Pulling The Radio In my '53

[keithb7]

My stock tube AM radio quietly died one day last fall. I never got around to pulling it to check it over.  It's about time I did. I have some tube amp experience and testing equipment. I think I can fix this once I get it out. I have an old tube tester as well. I suspect a dried up old capacitor or maybe a bad tube. 

 

I have a 1953 parts manual as well. No drawings in it. In my 1953 shop manual I see some info on removing the radio and speaker power unit.

 

Looking up under there with a flash light I see a few things. The radio is separate from the speaker/power supply? There seems to be tubes and cap-cans behind the speaker. You can see the radio in my pics here, then the clock beside it, then the speaker to the right of the clock. There is what I think is the power unit with tubes, behind the speaker. I see in the parts book they may call this a "shelf panel". Part number 150389, oval type speaker. Can anyone confirm if there are more additional tubes and caps inside the radio housing? I am wondering if I may have to pull the speaker shelf panel in addition to the radio unit to check over the circuit power supply. Or maybe I just pull the shelf panel and test everything there. I suppose I'll start there and see what develops.

 

I have never taken this part of the dash apart. I'll go with the service manual instructions and see how things progress. Any tips/experience appreciated. First time going in this for me.

Thanks, Keith.

 

 

[Thomba48]

Basically this radio has three main connections to the dashboard.

 

Connection 1: Front - both front dial knobs. Take the knobs of, underneath you should find a nut. Take it off and that part is loose then.

Connection 2: Underneath the dash. For that you will most like have to take the heater switch assembly off. Between the radio and the heater assembly there are most likely 2 or 3 screws that need to be unscrewed.

Connection 3: Firewall/ vent assembly. On the back of the radio there should be a final connector that connects the radio tightly to the firewall, vent assembly.

 

I hope this helps. Thom

[keithb7]

Thanks Thomba48. The power unit was easy enough to get out. I did have to remove a heater blower motor down there that impeded removal.

 

Here are a few pics for those interested.

 

 

[Dodgeb4ya]

Some one has already been into it..speaker replacement and plastic wire looks like.

[keithb7]

I agree with you on that Dodgeb4tya. Orange ground wire off speaker is new.

 

Under those tubes is where the brains of this hi-fi system is. Remove three screws, flip it over and you get full access.

The circuit appears 100% original from what I can tell. I will start by testing the tubes in my tube tester and see if the problem is as simple as a bad one.

 

While I am this far in I will consider ordering new coupling caps as these are 68 years old. The muti-section cap-can too. These electrolytic caps are prone to drying up and failing. They were not intended to be still around in 2018 lol. Many figured we'd be commuting in flying cars by now. Looking at the lack of a circuit board, the assemblers of this power amplifier did a great job back in 1953. Tight space and they made good use of it. I'll measure all resistors to see if they are in spec and replace any that are not.

 

More to come as I progress.

 

 

Edited September 21, 2018 by keithb7

[keithb7]

Great news! The schematic is still in place. I will tag radio info here so it will come up in future internet searches. Maybe someday someone will be looking for same info. Philco Models P-5206 D-5207 C-5209 Power Unit and Speaker chassis. Schematic part number 78-0894.  1953 Chrysler Windsor Deluxe. Detroit built. 

 

I'm off to refresh my memory on what the vibrator actually dues. It's the biggest metal cylinder can seen in the chassis shot above with the tubes visible. On the schematic it's shown as some sort of coil. Very bottom left of the schematic image here:

Edited September 21, 2018 by keithb7

[sser2]

The circuit is the last stage of power amplifier/phase splitter + power supply. In addition to capacitors, which should be all replaced regardless of whether they test good or not, the power supply  vibrator unit is one component particularly prone to failure. Check high voltage (should be about 250V under load) to make sure PSU is working. Bad vibrator sometimes can be fixed by opening it and cleaning contacts. BTW, it would be a good idea to replace the vibrator PSU with a modern solid state DC-DC converter All tubes in this unit are still cheap and plentiful. 6AQ5 tubes have to be matched for equal current through primary halves of the output transformer, so buy a matched pair if you need replacement.

 

To your question, vibrator is a buzzer that switches 6V DC through the primary halves of the power transformer T2. Upper contact on the diagram connects 6V to the upper winding half, and lower contact to the lower half. This sends short pulses of 6V opposite polarity through primary halves. The secondary winding of T2 raises the pulsating voltage to 2x250V. 

Edited September 21, 2018 by sser2
Add information

[keithb7]

Thank you @sser2. I will try and find a matched pair of 6AQ5 tubes. My tube tester is thermionic type. The two 6AQ5 tubes and the 6X4 rectifier tube show up as pretty weak. As you said, the tubes are cheap, I will order new ones. I do see a solid state 6V + ground replacement vibrator is available for $30 US.

 

Edited September 21, 2018 by keithb7

[sser2]

32 minutes ago, keithb7 said:

Thank you @sser2. I will try and find a matched pair of 6AQ5 tubes. My tube tester is thermionic type. The two 6AQ5 tubes and the 6X4 rectifier tube show up as pretty weak. As you said, the tubes are cheap, I will order new ones. I do see a solid state 6V + ground replacement vibrator is available for $30 US.

 

I have shitloads of NOS 6AQ5 tubes and can send you a matched pair for free, PM me. DC-DC converter should be 6V input 250V @ 50-100 mA DC output. Converter replaces the whole power supply, so no need for vibrator, power transformer, and 6X4 rectifier. I guess your $30 thing is electronic vibrator, that will still require T2 and rectifier. NOS 6X4 tubes worth about $5 apiece, don't pay too much for it.

Edited September 21, 2018 by sser2

[keithb7]

@sser2 PM-ing you. Thanks. Keith

[pflaming]

With that radio you can listen to three kinds of music, '50's favorites, country, and western! WOW. 

[keithb7]

Final follow up, the radio got all new caps and tubes. Resistors checked out in spec. I reassembled it and installed it back in my car.  It works again. Yay!

Unsure if it was a bad tube or capacitor. Either way, all were old and due for replacement.  The radio audio now sounds fuller to me and maybe a little louder too.

Tone control has a nice effect. I look forward to summer cruising again with the radio on. 

 

I did have an iphone Bluetoothed to a speaker for a while, when the AM radio was dead. Iistening to modern set lists via my iphone just wasn't right.

The AM radio adds to the 50's car cruise experience. Evening cruise with the ball game on? Or Sunday evening oldies? Now were talking. Where's the nearest ice creme stand?

 

[sser2]

Congrats on fixing it!

[pflaming]

You can keep the radio, I want the Chrysler! LOL 

[keithb7]

2 minutes ago, pflaming said:

You can keep the radio, I want the Chrysler! LOL 

 

This one? Sorry. Nope.  She’s a keeper.  ?