Olympic 6-501V won't tune below 600 Kilocycles

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Olympic 6-501V won't tune below 600 Kilocycles

Post by fifties on Sat Apr 03, 2010 6:40 am

I picked up a 1946 Olympic 6-501V off eBay, tweaked the cans, replaced the Oscillator/Mixer and IF tubes, speaker, and 330 uuf mica cap coming off the oscillator coil, but the radio won't tune below 600 Kc. I have tried two different Oscillator/Mixer tubes. It almost seems like the tube cuts off as it approaches 600, and once below makes loud crackling noise to about 570 Kc, then silence.

Putting my signal generator even at 590 Kc won't get a tone, but NP at the upper end of the dial; It tunes to 1690 Kc, and is very selective until below 900 Kc, when sensitivity starts to decrease.

I have experimented with several different values of micas, from 305 to 390 uuf, with no change whatsoever.

I even replaced the mica film in the two padders on the tuning cap.

The oscillator coil gives apparent good readings of a few ohms between each end, and about an ohm to the center tap.

To make matters more of a challenge, the online prints I have gotten do not seem to match the actual wiring! As an example, they display the 12SA7 as having an eighth pin!
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Re: Olympic 6-501V won't tune below 600 Kilocycles

Post by sprman on Sat Apr 03, 2010 11:26 am

Check the inductance on any inductors you can find.Try cleaning the tuning capacitor real good.Look for any broken wires or bad solder joints(cold)...Sometimes you have to fool with alinenment to get them to track right even bending tuning cap plates! Check voltages and resistances on all tubes.Sprman : )

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Re: Olympic 6-501V won't tune below 600 Kilocycles

Post by Bill Cahill on Sat Apr 03, 2010 12:32 pm

I'd say the plates on your tunning capacitor are shorting out at that point. I've seen this happen alot on radios.
You need to eyeball all the plates carefully, straightenning bent plates.
Bill Cahill

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Re: Olympic 6-501V won't tune below 600 Kilocycles

Post by fifties on Sat Apr 03, 2010 5:19 pm

Appreciate the quick replies.

I forgot to mention that I had re-soldered the connections between the padders and the tuning cap body.
I had checked and straightened plates that were slightly bent in both the oscillator and antenna sections of the tuner as well. I had also retouched all solder connections in the oscillator circuit, and all pins on the mixer/oscillator tube.

I notice that when I ran my finger over the antenna plates near the padder, it seemed to affect the tuning somewhat, in that it didn't "crackle" around 600 Kc, but still would not track below that.

Sprman, are you suggesting that bending the plates slightly might get it to tune lower? Which section, antenna or oscillator, and would you know which specific plates...outer, inner, etc? Thanks!
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Re: Olympic 6-501V won't tune below 600 Kilocycles

Post by Bill Cahill on Sat Apr 03, 2010 6:47 pm

For one, has it affected your tunning, ie is it still receiving stations at the right points?
I think where you went wrong was bending the plates before trying the radio?
I suspect your straight plates are part of the problem.
Plate placement is fairly crittical.
You might think you have it just right, and, you can have a major short occurring.
The hint is the crackling sound as you are trying to tune.

I have a Crosley five tube radio that had bent plates in both sections, and, was cutting out, and, making static noises in several spots.
The crackling occurs with intermittent shorting.
Completely dead usually indicates a solid short.
Perhaps an ohm meter between the frame of the tuner and, each of the two sections tunning it up, and, down, radio un-plugged, of course, might find the shorted areas.
Bill Cahill

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Re: Olympic 6-501V won't tune below 600 Kilocycles

Post by fifties on Sat Apr 03, 2010 7:57 pm

Thanks for the suggestions, Bill.
I touched nothing on the tuner before testing it initially. The oscillator section has cut plates, so it always tracks correctly, and there is no slug adjustment in the oscillator coil.
When I discovered it's lack of low end tuning was when I straightened a few plates that were bent.
I will use my VOM to test for shorts while the cap is being tuned over the dial and report back.
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radio

Post by denver on Sat Apr 03, 2010 8:21 pm

Ihad a problem like this .I noticed a lot of oxidation on the tuning condenser . took one of my wife,s wide finger files and filed it of . took awhile cleaned one at a time rotateing to get to every spot . Oh the sand paper kind of files. Very Happy
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Re: Olympic 6-501V won't tune below 600 Kilocycles

Post by denver on Sat Apr 03, 2010 8:24 pm

Oh i have a signal gen if it gets even just fine dust it will crackel &pop have to blow it out. once in awhile.
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Re: Olympic 6-501V won't tune below 600 Kilocycles

Post by fifties on Sat Apr 03, 2010 9:14 pm

That's a good idea, thx.
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Re: Olympic 6-501V won't tune below 600 Kilocycles

Post by denver on Sat Apr 03, 2010 11:20 pm

Did you replace thoses paper caps check resister to Rolling Eyes
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Re: Olympic 6-501V won't tune below 600 Kilocycles

Post by sprman on Sun Apr 04, 2010 10:11 am

Bending of plates help get the radio to track properly on both ends of the band ..Most times you never have to try thisI wonder is the IF set at the right freq? Try cleaning the Osc tube socket,see if that helps. Sprman : )

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Re: Olympic 6-501V won't tune below 600 Kilocycles

Post by sprman on Sun Apr 04, 2010 10:24 am

Did you change the cap .02/400? Did you check the resistor 8,200 ohms?What voltages are you getting on the Osc tube?Did you replace the .01 cap on the ant ?Sprman : )

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SUCCESS!

Post by fifties on Sun Apr 04, 2010 6:53 pm

I would like to thank everyone for their advice, and specifically for having me concentrate on the tuner as being the problem.

I had replaced the .02 uuf, 8.2K, and as mentioned, the 330 uuf mica, along with both the 12BE6 and 12BA6 tubes, with no improvement.

Concentrating on the tuner, manipulating, cleaning, gently adjusting, etc., I ended up using a cheap utility snap off blade knife (3/8" width x about 2 inche long blade), sliding it between plates when the tuning gang was fully closed and the radio was cut off, until finding the culprit, and then gently twisting the blade to open it up a bit. I get occasional crackling, but it is 90% improved.

It will now track and emit tone when I set my generator to 525 Kc, and using a Select-a-tenna, it will pick up LAX's information channel on 530 Kc, about 45 miles away.
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Re: Olympic 6-501V won't tune below 600 Kilocycles

Post by sprman on Mon Apr 05, 2010 9:59 am

Good deal finding the problem.You should be able to get it to work very well!Sprman : )

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Re: Olympic 6-501V won't tune below 600 Kilocycles

Post by Bill Cahill on Tue Apr 20, 2010 6:08 am

I think I've figured out your problem. Did you say you have IF's adjusted to 252 kc?
I believe this radio is actually 455kc IF's.
Try readjusting your set to 455KC.
Sounds like the set is close, but, needs major realignment.
Bill Cahill

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Re: Olympic 6-501V won't tune below 600 Kilocycles

Post by fifties on Tue Apr 20, 2010 5:22 pm

Thanks Bill, but if you'll notice in my post second above yours, entitled, "Success", the problem was the tuner plates shorting, and I have fixed it to where it only shorts around 800 kilocycles very briefly. It will track down to 525 Kc., and up to 1690.

I usually tune the two IF cans using a weaker local during the daytime, then will double check by using my generator at 455 Kc., but I am usually right on.
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Re: Olympic 6-501V won't tune below 600 Kilocycles

Post by Bill Cahill on Tue Apr 20, 2010 6:20 pm

O.K. Sorry. Missed that post.
Glad my suggestion on tuner helped.
Bill Cahill

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