64' Ford Falcon Radio Buzzing

[caphair]

Hi guys my friend's dad wants me to try repairing this radio from a 1964 Falcon.

He says it only buzzes and there's no audio.

I tested the PNP part# 8P404V TO-3 transistor that's mounted to the back of the case and all measurements from B to C/E seem fine but from C to E I get .018 one way and .044 the other in diode mode. When I ohm test C to E I get a reading of 43ohms.

Shouldn't it be a higher reading? A replacement transistor is $35 so want to verify its bad before ordering a replacement.

[R_J]

Re: 64' Ford Falcon Radio Buzzing

Is that measured in circuit or out?
is there a model number on it somewhere

[caphair]

Re: 64' Ford Falcon Radio Buzzing

Is that measured in circuit or out?
is there a model number on it somewhere

Out of circuit and there's a label on the underside but it's all faded and can't make anything out.

Would like to repair it as my friend wants it to be a Christmas gift to his dad. But it's so old school with wires everywhere and no circuit board that it's hard to follow lol

[R_J]

Re: 64' Ford Falcon Radio Buzzing

That does seem like its shorted e - c

[caphair]

Re: 64' Ford Falcon Radio Buzzing

That does seem like its shorted e - c

Wouldn't it show shorted from B to C/E too though or no?

Also when the radio is powered on it makes little crackling static sounds when the volume is turned up and down. Would that happen with a shorted output transistor or would there be no noise at all?

[goontron]

Re: 64' Ford Falcon Radio Buzzing

Sounds like the IF stage is gone.

Have you tried injecting audio into the audio amp/mixing stage?

[caphair]

Re: 64' Ford Falcon Radio Buzzing

Sounds like the IF stage is gone.

Have you tried injecting audio into the audio amp/mixing stage?

IF stage? I haven't tried injecting audio. I wouldn't know where to inject it. Never worked on audio stuff before

[goontron]

Re: 64' Ford Falcon Radio Buzzing

IF stage? I haven't tried injecting audio. I wouldn't know where to inject it. Never worked on audio stuff before

Ah, sorry. The IF stage is an intermediate step in reception. It shifts the carrier frequency.

Does the chassis have a nameplate with a chassis model number? I can look up the schematic for it.

[caphair]

Re: 64' Ford Falcon Radio Buzzing

Ah, sorry. The IF stage is an intermediate step in reception. It shifts the carrier frequency.

Does the chassis have a nameplate with a chassis model number? I can look up the schematic for it.

I'm not seeing anything on the chassis with labeling unfortunately. So you don't think the transistor is bad but the IF stage?

[goontron]

Re: 64' Ford Falcon Radio Buzzing

I'm not seeing anything on the chassis with labeling unfortunately. So you don't think the transistor is bad but the IF stage?

No, that transistor is definitely leaky. Actually that doesn't look like the an audio amp transistor, it's attached to an RF coil. And the transistors in the amp section are usually bigger, or non existent if it's a hybrid set. If i had to guess you may be looking at the IF section.

More than likely the majority of them are leaky like that. i count four on that side alone. Exact replacements (germanium IIRC) are expensive, i would go through the datasheet and try to find some modern equivalents. I would also do a recap.

EDIT: Digging on the radio forums it could be one of many.
5TBD, 5TPD or if Motorola made any for that year, 5TMD.

BTW, The model number is stamped on the side of the radio, towards the rear, followed by the serial number.

[kc8adu]

Re: 64' Ford Falcon Radio Buzzing

start by replacing all lytics.
including the multisection can.
old germanium transistors like to leak.even develop tin whiskers inside.
the to-3 is the output.many pnp ge will work.

[caphair]

Re: 64' Ford Falcon Radio Buzzing

start by replacing all lytics.
including the multisection can.
old germanium transistors like to leak.even develop tin whiskers inside.
the to-3 is the output.many pnp ge will work.

What would be the multi section can?

How do I find an equivalent pnp? I have some from a monitor that were part of the push-pull inverter section

[caphair]

Re: 64' Ford Falcon Radio Buzzing

No, that transistor is definitely leaky. Actually that doesn't look like the an audio amp transistor, it's attached to an RF coil. And the transistors in the amp section are usually bigger, or non existent if it's a hybrid set. If i had to guess you may be looking at the IF section.

More than likely the majority of them are leaky like that. i count four on that side alone. Exact replacements (germanium IIRC) are expensive, i would go through the datasheet and try to find some modern equivalents. I would also do a recap.

EDIT: Digging on the radio forums it could be one of many.
5TBD, 5TPD or if Motorola made any for that year, 5TMD.

BTW, The model number is stamped on the side of the radio, towards the rear, followed by the serial number.

That transistor was screwed into the back of the radio on the outside of the case. I'll double check for the model number tomorrow

[goontron]

Re: 64' Ford Falcon Radio Buzzing

That transistor was screwed into the back of the radio on the outside of the case. I'll double check for the model number tomorrow

That is output then.

[caphair]

Re: 64' Ford Falcon Radio Buzzing

That is output then.

Does that mean the other 4 are part of the preamp? Also would I need an antenna for testing? They didn't give me one but I imagine AM radio would be picked up fine?

[stj]

Re: 64' Ford Falcon Radio Buzzing

just start with a full recap - use 105' types.
then re-test.
it may just be caps - it's 52 years old!!!

[R_J]

Re: 64' Ford Falcon Radio Buzzing

I misread the readings, actually that output may be ok. I forgot it was a flower.
What did you have hooked up for an antenna? you will need a couple feet of wire, those things did not have a very sensitive front end
also what are you using to power it up, a car battery? or 12 volt power supply? (not a battery charger)
try injecting signal at the volume control, you can just use your finger and touch the center of the control and you should get a 60 cycle hum coming through the speaker.

[keeney123]

Re: 64' Ford Falcon Radio Buzzing

So here is a forum that may help.
http://www.oldclassiccar.co.uk/forum...a166fb9ce0ee08

I remember vaguely that a large capacitor was used to suppress emf noise coming from the electrical system. This noise interfered with radio signals even in the home.

[kc8adu]

Re: 64' Ford Falcon Radio Buzzing

its right above the ground bolt in your second pic.
the transistors are germanium.wont find them in modern stuff.

What would be the multi section can?

How do I find an equivalent pnp? I have some from a monitor that were part of the push-pull inverter section

[caphair]

Re: 64' Ford Falcon Radio Buzzing

I misread the readings, actually that output may be ok. I forgot it was a flower.
What did you have hooked up for an antenna? you will need a couple feet of wire, those things did not have a very sensitive front end
also what are you using to power it up, a car battery? or 12 volt power supply? (not a battery charger)
try injecting signal at the volume control, you can just use your finger and touch the center of the control and you should get a 60 cycle hum coming through the speaker.

I'm using 12v from an adjustable power supply. If I just touch the volume knob I don't hear any hums just little static at initial touch