[Retro Ron]

Hi Folks,
I fixed a '56 Chevy radio a while back for a gentleman and he was so happy with it he brought me a '54 Chevy truck radio 986771 to work on. I re-capped it and the voltages and resistance chart were right on. However it suffered from low volume and crashing booming noises. I tracked the problem to the first IF transformer. I removed the can, gutted the internal capacitors and installed silver mica replacements on the external leads. After peaking that IF transformer at 262kc, the radio plays great but now I have another (I hope unrelated) problem. The dial tracking is not stable. I can tune it to a good strong station and after several minutes, the signal will suddenly disappear. I can turn the tuner slightly and find the same station again. It will play for several minutes and then the station will again suddenly disappear. The signal can be found again at its original position on the dial. I'm not too familiar with these inductive tuning mechanisms. Could the problem lie there or in one of the osc padders or even the second IF? The radio was really grungy inside and I cleaned it best as I could. Any opinions would be appreciated.

Thanks,
Ron

[exray]

Hi,
Something I've seen more than once is the ferrite slug being loose on its shaft.

[Retro Ron]

Good thought exray but the slugs are snug. There are still a few moulded mica caps across the slug assembly I didn't touch. I wonder if one of them has a mechanical defect? I just don't trust old mica caps anymore. I suppose I should check whether the trimmer screws in the end of the slugs are too loose. This just seems like an electrical problem instead of a mechanical problem because of the behavior. There are just no mechanical stresses when the problem occurs.

Thanks,
Ron

[Texasrocker]

Hello Ron,
I would have suspected the prob just as Exray described as first solution. Ive restored many Chevy 47-53 truck radios over the yrs. And a few Mopars & Motorolas for Fords various yrs models tube radios.Im no expert, but have a few other ideas. Slug-tuning is "tricky" sometimes indeed!
Since you have asertained that the mechanical-integrity of the slug-tuning system is still good, I would next try making sure the next easiest solution of checking & fully cleaning the osc padders mica condensers, then realigning the set to 262 kc. Then 2nd solution after that, is to look further,into the "dreaded job" of having to take apart the other IF can you didnt rebuild already and rebuild it also.
Make sure you explain to your customer the "extra" work involved, time is money!, to cover your time invested! Most customers understand totally! Otherwise, you have the Radio working again ( which is something the customers should be thankful for), and they can simply "retune" the set themselves if they dont want to pay extra.
Sounds like youve done a great restoration already otherwise!
Also check closely both the IF cans wiring insulation going into the IF cans visually for deterioration. Resleeving them if necessary with heat-shrink may help settle it down? If your radio has both push-button & clutch type mechanical tuning knob system, make sure all moving parts are clean of debris & fully operating ( engaging & releasing) "independently" from each other. IE: if the radio has pushbutton knobs that are releasing "late" from their springs mechanical system, will throw the radio off once they fully extend, and moving the clutch tuning shaft abit along the way. WD-40 is a friend here in most cases after all moving parts are fully, carefully, cleaned. Most of those old radios were very dirty with debris in the mechanical tuning systems!
Ahh, those old Chevy radios memories! ( I drove my Chevy to the levy, but the levy was dry)! Slug-tuning is a great idea when it works! Otherwise, it can definately be a "head-scratcher". Just my .02,.. Best of luck, your about to homeplate indeed!!

[Arran]

That drift sounds like an oscillator/mixer problem, bad IF micas usually cause volume drops not station drift. Check the resistors in the oscillator/mixer tube circuitry, one of them might be drifting when power is applied. I had a Northern Electric model 5001 AC/DC set where half the broadcast band would disappear, it drove me crazy for months until an old TV man pointed me in that direction, it was a 30 something Kilohm resistor. Sometimes a bad condenser will broil a resistor enough to damage it but not burn it up, it's something that many people overlook while replacing the old condensers, I would suspect a resistor going bad before a mica condenser.
Best Regards
Arran

[Retro Ron]

Gentlemen,
I have really put my foot in it this time. I started investigating this problem again and noticed the second IF transformer would crack and pop as I tapped on it. Volume would rise and drop as well. I had hoped I wouldn't have to but I decided to perform the same delicate surgery on it as I had the first IF trans. Everything was going well until I attempted to turn the slugs. You guessed it. One of them was really stuck. I tried heat, light oil, and nothing worked. Finally it broke tearing out a nice section of the coil form with it. Can anyone direct me toward a good place to find a replacement 2nd IF trans. (262KHz)?

Thanks,
Ron

[kruc]

I have a basket case 57 Chevy truck radio I gave up on a few years ago. It wouldn't fit with A/C under the dash anyway so I removed the dial to use to fill the hole in the dash. I don't know how similar it is to your 54, but you're welcome to have it for parts. I'll take a look to see if the IF trans looks like the picture.
Dave

[BILL]

That IF was used in a lot of Chevrolet trucks and manual tuning car radios , 54-53 Chevy car, 55-56 manual tuning car are all the same same IF's also 55-59 Chevy and GMC trucks and 56-59 JEEP radio, the cars are ofcourse easyer to find and cheaper I've picked up several for the internal parts, If you need something feel free to dop me a line , BILL

[Retro Ron]

I gave it a shot but I have tried and failed to find a replacement. As mentioned, it's the second IFT, 262KHz, 6-lug 3/4" with a retaining clip. Bill and Dave, thanks for your offers. I haven't quite figured out how to contact you. Can you please send me a PM and we'll work something out?

Thanks,
Ron

[kruc]

Ron, I don't do PMs though I just corrected my email adx. I'm on comcast dot net as kruc

Dave