HI guys. I just finished my wreck. I used a old Traynor YGA-1 amp for chassis, transformers etc. I rebuilt this amp before and had no problems with noise. I left the choke in the power supply to reduce the voltage a bit. It is between the standby switch and the 1K resistor. This point is my B1 feed to the OT. It is 400vdc. The other nodes are 5vdc hgher than the Francheska schem shows.
The noise is a whine, not hum. When I turn the volume pot, it sounds like I'm tuning a AM radio. All the other pots do something similar. The noise goes away when I put my scope lead on the phase splitter input.
When I play my guitar thru it, I get a sound on some notes like bacon frying.
Bias is -31vdc which gives me 30mA thru each EL-34. The AX7s where working great before I modded so I dont think its a tube. Could be?
Any ideas or help would be welcomed greatly.
I don't think that choke is rated to carry that much current. In a Traynor, the OT center tap is connected to the main filters, BEFORE the choke. You can put a choke first -- if you want a lot of sag -- but it better be a serious chunk of iron. I think part of what you're hearing is the choke screaming in agony. Also not sure if it's a good idea to use a choke AND the 1K with no decoupling between them.
This is a follow up to my earlier post. I removed the choke which helped alot. However I still have a noise problem. The noise is like a fuzz sound along with the regular note. Sort of a ringing. As the note decays, the fuzz note dies quicker, chopped like a noise gate switching off. This noise is more pronounced on the low notes. Changing tubes has not solved it.
Anyone have a suggestion? Thanks in advance.
ronh,
I always start with measuring all the dc voltages throughout the whole amp. Every power supply node, every plate, every cathode, and even the grids too. Many times that will tell exactly where the problem is. It's my first step in troubleshooting an amp...and when you do get the amp running right IMO you should measure and record all these voltages so you'll have them for future reference. Tube swaps will alter the voltages a little but usually not too much.
