The PHILCO Phorum
testing equipment - Printable Version

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testing equipment - tim1 - 01-16-2014

I am working on a philco record player that has 3 transistors and it has low volume distorted. The speaker is good so I want to test the transistors that plug in to the circuit board. I am blind and I was wondering if there is a audible tester I can get to do this. Or another way I can find a radio that uses the same circuit and use that for testing. Did Philco use that circuit in radio's also thanks.

RE: testing equipment - TA Forbes - 01-16-2014

You can test PNP and NPN devices with a multimeter. I wonder if an "audible" one like some Fluke brands might be the ticket??

RE: testing equipment - morzh - 01-16-2014

Tim

Can you post the schematic of the circuit?
Meantime, transistors check with a multimeter (I only recommend an analog old type for that, a DMM does not work well) will only insure their integrity but not quality: you cannot simply measure Beta this way. Some multimeters have transistor check function. Then you can measure static and dynamic betas.

Schematic would be helpful.

Also we will need to know what kind of player it is, what you use for an output amp, or is this circuit the whole thing, from pickup to the speaker?

RE: testing equipment - TA Forbes - 01-16-2014

+1.

Quality is not measured with a multimeter. And you are correct, I use a Simpson 260 when measuring diodes. Transistors are way out of the realm I work on. Diodes only because some of my test equipment have them.

RE: testing equipment - TV MAN - 01-16-2014

I used to have a B&K transistor checker that would sound a tone when the transistor was good or bad. I cant remember the model, but they do exist. It had a large switch that you could change between NPN & PNP, and a cable with hook leads and sockets on the tester. I may still have it. A lot of my older test equipment is packed in boxes here and there. I'd be inclined to go after any electrolytic caps too. They do go bad in transistor circuits. Could also be a bad phono cartridge. Food for thought...

Tim

RE: testing equipment - morzh - 01-16-2014

Ideally (and I mean - ideally) a scope would be sufficient, better - with audio oscillator. This makes it a 20 minute troubleshooting (including setup time).
And a transistor checker - but this is not really needed, in a circuit like this one simple making sure your transistor works is enough so an analog multimeter will do. Also a non-working transistor with a scope and oscillator is so obvious you simply yank it and replace it without checking much.

RE: testing equipment - jontz - 01-16-2014

I'm just going out on a limb here guys and gals, but I'm guessing that an analog multimeter or a scope/audio oscillator are going to be rather hard for a blind person to use. His specific question was about a test device that can give him audible feedback about whether or not the transistor is any good. Any suggestions on that front?

RE: testing equipment - morzh - 01-16-2014

Missed the "blind" part, sorry.

OK then you can use a DMM on a "diode" setting. It beeps when seeing that Vf across a forward-biased diode, so when checking B-E and B-C, listen to the beep in one direction and the lack of thereof in another direction on both junctions.
Also check the E-C with the Ohmmeter with beep turned on for a direct breakdown (not sure how you will measure leakage being not able to read the value). But suppose it will be either good or bad.

Otherwise I got no good advice.....


Found a youtube video where a young guy made an inexpensive talking DMM for his blind friend using Arduino and some other stuff. It talks in Italian. But could probably made to talk in English.

RE: testing equipment - tim1 - 01-16-2014

I have a omega talking volt ome meter not sure if it is digital or not maybe I can use that for testing? just go to omes right?

RE: testing equipment - morzh - 01-16-2014

yes. If it is analog - it is even better but I am sure it is Digital.

Can you list the model? So I can see what it measures?


Also realize you cannot test transistors with a DMM (or whatever else) in-circuit, you have to take them out.

RE: testing equipment - jontz - 01-16-2014

I did some looking into Madmurdoc's suggestion, and it appears that the B&K 520B and 520C both had audible "good" test tones. These aren't made any more, but maybe one could be had on eBay?

EDIT: Found one. Click Here

RE: testing equipment - morzh - 01-16-2014

he says he's got one from Omega...maybe it is sufficient.

RE: testing equipment - jontz - 01-16-2014

Just giving an option in case it doesn't work out. The B&K can supposedly test the transistor in-circuit.

RE: testing equipment - morzh - 01-16-2014

Is what you have the HHM2 ?

RE: testing equipment - tim1 - 01-16-2014

The model I have is OMEGAS AYS® (MODEL HHM1A)