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City: Albuquerque, NM
(04-27-2016, 03:31 PM)Eric Wrote: The 12sa7 goes from a -.7 to -3 (distortion increases) but the 12sk7 is -.7 but the station is muted when I attach the probe and the value stays when I move off the station. I have changed both tubes but no change.
I do have a signal tracer that was given to me a Heathkit IT-5283 with probes doesn't look like it was used, but have never used it other than as an external pm speaker. looked at the inst online but it was less than clear( can only find a partial manual 9 pages)) to me like is the chassis energized? Hook the black lead to the antenna then probe with the prob with the diode selected on the probe?
Eric,
This site has a 40 page manual for $15. Think I've used them in the past?
John
https://sc2.vom.com/d8/index.fwx?C=MANUALS
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City: Edmonton AB CA
Eric, I just noticed that the substitute loop you are using is very different from the original. That may be the whole problem right there, the original shows 25 ohms and the one you have in there shows as 2.5 ohms, a lot less windings.
Gregb
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City: Cumming, GA
Greg
No the print shows 2.5 ohms I have Vol 18 so I'm looking at an original that is one of the problems with Nostalgia is you can't make out numbers and decimal points sometimes. I also have part of Sams photofact sheet which has a better parts list which lists it Part #29 Loop Ant 2.8 ohms.
Eric
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City: Cumming, GA
Found a really good video on YouTube
https://www.youtube.com/watch?v=zknp0FOkPXU
It even has the same tube line up only problem is it stops just before he starts the actual testing and he hasn't done part 2 yet. So I have some questions.
1 do you energize the chassis when doing this?
2 the probe has two setting DC and the Diode symbol I'm thinking the Diode setting?(red probe)
3 The black lead does that go to the B- or Chassis ground or some other point in the CKT
Ordered the full manual but probably won't get here till next week.
Eric
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City: Roslyn Pa
#1 Yes. Probably should use an isolation transformer connected to ac power powering the radio.
#2 Dc setting is used for any audio signal (from the volume all the way though to the spkr) Diode is for any rf /if signal (from ant loop though to the secondary of the second if transformer.
#3 B- is good.
Happy hunting!
Terry
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City: Cumming, GA
Ok Here is what happened while waiting for the Signal Tracer Instruction Manual. The only reason I wanted this radio was the price ($15 ) and the cabinet which is great shape. On the chassis it is was partial re-caped so I finished it. I have been concentrating on the RF and Audio sections thinking this was the source of the distortion after all I did voltage checks and 35Z5 side was on the money. I decided to check the wiring on the power section and C-14 .05 mf was not connected properly. the side that was connected pin 2 of the 35 was right but the other side went to the chassis not to 12sq7 pin 8. Once I lifted it the distortion went away apparently it was AC. I returned it per the print.
Now I have one more question I get 120v chassis to ground. I added a polarized plug so the hot side is on the switch and on the print the only thing I see besides Pin 1 on the tube's is C-20 .05mf and R-11 470k going to ground. Do I have another problem?
