Discussion:
Power Supply Repair, Part 2
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D Finnigan
2017-07-24 23:36:55 UTC
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In reference to this thread:
http://macgui.com/usenet/?group=1&id=284893#msg

Photo of my power supply:
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I have model Astec 11040B

Today the fuses and the RIFA filter capacitors that I ordered from Mouser
arrived, so I replaced C1 and put in a new fuse. When I switch on the power
supply I find that there is no output on any of the voltages, and no
clicking sound.

I tested C23 with my multimeter and it seems to be OK, and so does DB1.

But I'm not sure about transformer T1. This is the component that smoked
back in April when I attempted to bypass the fuse and apply power.
--
]DF$
Apple II 40th Anniversary User's Guide:
http://macgui.com/newa2guide/
retrogear
2017-07-25 01:27:56 UTC
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If your fuse held ok, do you have voltage at R28? Put your negative on R11 and positive on R28. Should get maybe 150VDC or more. Check voltage on both ends of R28 in case it's open. If you get that voltage, T1 is ok. If you have voltage, C7 looks swelled and that is your startup cap. If it is open then no output from PS.

Larry G
D Finnigan
2017-07-25 22:07:15 UTC
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Post by retrogear
If your fuse held ok, do you have voltage at R28? Put your negative on R11
and positive on R28. Should get maybe 150VDC or more. Check voltage on
both
ends of R28 in case it's open.
Did this. On both sides of R28 I got just over 155VDC, so this seems to be
OK.
Post by retrogear
If you
have voltage, C7 looks swelled and that is your startup cap. If it is open
then no output from PS.
I didn't take C7 out of the circuit, but I put a probe on one leg, then
probed a few other solder points and got about 15 Ohms. I didn't see any
needle movement on my meter that looked like the capacitor was
charging/discharging, so maybe C7 will indeed need to be replaced.
--
]DF$
Apple II 40th Anniversary User's Guide:
http://macgui.com/newa2guide/
retrogear
2017-07-25 23:28:56 UTC
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For C7, the manual says 220uF 10V but put in at least 16V. They were underated and failed even back in the day.
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