'57 T&C Radio seems to work, but no sound

[Pink T-Bird]

Hi All,
I have an odd issue with the '57 I just bought. The radio powers up, the signal seeking acts like it is working, stopping at the 3 strongest Denver station on TOWN and stopping at many stations on COUNRTY. But not a peep from the speaker. First oddity there is a 3 prong speaker jack, but there is only a single dash speaker in a '57 T-Bird, right? That's all I see on this car. The jack has one thick and 2 thin prongs. To me that implies 2 speakers and a fader, with the thicker pin being the common for the two speakers. However the dash speaker is wired to the two thin pins presently. Aha! I thought. I took a spare speaker, and put the leads into the socket for the thick and one of the thin pins. Nope, not a peep still. Took my multi-meter and checked the 3 prong socket. 0.0 V across any socket to the other two sockets.
On the left(driver) side of the radio there is another jack, looks like an RCA jack almost. there is a green lead connected to it coiled up and just hanging there. What is that for?
Anyone else have a similar issue, and is it a simple fix like a tube in the amplifier? Also how should the speaker be soldered to the 3 pin connector? One thick and one thin pin, or two thin pins as it presently configured?

Thanks
Pink T-Bird

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[jack-in-sac]

The three prong speaker pin and the matching socket on the rood luck , J.adio body are correct. the two thin wires do go to the single speaker. The larger pin is more of an attaching device and is not part of the speaker system per se.
Apparently you do have another problem with your radio. It appears you are somewhat familiar with electrical wiring. Do you have a manual for the radio. If so it may help you in diagnosis and repair. g

 

[NTouchOne]

I think the analysis and advice provided by Jack-in-Sac is right on target. If you can find someone with a tube tester that would be a place to start. If that doesn't provide a clue to the problem, there are a couple of guys who specialize in fixing these radios. One was located in Salinas CA for the longest time. I search through my Hemmings issues to see if I can find anything further.

 

[Gary Tayman]

A number of things here. First off, the three-pin connector is a holdover from the pre-war days, when speakers had a field coil. If I'm not mistaken the big pin is grounded, one of the small pins is for the field coil, the other is for the voice coil. By 1940-41 some speakers were permenent magnet, but most were still electrodynamic -- that crazy field coil drew 3 amperes from the 6 volt battery, just for the speaker! By 1946 just about all of them were PM speakers, but they were still wired, remembering that lots of pre-war replacement speakers were still on the shelves and needed to be compatible. By around 1949-50 they quit supplying power to that third pin, so it was just there with no connections. They didn't go to a two-pin connector until about 1960. Old habits are hard to break.

If you have an ohmmeter, measure each of the three pins -- one of them is grounded to the radio case. I think it's the bog pin, but check for zero ohms. The audio output pin will have a measurable resistance, as measured through the output transformer secondary, and the unconnected third pin will measure infinite.

You can test the speaker with a battery. You might also test it with the ohmmeter, but many newer digital meters may not push very much current through he coil. I'm not sure if this is a 4-ohm speaker (some were) or an 8 ohm, but you should measure about 7 ohms for the 8-ohm, or 3 ohms for the 4 ohm. Impedance is different from resistance, which explains the difference in number. But when you measure, you should hear a crackle through the speaker itself. You may or may not hear it with the meter, but you will with a battery. Use a AA, C, D, or 9 volt -- any will work. Touch the speaker wires to the terminals and you should hear the crackle.

If all is good and you hear no sound, bear in mind that this is a hybrid radio. The audio output is transistor, with a heat sink on the back, but the front end is tube. The detector, AVC, and first audio are combined in one tube. Jiggle the tubes around in the sockets -- it could be as easy as a bad connection. Is it a tube? Possible but doubtful. It's a misconception to think that "It's a tube." Tubes may get weak over usage, but rarely does a tube kill the radio. If you had a signal tracer you could check the top of the volume control (on the bench) to see if you get audio at that point, this would narrow down the problem. Aside from what I just told you, you would need to be a technician to take it further.

The RCA connector on the back of the set is for the Volumatic feature. Radio volume changes with engine RPM; the cable should go to the distributor. If not connected the radio will still work.

These checks should keep you busy for awhile.

 

[Gary Tayman]

I think the analysis and advice provided by Jack-in-Sac is right on target. If you can find someone with a tube tester that would be a place to start. If that doesn't provide a clue to the problem, there are a couple of guys who specialize in fixing these radios. One was located in Salinas CA for the longest time. I search through my Hemmings issues to see if I can find anything further.

You'll see me in Hemmings, but I've stopped offering repair some time ago. Specializing in conversion to AM/FM Stereo.

 

[NicholasK]

Hi All,
I have an odd issue with the '57 I just bought. The radio powers up, the signal seeking acts like it is working, stopping at the 3 strongest Denver station on TOWN and stopping at many stations on COUNRTY. But not a peep from the speaker. First oddity there is a 3 prong speaker jack, but there is only a single dash speaker in a '57 T-Bird, right? That's all I see on this car. The jack has one thick and 2 thin prongs. To me that implies 2 speakers and a fader, with the thicker pin being the common for the two speakers. However the dash speaker is wired to the two thin pins presently. Aha! I thought. I took a spare speaker, and put the leads into the socket for the thick and one of the thin pins. Nope, not a peep still. Took my multi-meter and checked the 3 prong socket. 0.0 V across any socket to the other two sockets.
On the left(driver) side of the radio there is another jack, looks like an RCA jack almost. there is a green lead connected to it coiled up and just hanging there. What is that for?
Anyone else have a similar issue, and is it a simple fix like a tube in the amplifier? Also how should the speaker be soldered to the 3 pin connector? One thick and one thin pin, or two thin pins as it presently configured?

Thanks
Pink T-Bird

The green is probably a ground wire.

 

[NTouchOne]

Found a few on Hemmings, PDF is attached. Good luck. Note: The giy I mentioned in Salinas no longer repairs, just converts. maybe that is an option??

 

[Pink T-Bird]

You'll see me in Hemmings, but I've stopped offering repair some time ago. Specializing in conversion to AM/FM Stereo.

Thanks Gary. I recognize your name as a radio guru. You designed one of the the AM/FM conversions, right? Maybe heard that from Karl Jacobs outside New Orleans? Karl was a wealth of knowledge when I got my '63 Comet S-22 convertible a decade ago.
I'll take the radio out next week after I get the VIN verification and plates on the car. My appointment is Monday. I think car needs to look intact for all those official tasks.

 

[Pink T-Bird]

The three prong speaker pin and the matching socket on the rood luck , J.adio body are correct.

Sorry, not understanding "rood luck , J.adio body ". what is that exactly?

 

[Gary Tayman]

You designed one of the the AM/FM conversions, right?

I didn't design it personally, but I indeed had a hand in developing and introducing the product.

Years ago I was a major dealer for conversions, with the PCB's made by someone else. As quality went south, I got frustrated and was making plans to move my business to offering other things. Then one day I got a phone call from Detroit. A Design Engineer for the auto industry was interested in designing and building a stereo PCB designed to work in these older radios. What better source than someone who designs OEM products for new cars? We worked together on building not just a better stereo, but the absolute best performing set that could possibly be made. The result was the Aurora Design FMR Stereo Receiver. I still have the prototype sitting here in a display case. By the time it hit market in 2013, two other dealers were involved, and it's cool because we're not so much competitors as friends in the business -- we chat and help each other out on occasion. Today just about every business offering conversions uses Aurora products.

The only down side to this is that the other guys are still around, making imitation sets. People confuse those with Aurora conversions, and the difference is like night and day.

If you wish to go the Conversion route, PM me.

 

[Pink T-Bird]

By around 1949-50 they quit supplying power to that third pin, so it was just there with no connections. They didn't go to a two-pin connector until about 1960.

My '58 Mercury and both '58 Edsels have 2 pin speakers. so Fomoco must have switched to 2 pin speakers then. That year was a quiet electrical upgrade as that seems to be when Ford went to the Neutral Safety switch allowing engine start in Park too for all car lines.

 

[doug7740]

If you are looking for someone to repair your AM radio, Classic Car Radio Doctor still does repairs as well as conversions. I have never used them, because I repaired my own radio.

Here's the link:

Antique car radio repairs

car radio repairs

classiccarradiodoctor.com

doug7740
1955 Thunderbird Blue

 

[Gary Tayman]

My '58 Mercury and both '58 Edsels have 2 pin speakers. so Fomoco must have switched to 2 pin speakers then. That year was a quiet electrical upgrade as that seems to be when Ford went to the Neutral Safety switch allowing engine start in Park too for all car lines.

You're right. I was thinking Fords. The Ford sets, bioth Motorola and Bendix versions, were similar through 1959, and when the redesigned 60 came out it had a different connector. The Thunderbirds had a similar radio from 58-60, with a separate heat sink, and if I'm not mistaken the 58-59 had the same 3-pin connector while the 60 had a 2-pin. Maybe they finally ran out of the others. Lincoln/Mercury began putting fader controls on their sets in 1949, and had a big round conector which could accept two 2-pin connectors, one horizontal and one vertical. Edsel had a different radio entirely, made by Stromberg-Carlson. It had a separate output unit, but the speaker connector was on the radio itself. Not sure, but it might have been that same four=pin setup as the Lincolns. By 1961, they pretty-much migrated to bullet connectors.

 

[zeroroadkill]

Hi All,
I have an odd issue with the '57 I just bought. The radio powers up, the signal seeking acts like it is working, stopping at the 3 strongest Denver station on TOWN and stopping at many stations on COUNRTY. But not a peep from the speaker. First oddity there is a 3 prong speaker jack, but there is only a single dash speaker in a '57 T-Bird, right? That's all I see on this car. The jack has one thick and 2 thin prongs. To me that implies 2 speakers and a fader, with the thicker pin being the common for the two speakers. However the dash speaker is wired to the two thin pins presently. Aha! I thought. I took a spare speaker, and put the leads into the socket for the thick and one of the thin pins. Nope, not a peep still. Took my multi-meter and checked the 3 prong socket. 0.0 V across any socket to the other two sockets.
On the left(driver) side of the radio there is another jack, looks like an RCA jack almost. there is a green lead connected to it coiled up and just hanging there. What is that for?
Anyone else have a similar issue, and is it a simple fix like a tube in the amplifiere wire) with the ? Also how should the speaker be soldered to the 3 pin connector? One thick and one thin pin, or two thin pins as it presently configured?
Thanks
Pink T-Bird

Only one dash speaker. The three prong plug connects to the speaker. The spare wire (mine is yellow) with the bullet pin is not used.

 

[Pink T-Bird]

Lincoln/Mercury began putting fader controls on their sets in 1949, and had a big round conector which could accept two 2-pin connectors, one horizontal and one vertical. Edsel had a different radio entirely, made by Stromberg-Carlson. It had a separate output unit, but the speaker connector was on the radio itself. Not sure, but it might have been that same four=pin setup as the Lincolns.

Absolutely correct on all counts. The S-C radio has a remote box behind the right kick panel. The 4 pin speaker connector is on the radio. One of my Edsels uses all 4 pins and the fader for the rear speaker, the wagon is dash only. Both are T&C, which was uncommon, but they came to me that way. I know my Merc is Motorola, but forget whether it has the 4 pin setup as it only has the 2 pin dash speaker and I haven't needed to mess with it in decades (jinx).

 

[Gary Tayman]

I think the only Stromberg-Carlson radio made for factory use was for the 1958-59 Edsels. I know they made an aftermarket (dealer-installed) set for the 1960 Ford -- I know that because i had one on the shelf for awhile. It looked just like the factory sets in the dash, except the tiny F-O-R-D letters were replaced with four square dots. Interesting because the 1960 Edsel was essentially a Ford, and had the same radio as the Ford. That external output transformer on the 1958-59 types are problematic, and no replacement is available. The "fix" is to install a modern audio amp (Radio Shack kit or similar) inside the radio, bypassing it. There are a lot of such fixes; diodes replacing rectifier tubes, modern individual electrolytics replacing (or in addition to, which is dangerous!) the original can, jumpers across IF's, etc. These tricks will get it going, but the set is no longer original, and if no longer original, why not convert? That's one of many big reasons why I no longer do repairs and why fewer and fewer dealers do.

The Edsel T&C sets are Stromberg-Carlson, but the seek tuner I believe is Bendix. Can't remember for sure been awhile since I've done one, but I know it's NOT the Motorola type with the planetary gears in the back. And getting back to Thunderbirds, the 56-57 Birds have Motorola sets with the planetary gears.

 

[Pink T-Bird]

Thanks for the tips folks. Here's an update:
with a 9V battery across the two thin pins there is normal sounding static from the speaker so speaker is OK?
3
2 1
numbering the pins with the large one as 3 and the thin pins as 2 on the left/front and 1 on the right/rear the case is G or ground - here are the ohm readings with radio off. None are 0 ohms.
1-2 Infinite
1-3 1.2
1-G 0.6
2-3 infinite
2-G infinite
3-G 0.3

 

[Gary Tayman]

If you hear static in the speaker with a battery, it means the voice coil is good and you should hear something if the radio is good and wired properly.

The big pin has zero ohms to ground, for all intents and purposes. I'm not looking at a set right now, but I was quite certain the big pin is ground. It only makes sense, as the bigger pin would be the one that carries the most current -- and in the field coil days that was indeed the case. Pin 2 is the open one, formerly used for field coils. Pin 1 has a low resistance to ground, reading through the output transformer secondary.

If your speaker wires are connected to 1 and 2, you have an open circuit. Connect the speaker across 1 and 3. Pin 1 should be the high side, IF you can tell which wire the high side is. If you wire it backwards it really won't make any difference as long as you're using only one speaker -- which is why, before the days of stereo, they didn't pay much attention to polarity anyway.

 

[Gary Tayman]

Just to follow-up:

I have a 57 Thunderbird radio on the bench right now, converting it. The original speaker connector -- the big pin is soldered directly to the case of the radio. The little pin closest to the back of the radio is not connected at all. The pin closest to the front of the radio is the audio output. The speaker should be connected between the output pin and the big ground pin.

 

[Pink T-Bird]

Excellent! I will move the speaker wiring to the correct pins and keep my fingers crossed. I forgot to post earlier the speaker shows 7.3 ohms across the leads, so 8 ohm impedance. And when I connected the multi-meter leads together today I got 0.3 ohm, so I would think that offset applies to all my readings above on 8/29.
I know you mentioned polarity isn't very important with a single speaker, but is there a way for me to determine which speaker lead is "correct" for the front pin vs the big pin? What I can see under the dash looks like home stereo speaker wire with the clear insulation rather than the brown insulation on my other old vehicles with original speaker leads, so maybe It's just my best guess.