Need Help With Early 60's Transistor Radio

[65blkbkgt]

I'm having a dilemma I hope someone might be able to shine some light on to help solve.

I have an early 60's am transistor radio I'm working on. The first thing I did was recap it figuring that would stop the LOUD sputtering sound (that the volume control wouldn't control).

Well, that didn't work so I also replaced the output transistor (pnp) and that didn't work either. It still sputters obnoxiously.

Does anyone know what this could be and what I should check (replace) next?

Any help would be greatly appreciated!

 

[crs1]

first what is the brand &model of the radio and i will see if i can pull up some schematics for it or maybe try you post on solid state ,analogue or every thing Else maybe some one there can help

 

[65blkbkgt]

Hi, It's a Bendix model 3TBO.

I have the schematic for it and replaced the electrolytic caps. I was still getting constant "sputtering". I did some more investgating and it turned out that one of the caps had pulled loose from the trace. Once I resoldered it I got rid of the sputtering but now there's just constant static up and down the tuning scale. The volume controls the static but the radio still won't get reception.

 

[crs1]

sounds like dirt in the tuner or a bad trim cap try and use some tuner cleaner in it and your pots and trim caps also can use rubbing alcohol

 

[65blkbkgt]

Just apply the rubbing alcohol with a Q-Tip?

 

[crs1]

yes then cycle the tuner a few times and do it again also do it to you pots but dont cycle the trim caps that would be bad

 

[crs1]

if that dont work your tuner or or a trim cap might be bad if it is a trim cap good luck geting it set

 

[65blkbkgt]

I'm going to sound really ignorant here but what's a trim cap? I have to learn sometime.

 

[crs1]

I'm going to sound really ignorant here but what's a trim cap? I have to learn sometime.

no not a bad ? it will look like a screw on a disc with 3 legs that is the best i can describe it i will try to get you a pic of one

 

[crs1]

it will look somthing like this

 

[65blkbkgt]

Okay........I'll be right back. I'll look.

Okay.........what I find is a square white platform on the circuit board with two screws. Those are the only screws I can see.

 

[65blkbkgt]

What purpose does the trim cap serve? Do those screws ever need adjusting?

 

[65blkbkgt]

I've determined that's what that is. According to the schematic.

 

[crs1]

it is to vary the capacitance of the circuit no they should have a drop of blue ,green or red locktight on them to keep from moving but they can burn out or get corroded if you can see the plates on it and it is black or discolored it can be bad but you have to know what value to set them at or it wont work so don't put a screw driver to it what ever you do

 

[crs1]

in tech school i had to build a radio on a piece of wood with nails pounded in it on top of the block diagram what a bitch

 

[65blkbkgt]

The screws on it are rusty but the rest doesn't look bad.

Are these replaceable? Where do you find them?

 

[65blkbkgt]

in tech school i had to build a radio on a piece of wood with nails pounded in it on top of the block diagram what a bitch

You must have been hating life at that point. LOL!

 

[65blkbkgt]

I'm really enjoying learning about this.

If you asked me 5 years ago if I wanted to work on electronics I would have laughed. I only wish I'd found it sooner!

 

[crs1]

yes they are but if you don't know what you are doing send it out but you can find them at digi-key ,mouser,or parts express

 

[65blkbkgt]

yes they are but if you don't know what you are doing send it out but you can find them at digi-key ,mouser,or parts express

I buy all my caps from Digi-Key.

That' the whole thing. I want to learn so I don't have to take it somewhere.

To this point I've pretty much been self taught because I don't like imposing on people.