'50 mercury radio stops working after a few mins

[jbivy]

So another car guy i know just had his radio rebuilt for 350 bucks... It worked for 30 mins and then didnt play. Now it only works for several minutes after turning on.

He asked me to take a look at it. I figured i can test the tubes, go through it with the photofact and see if theres anything obviously wrong.

So ive two questions.

What should i be looking for?

whats an easy way to power this on my stand? Perhaps a 6 volt lantern battery?

[Sandy G]

I THINK they used sumpin' back when called a "Vibrator"-Seriously-I dunno if a 6V supply by itself would work.

[jbivy]

Im mainly dumb founded that he paid 350 to have it rebuilt.

Id have tried and done it for parts cost. I know i couldnt do any worse than the guy he hired.

Well i just picked up a sams for this. Hopefully ill figure it out.

But powering it still makes me wonder. Ive seen referances to "vibrators" with old car radios, but cant seem to find out what they are.

[maxhifi]

I used a battery charger to power up an old radio from a packard. A lantern battery likely won't last very long. A lead acid or gel battery will last a while longer. Some battery chargers can be switched between 6 and 12V. Don't put 12V on it.

To figure out what's wrong with it will require a bit more work. Make sure to rule out problems external to the radio, like his car's wiring or antenna connection, etc.

[maxhifi]

whoever restored it likely put in a solid state replacement for the vibrator.

The intermittent could be anything, and may not be because the guy who repaired it did a bad job. For 350 I would expect he replaced all the capacitors, aligned it, and replaced the vibrator, tested tubes, etc. Could be a bad solder joint or connection, a bad tube (not too likely), a shorting mica cap in an IF can, etc.

[Reece]

I would think he'd go back to the first guy and have him fix it. That radio needs a strong 6 volt supply. A lantern battery won't cut it but a hefty 6 volt charger would do in a pinch

[jbivy]

Originally Posted by Reece

I would think he'd go back to the first guy and have him fix it. That radio needs a strongt 6 volt supply. A lantern battery won't cut it but a hefty 6 volt charger would do in a pinch

Apparently he wanted him to fix it for free (id have too, but then i cant imagone paying that to have it redone), the guy wouldnt do it. He knows im no expert but if its simple, i can figure it out.

Ive a battery charger that has a six volt setting, hopefully that will work.

So what are vibrators anyhow? (come on, no jokes here)

[bandersen]

It's a simple way to generate the higher voltages needed for the tubes. 6 volts is fine for the filaments, but not enough for the plate circuits.

Check this out: http://radioremembered.org/vpwrsup.htm

or kick back and watch the "old goat" explain it http://www.youtube.com/watch?v=Fp6PkRTmb8U

[teevee]

Check and see if the B+ stays up, on the vibrator sets there is a "buffer condensor" around the vibrator circuitry, typically a small 1600V unit. If they go leaky, they drag down the B+. Left on to long, they will either spew hot wax around, or just short and take out the vibrator and maybe power transformer..

[bob91343]

Listen to, or feel, the vibrator. It should be humming nicely. When the radio quits, the humming may or may not stop. If it stops, the vibrator is bad. If it keeps humming, measure the B+ on the tubes; it should be a couple of hundred volts or so.

Look for bad solder joints or corroded tube sockets. It's a normal troubleshooting exercise; I could do it easily here. But I am in Los Angeles.

When the radio stops, does it go completely dead, or can you still hear some speaker noise when you rotate the volume control? Put a finger on the hot side of the volume control to see if you get audio from the speaker.

[Don Lindsly]

If the vibrator hum stops, make sure the tubes stay lit. If not, it is probably a bad off/on switch. That was a problem in 6 volt radios.

[jstout66]

I remember going to a local TV store as a kid.. (circa 1980) to get a Vibrator for our 1955 Chevy, and wondering why the store owner and his wife broke out into laughter when I asked for one, and saying "oh.. not the kind you use at home, but for a car" which caused the owner to choke and run to the back room. (I'm sure I didn't know what that meeant) ha!

[bob91343]

I am sure there were many vibrators used in 1955 Chevrolets.

[DavGoodlin]

Choke-snort.....but seriously, I rebuilt a 53 Chevrolet 6-volt radio for a friend. The solid state vibrator came from a place in Florida called radiodaze. There are several kinds, 6 v negative ground, 6 v positive ground etc. I good used old tractor battery worked for me.

The buffer cap was hidden under an RF shield and I missed it on the re-cap. Blew up the first SS vibrator and I bought a second after discovering the mistake.

[old_coot88]

Jbivy,
Does the radio use a 0Z4 (cold cathode gas rectifier tube) or a vacuum rectifier (6X4 or 6X5) tube? In my experience, 0Z4s had a higher failure rate than vibrators.