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  #1  
Old 08-16-2015, 06:26 PM
Captainclock Captainclock is offline
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Voice of Music Tri-o-matic Model 560A Issues

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.

Last edited by Captainclock; 08-16-2015 at 08:15 PM.
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Old 08-16-2015, 09:10 PM
dieseljeep dieseljeep is offline
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Originally Posted by Captainclock View Post
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.
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Old 08-16-2015, 10:10 PM
Captainclock Captainclock is offline
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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.

Last edited by Captainclock; 08-16-2015 at 10:36 PM.
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Old 08-17-2015, 12:47 PM
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Clean the socket and tube pins, and if that don't work check the voltage at the heater terminals of the socket (wires can go open and cold solder joints can stop the flow of current so just because it is connected don't assume the connection is infallible).
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Old 08-17-2015, 08:12 PM
Captainclock Captainclock is offline
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Clean the socket and tube pins, and if that don't work check the voltage at the heater terminals of the socket (wires can go open and cold solder joints can stop the flow of current so just because it is connected don't assume the connection is infallible).
Ok, so if I'm checking the voltages at the heater pins (pins 4 & 5) How would I go about doing that? Should I have it powered on when I do this or should it be off?

Also hw should I go about cleaning the socket? I don't really have anything small enough to get down into those socket holes, and I don't have any de-oxit on me right now.
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Old 08-17-2015, 08:26 PM
dieseljeep dieseljeep is offline
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Ok, so if I'm checking the voltages at the heater pins (pins 4 & 5) How would I go about doing that? Should I have it powered on when I do this or should it be off?

Also hw should I go about cleaning the socket? I don't really have anything small enough to get down into those socket holes, and I don't have any de-oxit on me right now.
Go to an auto supply store and get a can of brake cleaner. Be careful and use it in a well ventilated area, as it's some nasty stuff. Also, be careful around plastics, as it will cloud or discolor them.
Checking voltages, you have to have the amplifier powered on. If you want to be sure that there wont be further damage to other components, remove the rectifier tube, probably a 5Y3.
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Old 08-17-2015, 08:33 PM
Captainclock Captainclock is offline
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Go to an auto supply store and get a can of brake cleaner. Be careful and use it in a well ventilated area, as it's some nasty stuff. Also, be careful around plastics, as it will cloud or discolor them.
Checking voltages, you have to have the amplifier powered on. If you want to be sure that there wont be further damage to other components, remove the rectifier tube, probably a 5Y3.
Yes the Rectifier is a 5Y3GT tube, but anyways I measured the voltage on the heaters for the 12AX7 tube and it measures at around 104 volts which I'm assuming is what its supposed to measure (I don't have a service manual for this unit so I don't know what the voltage is supposed to be exactly) and all of the other tubes glow like they're supposed to its just the 12AX7 that doesn't glow for some reason or another (unless the shorted 5Y3 that was in this thing originally took out the 12 Volt winding in the power transformer...)
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Old 08-17-2015, 08:50 PM
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If you are seeing 104 volts on the fimamant pins...it is some sort of bias applied to the line. That is NOT the filamant voltage...it should be either 6.3 or 12.6 volts AC_-NOT DC..ACROSS the filamant....NOT to ground.

I had to help someone working on a commercial clothes drier today...the heater would not come on. he had measured 120 volts AC--to GROUND on EACH heater pin...but he did NOT realize...you have to measure ACROSS BOTH PINS..to get the right reading of the supply to the element !! He had chenged nearly EVERYTHING...the element..thermostats, limits, even motor and centrifiigual switch....STILL no heat. It took me maybe SEVEN minutes...to find an open switch on the timer. Measuring ACROSS the element reveeled NO voltage... and when the timer switch was bypssed FULL heat began to work fine !! he just said "I have trouble reading diagrams" and i let him know...I have known how to read diagrams since about TEN years old !! This guy has worke don this stuff since I was a CHILD...not really SURE HOW one can effectively repair things like this... WITHOUT knowing how to read a SIMPLE diagram...for a MECHANICALLY controlled clothes drier?

SO..my point is measure ACROSS BOTH pins --to see if you are getting filament voltage...and likely it will be AC. It iS possible that it is a seperate DC supply....but nOT likely on that cute little amp. I have a couple of those nicely-built players myself. One was a goodwill purchase for a long time ago...the other I think I got at an auction for nearly nothing some years back...
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Old 08-17-2015, 09:02 PM
Captainclock Captainclock is offline
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If you are seeing 104 volts on the fimamant pins...it is some sort of bias applied to the line. That is NOT the filamant voltage...it should be either 6.3 or 12.6 volts AC_-NOT DC..ACROSS the filamant....NOT to ground.

I had to help someone working on a commercial clothes drier today...the heater would not come on. he had measured 120 volts AC--to GROUND on EACH heater pin...but he did NOT realize...you have to measure ACROSS BOTH PINS..to get the right reading of the supply to the element !! He had chenged nearly EVERYTHING...the element..thermostats, limits, even motor and centrifiigual switch....STILL no heat. It took me maybe SEVEN minutes...to find an open switch on the timer. Measuring ACROSS the element reveeled NO voltage... and when the timer switch was bypssed FULL heat began to work fine !! he just said "I have trouble reading diagrams" and i let him know...I have known how to read diagrams since about TEN years old !! This guy has worke don this stuff since I was a CHILD...not really SURE HOW one can effectively repair things like this... WITHOUT knowing how to read a SIMPLE diagram...for a MECHANICALLY controlled clothes drier?

SO..my point is measure ACROSS BOTH pins --to see if you are getting filament voltage...and likely it will be AC. It iS possible that it is a seperate DC supply....but nOT likely on that cute little amp. I have a couple of those nicely-built players myself. One was a goodwill purchase for a long time ago...the other I think I got at an auction for nearly nothing some years back...
Well they have both heater pins (pins 4 & 5) tied together (the terminals are bent together and soldered together with the heather wire soldered to that point) and then pin 9 (which apparently is a heater pin as well) is connected to ground so I didn't bother measuring that one. So I take it that I need to measure between both pins 4 & 5 and pin 9 to get the heater voltage reading?

Well measured across pins 4 & 5 and pin number 9, and I only got a little over 6 Volts AC instead of 12 Volts AC, So what does that indicate?

Last edited by Captainclock; 08-17-2015 at 09:05 PM.
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Old 08-17-2015, 09:24 PM
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Well...if you are getting about 6 volts AC between the pair of tied pins and the other one-- pin 9 ...BUT the tube STILL will not light..and you are SURE this tube is good (likely it IS)..I would DEFINITELY say you have socket issues !!
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Old 08-17-2015, 09:32 PM
Captainclock Captainclock is offline
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Well...if you are getting about 6 volts AC between the pair of tied pins and the other one-- pin 9 ...BUT the tube STILL will not light..and you are SURE this tube is good (likely it IS)..I would DEFINITELY say you have socket issues !!
well it would make sense like I said the tube socket itself appears to have a bad case of Cadmium Corrosion and I don't know how that would affect the tube socket itself and its ability to allow it to make contact between the socket and the tube. and yes the tube is a known good tube, in fact its a NOS Tung-Sol 12AX7 tube that I had found in an old tube caddy someone gave me that was full of NOS tubes of various brands.

And how could a 12 volt tube still work even with only 6 Volts on the heater pins? wouldn't that cause the tube not to glow or barely glow?
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Old 08-17-2015, 09:55 PM
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The 12AX7 tube is one of those that have a dual-filamant-- tied together-- with a tap in the center. If one ties the other pins at one end and then puts the other potential at the tap--you CAN use it on 6.3 volts--as is done a LOT. That is why those 2 pins are tied.
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Old 08-17-2015, 10:17 PM
Captainclock Captainclock is offline
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The 12AX7 tube is one of those that have a dual-filamant-- tied together-- with a tap in the center. If one ties the other pins at one end and then puts the other potential at the tap--you CAN use it on 6.3 volts--as is done a LOT. That is why those 2 pins are tied.
Ok, so then how would I fix the socket issue? I don't have any extra sockets laying around to replace it with, and I also don't have any way to clean the cadmium corrosion off of the socket which I have a feeling that the cadmium corrosion has something to do with why the tube isn't working.
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Old 08-17-2015, 10:21 PM
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Perhaps you could get a dental pick or such....and use it to scrape the contacts on each socket terminal where it hits the tube pins, to "clean them". It is VERY likely....this is the cause of no filamant on the 12AX7 tube.
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Old 08-17-2015, 10:25 PM
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rca2000 rca2000 is offline
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BTW...If this is really CADMIUM...you do NOT want to BREATHE the dust from it. ? I am not an "alarmist" by ANY stretch of the imagination"..BUT SOME things are VERY dangerous...and CADMIUM is at the TOP of that list !! I would say WORSE to breathe than ASBESTOS !!

use a RESPIRATOR or at least a good MASK over you nose and mouth...BEFORE yo mess much with those socket pins !! And try to have a LOT of airflow around you--to rtemove any build-up of cadmium diust in the air !!
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