Magnovox 2st257

[Twalt]

I did have to repair one blade coming out of my cartridge, it broke off so I soldered it back on.

 

[FlaCharlie]

Will a bad cartridge only allow sound from one channel? I have good sound on one channel, but very muted on the other. If I hook up both green speaker wires on the loud terminal, all the speakers sound good. But I think I only have one channel working.

Try it with the AM-FM tuner or some other source that has a volume control, like your phone.

 

[gadget73]

There is nothing special about carbon comp. I use a lot of carbon film and metal film. As my stock runs low on carbon film I have been replacing them with metal film but both are much less noisy. I also wouldn't go changing them immediately unless they are off value or bad until you have verified the amp is working correctly.

 

[Twalt]

Thank you very much, I will keep that in mind for future projects.

 

[Twalt]

I got this console back together, changed all the caps, and I have no sound on channel 2. If I plug in the channel 1 speakers, the other speakers work fine. No ,sound on either FM or the tt, only on one side. All my wires seem plugged in correctly according to the schematic inside the cabinet. Any help as to what I should be looking at from here. I'm lossed!

 

[gadget73]

what happens if you flip the two RCA cables coming from the tuner? Sound from the same side, or does it move to the other side?

 

[Twalt]

The sound is on the same side, the right side if you are facing the console. This is the channel 1 out put on the amp.

 

[gadget73]

ok so its definitely in the amp. Only quick and simple suggestion I can make is switching the 6bq5 tubes. If the problem moves you have a dead output tube. No change, either the 6EU7 is half-dead or there is something wrong underneath of the amp.

 

[Twalt]

I just switched the 6bq5 tubes and no change. The 6eu7 is barely glowing and it is almost cool to the touch, took another min to get only slightly warmer.

 

[cademan]

That's normal for the 6EU7. In a dark invironment, just make sure both halves of the 6EU7 tube is glowing. Since this is a single ended amp, if one side of the 6EU7 is not glowing, that would be your problem.

Can you shows us any pics of the amp working? Are your speakers connected properly? Are both 6BQ5 tubes lighting up and getting hot?

 

[markmcmuz]

Try another 6eu7 tube. Bad pin connection perhaps? Take the tube out and re-insert a couple of times.

 

[Twalt]

Here are some pics of it working.

 

[Twalt]

I cleaned the pins and reinstall it several times. Still no change. Not sure what only half a side working looks like.

 

[cademan]

Can't really tell if both halves of the 6EU7 is working. Look at the bottom. It has two identical triodes (plates) inside and both have heaters (parts that glow in the center).

Turn it off and pull the 6EU7 tube and take a look at it and you will see what I mean by both (2) halves. Essentially it has two identical tubes inside one bottle.

 

[Twalt]

Ok, I will take a look. Thank you

 

[markmcmuz]

I cleaned the pins and reinstall it several times. Still no change. Not sure what only half a side working looks like.

Without a digital voltmeter, isolation transformer and a healthy respect for the high voltages inside of that little amp I think you are confined to parts swapping ie: try a new 6eu7.

 

[cademan]

Also, you can use a cd player or phone connected to these RCA inputs to see if it is indeed an amplifier problem. See pic:



Are your speakers connected properly? These things can be confusing as there are 3 speaker lugs which would be printed as "C", "1", and "2".

"C" is common for both speakers, 1 and 2 would be left and right.

 

[Twalt]

It does appear that both sides are indeed glowing. I see what you mean by two halves.

 

[markmcmuz]

Can't really tell if both halves of the 6EU7 is working. Look at the bottom. It has two identical triodes (plates) inside and both have heaters (parts that glow in the center).

Turn it off and pull the 6EU7 tube and take a look at it and you will see what I mean by both (2) halves. Essentially it has two identical tubes inside one bottle.

Doesn't one heater circuit heat both halves? Just pulled one out of my 9300.

 

[cademan]

Yes, in most of these amplifiers, these tubes are wired in parallel. They are wired for 6.3 volts and not 12.6 volts.

If you look at the tube data sheets for the 6EU7, it will show how the heater can be wired for both voltages. The 6EU7 is basically a low noise 12AX7 tube just with a different pin out.