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LJ |
Posted: Thu Jan 22, 2009 6:57 am Post subject: |
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Maybe the problem is at transformer primary winding, try the board with another transformer to make sure if the board is ok.
BTW, for me, when i see the picture of your transformer, looks like a vcd player transformer made in china ( just joking ) |
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DeathlyKnight |
Posted: Wed Jan 21, 2009 2:50 am Post subject: |
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yes i do and the resistance between on caps increase the longer i test it so they are obviously working and not shorting out anywhere |
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jts1957 |
Posted: Mon Jan 19, 2009 11:06 pm Post subject: |
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Do you have meter to measure across filter caps? (The largest one for the single supply and the two 3300ufd for the +/- supplies). |
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DeathlyKnight |
Posted: Mon Jan 19, 2009 10:55 pm Post subject: |
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Nope its a shodow, there is no dis-colouring on the board except for around the caps to the left of the "char-coaled" part |
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jts1957 |
Posted: Mon Jan 19, 2009 10:44 pm Post subject: |
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Is it just my eyes, or shadows or photo? Over by three-ganged pot. R23 and next one to right "look" discolored? |
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DeathlyKnight |
Posted: Mon Jan 19, 2009 10:36 pm Post subject: |
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DeathlyKnight |
Posted: Mon Jan 19, 2009 10:33 pm Post subject: |
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here is two pics which should show that the rest of the board is just fine
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jts1957 |
Posted: Mon Jan 19, 2009 10:00 pm Post subject: |
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Remember your AC 12/13 volt winding is center-tapped. Usually so unit can get equal but opposite polarities of voltage (Plus & Minus 18 volts, for example).
Can't tell from your photo how D3, D4, D7 & D8 are connected, but suspect are either a 4-diode "Bridge" or Two full-wave for 12/13. Can't even tell how many or location numbers for diodes in burnt area.
If you can find the main filter electronlytics for each supply and connect a ohmmeter across each, there should not be any very low readings. |
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DeathlyKnight |
Posted: Mon Jan 19, 2009 9:38 pm Post subject: |
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ok thanks, i guess the previous owner tried to plug this in and get it going a few times because it feels like the wax around the copper has melted and thats whats causing it to short. thats why this gets very hot in in 20 sec...
I have a 15.2 volt transformer (thats what my multimeter reads out), is it possible for me to do a simple voltage divider (using resistors) and outputting 12 or 10volts to both inputs? |
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jts1957 |
Posted: Mon Jan 19, 2009 12:32 pm Post subject: |
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Can you say "ouch?"
I hope the top of board cleaned up nicely and the other side of board is O.K. I notice board says "BLU BLU YE GND YE," (BLU looks more like green to my eyes) "??10V" and "AC13V*2". So I assume center-tapped secondary (YE GND YE) can be 12 or 13 volts at .9 Amps (or more).
I'll take a look (Online and through my junk box) and post again if I find anything similar.
A "Wall Wart" is a transformer (sometimes with a simple rectifier/regulator built-in) that plugs directly into the AC wall outlet (usually blocking at least one other outlet, especially if you plug it into a multi-outlet power "strip"). It connects to the unit it powers via a wire (usually with a "barrel"-type plug & socket. |
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