Help with sta2100d amp

[Larryhere40]

I i’ve been working on this amp for a long time. I replaced all the transistors, capacitors, and the bad resistors I found, and any diodes that appeared bad. I tested all the parts I put in. They were new and I checked them. I have put the amp back in a few times and ended up shorting out somewhere. So that’s why I don’t wanna install it till I make sure there’s no shorts. My question is resistor 513 is coming out out of spec and I already checked the resistor I replaced it with and it’s still coming out off. Any ideas on what would be causing the 513 resistor to be off? I get a chance to work on it once in a while, so please be patient. I’m 70 and getting tired of trying to figure out this one issue. I’ll send some pictures so it might help someone who knows more than me. Thanks.

 

[Larryhere40]

I i’ve been working on this amp for a long time. I replaced all the transistors, capacitors, and the bad resistors I found, and any diodes that appeared bad. I tested all the parts I put in. They were new and I checked them. I have put the amp back in a few times and ended up shorting out somewhere. So that’s why I don’t wanna install it till I make sure there’s no shorts. My question is resistor 513 is coming out out of spec and I already checked the resistor I replaced it with and it’s still coming out off. Any ideas on what would be causing the 513 resistor to be off? I get a chance to work on it once in a while, so please be patient. I’m 70 and getting tired of trying to figure out this one issue. I’ll send some pictures so it might help someone who knows more than me. Thanks.

Electrolytic capacitors

 

[stillspin'n]

Do you have a dual rail power supply? Or two you could strap together to get something like +/- 20v to get the amp up and running. Looks like R513 supplies negative voltage to the preamp section. My first guess was that C507 was in backwards, but looks correct in the picture. Maybe check the voltage drop across R513 it to see how much current is being passed through it.

 

[sanjib]

According to the service manual, R513 is 68 ohm, 1W resistor, but from your picture, it looks like you replaced it with 68 kohm. I may be wrong, just check the value of the resistor you replaced.

 

[Larryhere40]

Do you have a dual rail power supply? Or two you could strap together to get something like +/- 20v to get the amp up and running. Looks like R513 supplies negative voltage to the preamp section. My first guess was that C507 was in backwards, but looks correct in the picture. Maybe check the voltage drop across R513 it to see how much current is being passed through it.

Thanks, any help is greatly appreciated! I did check c507 and it is in correct, I have been doing a comparison checks with the other channel, but it’s not as easy as it would seem, at least for me, with all the parallel circuits! As an amateur, am better at spotting burnt or shorted parts, lol! I wish there was someone nearby that was able to teach me. I took correspondence courses years ago, only get so far, then lost! Thanks for the help and I didn’t mean to chew your ear too much, ha ha

 

[Larryhere40]

According to the service manual, R513 is 68 ohm, 1W resistor, but from your picture, it looks like you replaced it with 68 kohm. I may be wrong, just check the value of the resistor you replaced.

That’s a possibility for me!!! I get confused easily! I will check it out today, thanks so much, this is an awesome site! Thanks again

 

[Larryhere40]

According to the service manual, R513 is 68 ohm, 1W resistor, but from your picture, it looks like you replaced it with 68 kohm. I may be wrong, just check the value of the resistor you replaced.

I can’t thank you enough!!! You were right, pulled it from a bag of 68 ohm ones from nte! I picked the one different one from 50 or so, did check it with the meter and didn’t see the tiny k! I wish that would happen again with a lottery ticket!!! Thanks for your eagle eye!