Hi everyone!I recently bought an Apple IIe platinum (that was used in a school!), the monitor, and a disk drive from an estate sale. I got it home, plugged it all in and turned it on. The monitor turned on fine, but nothing else. I quickly turned it all off. I then went into a DEEP rabbit hole of YouTube videos, along with finding the Apple II group on FB. I own about 20 original arcade games, so I'm comfortable around voltages, CRTs and electronics, so I decided to dive in. First. No power to main board. Lets work on the Power Supply. So, I asked and I learned about recapping and those darn Rifas. Upon lots of research, my PS is a Dynacomp model 699-0133. I guess this was a later model. I luckily found scematics on the FB page for these and confirmed the caps I needed. I removed all electrolitic capacitors, and tested each out of circuit. I found a few that were dead, and got exicited that this was it! Also, on research, I found out that the Rifas are the cause to the smoke of doom, but wont effect the PS really. But still, If I recap, then lets do the rifas too. Lucky for mine, the safety caps were not cracked or blown up. Also, the fuse on my PS is fine and has continuity. So, I ordered all the caps. and recapped. got everything back together and turned it on. Nothing. Same as before. So I got out the multimeter, tested the wall. 120v. Awesome. Tested the power cord. 120v. Cool. Tested inside the PS (CAREFULLY) and got 120v at the switch and at the wires that go from the switch, to the PS board. Then I went to the 6 pin connector that goes to the main board. I'm getting ZERO on the -12, -5, +5, and +12. So...that's where I am. Hoping I am in the right place to get this guy working again with the help of some of you. I know there is a *new* PS option from ReactiveMicro, but I reeeeally want to learn and fix the OG if I can. I love the process of learning how it all works, and trying to fix the orignal. So, what do I do next? Let me know below! I can send pictures of anything and let you know anything else! Thanks Fritter!
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PS After:
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FWIW you're basically getting many of the same eyes here as with the FB group... some exceptions but lots of cross-over.
Did you walk chcke the components I highlighted in the schematic to check?Since you got no outputs at all, unless there's multiple failures on the secondary side (that is possible), seeems the problem is on the other side of the transformer and why the directions to check the parts konwn to fail on the primary side. You got no obvious damages parts that I can see from the pictures and these pictures are better than provided previously on FB...
I see the fuse looks good, and see you checked that. The primary side transistors are what make the transformer do it's magic and since you've got no output best check there. No need to test hot, most of these can be checked in circuit. Testing the output of the diodebridge is dangerous DC so don't be probing that powered unless you really know what you're doing.
I hope you finally learned your lesson and no longer subscribe to this "recap first" brainrot.
My notes indicate the following weak points that should be checked in Dynacomp PSUs:
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Thanks Rob! Good news is, based on the sheet i have been using shown above, I actually replaced those 1uf 35v with the 1uf 50v caps! I will look into that half watt resisitor today! Thank you!
Honestly, I wouldn't waste any more time with that old Dynacomp power supply.
More likely than not there is an issue with the feedback circuit that is causing the supply to shut down before it even starts up.
My advice would be to buy a universal power aupply replacement kit from ReActive Micro, rwteofit it into your old case (no one will be th wiswr once it's complete) and be done with the repair dance on these old switching supplies.
Also, recapping a dead supply almost never fixes the issue.
I agree completely. Bad power can cause so many other issues. The modern Reactive Micro power supply replacement will bolt into the original powersupply case and nobody will ever be the wiser - and you will have known good power. This becomes more important as you add additional cards.