Ampeg transistor?

[drewl]

Rebuilding an old solid state Ampeg G212 which needs a couple output transistors.
I'll probably replace all four and standard NPN's will probably work, anyone have any idea on the specs for the stock ones?
The part # is 259N2C
thanks.

[Enzo]

That number looks like a lot code to me, but I could be wrong. I have G110 schematics but not G212. The G110 was complementary output so half NPN and half PNP. Are you sure yours is quasi-complementary?

I am sure we can find a replacement. MJ15003 ought to sit in there just fine.

ANy more numbers on them? Got schematics?

[drewl]

All four outputs NPN-Quasi.

DOH! under the house number on the schem is the part number barely legible-
this amp looks like it was sitting in a barn for a couple decades.

It's a 2N4348, plenty of subs available, thanks.

[Enzo]

And looking that up I still would use MJ15003, I think.

[Malo]

Help

That number looks like a lot code to me, but I could be wrong. I have G110 schematics but not G212. The G110 was complementary output so half NPN and half PNP. Are you sure yours is quasi-complementary?

I am sure we can find a replacement. MJ15003 ought to sit in there just fine.

ANy more numbers on them? Got schematics?

Hi, I'm searching for the G 110 shematics. Could-you help-me ?
Thanks a lot
Malo
malo.vallois@free.fr

[Malo]

That number looks like a lot code to me, but I could be wrong. I have G110 schematics but not G212. The G110 was complementary output so half NPN and half PNP. Are you sure yours is quasi-complementary?

I am sure we can find a replacement. MJ15003 ought to sit in there just fine.

ANy more numbers on them? Got schematics?

Hi,
I'm lookig for tus G110 shematics.
Could-you send it to me ?
Thanks a lot
Malo
malo.vallois@free.fr

[Malo]

Hi,
I'm looking for the Ampeg G110 shematics.
Could-you send it to me ?
Thanks a lot
Malo
malo.vallois@free.fr

[Enzo]

Hi Malo, welcome to the forum.

It is not necessary to post the same request three times in the same place. We can see them. I am not here 24 hours a day. Give me a chance to find the drawing and scan it.

[Malo]

Thanks a lot Enzo,
and excuse my multiple message, I'm not very skilful with forums.
I have now the possibility to repair my amp, thanks again
Malo

[leftybob]

Just wanted to update this info as I have the G-212 with this same problem the Transistors are complimentary 2N4348 with the letter U on them the two top ones are 7542 and the two beneath each is a 7545 RCA maker
looking from the back
7542 || 7542 <top
7545 || 7545 <bottom
... I'll get mine fixed eventually, it barks and crackles at me ... 8 (
Hope this helps someone down the road ...

[Enzo]

7542 looks like a date code. 42nd week of 1975 - when the part was made.

[leftybob]

7542 looks like a date code. 42nd week of 1975 - when the part was made.

Thanks so the 2N4348 is the only one that matters for ID ? I'm not into repair, I just want to share my info since mine are the originals. Honestly this is the only place where I was able to search any of this info. That amp is pretty old. '75 huh, I wonder how old the amp is ..

[Enzo]

Look for similar format date codes on other parts - larger parts like transformers, but also the controls. if you see a number on a volume control that looks like 1377542, that is that same 1975 date. 137 means CTS is the brand in that example. Often large caps have codes on them, and even the large cement power resistors. Get an idea of when most of the parts were made, and you have a good idea when the amp was as well. If those transistors were all late 1975, then see if the rest of the parts are also late 12975 or early 1976. If the transistors were replacements, then perhaps the amp is a little older.

[leftybob]

Another side note on this amp, the rear input is powered, so it the main amp is not functioning, put a drive pedal before the input, make sure the volume is down on the pedal, I tried a few pedals and they all sounded good, but needed an EQ pedal because it's not travelling through the amp EQ's.

[cashin]

Ampeg G-110

Hi Enzo, I have an Ampeg G-110, G110, G 110. Here as single pdf: Ampeg G110.pdf

The problem seemed like a burnt out / crackly volume pot that put out about half power (total resistance 50K ohms, rather than 100K.) I exchanged it and this didn't fix the problem. Seemed as if wiring the new pot into the circuit dropped the pot's total resistance. So I dove into some troubleshooting.

1) I found the juncture of IC1 pin 6 / Base of Q2 (the semiconductor / transistor labelled "Reverb Amp") reads 24 volts, rather than 13.5.
2) The Emitter of Q3 (labelled Preamp) reads 0 volts, rather than 13.
3) Q4, labelled FET on the schematic, was passing quite a bit of current in an unintended manner. I tested each transistor after removing it from the board like this: link.

4) I think Q7 is functioning properly, despite initial concerns that the collector pin was broken off the TO-126 package.



Seems that the transistor package & the heat sink to which it's mounted serve as the collector: I do get continuity between the broken collector nub and the heat sink and I rightly measure 24 volts between a heat sink and ground.

I'm asking for diagnoses, next steps, and where can I find replacement parts? I'm quite certain I'll need a new Q4- "610291-1." Google gives me nothing, and there are no additional markings on the transistor itself.

Thanks, Cashin