I purchased an assembled St 120 about 2 months ago when I got it one of the tubes red plated I replaced it and the resistor that it popped within the last week I have noticed some squeal that is intermittent coming out of the left channel I would hope somebody would have some knowledge of suggestions what I might do to fix this or can Do to pinpoint The problem..
4 posters
left channel squeal
rfbro- Posts : 27
Join date : 2014-12-28
Age : 69
Location : Vancouver WA
Roy Mottram- Admin
- Posts : 1838
Join date : 2008-11-30
was the tube and resistor that went bad also on the left channel.
Check all the wiring on the left channel, and re-solder any suspicious solder joints
Check all the wiring on the left channel, and re-solder any suspicious solder joints
rfbro- Posts : 27
Join date : 2014-12-28
Age : 69
Location : Vancouver WA
yes it was on the left channel I did not see anything that looks suspicious down there but I will double check thank you very much
Guest- Guest
looks can be very deceiving....our eyes fool us more than we realize. 
I would as a matter of course re touch all the solder joints on the sockets and ground connections, can't hurt!
And whilst you're at it, make sure no components, including on the pcb, show any signs of heat stress, ie darkened, also check for dry solder joints on the pcb as well
I would as a matter of course re touch all the solder joints on the sockets and ground connections, can't hurt!
And whilst you're at it, make sure no components, including on the pcb, show any signs of heat stress, ie darkened, also check for dry solder joints on the pcb as well
Bob Latino- Admin
- Posts : 3277
Join date : 2008-11-26
Location : Massachusetts
rfbro wrote:yes it was on the left channel I did not see anything that looks suspicious down there but I will double check thank you very much
Hi Robert,
Just to eliminate the fact that a TUBE is at fault.
1. Try swapping FIRST the two output tubes from one channel to the other to see if the problem moves to the other side.
2. Try swapping the left and right driver tubes to see if the problem moves to the other channel.
3. Swap the center driver tube for either of the other driver tubes to see if the problem moves to the other channel.
If it proves to be a fault of a tube, I can send you out another tube at no cost.
If it is NOT a tube at fault > Can you post a photo of the inside wiring of the amp in question so that we can look at the inside of the amp ?
Bob
rfbro- Posts : 27
Join date : 2014-12-28
Age : 69
Location : Vancouver WA
thank you for your response Bob I will do that but it won't be till probably Monday evening for I am away at work and am out of townout of town
deepee99- Posts : 2244
Join date : 2012-05-23
Location : Wallace, Idaho
fbro,
I would also check the tensions on your tube sockets, sometimes the individual pin-holders can get a bit loose (over-sized) and break contact. That's an easy, if a bit tedious, fix with a jeweler's screwdriver. Also, a little De-Oxit on the socket-holes and the tube pins themselves never hurts.
I would also check the tensions on your tube sockets, sometimes the individual pin-holders can get a bit loose (over-sized) and break contact. That's an easy, if a bit tedious, fix with a jeweler's screwdriver. Also, a little De-Oxit on the socket-holes and the tube pins themselves never hurts.