As for a diagram of something similar, Where would I look for era 1957-1960, of a whole house intercom, AM/FM radio, with transistors.

What brand is this unit? One of the big brands was Nutone, so you could start there to see what looks close.

RCA made PNP power transistors in great quantity at low prices and it appears yours uses one. What's the part number? I can't quite read it in the pic. I have old RCA transistor manuals so maybe I have the data on it.

Berns Air King intercom AM/FM radio, the transistor is 40254, could this be causing the hum?

The 40254 (yes I have the data) is nothing special, just a PNP power transistor for audio purposes. We really need to have a diagram of at least something similar. And you need to trace the circuit with an oscilloscope.

Many of these intercoms, being sealed up in a wall, were not isolated from the power line. So be careful.

oscilloscope! I guess I will need to find someone to fix this unit, as I don't have one and not even sure how to use one. I could possibly find one to use.

It would be a great education to fool with an oscilloscope.

If I wanted to sub in a power transformer, what is a suggested transformer. The current out put on the unit is 11.5 volts, with two leads and center tap. 11.5 on each lead and center tap.

A wall wart might do the job.

transformer at wall mart???

I didn't say wall mart. I said wall wart. You know, those sort of cubes that plug into the wall and supply power to various goodies. The older ones are transformers, sometimes with rectifiers. They put out various voltages from maybe 1.5 through 18 Volts at currents up to maybe one Ampere. I have a box of them and often find uses for these things.

You will often find boxes full of "wall warts" at flea markets or habitat recycle stores, etc., with all sorts of voltage outputs, for a buck or two.

Sorry, the old eyes are not what they used to be. I need to do some digging, I think I have some of those transformers also. If I find a 12 v DC, I could replace the current power with one of these?

Can I connect an 12 VDC transformer,and is the capacitor bypassed. Picture attached. Disconnect leads to capacitor and add new transformer.
Current voltage is 11.26 is 12 VDC going to be OK?

I can't answer that directly. The wall wart marked 12V will probably put out somewhat more than that, so you will have to measure and see what you get.

Puts out 12.19, think that will be ok?

Yes but that will change depending on load. Just be careful not to put too much into the radio or you will cause damage.

Hum is gone, all I get now is the sound of power on and off. No AM or FM which I don't really care, I'm hoping to get the intercom only going. I hooked up one of the room speakers and we can also hear the click of the power on thru the speaker. By turning the volume down the clicking sound is reduced. But no activity when the intercom switch is pushed and talk into the speaker. Where to now??

Just checked, I have a buzzing sound on AM around 800, buzz will increase and decrease with volume control. Nothing on FM, but that might be to no antenna, I have a wire connect to the AM, what would be needed for FM antenna?

Hooked up an antenna to the FM, I have a radio that works, but no volume. I'm getting feed back thru the speaker for the intercom, but no volume. What do I look for now.

Took out current power transformer, checked voltage was 12.6, transformer has a center tap, both outputs the same. What would be the average amps for a power transformer, no markings on this one.

Measure the loaded voltage. There are no 'average' amperes. Compare to another transformer of the same weight, power wise.

The two rectifiers are 1N2858 RCA, would they have caused the hum? Instead of the transformer? Been looking for a replacement transformer, but they come in many different amps.

how do you measure loaded voltage?

With a voltmeter, while the set is operating.

the power transformer has been removed, I will need to put it back in, when the wall wart worked and hum was gone I removed it, now trying to figure out a replacement.

Any ideas on the volume problem??

I suggest measuring voltages on all the transistors to see if they are reasonable. Look at the local oscillator with an oscilloscope and verify the approximate frequency. Put a known signal into the front end and trace it through the stages.

There is no magic here. There is no substitute for understanding the circuit and having adequate test equipment.

On my way to the local library see if they have a book on old radio circuits. Getting way beyond my knowledge of radio circuit. Hopefully I will be able to gain enough to get this set working. Been unable to find anyone in this area that works on old radios.

I doubt if the library will be of much help. Perhaps perusing some diagrams you may find on the web will yield more useful information.

Look for germanium transistor radios, or just find the oldest solid state diagrams you can.

Thanks, been looking via the net, but was not having much luck. Same as the library, nothing about vintage radios.

Maybe this is similar.

When I enlarge your diagram its unreadable. What I can see, it might be close, but again Im a newbie to this radio stuff.

Rather than try to repair this radio just yet, perhaps you need to do some reading on how this stuff works.

You can Google the model number and perhaps get a better image of the diagram.