I couple of days ago I noticed my left channel had a drop in volume. I swapped the input cables and it stayed on the left channel. I swapped the speaker cables and and it moved over to the right speaker. I swapped the power tubes side to side and it stayed on the left. I swapped the outer driver tubes and it stayed on the left. I haven't put it on the bench yet. What should I be looking for, or at, once I get it on the bench?
5 posters
Left channel sounds deminished, lower volume. ST-120
Mr C- Posts : 99
Join date : 2019-07-11
Age : 69
Location : Visalia CA.
peterh- Posts : 1869
Join date : 2012-12-25
Location : gothenburg, sweden
- Post n°2
Re: Left channel sounds deminished, lower volume. ST-120
by peterh Fri Oct 18, 2019 9:01 pm
Mr C wrote:I couple of days ago I noticed my left channel had a drop in volume. I swapped the input cables and it stayed on the left channel. I swapped the speaker cables and and it moved over to the right speaker. I swapped the power tubes side to side and it stayed on the left. I swapped the outer driver tubes and it stayed on the left. I haven't put it on the bench yet. What should I be looking for, or at, once I get it on the bench?
Look for a repair man !
cci1492- Posts : 331
Join date : 2016-05-09
Age : 64
Location : NJ
- Post n°3
Re: Left channel sounds deminished, lower volume. ST-120
by cci1492 Sat Oct 19, 2019 10:27 am
peterh wrote:Mr C wrote:I couple of days ago I noticed my left channel had a drop in volume. I swapped the input cables and it stayed on the left channel. I swapped the speaker cables and and it moved over to the right speaker. I swapped the power tubes side to side and it stayed on the left. I swapped the outer driver tubes and it stayed on the left. I haven't put it on the bench yet. What should I be looking for, or at, once I get it on the bench?
Look for a repair man !
Ouch! I would check for cold solder joints, try a new phase inverter, check caps in place with cap checker (unlikely as this is a new build).
LeGrace- Posts : 390
Join date : 2016-08-07
Location : Ontario, Canada
- Post n°4
Re: Left channel sounds deminished, lower volume. ST-120
by LeGrace Sat Oct 19, 2019 1:53 pm
Double check PIO coupling caps, values should be a close match within pairings.
rjpjnk- Posts : 262
Join date : 2018-07-18
- Post n°5
Re: Left channel sounds deminished, lower volume. ST-120
by rjpjnk Sun Oct 20, 2019 12:14 pm
Mr C wrote:I couple of days ago I noticed my left channel had a drop in volume. I swapped the input cables and it stayed on the left channel. I swapped the speaker cables and and it moved over to the right speaker. I swapped the power tubes side to side and it stayed on the left. I swapped the outer driver tubes and it stayed on the left. I haven't put it on the bench yet. What should I be looking for, or at, once I get it on the bench?
Swap the center tube with one or both of the PI (side) tubes to see if anything changes. The center tube has two triodes in it: one for left and one for right. After that it's off to the bench.
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