Radio Road

RE: hmm, did I bite off more than I can chew for this tuner?

24.12.41.4

fredtr

In Reply to: RE: hmm, did I bite off more than I can chew for this tuner? posted by ltman on June 23, 2023 at 17:15:16

Clean it up, and I bet you will be fine. If not, I have one in pretty good shape, worked last time I turned it on. I bought it for $50 at a yard sale. I'm located in AZ.

Follow Ups:

RE: hmm, did I bite off more than I can chew for this tuner? - ltman 19:05:32 06/26/23 (0)
thank you for the offer. I have read that one should always have two of these units for a restoration project. I may be interested in picking up another unit in a few weeks at this project progresses. I will reply here.
I agree (FWIW), plus, I'll share my secret vintage tuner repair trick :) - mhardy6647 06:11:06 06/26/23 (1)
If one has a vacuum tube tuner that "works" in an electrical sense, but not in a "radio" sense (i.e., lights up, tubes heat, power supply supplies - without getting hot(!) - audio output puts out ) -- in that the radio does not receive any signal, try removing each tube (one at a time!), cleaning the pins (Q tip and DeOxit, if you like, or just a paper towel), then reseat each tube.
I've "repaired" a number of silent FM tuners just so.
RF and IF circuits are rather precisely tuned (for resonance and oscillation) and, over decades, can go out of whack* for remarkably subtle reasons. Or at least that's my assessment. ;)
Try it! Just be careful as there are delicate things in these beasties -- especially (!) 40-plus year old PC boards of at-best moderate quality to start with, and the "main" tuning capacitor, coil/transformer tuning slugs, and trimmers (see also below).
I'd "worry" more about the HV power supply more than anything else, FWIW. I'd also think about replacing capacitors in the signal path (particularly the one or two on the output side), but I'd stay the heck away from doing much of anything in the "radio" side of the circuit (including the IF stages). That said, the Dynaco tuners are meant to be straightforward to align, so they should be a bit more robust than a (nominally) better tuner to amateur troubleshooting.
PS Do be extremely careful cleaning -- especially around that "air variable capacitor" which is the user's primary lifeline, so to speak, to tuning a radio station. Don't spray stuff around it, don't bend the fins, etc.
Apologies to the OP if this is all old hat! :)
____
* "Whack" being, of course, an important concept in VHF circuit design, operation, and troubleshooting. :)

all the best,
mrh

Edits: 06/26/23 06/26/23 06/26/23
- RE: I agree (FWIW), plus, I'll share my secret vintage tuner repair trick :) - ltman 19:02:56 06/26/23 (0)
  not old hat at all, I appreciate the input. I have no formal electronics training. Just kit building experience.
  
  I will confirm the power filter caps are depleted, then do a more thorough cleaning and try and bring it up with my variactor and see if I can get any sound out of it before I again deplete the power caps and replace some of the electrolytics I got from a kit on EBAY.

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