Thread Rating:
  • 1 Vote(s) - 4 Average
  • 1
  • 2
  • 3
  • 4
  • 5

testing equipment
#1

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.
#2

You can test PNP and NPN devices with a multimeter. I wonder if an "audible" one like some Fluke brands might be the ticket??
#3

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?
#4

+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.
#5

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
#6

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.
#7

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?
#8

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.
#9

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?
#10

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.
#11

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
#12

he says he's got one from Omega...maybe it is sufficient.
#13

Just giving an option in case it doesn't work out. The B&K can supposedly test the transistor in-circuit.
#14

Is what you have the HHM2 ?
#15

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




Users browsing this thread: 1 Guest(s)
[-]
Recent Posts
Philco 38-2 Automatic Tuning
hello dconant , my set is the tabletop one and it also needs refinished someone put plant or something on top and the f...radiorich — 02:56 PM
Philco 38-2 Automatic Tuning
Well, you could take a look at most features of those radios, and other than some very few of them, they all are selling...morzh — 02:20 PM
SABA 400 Automatic Stereo 11
I actually got to hear the SABA play today when I took my Westinghouse AM-FM up to be worked on and also now know a pric...Jayce — 02:08 PM
Philco 38-2 Automatic Tuning
Seems more like a selling point to me. I too have have a Philco with the Cone-Centric tuning. Hopefully I will get the ...dconant — 12:17 PM
Philco 38-2 Automatic Tuning
I found out, I never use it in my 37-116 and 38-690. I made sure it works, but this was it: I always hand tune.morzh — 10:55 AM
Philco 38-2 Automatic Tuning
Does it wash your windows? Then it would be useful and worth fixing. Music and window washing.RodB — 10:00 AM
Philco 38-2 Automatic Tuning
You press the lever (crank) and you rotate the dial into the desired position. Also, while pressed, the contact that it...morzh — 09:50 AM
Philco 91 Speaker Replacement
I do not have much experience with speakers, but acetone sounds right. It does not affect paper but does dissolve about ...morzh — 09:48 AM
Philco 38-2 Automatic Tuning
Hello Dconant, In my collection I have a model 38-7T which Philco called their famous "Cone-Centric" dial me...radiorich — 08:14 AM
Philco 38-2 Automatic Tuning
I'll have to see how this works out once I get my dial back from Radio Daze. I sent mine in for them to reproduce. I ord...dconant — 07:22 AM

[-]
Who's Online
There are currently 1093 online users. [Complete List]
» 2 Member(s) | 1091 Guest(s)
AvatarAvatar

>