[R3Sons]

Hello, I have a Philco (Ford) 6TPZ and a 5TPO radio.  I replaced the electrolytic capacitors in both.  I have the SAMS manual.  When I connect power, ground, and antenna, the bulb lights, but there is no sound at all.  Volume all the way up and down, power on and off.  No static, no nothing.  If I scrape the speaker connections I can hear a faint hiss, but that's it.  I'm trying to get my signal generator working, but so far, I'm not sure where to look.  The potentiometers both test ok.  Visually everything else looks ok. Am I missing something big, or just overlooking something simple?  I just find it really odd that both radios have no output at all.  I've searched for any troubleshooting info, but I have not been able to find anything.  I would really appreciate any assistance. 
Thank you

[GarySP]

Welcome to the Phorum, R3Sons! I have very limited experience with car radios other than installing custom radios back in my early years working for Montgomery Ward Auto Service. Plenty of our members here willing to help you out, however. Take care and BE HEALTHY! Gary

[morzh]

I am not a specialist in car radios.
I suspect they might use vibrators to convert 12V to acceptable tube voltages, so you need to measure your voltages (tubes plates or B+ towards the common/chassis), and only spend effort troubleshooting the radio itself if those are OK.
If not, you will need to fix your power supply first.

[R3Sons]

Thank you Gary. Hi Morzh. These radios are 6 transistor radios. Sadly no tubes. Thanks though.

[GarySP]

Since these radios operated in harsh environments (temp changes and vibration) you could touch a soldering iron to all the solder points on the boards to eliminate possible cold solder joints. Just a thought... - Gary

[morzh]

Transistors are easy.

No converters. If you have input voltage, then just put some signal through.
Or touch your finger to the Base of any audio-amp transistor and see if it hums.
You might also check the speaker first to make sure it works. Desolder one wire and touch a 1.5V battery to the lugs, see if it makes that scratchy sound.

If you put the manual link or PDF file here, we could be more specific.

[R3Sons]

https://www.worldradiohistory.com/BOOKSH...Vol-28.pdf
https://www.worldradiohistory.com/BOOKSH...Vol-32.pdf

Here are the links. 6TPZ and 5TPO

The speakers are good. I've tried several known good ones. I just have to find a tiny cap for the signal

[morzh]

5TPO-radio.pdf Size: 247.03 KB  Downloads: 98

This is what I meant.


I would start from touching Test Point 12 on the sch.
See if you hear hum.

[R3Sons]

Thank you morzh. I will try that today.

[R3Sons]

Well.... Test point 12 is confusing. The capacitor shown is not there. Apparently it was optional. One radio is pulling enough amps to melt the wire from the pot to R15, the first resistor. The second is only pulling 9 volts. So confusing. I'm going to try to trace some circuits out. Could the pots be the problem? Thanks.

[morzh]

R3,

Let me ask you this: how much, if any, experience do you have in radio repair?
If you don't have much, I suggest that instead of powering up radios and see wires melt and amps drawn, you step away, think a bit, and develop a plan of testing (this is where we can help) that is safe and methodical.

One way that safe and methodical is not, is turning the radio on without making sure it is safe and ready.
And while this is a transistor radio and does not work with dangerous voltages, so electrocution is not likely, this still can put things on fire.

My suggestion:

1. Whatever you have replaced: trace it to the schematic and make sure you followed what's in it.
2. Check the power in for shorts, where it goes to the rest of the radio (In 5TPO it is 18 ancd 19 to GND).
3. Check every transistor for integrity and leak. My favorite is an analog arrow multimeter set on Ohms. B-C, B-E and C-E.
Do not power before you make sure all above is good.
4. If after power-up it still draws excessive current, try to see what draws it. There are ways. From smelling, running the back of your palm or back of fingers near parts and see if anything is hot, to measuring voltage drops across the circuitry and trying to see what drops it etc.

It is fairly simple: transistor schematics are way simpler than tubes to work with, but transistors are at the same time are very easy to kill, unlike the tubes.

PS. for the TP12 in 5TPO use the X8 diode's Cathode (bar).

[R3Sons]

Thank you morzh. I sincerely appreciate the advice. That's why I'm here. I am ready and eager to learn. I have a lot of experience in electronics in general (mostly pc circuit boards). I have been successful in tube radios and transmitters, but maybe i've just been lucky. I've been tracing the schematic out. Everything I replaced is correct (quadruple checked). I used the values that are listed, which happily matched the ones I replaced. I removed and checked the capacitors again, then replaced them. I have not checked all of the transistors. Everything was doing ok, just no sound. Voltage and amps were stable. Then, (now both radios) only want to draw 5-7 volts. So, I'm having a lot of trouble tracing out any voltage drops. While trying to measure voltage I scraped my hand across a few solder points and could hear scratching in the speaker. I really was trying to be methodical. Clearly I missed something big. Point 18 was 12.6v and point 18 was 10v. This was good for a while. I was testing the other points and then things started fluctuating with the voltage. I will try testing the transistors now. Thanks again.

[R3Sons]

Sorry, point 19 was 10v

[morzh]

OK, experience with electronics helps.

What do you mean by " draw 5-7 volts"?
Amps are drawn, Volts are applied.

Where do you have these 5-7 Volts measured?

And let's at this point limit ourself to one radio: 5TPO, now that we are looking at this schematic.

[R3Sons]

One radio, check. I connected the power wire to 12.2v. I measured all of the voltage on the wires on the potentiometer. While I was measuring the power input wire, the voltage started to drop. It went from 12.2v to 9, then to 7 within 20 seconds. Now, when I turn it on, it drops immediately to somewhere between 5v and 7v. This is the wire from the power source to the potentiometer. This is also the same for the power wire for the light. When I turn the power knob to turn it on, it starts at 12, then drops to 5-7v within 5 seconds. This is very confusing. I understand when amps change based on draw, but I really don't understand why the voltage would drop like this.