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Old 10th October 2008, 12:32 PM   #1
Tachyon is offline Tachyon  Sweden
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Question Trouble with amp 6V6

A tube (6V6) was inserted the wrong way in its socket, the middle guide pin was missing.
Now one channel is dead
What components can possibly have been broken?

Two output tubes 6V6 in triode mode, one 6NIP and one 5Y3. The amp is homemade, not by me, and I dont have a schematic for it and sadly no way to aquire it.
The man who built the amp is no longer with us.

I would really appreciate help with troubleshooting.
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Old 10th October 2008, 01:42 PM   #2
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Measure the voltages on the two 6V6 sockets and post them here.
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Old 10th October 2008, 03:02 PM   #3
Tachyon is offline Tachyon  Sweden
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Both channels same values +/- 1V

BTW. the tube is still ok , tested on the other channel and it works fine..
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Old 10th October 2008, 03:54 PM   #4
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Are these voltages with tubes removed? If so, measure from bottom with tubes in place. Screen or cathode resistors could have gotten zapped, which may not not show when it's unloaded.
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Old 10th October 2008, 04:11 PM   #5
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Is there smell from output transformer ?
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Projects: OTL-OCL 6AS7 Gen. Electric, SEs 2A3 RCA, 300B JJ, 6S4S, 4P1L, EL11 Telefunken, 6AS7 RCA, 6S33S, 6S41S, 6S19P, E84L Siemens, E236L Telefunken, headphone ampl. OTL Loftin White 6AS7 RCA,... PPs 6005 Gen. Electric, EL34 Mullard, 6L6....
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Old 10th October 2008, 04:47 PM   #6
Tachyon is offline Tachyon  Sweden
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Previous measurement was without tubes.
With tubes voltage is now 231-234V

The resistor 1k shown in photo was bad, I don't know if it's screen or cathode resistor, changed to new but still no sound..

Please advice on which pins to measure and settings on multimeter.

azazello -> No burned smell from output transformer.

Thanks for your guiding me!
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Old 10th October 2008, 06:02 PM   #7
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if you have a working channel and a non-working channel, then you have to start making measurements comparing the two. You can even sketch out the basic schematic to get a feel for whats going on.

Check plate and cathode voltages with the tubes in it. Is it fixed or self bias?

You can also measure and compare transformer resistances between the two channels as a method for shorts or open circuit.

As always, be careful when working with high voltages.
Safety Practices, General and Ultra-High Voltage
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Old 10th October 2008, 07:24 PM   #8
Tachyon is offline Tachyon  Sweden
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Thanks for your concern, I read the Safety Practices sticky before I started to probe.

Both channels measure very similar, 6.6V on both,
234V-236V on the other chanel.

I belive that the 6.6V AC is filament and the 234V DC is plate. Could cathode be -12V?

The 234V and 231V is connected togheter with a 1K ohm resistor.

Dont know if its fixed or self bias, there is a bunch of big resistors in series, 174ohm.

Please elaborate how to measure the output transformers.

This is where I soak up info..this is all new to me..

http://www.radiomuseum.org/tubes/tube_6v6g.html
http://boozhoundlabs.com/howto/


Click the image to open in full size.
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Old 10th October 2008, 09:57 PM   #9
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Tachyon,
Mesure is there connection between cathod and ground. It must be
0-1 ohm /for fixed bias/ or more 240 ohm /for self bias/.
Burned 1 kom is for triod mode 6V6.
Can You change 6N1P ? Or put 6N2P, 6N23P, ECC85 ?
Is there capacitor between 6N1P and 6V6 ?
How You wrong put 6V6 ? To clockwise, or contre clockwise ?
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Old 10th October 2008, 10:34 PM   #10
Tachyon is offline Tachyon  Sweden
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azazello

Between cathode and ground its 174ohm,
five resistors in series.

I belive the tube was rotated 3 pins clockwise.

At the moment I dont have any 6N1P. I ordered new tubes today, all of them just to be safe

I have some ECC82 that are from my old tube pre-amp, could that temporarily replace 6N1P?

I measured the output transformers, between the two primaries its 0.27ohm and between the two secondaries (speaker) its 0.5ohm. That is measured with amp off, as a newbie to this I'm not sure if that the correct way..
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