Hi Folks,
I have an old TU-8200 I built around 10 years ago which developed an intermittent channel issue a couple of years ago which now seems permanent. It's an odd failure as you'll see so hopefully someone has an idea of what's going on.
The setup:
Source is a new laptop or android phone via stereo 3.5mm jack to either the 3.5mm stereo input on channel 2 -or- the 3.5mm stereo input on a BBE sonic maximizer 282i. When the BBE device is in the chain, a pair of RCA cables from it's outputs to channel 1 or channel 2 on the TU-8200. TU-8200 uses tung-sol 6550s and JJ ECC802s tubes in ultralinear configuration. Regular speaker cable to a pair of Klipch bookshelf speakers.
When connected correctly, with and without the BBE device, there is sound out of one channel only(R). when I swap the RCA cables so that R=L and L=R, the sound moves to the other channel(L).
When I pull the 3.5mm cable a bit out of it's jack, in either the BBE input or the TU-8200 input, I get mono sound out of both speakers, though there is a bit of hum as well.
I've swapped cables, BBE devices, and tubes with the same result. I opened up the TU-8200 and inspected for bad solder joints, repaired a few questionable ones. caps all look fine as well.
So, what am I missing? I'm pulling my hair out on this one!
I have an old TU-8200 I built around 10 years ago which developed an intermittent channel issue a couple of years ago which now seems permanent. It's an odd failure as you'll see so hopefully someone has an idea of what's going on.
The setup:
Source is a new laptop or android phone via stereo 3.5mm jack to either the 3.5mm stereo input on channel 2 -or- the 3.5mm stereo input on a BBE sonic maximizer 282i. When the BBE device is in the chain, a pair of RCA cables from it's outputs to channel 1 or channel 2 on the TU-8200. TU-8200 uses tung-sol 6550s and JJ ECC802s tubes in ultralinear configuration. Regular speaker cable to a pair of Klipch bookshelf speakers.
When connected correctly, with and without the BBE device, there is sound out of one channel only(R). when I swap the RCA cables so that R=L and L=R, the sound moves to the other channel(L).
When I pull the 3.5mm cable a bit out of it's jack, in either the BBE input or the TU-8200 input, I get mono sound out of both speakers, though there is a bit of hum as well.
I've swapped cables, BBE devices, and tubes with the same result. I opened up the TU-8200 and inspected for bad solder joints, repaired a few questionable ones. caps all look fine as well.
So, what am I missing? I'm pulling my hair out on this one!
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I reviewed them all, yes. resoldered a few of the joints that were not shiny, but honestly it didn't look too bad.
The weird effect pulling out the jack must be that one channel(the ring on the connector) is now in contact with the input ground but swapping the RCA cable also swaps the working channel. It seems like some sort of grounding issue on the amps input must be the culprit.
The weird effect pulling out the jack must be that one channel(the ring on the connector) is now in contact with the input ground but swapping the RCA cable also swaps the working channel. It seems like some sort of grounding issue on the amps input must be the culprit.
