Jukebox amplifier not coming on ? GP 160

[Gary Mattis]

View attachment 786863 View attachment 786864 I'mView attachment 786863 View attachment 786864 trying to repair a 1966 Rock-Ola GP 160, model 432, the latch relay stays on and the amplifier lights up and tubes are glowing but there is no sound, I can play records by pushing a selection pin on the drum, they play and stop and the record returns and the drum goes back to its park position. I cleaned the relay in the power supply and changed the one in the amplifier but neither one helped any to turn the sound on ? The service manual is not much help , It has no trouble shooting section in it at all and very little information that is of any use ! . Anyway maybe someone here has experience with Rock-Ola and can steer me in the right direction ? Usually I can figure this stuff out but this one is giving me some trouble, Any help is greatly appreciated. I have done some research and read about how they work and studied the SKU but no one has covered the no sound issue that I could find.

 

[century tek]

I'm not familiar with Rock-Ola but I read somewhere that the amp stays in stand by mode until a record is selected. Meaning that either the tubes stay lit at half voltage or they stay lit at full voltage with no B+.

If you have a meter, best would probably take some voltage measurements at the plates to see if they are getting any B+.

The other thing I read was that some juke box amps have a muting circuit which in your case, could be defective.

Can't see your attachments. It might be my computer but every time I click on any of your attachments, it says, "ERROR". Maybe try uploading pics directly to your thread. It's easy! Just click on the "Upload a File" button at the bottom of your post.

 

[Gary Mattis]

This thing is hard to work on, the relays are inside the amp and power supply and there is no where to set them for testing while things are hooked up, a real design nightmare for testing things. I have worked on Whirlitzer juke boxes before so I understand a little about the muting systems on them and how to make them free play without burning up solenoids. Let me try uploading the pictures again.

 

[Gary Mattis]

Dug into it deeper and found another hidden fuze to the amplifier blown, a rod was also disconnected on the turntable gears and there is rust all over the inside of the coin counter control box plus a bad spring, first a re-capp and repair the known issues , before anymore testing and troubleshooting is done. Shorted filter cap or a backwards polarity problem is my thought. I marked the power plugs, but who knows if someone else reversed one of them on something in there.

 

[s-petersen]

If the amp has RCA jacks on it you may be able to connect a source directly to the amp to bypass parts of the mech for troubleshooting

 

[Gary Mattis]

No RCA jacks on a Rock-Ola, I found the problem today, a blown power resistor and shorted green bean cap, amps up and running, new parts have been ordered for a amplifier rebuild. The short was on the plate secondary of the second power transformer, this amp has two PTs a main PT unit and a second plate one. The plates were not getting any power because of the shorted green bean cap and blown resistor. I learned a good lesson here , do not assume that anything is OK with the PT section just because all of your tubes light up ! I found the problem on the bench testing the amplifier alone , not while it was in the record player. Someone had removed a hidden fuse to mask over the PT short problem. People do all kinds of stuff to sell what they consider defective electronics without saying to you - it has a short somewhere. They say stuff like it doesn't work at all , it does nothing ! . What they say is true also because it does nothing if you remove the fuse holder or relay or wire in a hidden location. This is not the first time I ran across something like this. Now north to the selection and latch solenoid problems and south to the coin counter mechanism problems , got my hands full on this one ! , but the record player and amplifier are both working now and 2 out of 3 ain't that bad for the first week. Juke boxes can certainly test all of your electrical and mechanical abilities, takes a lot of patience and time with these things.

 

[Gary Mattis]

Now the hard part finding 2 of the old style 1/4 turn fuse caps for the one I misplaced and the one they took out before I got it. Now I have 2 other amps without them because I just robbed peter to pay Paul. I can get them new if I have to for about 20 or 30 dollars, the new cheap fuse holders are smaller and the caps screw into them , Be much easier if I can find 2 of the old 1/4 turn fuse caps.

 

[s-petersen]

I have been rebuilding Seeburg parts for a friend, amps, and selection units.I am to go to his house for a day,sometime and get his house in order so to speak.

 

[Gary Mattis]

I have been rebuilding Seeburg parts for a friend, amps, and selection units.I am to go to his house for a day,sometime and get his house in order so to speak.

It may be a real mess when you get there, unless it was already working good before the repairs !

 

[s-petersen]

I've been pretty deep in Seeburgs before,The ones he has have been dormant for many years, likely they have frozen mechs by now