the AX6123 is a PNP germanium, try a NTE158 as a replacement

http://www.nteinc.com/specs/100to199/pdf/nte158.pdf

Now I'm confused again? I measured the other AX6123 on the other good driver board and It read 640 from base to collector and 652 from base to emitter? that's got to be silicon isn't it ? Where did you get your information from that it was Germanium Dodgy?

 

You have a working channel. Measure the voltages at the base, collector and emitter of the working transistor.

 

You have a working channel. Measure the voltages at the base, collector and emitter of the working transistor.

Base 25v,collector 13.8v,emitter 25v. I found another schematic for this radiogram with different silicon drive transistors AT463. But as usual I cant upload the file to show you.You'll just have to take my word for it.

 

With the base and emitter both at 25V, the transistor is CUT-OFF.

Transistor (21) SE4002 is also non-conducting.

Can you provide the voltages to two decimal places (10mV) at both transistors (21) and (22) of the WORKING channel?

 

Working channel Transistor (22) B 25v, C 13.8v, E 25v. Transistor (21) B 12.7v, C 25v, E 17.6v. I probably need to desolder the power line to the non working driver board,what do you think?

 

Those voltages don't make any sense. I will have to run a simulation.

 

Let me make sure I understand this.

The channel is working properly. You have a music source connected to the input and an 8-ohm speaker on the output.
The sound is normal and not distorted.

The reason I ask is that according to the voltages you have indicated, NPN transistor (21) is receiving 17.6V feedback at the emitter.
Transistor (21) is turned OFF.
Transistor (22) is turned OFF.
There should be no sound coming from the speaker.

 

Let me make sure I understand this.

The channel is working properly. You have a music source connected to the input and an 8-ohm speaker on the output.
The sound is normal and not distorted.

The reason I ask is that according to the voltages you have indicated, NPN transistor (21) is receiving 17.6V feedback at the emitter.
Transistor (21) is turned OFF.
Transistor (22) is turned OFF.
There should be no sound coming from the speaker.

No I didn't have the radio on or speakers connected? I just took the voltage readings off the transistor the way it was as I was working on it? I had taken the bad transistor out and the power is disconnected on the output side of the bad board so I can get at the good board to measure its transistor. Ive tried to upload photos so you can see what I'm doing as I go but I still cant do it? I installed BD140 transistors in both drive boards in place of the AX6123. The measurements on them are,with the radio playing at the same time. Right Driver board;(Bad Side) B, 23.50v,C, Up and down from 12.00v to 12.80v? E, 25.40v. Left Driver Board; (Good Side) B, 23.70v, C, 23.60v, E, 24.20v, I'm getting a bit of distortion in the right channel.The left channel is still OK,I set the bias on it but not on the bad right channel it sits on 3.5ma and wont move? With it set to AUX I measured on the drivers with no sound coming out.Right side (Bad) B, 23.4v,C, 11.8v, E, 24v. Left Side (Good) B 23.5v, C 11.4v, E 24v. I still have the same problem with the balance being out of whack?

 

You have lost me totally.

I will get back to you after I can analyze this and can come up with a working strategy.

 

You have lost me totally.

I will get back to you after I can analyze this and can come up with a working strategy.

The good left side is excellent,when I turn the balance to the right I'm getting a faint sound some distortion and a beat frequency type of thing? Same as when I play an MP3 through it? Ive been pulling my hair out over this thing for months LOL

 

I found a back to front BC108 transistor on the right tone board,I fixed that and re-soldered the bias link N-O on the driver board and anything that looked like it might need it on the tone board . I still have the same symptoms though except for the distortion and that beat frequency? This is a true mystery! Ah! Ha! The upload worked this time.

 

I am still studying your problem and where we're at.

We know BD140 is silicon PNP.

Do we know if AX6123, the original transistor, is germanium or silicon?

 

I have lost track of where we are.

Have you performed the tests I itemized in post #40?

These are audio tests with everything connected, music source, speakers, power, balance at mid-point, etc.
I would like to confirm what is working and what isn't.

We have to tackle the balance control problem later. Something does not jive from what you have said so far.

 

I am still studying your problem and where we're at.

We know BD140 is silicon PNP.

Do we know if AX6123, the original transistor, is germanium or silicon?

According to a vintage radio repairer that I emailed the AX6123 was made by Fairchild in Australia in the 1960s, he said they were at the forefront of silicon technology at the time and there is no data on the internet about it.He said to test it with a DMM to make sure. The AX6123 reads as a silicon device with a DMM on diode setting. From memory it was Base to Collector 640,Base to Emitter 652. I found another schematic for this model that has AT327 & AT463 silicon transistors in the driver board. The right channel AX6123 has failed while Ive been testing things and since Ive installed the BD140s its back to (normal) with the right channel not responding to the volume pot when the balance is fully turned to the right. If I turn the balance pot full to the right with the volume off I can still hear the radio at a low volume with no distortion. If I turn the volume up nothing happens.If I turn the balance pot to the left it acts as a volume pot and smoothly turns the volume down? If The balance pot is turned about a third of the way to the left that left channel comes good and works as it should with heaps of volume. That's it in a nutshell as clear as I can explain it. It seems like the right channel wants to work but its shorted somewhere somehow? P.S. I cant set the bias on the right channel either,Ill install another 100 ohm variable resistor in it today and see what happens?

 

I have lost track of where we are.

Have you performed the tests I itemized in post #40?

These are audio tests with everything connected, music source, speakers, power, balance at mid-point, etc.
I would like to confirm what is working and what isn't.

We have to tackle the balance control problem later. Something does not jive from what you have said so far.

I didn't see that post (#40)for some reason? Ill do that today and get back to you.Thanks for sticking with me on this MrChips its appreciated.

 

Hang in there. I truly believe that your problem can be solved. We just have to clear up some inconsistencies reported so far.

 

#1 With balance set to the middle and jumper wire from disconnected E terminal on Left driver module to Left tone module R28;the sound is very low and volume pot works.#2Right tone module.Same as Left tone module but no volume. #3Right side driver module E terminal to left tone module R28,no sound just low hum on left speaker,dead quite on right speaker,no volume. #4 Same as #3 No volume. When I last tried to bias the right driver module It was stuck on 35ma I had installed a 100 ohm 25 turn VR in case that was the problem?

 

#1 With balance set to the middle and jumper wire from disconnected E terminal on Left driver module to Left tone module R28;the sound is very low and volume pot works.

Let's stop and examine this more closely. We need some clarification.

You had previously reported that the LEFT channel works correctly.

How is it that you are now reporting that the sound is very low? (even with the volume control turned to the max?)

 

When the wire clip from the driver module is connected to R28 on the tone module it has a very low volume. Otherwise it works fine when connected normally,I don't know why its like that I'm just reporting the results. I just found the right channel output transistor AD161 is shorted between collector and emitter. All the rest of the outputs are OK. I hope this is the original problem but somehow I don't think so because that transistor read OK before? Now Ive got to find an AD161? And so the saga continues. Do I need to get a matched pair of AD161 & AD162s?

 

I would like to focus on one thing at a time and I can only go by what you have reported.
My diagnosis can only be good as the information received.
Remember they say, Garbage In, Garbage Out.

When an inconsistency appears, I prefer to have that cleared up before moving on because it just might be meaningful information.

When you connect E input of the DRIVER MODULE to R28, which side of R28 are you connecting to?
Try both sides of R28. There is no amplification after R28 and before E input. You ought to be able to experience maximum sound output from the loudspeaker.