I'm actually pretty excited about this stuff despite being lost in space 🚀 

One of many things I wonder about now is why don't amps just use one BIG POWERFUL transistor instead of an array of components  maybe they have to build up the signal to get it to a minimum level for input on the output transistor 

Also I want to connect the output of a transistor to the input of another transistor and maybe more so now I'm wondering if they can be the same (NPN +NPN...) or have to be different 

At the end of the day I really need to find a schematic for a signal tracer type audio amp even battery powered and use that for a template 

Yes sir thanks I will definitely be making some changes to the circuit and I believe your suggestions will help tremendously 

Meanwhile I tried to see what was wrong with the original circuit by trying to make a load line and Q point and perhaps there is not one correct data item but if it is then I'm drawing a conclusion that my collector current is too low and needs to be increased by increasing base current by decreasing the value of the base resistor

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Also another resistor will be added from base to ground so there will be a voltage divider

Yes sir thanks I have a big box of old radio shack stuff I don't think there is much of anything special but if you are looking for something in particular lmk I'll pack it up and get it headed south 

Also about a dozen large diodes   

Where did you find THESE?

I used both A LOT back in the day, also single 741 and LF351, but that was in the early 80s.
Then TL072 became the Industry standard.
Notice 1975  1.68 USD price for ONE is officially about 11 bucks today and in real life about $20

Notice they were individually packaged.

In 1969 I bought just arrived LM741 single Op Amps each in its own cardboard box, as if it were a 12AX7 or something, go figure.

Current TL072 price is about 50 cents each. on a VERY devalued USD.

Try 1M Base to collector and 3k3 collector to +V and get ready to ride.

Inject 100 mV into Base through a 1 or 10 uF cap, positive end towards Base and scope collector.

You´ll have so much gain that probably signal clips, go figure.

Attenuate signal drive and tell us how many mV it takes to reach clipping.
Gain will be HUGE.

This is a basic gain stage around which I built many projects, from signal boosters to 8 channel mixers back in the 80s, published in Music Magazines, Argentine Musicians built tons of those and used them live .

Google says:
------------------------------------------------
Overview created by AI
"Project Primavera" was a famous electronics and audio project DIY (do it yourself) published by the renowned Argentine technician and manufacturer Juan Manuel Fahey in the pages of the mythical national magazine El Musiquero in the late 80's.
The project consisted of design and step-by-step schemes to build a home or studio audio mixer console.
Project Details

    The Author: Juan Manuel Fahey, an eminence in the manufacture of national audio amplifiers (much remembered for equipping bass players like Ricardo Iorio), was part of the staff of the magazine providing their knowledge in technical sections.
    The Publication: It was distributed in the form of monthly deliveries or fascicles within El Musiquero, allowing musicians and enthusiasts of the time to buy the components in electronics houses (such as those on Paraná Street in Buenos Aires) to assemble their own console.
    The Legacy: Today it is a cult project between vintage audio technicians, music lovers and nostalgic Argentine analog electronics.

Are you looking for the electrical schematics or the list of components of a specific module of the Primavera console, or are you interested in knowing what exact numbers of the magazine was published?
-------------------------------------

Scopes see voltages.
IC5 is a current amplifier, no voltages to see.

Since we usually work with voltages, we must be able to convert one into the other.

Here:

Audio voltage present at left of R2 gets converted to current thanks to R24 which is injected into IC5 pin 13
Say you have 1 V RMS , it gets converted into 1 V/24k = 0,042 mA

IC5 outputs 0.042 mA into pin 6 of IC6B which converts it back into 1V RMS.
If you get signal there, then you DO have functioning IC5 and OC6 so replace nothing.

The whole circuit block between C1 and C7 is a unity voltage gain stage, that´s why I suggested replacing it with a piece of wire for testing.

That with zero voltage control injected on IC5 pin 9, that´s why grounding it with "compression" switch turns compression OFF

To make compression work, you have a "perfect" rectifier built around IC2a and IC3a-b into IC4b.
Here again positive rectified voltages become positive currents into IC4b pin 6 thanks to R22/23
Now IC4b turns that positive current into a negative voltage which gets applied to IC5 pin 9
My educated guess is that IC5designers (same as modern THAD IC) found a way to Gain control using currents

Musical instrument compressors are way simpler, usually through a LED/LDR or FET or even a humble bipolar transistor or Diode, this is a Studio Quality compressor.
Bet SUNN designers just took the short path and adapted it to a Musical Instrument amp.

Just check a Boss or MXR or DOD pedal compressor.
Or a Crate/Ampeg optical one.

I guess I didn't understand how IC5 functions. And I still don't. I was checking for signal on pins 13 and 4 on IC5 and there was nothing. Now I see there is signal on pin7 of IC6b. How is that possible?
I clearly don't know the signal path. There is signal on the top side of the Zener D1 but nothing on the other side of D2. Should I see signal of both sides of the diodes when the 'contour' switch is off?
I will trace from IC6 with the compressor on. At this point I'm not sure where it goes when it's off.
Sorry about this.

Ok yeah the signal (at least half of it) thinks the V+ is ground

Anyway I went back and read some stuff here and decided to heed their advice and add a base resistor to ground

Which I did and it helped but I had to accommodate both V+ and the ground resistor thinking about voltage drops.

I saw where there was a threshold where Vbe would hold up then start to decrease to head south and that coincides with the onset of clipping of the output.

That said I don't expect anyone to make heads or tails of this nonsense I'm gonna have to keep working on it for a while.

Thinking out loud I guess the base voltage needs to exceed the input signal voltage so maybe increase the value of the base to ground resistor

 

So yeah I'm getting my rear end handed to me that's a good thing 

And one problem that needs to be worked out and I had noticed this before

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And as the input signal is turned up it gets worse (base gets more negative)

I have the positive terminal of the electrolytic facing the circuit

Probably something simple doh 

Ok I went back and constructed the circuit and took some readings

About the V+ value I think I just wanted enough to get the Vbe I needed

Anyhow

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Seems like I remember the emitter and current should be about the same but that doesn't mean the resistors are the same.  In fact all those little circuits I made I don't recall that being the case.

Seems like I do need the collector voltage more positive than the base voltage and I'm pleased with that 

I better do something so maybe I'll increase the value of the collector resistor