Project/One Solid State Stereo Receiver help.

Ok, here's the thing. Even though you are reading DC voltage on the speaker connectors it is (phantom) voltage. Because of the cap in series there is not a direct connection to the DC line voltage on the out line. So there is no DC current at the speaker connector which is why as soon as you connect something to it all is gone. I would think those resistors on the relay board should take care of this phantom voltage but your still get a reading. This is why i asked if you had another volt meter to test with because some meters will act different then others. So altho I am not thrilled with what your meter is telling us it appears after all your test that it should be ok to run the amp like this as long as the sound output is good. Again, this could be just your meters but there is surely no DC current there because of those caps. Maybe hook it all up and play something for a while and see if the speaker coils get hot. Just not to much bass as this may heat them up somewhat normally.

Ok, replaced the original filter cap. left the resistor and cap to GND connected . It has been playing for about 30 minutes and the amps are not even getting warm?!?! Is that suppose to be ? I figured they'd get at least a little warm. about 85-88°

Also i hardly have to raise volume for it to blast and it distorts obviously from being over driven. Volume is pretty clear only at about 8 O'clock and its minimum is between 6 and 7 . At 9 O'clock its pretty loud but still clear.

I think this time its the preamp section . This is with auxiliary and the phono sections and tuner.

So I ask, how important is the bias voltage for proper sound quality, I assume very.

Do you think maybe 5 mV's is too little and maybe bump it up ? How would I test this?

I read this Article and found it interesting. Tomorrow I may try to raise bias. How can I figure out the bias of these transistors with the data we have from the data sheets, or is that not possible?


Athanasios.

I figured out why it didn't sound right and had distortion. Something in the pre amp section. 

I decided to use my iPhone as the preamp . No distortion at all and the amps in here sound really good even with the iPhones crappy pre amp.

So now I am going to take that out and check transistors and caps etc.

ugh more work but also more learning!!!! I love learning and You Mac are a great teacher. Thanks so far

So now off to start removing the preamp board. And to do that the whole from needs to come off to get to it.

Thing I hate about pre amp boards is all the parts connected to them.

Any suggestions as to what parts to check first? Probably the transistors correct? With the volume up at higher volumes with no input you could hear two things.
Hum that would get louder as volume increased and the same with just scratchy noise or distortion.


Athanasios

Yes jumpers removed , and it is a two prong plug.

nashou

Yes, i am going to go through that as well. Thought I did clean them well as adjusting them while playing amp I heard no scratchy doing than.

But I did on the Tape monitor switches but not too bad.

I think what I removed is more of the tone board. have to look for other boards that might be the pre amp, or maybe this is it?

one part on the board is a


Sanyo LD3120
Integrated Circuit
9 Pin ZIP
audio preamplifier with equalizer
Replaces ECG1019

What is this part for? Is is then the preamp board ?