Totally beginner magnavox 8608

Ok, i found out that on clip on the 12au7 socket is a kinda loose ( the pin of the tube is holding it otherwise it would fell off) could it be the problem?
 
Shorting the inputs just means to take the left and right input wires and ground them to the chassis. It's not an electrical short like a shorted wall socket or power cord so it won't hurt anything but it might tell if you something if that one channel quiets down. The loose pin on the 12AU7 could certainly be the culprit so make sure it is soldered solidly.
 
Shorting the inputs just means to take the left and right input wires and ground them to the chassis. It's not an electrical short like a shorted wall socket or power cord so it won't hurt anything but it might tell if you something if that one channel quiets down. The loose pin on the 12AU7 could certainly be the culprit so make sure it is soldered solidly.
So I did try the short but nothing changed. But I’ve bought a new socket as I realize that all tube light up except that 12au7. So the wait game start again. Thanks guys
Fred
 
Are you sure? The 12AU7 family of tubes sometimes look like they aren't working when they really are. Look closely at the tube in a darkened room. PS, you wouldn't be getting any sound if the tube were not lit up.
 
Are you sure? The 12AU7 family of tubes sometimes look like they aren't working when they really are. Look closely at the tube in a darkened room. PS, you wouldn't be getting any sound if the tube were not lit up.
Hmmm. Make sense. Well I did short it and the sound was the same more or less
 
And I just re power it and I’m still pretty sure it ain’t lighting up at all. I did had a Sherwood a-5500 and the 12au7 were lighting up, I could see them but this one nada

There is no 12AU7 in this amp. The tube lineup is (1) 6CA4 / EZ81 rectifier, (1) 6EU7 input tube and (2) 6BQ5 output tubes. The 6EU7 has a completely different pinout (pin arrangement) than tubes like the 12AU7, 12AX7, 12AT7 and similar. If you have the wrong tube in there it won't be lighting up because the heaters are on different pins.

If you wanted to use one of those others you would need to rewire the socket. The 6EU7 is essentially the same as a 12AX7 electrically.
 
There is no 12AU7 in this amp. The tube lineup is (1) 6CA4 / EZ81 rectifier, (1) 6EU7 input tube and (2) 6BQ5 output tubes. The 6EU7 has a completely different pinout (pin arrangement) than tubes like the 12AU7, 12AX7, 12AT7 and similar. If you have the wrong tube in there it won't be lighting up because the heaters are on different pins.

If you wanted to use one of those others you would need to rewire the socket.
Sorry my bad, it is a 6eu7 and everything was lightning up before but now they all glow except this one and the buzzing sound is only in the right channel
 
Sorry my bad, it is a 6eu7 and everything was lightning up before but now they all glow except this one and the buzzing sound is only in the right channel

It looks like you have the 6EU7 wired wrong. The green wires that are coming from the 6BQ5 (pins 4 and 5) should be going to pins 1 and 2 of the 6EU7. The pic seems to show them going to pins 2 and 9?? You need to recheck the wiring on all the pins of the 6EU7. Here's a link to the data sheet which shows the connections of the various pins. The pin numbers are as seen from the bottom. https://tubedata.altanatubes.com.br/sheets/093/6/6EU7.pdf
 
It looks like you have the 6EU7 wired wrong. The green wires that are coming from the 6BQ5 (pins 4 and 5) should be going to pins 1 and 2 of the 6EU7. The pic seems to show them going to pins 2 and 9?? You need to recheck the wiring on all the pins of the 6EU7. Here's a link to the data sheet which shows the connections of the various pins. The pin numbers are as seen from the bottom. https://tubedata.altanatubes.com.br/sheets/093/6/6EU7.pdf
I used Dave amp as a tamplate and it was wired this way. Could it be that it was wired for a 12ax7 and mine is a 6eu7??
 
I used Dave amp as a tamplate and it was wired this way. Could it be that it was wired for a 12ax7 and mine is a 6eu7??
Here’s the schematic I used and a pics of his amp if it can help understand what I did
 

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His schematic shows the input tube as either 12AX7 or 6EU7 but you'll notice that there are no pin numbers because they would be different, depending on which tube you choose to use.

Not sure why you'd get sound from one channel. Perhaps the source is very strong and it's able to drive the 6BQ5 just enough to hear it??

Here's a factory schematic.
 

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His schematic shows the input tube as either 12AX7 or 6EU7 but you'll notice that there are no pin numbers because they would be different, depending on which tube you choose to use.

Not sure why you'd get sound from one channel. Perhaps the source is very strong and it's able to drive the 6BQ5 just enough to hear it??

Here's a factory schematic.
Ok well I had a 12au7 and I just try it in and the same thing is happening ?!
 
Ok well I had a 12au7 and I just try it in and the same thing is happening ?!

If you're going to rewire you need to use a 12AX7. The 12AU7 shares the same pinout but its amplification factor is only 20 while the 12AX7 (and 6EU7) is 100. So a 12AU7 will function but not optimally. The signal will be much weaker.

Also, if you're using a 12AX7 (or 12AU7) how do you have the heaters wired? In order to operate at 6.3v you should have pins 4 and 5 connected with each other and one of your heater wires connected there. The other heater wire connects to the heater's center tap, which is pin 9. If one of your heater wires is going to just pin 4 or pin 5 (not both) and the other is going to pin 9 you are only lighting up one of the two triode sections, which would explain why you're getting sound out of one channel only.

If you're using a 6EU7, the heaters are only pin 1 and pin 2. There is no center tap on the heater. Of course the other pins are different too so you need to decide which type of tube you want to use and make sure the socket is wired correctly for that type of tube.
 
If you're going to rewire you need to use a 12AX7. The 12AU7 shares the same pinout but its amplification factor is only 20 while the 12AX7 (and 6EU7) is 100. So a 12AU7 will function but not optimally. The signal will be much weaker.

Also, if you're using a 12AX7 (or 12AU7) how do you have the heaters wired? In order to operate at 6.3v you should have pins 4 and 5 connected with each other and one of your heater wires connected there. The other heater wire connects to the heater's center tap, which is pin 9. If one of your heater wires is going to just pin 4 or pin 5 (not both) and the other is going to pin 9 you are only lighting up one of the two triode sections, which would explain why you're getting sound out of one channel only.

If you're using a 6EU7, the heaters are only pin 1 and pin 2. There is no center tap on the heater. Of course the other pins are different too so you need to decide which type of tube you want to use and make sure the socket is wired correctly for that type of tube.
Ok so I went to bed to start fresh, if I understand correctly; I’m presently semi wired for a 12ax7 (which I have one at home so I’ll stay this way for now) so I should solder a wire between pins 4-5 but then what ? It’s the heater I’m not familiar with. If you could tell me which wires goes from where to where that would help me
Thanks
Fred
 
To use a 12AX7, one heater wire goes to pin 4 and 5, the other goes to pin 9. The 6bq5 heater wires are on pins 4 and 5. I would connect 4-5 on the 12ax7 to pin 4 on the 6bq5, and pin 9 on the 12ax7 to pin 5 on the 6bq5.
 
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