pepster! Tuner info... Your in-box is full!

mhardy6647

... here's the answer to your question :-)

One actually has to be a little bit circumspect rooting around in a tuner; there are multiple precisely tuned circuits and it is pretty easy to de-tune things (e.g., by cavalierly "recapping" or changing tubes) to the point that the radio will not receive a signal!

That said, here is my favorite, top-secret vintage vacuum tuner repair technique :-) One at a time, remove each tube and clean the pins (with a Q-tip and DeOxit or just some isopropyl alcohol). It is also a good idea to clean the tube socket if one has a suitable way to do it (I use a dental pick very gently). Dry the pins (with another Q tip or with a paper towel - or just wait a bit) and re-install each tube before pulling out another one (i.e., put each tube back in the exact socket from whence it came - the tuned circuits are tuned for the specific tube in each section - all of those 6AU6 tubes may not be exactly operationally identical!).

It is always a good practice to replace the multi-section "can" capacitor in the power supply, but they're not inexpensive as new production items and it is not always necessary. The best thing to do is to 're form' old capacitors using a variac or a home-made "dim bulb tester" (a search at audiokarma will explain the latter). If the tuner's been recently used, it may be fine 'as is'. The symptom of a bad P/S filter cap will be hum (soft or perhaps very loud) - a bad filter 'can' cap may also get quite warm after some power-on time due to high internal resistance. The can cap should stay quite cool (although it can pick up heat from other, nearby components).

The only component in a tuner like that that "should" get really hot (i.e., too hot to touch!) is the rectifier tube (probably a 6X4 or a 6CA4 in that tuner - I don't actually remember).

HTH!

mrh