Simple SE with 6BG6GA - magic smoke escapes... - diyAudio
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Old 13th October 2009, 11:28 PM   #1
chrish is offline chrish  Australia
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Default Simple SE with 6BG6GA - magic smoke escapes...

Having just moved house a short time ago and with no workshop set up, I decided I could at least put together some of the 6BG6GA to 6L6 converters I bought a while back and see how the 6BG6GAs go in the Simple SE.

Well, I thought I had done everything OK, so decided to plug these guys in to the Simple SE to see how they sound. After things warmed up I got music from the left channel, but nothing from the right, then a strange sound and a bright blue light emitting from the cooling holes in the chassis. Switched things off. opened her up and see that R18, the 100R 2W resistor that ties G2 to the plate was fried. Have not looked for further problems or failure yet.

Wondering what might be the problem. I have checked the converter sockets, and they appear to be wired correctly with no shorts. Just to double check, this is how I have them wired:

Base (plugs in to PC board) Socket (that 6BG6GA plugs in to)

2 (f) - 2
3 (plate) - top cap
4 (G2) - 8
5 (G1) - 5
7 (f) - 7
8 (k) - 3

The triode/ultralinear switch was in triode mode for the test.

Think I might replace the resistor and then try looking at some voltages with the converters in place, but tubes out.

Any tips for obvious problems?

Would a poorly fitting top cap make G2 act like the plate, drawing too much current through R18?

Regards,

Chris

Last edited by chrish; 13th October 2009 at 11:37 PM.
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Old 14th October 2009, 01:18 AM   #2
chrish is offline chrish  Australia
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Hmmm, curious...

Double checked everything and it looked OK. Replaced the burnt resistor. Checked the voltages, all OK.

Placed a pair of old 6P3S in and an old ECC81 just in case she blew again, and it worked fine. Swapped in the 6BG6GAs and it worked fine. What I did notice, however, was that the 'key' on the socket adaptor is quite small, and it is possible to place the adaptor in mis-aligned. I suspect that this is what I must have done in the first place.

Cheers,

Chris
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Old 14th October 2009, 01:43 AM   #3
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First, I'm happy to read that you found the trouble. This reminds me of something a friend told me about Chinese tube sockets. They sell porcelain 4 pin sockets for tubes like 2A3 and 300B. There are two big holes and two small holes as there should be. The thing is that the two small holes are big enough that the tube can be inserted wrong! Another blow for Chinese garbage products. So I'm curious, where did your adaptors come from?
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Old 14th October 2009, 02:19 AM   #4
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Quote:
Originally Posted by chrish View Post
Swapped in the 6BG6GAs and it worked fine.
Good thing the 2W resistor acted as a fuse. So how do they sound in the Simple SE?

Jeff
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Old 14th October 2009, 06:20 AM   #5
chrish is offline chrish  Australia
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Thanks for the replies,

The adaptors came from the supplier of the 6BG6GAs - www.vacuumtubes.com

The adaptor kit was pretty much just an octal tube base, a ceramic socket and a length of wire.

I did not get much of a chance to listen, but they sounded pretty much the same as the 6L6s and 6P3S. When the dust settles from the move and I can organise a space to build stuff, the plan is to have these available for a 6L6 PP amp with MOSFET source followers and regulated supply I have been planning with help from Tubelab and others.

Cheers

Chris
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Old 15th October 2009, 12:08 AM   #6
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Quote:
Originally Posted by chrish View Post
Thanks for the replies,

The adaptors came from the supplier of the 6BG6GAs - www.vacuumtubes.com

The adaptor kit was pretty much just an octal tube base, a ceramic socket and a length of wire.

I did not get much of a chance to listen, but they sounded pretty much the same as the 6L6s and 6P3S. When the dust settles from the move and I can organise a space to build stuff, the plan is to have these available for a 6L6 PP amp with MOSFET source followers and regulated supply I have been planning with help from Tubelab and others.

Cheers

Chris
Do the ceramic sockets fit snug in your tube bases. I bought a set of those and the kit he sent me it doesnt seem like even with glue the sockets will sit nice in those tube bases. The fit is too loose.
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Old 15th October 2009, 02:34 AM   #7
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Originally Posted by nic6paul View Post
Do the ceramic sockets fit snug in your tube bases. I bought a set of those and the kit he sent me it doesnt seem like even with glue the sockets will sit nice in those tube bases. The fit is too loose.
I had two that were loose and two that had to be ground down to fit. The diameter of the ceramic sockets is going to vary, they're not going to have a consistent fit in the plastic bases.

Jeff
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Old 15th October 2009, 03:52 PM   #8
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I had a tight fit with my socket adapters. I only pushed them in far enough so the epoxy would do it's job. I snapped the key off of one of them, so I have to be super careful when plugging it in.
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