Packard Forum Index » V-8 (1955-56)

My Wonderbar radio does not stop on the selected preset button station, though note that I don’t have them set to actual stations. Does the radio need to receive a signal from the selected station to stop there, or should it stop there regardless?

I believe it is a combination. The radio needs a broadcast signal, strength of what the radio responds to being modified by the sensitivity selection lever. That part of the circuit is what the large seeking bar on top responds to.

When a specific button is pushed part of the automatic seeking circuit is bypassed. Each of the individual buttons has a sliding contact which makes a connection to a copper foil trace on the phenolic board that holds the sliding contacts. Another contact on the end of the dial arm slides over the sliding contacts to complete a circuit going to the tuning circuit. That completed connection triggers the stop tube so the pointer stops at the selected station.

If you flip down the thin door above the individual buttons you can see the sliding contacts and phenolic printed circuit board that holds them. One probable issue is the copper traces on the board have oxidized and lost good contact with the sliders. Another issue is the contacts on the individual slides or arm assy is also dirty or has been damaged and is not making good contact as the arm slides over.

There is a schematic of the 55 signal seeking radio in the literature archive. As I recall, the 56 power supply is slightly different but the tuning section is the same.

Thanks Howard. Per my inspection the contacts appear to be in good condition. I can hear the “fuzz” specifically when the pointer passes over the selected contact. If the station is required to exist for the mechanism to actually stop there, that would be the problem.

All of below are my results and feeling of My 57 Clipper and Randy (my) Caribbean radios with dual power antennas. Both radios were rebuilt by army friend of mine both work same way. When in garage will not stop at some of weaker station button is set for. Radio reception not as good when inside garage. Both radios work better with antenna extended. I can not have antennas up all the way and clear garage door. Don't like look of antennas fully extended . For looks I keep them lower and and unplugged from power as they will only be same height when up all way or down. When fully extended remind me of some kind of deep sea fishing boat. When down worry about someone getting eye poked out looking at back of cars

The fender antennas are indeed quite tall! One of my mid-60s cars had one that made Packard's look like a stub. I had never seen such a tall antenna even on cars of the same year and make. The car was coachbuilt so I expect the antenna and a couple other things were special order over the opulence it already had. Back to the topic, it had two signal seeking radios and both required a signal to stop so it was something common to the design rather than to the make.

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Noticed this in the schematic. The top-middle wire in this crop is the cathode connection from the RF amp tube which normally grounds out which is required for the RF amp to function. When one of the buttons is pushed, this ground connection is broken which halts the output of the radio by stopping the RF tube from working, meaning no signal will get to the rest of the amplification circuitry. Only when it the arm passes over the correct contact is this connection restored to allow the rest of the circuitry to react to the strong radio signal. Hence if the preset does not correspond to a station which the Wonderbar would stop at at the most sensitive setting, then the preset button will not stop there. All of this is noticeable in the audio output (mostly the lack thereof) during this process.

To see if it is signal strength or another issue with the Wonderbar tuned pick a strong AM station and set one of the buttons to that station. Then give it a go.

I had the radio in my '51 serviced a few years back. The shop's owner worked and worked on it and never could figure out why the auto tune function wouldn't work.

Good Luck.

Currently I have been bench testing it with a switching power supply which garbles up the output. I will test with a fuse and battery later.

Perhaps the trigger tube was going bad? With new caps, new tubes, and polished contacts there is very little that could cause a problem unless it was pulled out of a swamp or something. The trigger tube monitors the AVC line to get the current signal strength. When the AVC line is pulled low enough (strong signal) the trigger tube reduces its amplification. Instead of amplifying an audio signal it "amplifies" the power available to the solenoid that keeps the tuner from stopping its progression. Less amplification = less power for the solenoid, and it releases the catch to stop the autotuner.

I was curious today whether any solid state tube replacements were available but all I spotted was the 0Z4 which, of course, is a simple rectifier with no filament. In any event, I can't find any information in the radio schematic section for the 1955-1956 signal seeking radio so if you have a PhotoFact or similar, any chance that you can scan and upload it?

The Wonderbar radio is in the radio sheets section. The 55 push button is not, but I sent Kev the photofact to add. Also an alternate schematic for the Wonderbar.

Considering all the tubes still have plentiful NOS that work perfectly, I'm unsurprised there are not alternatives. The 0Z4 is not even a heated tube, so I doubt it would go bad very fast, but it could also almost certainly be replaced with a pair of diodes, though according to the datasheet it has a forward voltage of 24V! Compared to under 1V for any diode, so the output voltage would be a bit too high and would need a resistor to drop it a bit.

FYI here is a list of all vacuum tubes currently manufactured:web.archive.org/web/20211224031643if_/ht ... asno.ca/articles/vacuumtubemans.htm