How much hum is too much?

[ldatlof]

Thanks for the quick responses. I have ordered a new output tube which should arrive early next week. Hopefully, the new tube will solve the problem as it is the easy fix.

Originally Posted by vintagecollect

As a further note: A half wave rectifier will have more AC ripple voltage than Full wave rectifier output voltage using same filter caps. Give it a shot and let us know!!!!

Vintagecollect - If the new tube doesn't eliminate the hum, did the above quote mean I should change out the half wave (1N4004) with a full wave rectifier? The ones I have seen have 4 leads instead of two. I am not exactly sure how to hook it up.

BTW, I bypassed the 1N4004 with a .01mF 500V ceramic cap. Didn't seem to make much of a difference though.

[vintagecollect]

Actually, I meant larger main filter caps for your power spply section in your radio. This would be easiest to do. You said put in 50/50/50 in set. If new tube doesn't solve problem, try a 80/80/80 cap. The cap you have in their now is close to original value, that's probaly why there's not much difference. Working on more sets, you'll find out larger caps were used mainly for hi/fi & TV due to part costs.--- Larger value caps are now mass produced and cheaper. Do this intead of attempting to install full wave rectifier as set is not designed for this and more involved. I only mentioned difference between half & full wave recifiers as a discussion------- & no suggestion as replacement unless you can do all needed modifications to make upgrade work properly. I'm just saying ------ half wave rectifiers REALLY do need larger cap values for main filter caps. GOOD luck. This will be nice upgrade to your set.

I have a 1950 zenith am/fm set that recapped. The tone control didn't make much difference in tone so I had to upgrade to larger value--- tone control cap. The original speaker was disconnected and a newer panasonic hi-fi speaker with sub woofer connected by speaker wire, original zenith speaker still in cabinet. Used new speaker to take advantage of full sound quality of fm!!! Quality of sound/tone is excelent rivalling newer stereos. Unorthodox upgrade but fantastic results!!! I was stupid once and wanted to sell set, my wife enjoys listening to it too, so wont sell set. She insists we keep it to listen when on patio..