I don't have computer access at the shed and I do have jumper hooks but they've fallen apart and are useless. I do how-ever have 25v between resistors 34 & 35 and 36 & 37,its supposed to be 11v? There is also 25v at K on the driver board? I have an oscilloscope and a signal generator although Ive never used them .

 

Assuming that you can work on the system, here is the plan of attack.
You are going to test the integrity of the system using only your ear as your diagnostic tool.

You are going to test:

Left Channel VOLUME control
Left Channel TONE module
Left Channel DRIVER module and AMP

Right Channel VOLUME control
Right Channel TONE module
Right Channel DRIVER module and AMP

BALANCE control

STEP #1

Unsolder the connection feeding into terminal E on both LEFT and RIGHT DRIVER MODULE.

STEP #2

Set BALANCE control to mid point.

Connect jumper wire from terminal E of LEFT DRIVER MODULE to either leg of R28 on LEFT TONE MODULE.
Listen to LEFT channel speaker and verify that VOLUME control works as expected.

Connect jumper wire from terminal E of LEFT DRIVER MODULE to either leg of R28 on RIGHT TONE MODULE.
Listen to LEFT channel speaker and verify that VOLUME control works as expected.

STEP #3

Repeat STEP #2 using jumper to terminal E of RIGHT DRIVER MODULE.
Listen to RIGHT channel speaker and verify that VOLUME control works as expected.

To be continued...

Its getting late here again,Ill do the tests and get back later.Thanks for sticking with me on this fellas I really do appreciate it.

 

I don't have computer access at the shed and I do have jumper hooks but they've fallen apart and are useless. I do how-ever have 25v between resistors 34 & 35 and 36 & 37,its supposed to be 11v? There is also 25v at K on the driver board? I have an oscilloscope and a signal generator although Ive never used them .

we need the rest of the amplifier circuit from the positions 9,10 where you measured the 11v at, to the speakers.

 

Hello,

Did you measure the voltages correctly?
I have drawn the points with some explanation in the picture:

Bertus

 

we need the rest of the amplifier circuit from the positions 9,10 where you measured the 11v at, to the speakers.

This one? I cant upload the file for some reason,Ive been having this happen every third or so try?

 

Here you go Dodgy it worked this time?

 

Its possible that the ground terminal for the transistors 60,62 is missing,causing them to be off,which causes the 11v to go up to 22v.

 

Hello,

Did you measure the voltages correctly?
I have drawn the points with some explanation in the picture:

Bertus

I didn't get any voltage readings whatsoever on AB,CD,EF,GH ,my DMM was set to 200mv,2v,20v and then 200v? I got 25v when I measured at +cap 10 that's supposed to be 11v? I got 25v on on the driver board letters G,H.J.K,L? Its done this before but after Ive been fiddling around with things (I cant remember exactly what it was I did) it comes good at 11v?

 

Its possible that the ground terminal for the transistors 60,62 is missing,causing them to be off,which causes the 11v to go up to 22v.

That's what I thought Ive checked it a few times though. Ill check it again and get back it could be a bad solder joint?

 

I took the link off from the tweeter switch that I had soldered on and the left side dropped in voltage to 20v,then I de-soldered the power wire to both drivers the left one now measures 11.9v at the positive end of capacitor 10. The right side still reads 25v,so I checked the right board again and found transistor 22 is shorted. The transistor is AX6123, I have the VRT TP Tech/Eca Asia Pacific Edition 1996 and 2009 but there is no mention of it? I downloaded another copy of this same service manual but it had different transistors in the driver boards AT327 (NPN) & AT463 (PNP) so I assume the AT463 is the same as (PNP) AX6123? Do you think I could get away with using a BC640 as a sub?It is To-92 PD Diss 830mw, Vc 100v, Ic Continuous 150ma. The AT463 is Si.PNP,Lo Power BJT. V (BR)ceo (v) 40. V(BR) cbo (v) 40. I (cbo) Max (A) 1.0. Max PD Dissipation 800mw.

 

Hello,

As the output transistors are Germanium, I would assume that the driver transistor are also Germanium.
You can not replace a Germanium transistor with a Silicium transistor as the B-E voltages are completely different.
You could try to measure the B-E voltage on the working board and see what that voltage is.
When it is about 0.3 Volts, the transistor is a Germanium type.

Bertus

 

The good one on the other board reads from B to C & E, 640 x 684 on my DMMs diode setting but the only datasheet type of thing I can find on google is from the radio museum Ive never heard of selizium?Must be silicon in another language?I bought an 80 watt soldering iron and resoldered the earths to the chassis so that might have had something to do with the voltage drop on the left side as well? It seems to be pot luck on whether I can upload any pictures here,sometimes I can load 2 pictures/photos but most times its one if I'm lucky,am I doing something wrong? I click the upload a file button sometimes and nothing happens?

 

I'm not real cluey on matching transistors and I'm wondering if I can use a 2n3019 as a sub for the AX6123 that has failed I cant find a datasheet for the AX6123 but the sub for it is NTE129. I cant upload the 2n3019 datasheet so Ill try again on the next post.

 

Here is the 2N3019 Datasheet its the closest transistor of this type that I have,Im just hoping it will be OK for a sub? Oh well I cant upload this one either? Does everyone have this problem or is it just me not configuring something correctly?

 

When you click 'Upload a file', do you get a pop-up with a 'Browse' button?

 

Hello,

Is this the datasheet you where trying to upload?

Bertus

PS I noticed that you sometimes have to click the upload button twice.

 

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

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

 

Hello,

If you want to have a second oppinion, have a look at this vintage repair forum:
http://www.vintage-radio.net/forum/index.php

Bertus

 

When you click 'Upload a file', do you get a pop-up with a 'Browse' button?

No, I don't get the browse pop up? It doesn't matter how many times I click upload a file,if it doesn't work by say the second try its not going to work ?

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

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

id you find that out? I have the transistor books and they didn't mention it plus I googled around for ages trying to find a datasheet etc...The only thing I could find was that NTE129 a silicon transistor was a replacement ? You really cant believe everything you read on the net LOL Except here of course,you blokes are excellent!

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

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

When you click 'Upload a file', do you get a pop-up with a 'Browse' button?

Yes it pops up but only intermittently when it wants to work?

 

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

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

Wow! I wonder why that other silicon NTE129 was recommended as a sub? Just goes to show you that forums like this with people that know what they are talking about are the place to get your info.Good on you mate.