Hi all,
I have a Hamlin's 20-20 (Trio W-45) that I have been rebuilding.
It has been recapped (except for mica and ceramic discs). Balance meter was replaced as well as the two germanium diodes in the meter driver circuit. Amp sounds great. One small problem left is when the balance control is set full left I get a chirping oscillation in the right channel. Does not occur in the left if balance is set full right. I tried swapping some tubes around but no change. Problem does not occur until the amp is fully warmed up. If I switch the meter circuit off the chirp does not occur at all. Seems like there some kind of feedback is occurring when the meter is switched in but the schematic is very difficult to read, even with a large magnifier so looking for possible feedback paths is quite difficult.
The best schematic I could find online is of pretty poor quality and I don't believe it is for exactly the same amp. It has things like a headphone jack, speaker on/off, and rumble filter switch that are not present on my unit but, from inspection, much of the circuit seems the same...
I have started to trace out the circuitry but before I spend hours at this, does anyone possibly have a useable schematic for this amp?
~W
I have a Hamlin's 20-20 (Trio W-45) that I have been rebuilding.
It has been recapped (except for mica and ceramic discs). Balance meter was replaced as well as the two germanium diodes in the meter driver circuit. Amp sounds great. One small problem left is when the balance control is set full left I get a chirping oscillation in the right channel. Does not occur in the left if balance is set full right. I tried swapping some tubes around but no change. Problem does not occur until the amp is fully warmed up. If I switch the meter circuit off the chirp does not occur at all. Seems like there some kind of feedback is occurring when the meter is switched in but the schematic is very difficult to read, even with a large magnifier so looking for possible feedback paths is quite difficult.
The best schematic I could find online is of pretty poor quality and I don't believe it is for exactly the same amp. It has things like a headphone jack, speaker on/off, and rumble filter switch that are not present on my unit but, from inspection, much of the circuit seems the same...
I have started to trace out the circuitry but before I spend hours at this, does anyone possibly have a useable schematic for this amp?
~W
Attachments
This one seems readable.
Trio W-45 Schematic Photo by sa900 | Photobucket
Found it in this thread.
http://audiokarma.org/forums/index.php?threads/trio-w-45-integrated-el84-amplifier.63153/page-2
John
Trio W-45 Schematic Photo by sa900 | Photobucket
Found it in this thread.
http://audiokarma.org/forums/index.php?threads/trio-w-45-integrated-el84-amplifier.63153/page-2
John
- Status
- Not open for further replies.