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Hi guys! I'm quite good with soldering and electronic in general but when it comes to TUBE AMPS I have no idea of what to change ti reduce the HUM. I bought this amp for 20$ and it souds amazing! But Huge hum into it! I vhange the AX7 for a new one and nothing changed. So here are some pics and shcematic. Please guys tell me what to change and with what kind or parts.

Thanks a lot!

Westinghouse H48SE1 1959

https://imageshack.us/g/1/9986125/
http://techpreservation.dyndns.org/sche ... 1_168.djvu

Hi Max,

Perhaps the filter capacitors are the cause of fault due their age.

Try to replace each section of C7 with a discrete electrolytic of similar or higher value, and rated at 250Vdc

Be aware that this amp is not isolated from the mains network !!!! This can be fine to play a vinyl record but is unsafe to plug into it an electric guitar in case you inadvertently invert the mains plug.

Look for an isolation transformer of 120 to 120 volts capable to handle 60 or 70 watts, to use this amp safely.

Cheers,
Josè

Those filter caps are a place to start... That amp as mentioned could be a fry machine for you plugged into it. Get an isolation xformer asap. Hum could be from a lot of things. too much ripple in the B+ supply is common. Unfortunately with that design you can't pull the preamp tube and see if the hum is just in the power section.

What would happen if I don't isolate it? Would it burn my pickups? Will I electrocutre myself? It's plugged into a power bar with a ''reset'' is it a good enough protection???

Yes could be electrocuted without isolation transformer.

About hum ; same hum with volume or not or change with volume ?

If same hume with no change in volume it is filter capacitor

If change with volume more chance is not the filter cap.
No power transformer ( insulating transformer) mean no heater ground / center tap = hum
Those tubes have heater in series , 35 v + 35 V + 12 V + power resistor = AC wall outlet. You can't install heater center tap.

Also it is a single ended output tube , not push pull . SE = hum.

stratele52 wrote: Also it is a single ended output tube , not push pull . SE = hum.

Looking at http://techpreservation.dyndns.org/sche ... 1_168.djvu It looks like push/pull to me.

I haven’t seen anything with a live chassis for years. Quite a museum piece, but also potentially dangerous unless you run the mains through an isolation transformer and the earth the chassis.

Push need two outputs tubes, your amp have only one ; 50C5

I was looking at the schematic, I cannot make a lot out from the photos.