Have sound but low volume now. Phonograph

Kryptosmaster · by **Kryptosmaster** » Sat Aug 17, 2013 5:16 am

I have a sears Silvertone model 7056. Restoring it.

Ok, seems like one step forward two steps back every time I work on this

I do have some out of spec resistors but it was responding fine.

I had a broken needle but tested and found noise response from remnant of needle when rubbing finger across.
So I ordered a new needle. Rebuilt the motor. Rebuilt idler wheel, etc. all working great.
Replaced needle, assembled. Replaced the rectifier I blew out testing on another radio.
Fired it up. Still has hum but works great on radio. Switched to phono...needle on record...
NO SOUND!
The radio sound turns off when switched into phono mode and comes back on when phono is off as it should.
What happened? Nothing now when touching needle or terminals coming out of cartridge.
Arrrrgghhhh!

Not sure what to check. I tested the wires from the needle cartridge all the way to the 3 prong plug on the chassis and have continuity and no shorts.
All I've done is recapped the radio and can't recall if I did the needle rub before or after I did that.
Here's the diagram

http://www.nostalgiaair.org/PagesByModel/636/M0017636.pdf

MattTech · by **MattTech** » Sat Aug 17, 2013 4:42 pm

Crystal cartridges deteriorate after decades, due to aging.
You didn't mention replacing it.
It's mandatory.

Kryptosmaster · by **Kryptosmaster** » Sat Aug 17, 2013 5:40 pm

It's not the original cartridge. It's already been replaced.
I tested and had sound when rubbing my finger across the needle area.
Now I have nothing and also nothing when touching wires coming out of back of cartridge.

Kryptosmaster · by **Kryptosmaster** » Sat Aug 17, 2013 6:29 pm

Ok I fixed a wiring issue. I had electrolytic caps grounded wrong.
Now I have some sound from the phono but only with volume cranked all the way up. Radio works normally.

Thom · by **Thom** » Sun Aug 18, 2013 12:53 pm

If the replacement cart is not crystal it probably doesn't have the snot to drive the amp. Ceramics do not put out the high signal voltage of crystal carts. Given the age of that unit I am sure it had a crystal cartridge.

Record-changer · by **Record-changer** » Fri Sep 06, 2013 1:55 am

Right.

Crystal cartridges usually put out a volt or more at normal listening levels.

Ceramic cartridges put out about a tenth of a volt.

Magnetic cartridges usually put out about 3 thousandths of a volt.

A pre-amp stage is needed to boost the output to crystal levels.

Often a voltage divider is supplied inside the radio to lower the output of the crystal phono pickup to match the radio level. If this exists, the values of the resistors could be changed to produce the correct level.