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Old 9th July 2007, 05:03 PM   #1
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Default Stumped on 2nd Re-Cap and need help

I just finished recapping my second am radio. After the first recap was a success I was thinking no problem now. HA!

Guess again...I had no problems replacing the caps in the second radio except when I put everything back together again and went to bench test it.............nothing. I checked all of the wiring and all of the solder joints look fine. All values are in line with the originals too. The only thing I can think of was that when I replaced the 3 caps that were in a can originally Sam's called for 2 caps=400uf/16v and 1 cap 100uf/16v. I replaced them with 2 caps=500uf/50v and 1 cap 100uf/50v. Are the two larger caps too high in uf and would this cause the radio to not function at all?

As always thanks for your help guys !
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Old 9th July 2007, 06:25 PM   #2
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No, the radio should function just fine with the caps you put in. You likely have a problem somewhere else. Based on 2 @ 400uF, 16V, it sounds like those are +/- rails for a bipolar power supply. Verify, it it is a switching power supply, that you are getting AC through the transformer.

Also check for blown fuses, rectifiers, etc.
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Old 9th July 2007, 06:34 PM   #3
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Quote:
Originally posted by zigzagflux
No, the radio should function just fine with the caps you put in. You likely have a problem somewhere else. Based on 2 @ 400uF, 16V, it sounds like those are +/- rails for a bipolar power supply. Verify, it it is a switching power supply, that you are getting AC through the transformer.

Also check for blown fuses, rectifiers, etc.
Thanks for your reply ZZ. You see, that's just the thing. I'm so new at this that I don't know what to look for when you say rectifier, fuse or switching power supply. I'm really new at this so I'm learning as I go. I guess this qualifies for "something new". Any tips or suggestions? Thanks
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Old 9th July 2007, 08:49 PM   #4
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Quote:
Originally posted by 65blkbkgt
I don't know what to look for when you say rectifier, fuse or switching power supply.

That will certainly make things difficult. Any way you can take a picture of the guts? I could probably try and identify some critical parts.
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Old 9th July 2007, 10:27 PM   #5
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Here are a couple of shots. One from the rear and one from the top. Maybe you can identify some parts with these? Thanks again!
Attached Images
File Type: jpg philsides 002.jpg (65.1 KB, 66 views)
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Old 9th July 2007, 10:28 PM   #6
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Here's the second one........
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File Type: jpg philsides 003.jpg (54.1 KB, 59 views)
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Old 13th July 2007, 02:00 PM   #7
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I took the radio apart again on Thursday and checked for loose connections etc. and still nothing. Before I put it back together again I still had it hooked up and touched the output transistor to the radio case and got some static? Anyway I changed the output transistor, put the radio back together and again.....nothing. I need help...please....anyone?
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Old 13th July 2007, 04:06 PM   #8
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Sorry, but your pictures are just a little difficult to interpret.

Do you have a multimeter?
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Old 13th July 2007, 04:34 PM   #9
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Hi ZZ.......yes I do have a multimeter and, stupid as it sounds I don't really know how to use it well. I'm new to this........what can I say?
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Old 13th July 2007, 05:16 PM   #10
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At this point I would say you got one shot at this working, and that is to get the power supplie(s) working. Anything beyond this is probably a little too complex for the beginning techie, and will most certainly be impossible for anyone to help out without a schematic.

You are looking for DC supplies, maybe just 15V, maybe bipolar supplies (plus and minus 12V). Measure across the two leads of the larger uF capacitors, and see what you get. Your caps will be labeled with negative terminals. Connect your black lead of the multimeter to the negative terminal on each cap.

Report back.
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