SX-1500TD Rebuild help

Hmm,they are wired in with the coupling caps. But what is the purpose for doubling the coupling caps? Can someone without the extra caps find out what value the coupling caps are in your unit?
SM calls for just the onboard 1000uf 50v caps.
 
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pull the outputs and try dbt again .
or just thought its easier to pull each amp board fuse in turn and dbt again . might save pulling all output transistors .
 
OK,pulled fuses and DBT'd. It has issues somewhere in the left channel of the output board. Would it be safe to remove both fuses from the output board and try out the preamp? Summary of what I did to output board; recaped,removed and tested all transistors,replaced two output transistors (left channel), and redid the hacked up wireing.
 
I would like to mention about the grounding the amp needs. Without it (them) voltage will build up and cause alot of heat. Check over the board and make sure all the connections are secure both on the board and chassis wire connections.
 
Ok,one output transistor on the left side of the board is getting low voltage,going to trace that then see where that puts me.
 
Flickering bulb on DBT,any ideas? Not on/off, more bright/not as bright. Played with bias and replaced a transistor then got this.
 
what did you set the bias to ? have you got a load connected to speaker terminals ?
what voltages at output transistor cases ? these are collector voltages by the way .
and what transistor did you replace ? and with what ?
and what wattage lamp and line voltage ?
 
minimum under the assumption of high bias.No.
Ill have to check.
2SA497 with KSC2690AYS
"100w equivalent" ("72 actual watts used!") I guess 120v? Haven't checked it recently. Receiver is set to 130v

Whatever is going on,its in the left channel of the output board.
 
righto you replaced a PNP transistor with an NPN one ..obviously this wont work .

2sa 497 .....PNP
80V, 0,8A, 0,6W, 70MHz
2sa497 is obsolete so you will need an equivalent .
closest i can find up to now is 2N4036 . there will be others .maybe start a new thread to ask .
 
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Really? Somewhere on this site KSC2690AYS is listed as an equivalent.

Well crap,I'll swap the other transistor back in and see what that does. It wasn't shorted i was just part swapping.
 
Echowars was referring to the push pull driver pair. You missed the concept.
 
i am wondering why they used 70mhz transistors ? not too sure about putting a 1mhz one in there ?
anyway if original one is ok it is best to use it .
its no use swapping parts for the sake of it .it needs properly troubleshooting . this is why i ask for the collector voltages of the outputs first . then we can move backwards through the circuit looking at the base and emitter voltages .
 
I know part swapping isnt the best,but I was placed on a time crunch. I copy pasted from the thread to mouser and got that. OK,I'll swap the old one back in then get collector voltage.

Edit: Ok, I see where I got the numbers swapped from the thread, I have those as well but somehow flipped the numbers.
 
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14.7 & 17.9

Meter set on 200 vdc,stereo on dim bulb, back on old transistor,black lead of meter to chassis ground,positive to OT case (collector).
 
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