. Well, this clearly helped me find the fault faster as resistors R2 and R3 had both failed, nearly completely open or 1 M Ohms in resistence. They are 150k Ohms at ½ watt. Replaced them with brand new equilvalents and my Apple Iie is now back up and running.

 

I hope this helps anyone in the future. My Googling earlier mostly pointed at the infamous RIFA cap (which was the first thing I replaced) but pretty sure I never encountered these resistors failing.

 

Thanks again for the help and suggestions.

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