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I have a wonder bar am radio in my 1960. The radio works, but every time I press the wonder bar to scan for stations it blows the fuse for the radio. Anybody have any ideas?
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Re: wonder bar problem
Most likely, one of the solenoid coils is shorted out. This was a common failure item, since if the radio did not lock on a signal, the radio just keep looking which meant the coils just kept firing until they overheated and burnt up. There are two coils, one to charge the spring and the other drives the tuner to the begenning of the dial after it has completed it's cycle. If you are not electronically inclined and do not have detailed schematics of the radio, I would advise against a self-repair on the radio. There is a guy on Ebay who advertizes that he is reproducing these coils, but I have never bought from him. Every time I get a chance to buy some junk radios, I will, just to get the solenoids and volume switch. These are 2 parts that up until just recently were only available from salvage sets. These old radios are very durable and can be repaired if you can find the parts. Do the repair right and replace all the capacitors with modern ones while it is apart, and it will probably work for another 20 years. That is asuming there is anything to listen to on the AM dial by then!
Regards, John McGraw -
Add-on
John's on the money here. The typical WonderBar 'syndrome' includes the radio blowing fuses during seek operation(s). What many don't understand is the design of the radio is essentially a mechanical 'swiss watch' with drift rate of the seek mechanism and the ability to stop on station, being CRITICALLY associated with the MECHANICS of the radio and not the electronics.
To compound matters, the Corvette WB operates in a 'hostile' environment... Since the chassis HAS to have cooling vent holes, the 'innards' are exposed to the atmosphere and the radio is positioned in-line with the car's vent cowl. This means it's prone to picking up airborne debris and moisture via the natural effect of convection cooling through the chassis.
When you punch the seek button, a relay latches to disengage the tuning mechanism's clutch allowing the drive spring to propel the tuner up the dial. A one-shot circuit monitors received signal strength and when signal strength is above a critical threshold (set by the 3-position, red, sensitivity switch just below the seek button), the one-shot fires to release the clutch and stop on station.
If the tuner hits the upper end of the dial, a mechanical ratchet/prawl fires a solenoid to re-cock the seek spring and return the tuner to the low end of the dial. Later versions of the WB (circa '62) would combine the seek/stop and re-cock/return functions into a single solenoid circuit vs. two discrete solenoid circuits.
Since there are HUGE transients involved in firing the seek mechanism's solenoid(s), there is NO internal protection for current overload. Everything depends on the 7.5 Amp external fuse in the fuse block! Even with the 7.5 amp external fuse, the circuit topology is such that you're playing with FIRE if you allow the WB to go into an 'infinite seek' mode. It's a crap shoot as to which will fail first: one or both of the seek solenoid(s) vs. the fuse in the fuse block!!!!
The WB 'syndrome' is this. Everything worked A-OK and we drove & listened for a number of years. Eventually, atmospheric bore 'crud' inflitrated the chassis, gummed up the tuner mechanism, changed its friction coefficients and 'unreliable' auto-seek operation resulted.
Instead of pulling the radio and having it's mechanics serviced, the prior owner drove on, putting up with 'quirks' in the seek function. Finally, the radio started to blow external fuses. Again, instead of seeking service/repair, the owner drove on and replaced fuses as necessary. Eventually, he tired of the 'nuissance' and upped the 7.5 amp fuse to one with a larger value.
Eventually, there was a puff of smoke (one or both seek solenoids burned out) and the WB radio was pulled. Then current repair techs, counciled it was more costly to repair the original AM only radio vs. replacing it with a modern, all electronic AM/FM/Stereo unit and the WB hit the shelf in someone's garage.
Later, it would be 'discovered' and sold as a rare, concours, original radio WITHOUT being serviced! Most radio techs with any vacuum tube experience know how to put one of these 'gems' on the bench and get the AM portion of the radio working again. But, FEW have any experience with servicing/maintaining the electro-mechanics of the WB seek system. So, you need to shop your repair/restoration technician CAREFULLY in terms of his credentials. There's more than one 'quack' out there advertizing himself as a WB 'pro'...
Last, as John aluded to, the technology of the capacitors used in these radios is 'archane' to say the least... They're prone to aging with the effect being excessive internal leakage and loss of absolute capacity. This can effect not only the radio's ability to couple demodulation and amplification stages (weak output, buzzing, Etc.) but to deteriorate the precision of the seek mechanism's sensitivity threshold along with it's one-shot signal detector/solenoid control circuit.
The real pros who work on these radios do NOT simply repair them! They understand the aging effect and GUT the circuit boards for their factory original capacitors and replace them with contemporary components (typically polypropeleyne capacitors) that are ROCK solid and virtually invincible to aging. While they're at it, these pros have a full Delco Radio support library and they go ahead and install ALL of the circuit fixes/improvements that Delco discovered and alerted their tech network to over the years....
So, when shopping for a repair facility, ask up front what you're going to get for your repair dollar. If it's simply a bench repair to get the radio grossly functional again, I suggest you keep looking....Comment
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Regarding the ventilated chasis:
I found a mud dabber (wasp) nest in my wonderbar.Comment
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