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Noresco NC-321/Dual1210 Combo

 

New member
Username: Cptnelectron

Post Number: 1
Registered: May-17
low sound from speakers. Amp is ok, problem appears to be in preamp. I cannot find a schematic for this unit. Any suggestions with help or where to go for help would be greatly appreciated.
 

Platinum Member
Username: Jan_b_vigne

Dallas, TX

Post Number: 18412
Registered: May-04
.

Looks like you're dealing with a 40 or so year old receiver. How has it been stored or used over those years? If it has been in storage, are you certain it was operational when it was placed in storage?
 

New member
Username: Cptnelectron

Post Number: 2
Registered: May-17
Yes it was operational then, I'm wondering if it could be the carbon tracks have worn away over time on the volume and tone controls?
 

Platinum Member
Username: Jan_b_vigne

Dallas, TX

Post Number: 18413
Registered: May-04
.

Operational "then" doesn't mean it should be operational now. That's why I asked about storage, which you didn't answer.

Parts age and they tend to age more dramatically when they have not been used. Carbon tracks are possible though, again, if they weren't on the wipers when it was placed in storage, there's little chance they have developed over time. Besides, noise is more commonly associated with such buildup and it will typically be intermittent as you turn the control.

My best guess would be the storage caps in the power supply have dried out, failed and are not providing sufficient Voltage and Amperage to the power circuits. A few coupling caps might also need replacement. If this might be the case, that could also take out a few resistors with it.

Could also be just a sticking relay used for speaker protection if this amp has one. Relays went the way of the dodo decades ago due to their poor reliability.

This isn't the sort of job you should tackle yourself, particularly if you have no schematic to indicate proper Voltage measurements.

Find a shop that is willing to take on a little known name from the mid 20th c/ and let them give you an estimate for repairs. Typically, unless the component was considered to be rather high end at the time, it isn't worth trying to bring back any component with iffy parts. You may sink $$$ into the repair and still have an amplifier that craps out from another part going South in just a few weeks.

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New member
Username: Cptnelectron

Post Number: 3
Registered: May-17
I did not answer about storage as it belongs to a friend although it is in great condition appearance wise, very clean.
As stated all caps are ok by test and labeled voltage, all semiconductors as well.
I connected a outside input to the amp where the pre amp connects and sound is loud but because it is after the preamp and controls there is no use of the controls allowing for my question of the question about carbon tracks. I also tested all resistors on both boards and they are well within tolerance.
 

Platinum Member
Username: Jan_b_vigne

Dallas, TX

Post Number: 18414
Registered: May-04
.

You pulled all these components out of circuit to individually test them?

And the pre amp circuit tested OK? How do you know that if you have no schematic? What in circuit values did you apply?

You have me confused. If you have the equipment and the know how to test these items, how can you not test the tracking on the controls?


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New member
Username: Cptnelectron

Post Number: 4
Registered: May-17
I am glad that your confused as well. The actual value of the controls are not noted on the control as it typically is, and I am wondering if there off would that reduce the signal that much. Obviously my next step could be to remove each control and jumper the circuit to prove this.I was hoping someone out there with some more experience with this situation might of had a quicker answer. Thankyou
 

New member
Username: Cptnelectron

Post Number: 5
Registered: May-17
I now have the stereo working quite well, changed tone arm wires,replaced cartridge and cleaned all switches and contact locations especially where there is physical pressure used to transfer signals and supply. I found a piece of wire inside the balance control which caused much of the loss of signal and volume. Thanks
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