New guy here, scratching my head with radio problem.

Thanks. I'll try that and see how it goes. I'll get back with results.

Nope. no sound at all after touching center terminal. I suppose the next stage is to check the transformer and resistors. There's only a few resistors in the amplifier stage so I might just go ahead and replace these while I'm at it. If I get the radio working, there will be very little original electronics left!

Do you have a voltmeter? That would confirm that there is actually B+ voltage available.

My housemate has one and he is on vacation. Mine for some reason bit the dust.Had i for 15 years. I need more components anyway, so I might as well buy a new one.

Hi i mean the intermedate freq amps.Some have silver/mica caps in them and they migtate and cause set not to work.Most are set to 455kc or some other feqs.Sprman : )

mbird97x wrote:Marcus and Levy's book on servicing radios suggests touching it with tip of soldering iron. Most just touch it with a finger.

The book recommends either method.
I'm too squeemish to use my finger on the bottom side of a powered chassis.
There shouldn't be much voltage on the volume pot unless a few things are wrong with the set but.....I don't do it.
I use an insulated screwdriver or the soldering iron.

Ya, I too am a bit leery of touching it with my hand. Some of the caps I replaced are extremely high voltages. I'd kind of hate to accidentally touch something wrong in there. Thanks for all the advice so far!

Thanks Sprman.intermediate freq amps... we're talking the big square boxes mounted topside? Are the mica caps replaceable in these? Never taken one apart which is why I ask.

Looking at thr Riders on Nostalgia Air, They look like the type w/2 trimmer caps in them. Usually not a problem.

Bob, when you go to a doctor, the first thing they usually do is check your blood pressure, right? This is because it gives the Doc a good preliminary indication of your over-all health. It can tell him if you are about to drop dead from some pervasive system-wide malfunction or if you've just got some local trouble somewhere. Same thing with a radio. You want to check some voltages to see if all the stages are getting the proper power currents that are needed by them, just like your body needs proper blood flow in order to work.

The Rider's information gives a nice table of voltages at the tube socket pins. Connect the negative lead of your voltmeter to the chassis and the positive lead to the pins indicated. Count the pins clockwise (when viewed from the bottom) starting at the keyway on the black plastic center prong of each tube. Switch to "A.C." on the meter where indicated.

Once you have made these measurements, if you post the results, or at least any that are significatly different, many folks on this forum can give further help. Until you know that the voltages are more-or-less correct, you are just speculating and probably spinning your wheels.

Terry Davidson

Thanks again for all of the help thus far. Will be checking those voltages out once I procure a multimeter.

So ah how did you make out with the voltage checks Bob?

have you tested the speaker to see if it works?

bobwilson1977 wrote:Apologies, its actually a 6 tube unit. The model is a A300 Hoffman. Now, when I touch the center tab of the Vol. control, I assume I would also be touching the chassis? Thanks in advance.

No just touch the center tab on the volume control, if the set has DC then the stray AC voltage would be amplified to produce a buzz. If it buzzes then the audio section is OK. That is a first quick step.

If it doesn't buzz then I would question the High voltage at pins 3 and 5 of tube 6X5 for 290VAC
then if thats present,
then the voltage at the cathode, it should be 325VDC.
If that checks OK,
then the next location to check would be the field coil winding or its replacement R14 of 1500 ohms. If it has an open then you would not see a voltage on C10,C19, or pin 4 of the tube 6K6 of 227vdc.
If you have that voltage then check to voltage of the plate of 6K6 (pin 3) of 217v
if you get that then the primary winding of the audio transformer is OK.
I would then suspect either the secondary winding is bad,
or the voice coil is bad.
If not then you will have to continue by signal tracing each stage in turn.
But these are the most obvious steps I would try first.

It sounds like the output trans to me