100G Audio Problem

[scooter465]

Hi
I have a intermittent problem with my 100G.
I occasionally loose output when a selection is made.
Record selects and plays no sound just sound of needle on record. If I power unit on and off output will come
Back. I have and read manual it list serveral reasons for this. I thought it might be a problem with the mute circuit. So I cleaned contacts associated with the mute circuit no change.
So I was hoping someone in the groupe with many years experience with these units could suggest the likely cause of this and a fix.
Thanks in advance for your help.
Bob Haag

[Ron Rich]

Hi Bob,
This won't be in the mute circuit, as you found out-- look at the 5U4 the next time this happens--is it lit or not ??
Ron Rich

[scooter465]

Thanks for the reply will do.

[scooter465]

Hi Ron
I had to Waite for box to act up.
Tube 5U4GB was lit while I had no audio.
Tube is off till a selection is made then lights up.
Any ideas it’s never easy.
Should I try replacing tube and see if it works.
Thanks for your help
Bob Haag

[Ron Rich]

Hi Bob,
It's probably NOT that tube, if lit without audio. I would suspect the first tube in the string, and also the speaker plug. With the power off, remove both. Spray the PINS (not the sockets !) with Deoxit-5--install the plug/tube with the pins wet- remove, and reinstall several times till dry--try playing it now-- You may also, the next time it fails--wiggle all 4 of the switches--one or more may be failing to make good contact (Deoxit works well- here too !). Ron Rich

[scooter465]

Hi Ron
Will try what you say but what 4 switches are you referring to pardon my ignorance.
Bob Haag

[scooter465]

Sorry Ron
Looked at print I guess you mean bass and treble control switches and AVC control switch and speaker volume switch.

[robnyc]

Bob, if you've determined that none of the switches or volume control are at fault consider looking at a few other areas;

1) I would not rule out the mute ckt. I had a similar problem in a VL mech that had well over a million plays. Slight wear in the cam or follower resulted in the lower mute blades not thoroughly opening during play. My usual check is to run the blunt end of a felt tip pen casing across the blades and also, slightly jog them with it. Do this on the upper blades as well.

2) Though i doubt it applies here, a break in the cable is possible (I've had several). First try wiggling it during play and follow up with a continuity test across the RCA plug male as the mech scans.

3) Tap/slightly wiggle the tubes when sound fails. Slight corrosion on the sockets and pins can easily cause this problem.

4) As above, check RVC and speaker sockets.

Has the amp been rebuilt? Do you have spare tubes to sub?

RobNYC

[scooter465]

Thanks for your reply
Will check switches and tubes and speaker socket.
Also mute cam contacts.
Jukebox is a survivor I have owned sence the 70s.
Amp is to my knowledge is original. Replaced all tubes when I got it
In the 70s. I did a lot of long needed maintenance recently.
Fixed a lot of problems. This is last item to knock off list.

[Ron Rich]

Rob,
Hint: get a very bright white, piece of paper, and place it under/behind contacts that you need to check for gap-- You'll be surprised at how easy that makes it to see the gap size (specially as you age--gaps seem to get smaller !!--lol---
Ron Rich

[scooter465]

You are so right LOL

[scooter465]

HinRon
A quick update cleaned all tube scokets and switches also all plugs going to amp. Wiggled speaker wires and and tubes .No change so I guess I will go back and look at mute system.
Question if when unit has no output what would happened if I unplugged the mute plug from amp? Would audio come on and that would tell me mute system is at fault..
Would doing this cause any damage?
Thanks for you help.
Bob H

[Ron Rich]

Bob,
No problem to either un-plug it, or, just leave it un-plugged ( You will hear all sorta pops--but no damage will happen).
Ron Rich

[Ron Rich]

Bob,
How, didja "clean" things--didja use Deoxit, as I suggested above ?
Ron Rich

[scooter465]

Yes cleaned tube sockets as you said sprayed tube contacts and installed and removed tubes till contacts dry.
I also did same with all plugs going to amp.
Also sprayed all switches on amp and worked them through full range settings. No change I guess I will revisit the mute system . And ck contacts using your paper trick.
And try unplugging mute plug next time it acts up.
Thanks for your advice this old box is like a member of the family. I try and keep it going. I just found And checked counter 380 thousand plays and it does still work is that a lot?
Bob H