A lot of older amps have all transistor power amps in them, like the Marshall 12watt amps, Marshall 20watt and 30watt amps. They used Darlington power transistors in some of them.

Randal RG100 has all transistor pre-amps I think.
Yamaha G50 is all transistor apart from the reverb tank.
Roland Blues Cubes used to be all transistors except for one IC for the reverb tank.

Lets not forget the fantastic Albert Kreuzer 2002 BASS JFET Preamp, it might be re-voiced for guitar but might be too clean sounding.

Hopefully someone more experienced can make some suggestions of all transistor pre and power amps.

Just search around for some old schematics and borrow parts of them and get the breadboard out and experiment.

Also if you have some 4069 hex inverters or similar they can be used as Op-Amps.
Sunn Beta used the 4069 chip, and I know there are others that used them as well.

https://www.drtube.com/marshall-jmp-solid-state/
https://www.drtube.com/marshall-jcm800-solid-state/
https://music-electronics-forum.com/forum/amplification/solid-state-hybrid/923640-why-does-cmos-get-such-a-bad-rap/page2

Good luck, I will be interested to see what you do.
Cheers
Mick

 

It seems there are a few around with the same problem.
https://www.tdpri.com/threads/orange-crush-35rt-speaker-buzz.834557/
https://www.reddit.com/r/orangeamps/comments/zyl3y0/35rt_constant_buzz/

Is the 24v 40VA transformer centre tapped, or is it just one output of 24v?
If you have 12v + 12v it would make it easier I think.
Do you have any Op-Amps or will it be all transistors?

There are lots of old transistor amp schematics around that you could borrow sections from, maybe a proven pre-amp that sounds good already.

It all depends on what transistors you have, I would like to see just the part numbers, I don't need to see the specs for each one.
Cheers
Mick

I keep thinking/hoping that Phil plays Bass guitar with a moniker like PHATT, Phatt just makes me think of a deep fat bass riff being played.

I know its made up from parts of his name, but still, what a cool name for a bass player.

I totally agree with Phil, somewhere between the volume pot and IC102.
It would be best before or after R131, if the picture I found on the net is correct then there are 2 PCB's in that amp.
I would find the correct wire between the pre-amp PCB and the power-amp/ power supply PCB and cut that wire to install the 2 Jacks.

I think I spy a shorted track ?You cannot view this attachment.

The 2N3819 is a JFET transistor, you are looking at an old style TO-9 one in your amp, the new ones look different in the TO-92 casing.
You can still buy the old style one if you shop around, but I would not.
New ones are more likely better quality.

https://electronic-studio.com/2N3819-JFET-N-Ch-25V-005A-035W_1

https://www.digikey.com/en/products/detail/nte-electronics-inc/2N3819/11647880

Guzzies3, have you considered trying to build some of BajaMans Pre-Amp pedals from https://www.freestompboxes.org ?
Some of those can work well in front of an amp I believe.
He has made Amp sims for several different amps as well as speaker sims etc.
They all have vero board layouts for them.
I made up some of them as PCB's but I havent had time to make any yet.

As far as hijacking a thread goes, I don't think Joecool85 minds it happening, at least I hope he doesn't.
As long as it is in a friendly manner and it keeps this site as a friendly forum where like-minded people can have a chat and share ideas and stuff.

Michael

Enzo was a great man, he was always helpful AND informative.

Most of the time when Enzo gave you an answer he also explained it so you learnt something.

He always made me think of the old saying:
Give a man a fish and you feed him for the day.
Teach a man to fish and he has food for a lifetime. (or something like that)

Guzzis3, where are you getting the Hotone Boogie Siva for $72 from ?
I might be interested at that price.

I am not worried if this topic has drifted a tiny bit of topic, and I started it.
As long as I find out new things I'm happy.

I am especially happy now since I have found out about the Hotone Nano series.

Michael. 

Thanks Phil for pointing out the JC models page, I have just finished reading it for the second time and it was very informative.
I have also re-named the JC-100 84 file to head only single channel.

I would do what Phil said regarding the effects loop, ignore what I said.  

Phil, unfortunately Enzo passed away in August last year.

https://music-electronics-forum.com/forum/music-electronics/967156-rip-enzo

I had a look through my files and found a 84 JC120 schematic with an effects loop,
if you compare the circuit after the return jack you will understand what I meant above.

Never mind, that's a single channel head only.  (Thanks Phil)

You can also remove those resistors and use the holes for wires to run to the send/return jacks, just replace the resistor along the wires so it goes back in the circuit.
I would solder the resistor to the send jack and then add the wire to the resistor.
If it works ok then put a bit of heat-shrink tubing over the resistor.

I would have thought that the place to insert the send/return would be at C26/C126, or just before C26/C126.
I think it looks like the circuit between R19 and C26 is where the effects and distortion might enter into the circuit.
I might be wrong as I am not familiar with this amp.

G'day guzzis3, welcome to the forum.
I often drop in on the Marshall forum as well.
I don't own a Marshall, but one day....
I can't afford one on a disability pension.
I sent you a PM for your mailing information.
Well se what happens next time I go into town.