What do you think about it @JoeJester, seems like an ok intstrument?

 

Here is the Operating Instructions for the GDM 354A.

 

It's a good instrument. High impedance input.

Measuring less than 400 ohms, so you will be hearing a lot of beeps with the tests of those emitter resistors.

The only thing I wondered was the count and the tolerances for measurements. A 3.5 display will measure 0.00 ohms + 1 count. When you short the leads together, you expect 0.00 but 0.01 is acceptable. Knowing we are measuring 0.22 ohms, if it reads 0.24,we can probably call them good attributing one 0.01 to the meter and the other 0.01 to the leads used. That's all.


So, when you get to posting the readings we can move forward. The contribution of some of these errors have me frustrated. So we will soldier on to solve this problem.

 

I know it is hard to read the Operating Instructions but it beeps at less than 40Ω not 400.

 

OK .....
First off,
TP502 + TO Q508 E should be zero
TP502 + to Q510 E should be 0.44 however, IF you used those mini-clips .... 1.5 is possible. as you already reported a 1 ohm error. Since this is a no power applied test, just use the probes.
TP502 - TO Q508 E should be 0.44
TP502 - TO Q510 E should be zero.

That's good for one set of transistors. Q509 E and Q 510 E emitter resistors would need to be tested as well. Use the probes that came with the DMM. Check the zero by shorting them and note the reading.


TP501 + to Qxxx E tests the following:
Q509 E ... Tests the connection between the + and the emitter
Q510 E ... Tests R548 and R550
Q516 E ... Tests R548 and R570
Q518 E ... Tests R548 and R572

Each resistor is 0.22 +/- 2% Your meter is has a tolerance and a plus digits count. The resistors alone can be 0.216 - 0.224 so two of them would be double that.

Do the tests over, as I described to the four emitters. Report your results.

I have done some testing now, i hope i understood right.

Meter at 200 ohm setting, checked the probe value first: 0Ω
Not using mini grabbers.

TP502 + TO Q508: 0Ω
TP502 + to Q510E: open circuit
TP502 - TO Q508E: open circuit
TP502 - TO Q510E: 0Ω

TP501 + Q509E : open circuit
TP501 + Q510E : open circuit
TP501 + Q516E : open circuit
TP501 + Q518E : open circuit

Maybe TP501 has wrong print at the pcb also?

 

Maybe TP501 has wrong print at the pcb also?

No biggie ... now do the same test from the TP502 negative terminal. TP501 is the left channel and we are concentrating on the right one now .... however if we find the problem in the right channel, we will repeat the tests in the left channel to make one parts order ......


This could explain why you got zero volts when you measured it and why you go zero volts when you measured TP502+ to TP502-

 

TP502 negative to these?
Q509E
Q516E
Q518E

 

Sorry, I made a mistake when I said TP501 .... as we are working with TP502, the right channel.

TP502 + to Qxxx E tests the following:
Q508 E ... Tests the connection between the + and the emitter
Q510 E ... Tests R548 and R550
Q516 E ... Tests R548 and R570
Q518 E ... Tests R548 and R572

TP502- to Qxxx E tests the following
Q508 E ... tests R550 and R548
Q510 E ... tests the connection between the - and the emitter
Q516 E ... tests R550 and R570
Q518 E ... tests R550 and R572


Other that the direct connections (zero ohms), all others should read 0.44 ohms

If there are any problems we can check the left channel prior to ordering any parts.

 

Don't jump to any conclusions too quickly.
Your readings do not match what you had previously measured and reported in post #508.

 

Sorry, I made a mistake when I said TP501 .... as we are working with TP502, the right channel.

TP502 + to Qxxx E tests the following:
Q508 E ... Tests the connection between the + and the emitter
Q510 E ... Tests R548 and R550
Q516 E ... Tests R548 and R570
Q518 E ... Tests R548 and R572

TP502- to Qxxx E tests the following
Q508 E ... tests R550 and R548
Q510 E ... tests the connection between the - and the emitter
Q516 E ... tests R550 and R570
Q518 E ... tests R550 and R572


Other that the direct connections (zero ohms), all others should read 0.44 ohms

If there are any problems we can check the left channel prior to ordering any parts.

okey!
Measured.. i only get open circuit except at Q518.... not 0.44 ohms...

TP502 + to Qxxx E tests the following:
Q508 E ... Tests the connection between the + and the emitter : 0 ohms
Q510 E ... Tests R548 and R550 : open circuit
Q516 E ... Tests R548 and R570 : open circuit
Q518 E ... Tests R548 and R572 : open circuit

TP502- to Qxxx E tests the following
Q508 E ... tests R550 and R548 : open circuit
Q510 E ... tests the connection between the - and the emitter : 0 ohms
Q516 E ... tests R550 and R570 : open circuit
Q518 E ... tests R550 and R572 : 0,6 Ohms

 

What is the reading between TP502 + and TP502 - ?

 

What is the reading between TP502 + and TP502 - ?

I get open circuit at 200 Ohm setting ( 0L. )

 

Don't jump to any conclusions too quickly.
Your readings do not match what you had previously measured and reported in post #508.

Because i used the mini grabbers with 1.3 ohm error. Might have increased when connected to the pins

 

Damn, I don't like it but it does appear the emitter resistors to Q508 and Q516 are open.

With that being said, Measure TP501 to it's associated resistors in the same manner ...... to see if other emitter resistors are open before ordering any.

For further confirmation you will have to measure the resistors individually. Make a list of resistors and measure them individually. One of the resistors on the 0.6 reading is probably exceeding the 0.22 if not both of them.

I hope you used only the probes for that test.

 

Damn, I don't like it but it does appear the emitter resistors to Q508 and Q516 are open.

With that being said, Measure TP501 to it's associated resistors in the same manner ...... to see if other emitter resistors are open before ordering any.

For further confirmation you will have to measure the resistors individually. Make a list of resistors and measure them individually. One of the resistors on the 0.6 reading is probably exceeding the 0.22 if not both of them.

I hope you used only the probes for that test.

Okey, so i will measure TP501(?) not TP502? To what resistors?

I measured the resistors you have listed earlier..

R548: open circuit
R550: 0.3 Ohm
R570: open circuit
R572: 0.3 Ohm

So R548 and R570 needs replacement as i understand.....

Any more resistors i should measure individually ?

 

Ok....as surmized from your major test, we identified two open resistors.

Now R550 and R572 measured 0.300 on your meter or did you round it up?

Those 0.22 ohm resistors are 2 percent tolerance meaning they can be anywhere from 0.2156 ohms to 0.2244 ohms. We need to tighten up on your reading when doing these smaller value of resistors.

 

Ok....as surmized from your major test, we identified two open resistors.

Now R550 and R572 measured 0.300 on your meter or did you round it up?

They showed 0.2 at first, then stabilized at 0.3
Same at both..

My probe to probe reading sometimes showes 0.1 .........

How could we tighten up the the readings...

 

wow... i need more decimals at my meter.... should i just replace them with new ones?

I'm now using the probes that comes with this meter.. and i usually get 0 ohm reading, but sometimes i only get 0.1.. a little frustrating

 

well, you can't. We can assume with 0.2-0.3 we are good.

We know you have two open resistors in the right channel. We should check the left to see if any of those are open.

I thought your meter had more decimals ...... so that chart was only accurate for three digits.

On edit ... I deleted the previous post and adjusted for your meter reading .....



That count error is a maximum. your 0.3 is within 1 digit, so I'm thinking those resistors are probably in tolerance.


I'll get you a list of the left channel resistors .... and the same test for the TP401 pins

 

That means that R548 went open between post #508 and #525.
I am a bit suspicious. These are ceramic 0.22Ω 2W.

I think there is more than meets the eye.