3 W Ge Transistors Power Amp

himister · Post by **himister** » 24 Nov 2009, 00:27

Type: AA 119
Device: Germanium diode
Desription: Dem, h-ohm, 45V, 35mA
Comparison types: AA 113, 1N60

I believe that any GE diode within specs will work. Just tried to find some data about OA119 in old books but nothing so far.

Fernando · Post by **Fernando** » 24 Nov 2009, 01:10

I can't find anything about OA119 either (online) Just a mention about the change in nomenclature to AA119...

himister · Post by **himister** » 24 Nov 2009, 01:31

Yep. They're obsolete for many years back.
Only thing I've found is few comparing sheets from the book printed in 1965

Maybe these would be helpful at least in small amount in the future. I really love this old stuff.

: sheet1.jpg (61 KiB) Viewed 2011 times

Guys I'm redrawing schematic so it should be nice and neat for interpretation.

himister · Post by **himister** » 24 Nov 2009, 02:41

Here you go fellas. Enjoy the GE Mojo..

3W_GE.TR.M.AMP_SCHEMATIC.GIF

SPeter · Post by **SPeter** » 24 Nov 2009, 06:29

Thanks Mr. Himister!

Fernando · Post by **Fernando** » 24 Nov 2009, 10:58

Thanks a lot Himister!

So manufacturers didn't use the same numbers...! (and what I found about a change in nomenclature seems incorrect)

Siemens AA119 = Ei AA121 = Philips OA79

OA119 = ???

About the newly redrawn schematic: I think the gain trim should be 10k. Also, I'd specify that it is the "gain" trim and that the other is the "distortion" trim. And, well, can't see credit to the original author!

Fernando · Post by **Fernando** » 24 Nov 2009, 11:38

I asked the semiconductor museum people, let's see if they can help

himister · Post by **himister** » 24 Nov 2009, 12:37

Fernando wrote:Thanks a lot Himister!
So manufacturers didn't use the same numbers...! (and what I found about a change in nomenclature seems incorrect)
Siemens AA119 = Ei AA121 = Philips OA79
OA119 = ???
About the newly redrawn schematic: I think the gain trim should be 10k. Also, I'd specify that it is the "gain" trim and that the other is the "distortion" trim. And, well, can't see credit to the original author!

Sorry fellas, this was a quick one and it was late. I'll change it accordingly.

What was the name of the author, designer of this circuit..

Fernando · Post by **Fernando** » 24 Nov 2009, 16:07

SPeter, you used the OA119 for some reason? Or it was the GE diode you had around?

Wich are the specs to meet???
I guess that if it's limiting something it should be a GE diode with very similar specs?
Otherwise it could be a GE diode with greater voltage and current?

And anyhow, wich are th especs to look at?
- reverse voltage?
- fwd voltage?
- fwd current?
- reverse current?

Usually only two specs are listed for GE diodes. Are these Reverse Voltage and Fwd Current?

SPeter · Post by **SPeter** » 24 Nov 2009, 23:16

Fernando wrote:SPeter, you used the OA119 for some reason? Or it was the GE diode you had around?

Wich are the specs to meet???
I guess that if it's limiting something it should be a GE diode with very similar specs?
Otherwise it could be a GE diode with greater voltage and current?

I didn't use OA119!
Similar specs should work!
In my opinion it's safe to use Ge diode with greater voltage and current ratings!

Fernando · Post by **Fernando** » 24 Nov 2009, 23:37

>I didn't use OA119!

What did you used?

Why OA119 is on the schematic?

himister · Post by **himister** » 24 Nov 2009, 23:40

I hope it's better like this. Apologies again.
I missed input to ground cap 820p. Fixed now.
Cheers

3W_GE.TR.M.AMP_SCHEMATIC2.GIF

Fernando · Post by **Fernando** » 24 Nov 2009, 23:55

the trimmer still say 18k... it should be 10k and be labeled "GAIN"
The 2k2 trimmer should be labeled "distortion trim"
Also the 820pF is before the 10uF on the original

SPeter, what GE diode did you used?
And why is OA119 marked on the schem?

wait, SPeter, I'm taking you all the time as the author of the circuit and you are not, are you? Sorry!

himister · Post by **himister** » 25 Nov 2009, 01:16

Sorry guys...my concentration today is really shitty.

Here it is:

Fernando · Post by **Fernando** » 25 Nov 2009, 01:34

thanks a lot it looks great!

Fernando · Post by **Fernando** » 25 Nov 2009, 12:49

- the 47 ohm resistor should be between the trimmer and the AC127 (apparently not important but just in case)
- also there's one 220uF that should be 470uF (up, center)
- there's a 18 ohm that should be 10 ohm (AC127 emitter)

I'd also add two notes:
- the one on original schematic about the large heatsink on AC187k/188k transistors
- and the one in the text about placing the GE diode near the AC187k/188k transistors, since it is working as a temperature compensating element.

I asked Alex about the diode. If he answers about specs/equivalent I'll tell you so you can include it.

thank you!

himister · Post by **himister** » 25 Nov 2009, 13:59

I don't get it...

Hey Fernando, where did you come with these values? I've redraw schem from original posted on that site but didn't see the values you mentioned for changes. Sorry for the lame question?
Let's fix this damn schem and make it finally right...Ok?

Fernando · Post by **Fernando** » 25 Nov 2009, 14:13

hehe, the same source as you! (and the only one afaik)
http://topopiccione.atspace.com/pjimage ... ia.sch.jpg

10 ohm res.: that 0 looks a bit like an 8 but it's a 0, just compare it with the other 0s
For the 470uF cap and the position of the 47ohm res., just watch the schematic carefully! :p
For the notes: just look at original schem. and text.

thanks for your patience and your wonderful schem!

himister · Post by **himister** » 25 Nov 2009, 14:47

Fernando wrote:hehe, the same source as you! (and the only one afaik)
http://topopiccione.atspace.com/pjimage ... ia.sch.jpg

10 ohm res.: that 0 looks a bit like an 8 but it's a 0, just compare it with the other 0s
For the 470uF cap and the position of the 47ohm res., just watch the schematic carefully! :p
For the notes: just look at original schem. and text.

thanks for your patience and your wonderful schem!

Hey no problem but I guess I'm distracted in some way so I couldn't gather simple schematic...feel like a 1-st grader

Here's new:

lolbou · Post by **lolbou** » 25 Nov 2009, 16:22

The output stage (AC187/AC188) reminds me of old Philips TVC5 audio circuit...

See here viewtopic.php?f=17&t=4845&p=70469&hilit=TVC5#p70469

Was powered with 22V, as far as I remember, with baxandal EQ... Should have the schem somewhere at home, I'll look for it tonight, might be interesting to compare?