Voice of Music Tri-o-matic Model 560A Issues

[dieseljeep]

Originally Posted by Captainclock

Hello Everyone, today a buddy of mine over at one of the local flea markets had purchased at auction a Voice Of Music Tri-O-Matic Consolette Model 560A and he let me work on it for him so he could eventually sell it in his shop, anyways when I took the unit apart I noticed it was full of Helicopters (maple tree seeds) and other kinds of yard debris which I'm not sure how they got in there except maybe a mouse tried nesting in the unit at some point and used the helicopters and other yard debris as nesting materials (I'm suspecting this record player may have been stored in a back yard shed or a barn.) anyways when I got the unit cleaned out with the vacuum and replaced a gassed 12AX7 and a shorted 5Y3GT tube I fired up the unit to see if it worked or not and sure enough every tube in the record player glowed except the 12AX7 tube so I'm guessing it has a loose wire or two on the 12AX7 socket that needs to be reattached for the heater or something (this unit has a power transformer so it was apparently a higher end unit and it has push-pull 6V6s in the amplifier stage which also tells me this must of been a higher end unit.) The unit is a Hi-Fi record player (mono but hi-fi mono as its got 3 speakers in the cabinet which would explain the push-pull 6V6s) anyways I was wondering what wires could of possibly came loose on the 12AX7 socket to cause it not to work anymore (the non-functioning 12AX7 explains why I had no audio through the record player when I tried to play a record on it.)
Any help would be appreciated.

-Levi

EDIT: I just noticed that there's a 220k Ohm Resistor and part of the tuner input wiring that seems to be disconnected from somewhere in the circuit but not sure where and the schematic in the bottom of the cabinet isn't of much help (it seems that its supposed to connect to pin 2 of the 12AX7 socket according to the schematic, but when I look at pin two of the 12AX7 socket it doesn't look like anything broke off of it) some help is needed here concerning the no audio output issue when trying to play a record and a non-glowing 12AX7 tube issue.

Thanks.

You have to check if there's AC voltage on the 12AX7 tube socket. Ordinarily, the pins 4&5 are tied together and the 9 is going to ground.
Is that the only 1st amp tube before the output tubes. One section would be the 1st amp and the other, the phase inverter.
As of now, don't worry about the 220K resistor, until you resolve the 12AX7 heater problem.

[Captainclock]

Originally Posted by dieseljeep

You have to check if there's AC voltage on the 12AX7 tube socket. Ordinarily, the pins 4&5 are tied together and the 9 is going to ground.
Is that the only 1st amp tube before the output tubes. One section would be the 1st amp and the other, the phase inverter.
As of now, don't worry about the 220K resistor, until you resolve the 12AX7 heater problem.

Well from what I can see of the amp and how its wired currently it doesn't look like there's any wires disconnected from the 12AX7 tube socket, and from what I can see of the schematic glued to the inside of the cabinet the 12AX7 is just a preamp/phase inverter tube in the circuit (its a push-pull 6V6 hi-fi mono amp so its not stereo so it only has one 12AX7 that is divided into to sections section 1 being the preamp stage for the phono pickup and the second section being the phase inverter stage for the audio amp stage for the push-pull 6V6s.

anyways like I said I'm really not sure as to what could be causing the 12AX7 to get no power because its got all of the connections to the socket intact from what I can see...

EDIT: Just noticed that the 12AX7 tube socket is suffering from Cadmium corrosion (where the Cadmium Plating they used to plate the contacts on the tube socket turns into a fine yellowish colored powder on the socket) I wonder if that Cadmium corrosion is what's causing the 12AX7 tube to not work right.