Help please

[ZippyTs]

No noise from center pin on front input. Do you want me to check the IC pins also?

also the background hum is gone/diminished

 

[Perry Babin]

Do all of the outputs produce clean output now?

 

[ZippyTs]

I get clean sound from only the left channles on the output, and no sound from right or sub

 

[Perry Babin]

Swap the RCAs at the input. Does that produce output through the right channels?

 

[ZippyTs]

nope all rights and sub still no go

 

[Perry Babin]

Have you tried moving all of the controls/switches through their entire range to see if any of the dead channels begin to function?

 

[ZippyTs]

did that now, and sorry had it backwards Left is not working, right is working. Sub works now, had it turned down too low and could not hear it

 

[ZippyTs]

new revelation..
if i use front input and turn on front i get both left and right high/mid. plug into rear input i get right only high/mid, and plug into sub input with sub on i get left and right.
If i use just the rear input to feed all outputs (front and sub off) I only get right channel for all outputs

 

[Perry Babin]

With RCA inputs plugged into the front inputs, which pins (1 or 7) on the op-amps (!C101, 102...) on the input board have audio?

 

[Perry Babin]

Instead of front inputs (in post 49), use the rear inputs and post what you find.

 

[ZippyTs]

on 101 and 102 sound on pin 7 no sound on pin 1
104 no sound on both

with rear:
101 pin one sound pin 7 no sound, 102 no sound both pins, 104 no sound both pins

 

[Perry Babin]

Can you move IC104 to the position of IC103?

If you do that and set the sub input to off, the sub should work and the front/rear should work properly. You'll remove the ground jumper that you installed.

If it does work properly, all that you'll need to replace IC104.

 

[ZippyTs]

I am not able to get 104 to release from the pads. Looks like there is some red glue stuff under it preventing me to lift it

What is the part number or place I need to order these from? and I will get a few of them if they are cheep

looks like 4570 on the ic103 damn things so small its hard to read

 

[Perry Babin]

UPC4570 is the original part number.
B&D Enterprises: Part #UPC4570G2-A

 

[ZippyTs]

Well with that site I need to order $15 min, and all i need is $4 in parts lol
anywhere else I could get them?

There is a local shop here that carry NTE stuff will an NTE equivalent work?

 

[Perry Babin]

I don't generally like NTE replacement parts but this part isn't likely critical. See if they have a TL072. That's a reasonably good replacement for most applications. This is the part at Mouser:
511-TL072CD

 

[ZippyTs]

Thanks perry I will check around town tomorrow and see if any of the local boys have them. I want instant gratification!! lol


Also now that I am thinking about it I bet if we where to send p1 and p7 on ic103 pads to ground I bet both left and right would have worked

 

[Perry Babin]

No. The left rear channel passes through the op-amp that has pin 7 as the output. The left rear channel isn't getting through because the op-amp is out of the circuit. You could probably short pin 5 to pin 7 and get audio to pass through that channel but that won't do much. The op-amp needs to be replaced to confirm that that the problem was the op-amp and not any of the components connected to the op-amp channel (pins , 2 and 3) that's used as the ground buffer.

 

[ZippyTs]

Well Perry your the man, all channels now work A+ nice and clean all the way to clipping.
Just used 2 TL072CPJP, and some enamel wire I had.

Thank you as always for your help on this one!
Zippy