Sl-7 Almost no volume - Muting Circuit?

[Mark E Smith's Dentist]

I've got an SL-7 which was working OK a few weeks ago, I'd had a problem with the armdrive belt but that's been replaced and it's tracking correctly.

But, I'm getting virtually no sound out of it. I need to turn the volume to max to get anything and it's very cut off at the top end. I'm wondering if there's a fault with the muting circuit not closing properly. The sound is equal on both channels and I got the same result with a different cartridge.

Any ideas? If it is the muting circuit at fault, how easy is it to repair?



JT

[fscl]

Generally on the linears, there's a couple of "clicks" after the "Start" button is pushed:

1. "Click" when the arm lift solenoid releases the arm down:
2. Very soft "click" when the muting circuit releases / cuts out.

What do you experience?..... Have to pull out the service manual to give some other pointers....

Fred

[fscl]

With a cartridge installed, try taking readings at the RCA plugs for both the L & R channels, the cartridge should measure as per this topic:

viewtopic.php?t=22754

IIRC, I was able to measure cartridge resistance at the RCA plugs when I was troubleshooting my SL-10 (to find why I had an intermittant channel cut-out) while the unit was off.....

Page 23 of the service manual shows the block diagram of the muting relay (lower left of the page) and paging directly down to 24 shows RL1 physically on the circuit board.

If you still do not get any sound, you will have to open up the SL-7 while off and try giving RL1 a couple of sharp taps. Hopefully this will free / unstick the relay.....

While you are in there, clean the connectors CN 302 & CN 303 with some contact cleaner.

Hopefully, this will square away the SL-7.

If not, make sure there is 12V energizing the coil and you can try replacing RL1:

http://www.encompassparts.com/products/?MSCSFDSC07-01

Or eliminate the relay and hard wire the phono input to the phono output on the circuit board, refer to page 24.

Good luck.

Fred and my bet is a sticking relay which you should be able to unstick with a "hit with a hammer"...... albeit, a light one.....

[Mark E Smith's Dentist]

Thanks for the suggestions, Fred. I had a visit from Richard @ Vantage Audio. He thought it was the relay, replaced it but we still had the same trouble.

He had a think about this, fitted a moving coil cart and tried it into my MC-only phono stage. It worked perfectly. So it turns out the MM phono stage built into my pre amp chose this week to fail. He tested the old relay and it works perfectly .

Oh well, the relay would have failed at some point and now there's a new one!

JT

[fscl]

snippage......
So it turns out the MM phono stage built into my pre amp chose this week to fail. He tested the old relay and it works perfectly .

Oh well, the relay would have failed at some point and now there's a new one!
JT

Nothing like vintage hifi...... you never know what / which / when is going to give up the ghost.....

Glad it's all sorted.

Fred and slowly coaxing a TC-252D back to life.... And I thought Technics old hardened grease was bad.....