C98 and the zenerare soldered to the same points. If either one measures shorted, then it has to be removed to test for sure. That is why I suggested just taking all three of those parts off the board and checking each one for shorted condition on its own. And checking where the parts were to see if the board itself is shorted, rather thanthe parts. If you feel the cap is shorted, then re,move it and measure it while out of the board.
The value of that cap is not critical. If you have no 35v caps of the right value, a 50v one will do fine. And if you have no 220uf, a 100uf will work well enough.
And I am sorry, just one TDA7293 module on this model. I am used to discussing the AVT150 wwhich has two of them in parallel.
The value of that cap is not critical. If you have no 35v caps of the right value, a 50v one will do fine. And if you have no 220uf, a 100uf will work well enough.
And I am sorry, just one TDA7293 module on this model. I am used to discussing the AVT150 wwhich has two of them in parallel.
ok got in the caps replaced c98 and still i got nothing. I started from scratch pulled zener c98 and tr2 out tested zener it was good .621 put that in I tested cap it was good I put that in tested .621 measured at the transistor tr2 isnt shorting but I did not put it back in I left it out remeasured the zener it working proper now the cap as well so tr2 I am going to replace since I have it out and it the only thing left to replace only thing is I amhaving trouble with this little guy I am researching stuff about transistors but a link to one to buy would be great since at this time I am currently not having any luck for some reason.
ok i tested it and its my flaw it has a diode check of 0.050 and is shorted of the stuff I have read it says .621 like everything else should be so I will go with what I have now checked and learned still if anyone can find a value or a replacement it is labor day weekend and radioshack is the only thing open tuesday I will order a new one online but I have to find one first.
ok heero1 as I have learned there are only a few things in this small circuit that need to be replaced. The circuit is called a standby circuit remember to never check anything with the power plugged into the amp. first remover the main board to help check the values as I learned it was easier. next locate the zener the cap and transistor c98 c76 and d14 d14 being the zener diode. next put the meter on diode setting and check one side to the chassis and the other to one side of the zener one side will read nothing as the other will read 400-600 if you dont have that value check all over the main board for anything burned just to be safe. next just poke around on the cap and transistor you are looking for that value. if I have to I will go ahead and get busy on making a quick vid for youtube on exactly what i did and where everything is located for everyone to see I was going to do this anyways.
ok Ram, these are the measures: Multimeter in diode setting
D14: red(anode) - black (chassis) = 0
red (catode) - balck (chassis) = 0
TR2: red(base) - blck(collector) = 0,068..
red (base) - blck (emitter) = 0,68..
red (emitter) - blck(collector)= 0
D17: red (catode) - blck( chassis) = 0,68...
red(anode) - black (chassis) = 0
OK, it seems that D14 it is damaged...i could not get any lecture. The TR2 and the D17 seems fine.
I'm thinking in remove the D14. In other hand, i'm not pretty sure how to check the C98 and C76.
D14: red(anode) - black (chassis) = 0
red (catode) - balck (chassis) = 0
TR2: red(base) - blck(collector) = 0,068..
red (base) - blck (emitter) = 0,68..
red (emitter) - blck(collector)= 0
D17: red (catode) - blck( chassis) = 0,68...
red(anode) - black (chassis) = 0
OK, it seems that D14 it is damaged...i could not get any lecture. The TR2 and the D17 seems fine.
I'm thinking in remove the D14. In other hand, i'm not pretty sure how to check the C98 and C76.
Look at the schematic, the three parts are in parallel. Normally a few volts lives there, but when the power amp IC fails, sometimes it can short that standby line to one of the high voltage rails, and destroy parts. If one of the parts shorts, then they will all measure like they are shorted when they are on the circuit board.
If you think the diode is shorted, then unsolder one end and lift it from the board, nit test it by itself. If it is shorted, replace it with another zener. Before installing a new one or re-installing the old one, measure where it used to be and see if that point is still shorted to ground. If it is, then the cap or transistor is shorted.
Look at TR2, You got readings from Base to EMitter, and Base to COllector that look more or less normal. But the EMitter and COllector appear to be shorted together. That could actually be the case, or it could be because the parallel zener diode is shorted. Just to demonstrat, take a good transistor from your drawer and test it with your meter. Base to emitter and base to collector will show that half a volt or so reading. but the emitter to collector should show open, not zero.
If the caps do not test like they are shorted, they are probably fine.
In my experience as a Marshall repair shop, I find those three parts fail in roughly equal amounts. Probably the zener most often, but any of them could be at fault on any repair.
If you think the diode is shorted, then unsolder one end and lift it from the board, nit test it by itself. If it is shorted, replace it with another zener. Before installing a new one or re-installing the old one, measure where it used to be and see if that point is still shorted to ground. If it is, then the cap or transistor is shorted.
Look at TR2, You got readings from Base to EMitter, and Base to COllector that look more or less normal. But the EMitter and COllector appear to be shorted together. That could actually be the case, or it could be because the parallel zener diode is shorted. Just to demonstrat, take a good transistor from your drawer and test it with your meter. Base to emitter and base to collector will show that half a volt or so reading. but the emitter to collector should show open, not zero.
If the caps do not test like they are shorted, they are probably fine.
In my experience as a Marshall repair shop, I find those three parts fail in roughly equal amounts. Probably the zener most often, but any of them could be at fault on any repair.
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