Old DIY Power Amp Design - What is it?

[PB2]

I was recently given an old very home made looking power amp from a friend that
passed away. It looks like an 80s or 90s design.
The PC board has Z8 printed on the back, uses a 2N2920 dual NPN diff pair, TO126 drivers
and looks like it was intended to have a pair of the old TO3P outputs - TO246 IIRC.

The board is actually wired up to some big MT200 Sanken outputs.

Anyone know what this was? I'm looking for a schematic.

TIA

 

[djoffe]

Z8 reminded me of Clive Sinclair's stuff...so as a shot in the dark, I present this link:

Doz' Blog: Sinclair Stereo Sixty Amplifier.

 

[Doz]

Z8 reminded me of Clive Sinclair's stuff...so as a shot in the dark, I present this link:

Doz' Blog: Sinclair Stereo Sixty Amplifier.

I wondered where all the hits where coming from ...

 

[PB2]

I didn't know about that amp but no the boards don't look the same.

 

[johnsurnamerobinson]

It could be a sinclair amp if the pcb is about 1.5" by 3" with 2off TO3 power transistors it prob is.Any chance of posting a picture ??

 

[PB2]

I'll take a few tomorrow when I'm home, thanks!

 

[PB2]

Pictures:

 

[JMFahey]

Will check on an old manual ... if I find it.

The hand applied black crepe tape design plus the dual package differential input transistor makes me think of early 70´s Motorola "Complementary Transistors Power Amplifiers" ; they published a range from 15W to 120W .

Some Manufacturers, notably Marshall, adopted them but on their own design PCBs.

 

[johnsurnamerobinson]

Well its NOT the sinclair amp I was thinking of.It looks home made like a hobby project fro the pubished periodicals of the period.

 

[PB2]

Thanks everyone, for the help!

 

[johnsurnamerobinson]

OK but it still would be nice to find out just what it is.My best guess is homemade BUT!!!!!!!

 

[PB2]

I forgot to mention the marking opi-vo in the lower left corner of the bottom
picture and there is a bar over the letters o and p.

 

[PB2]

The other channel has a different dual diff pair MD8001,
VAS is MPSA56
VAS current source is MPSA06
Drivers are MJE182/172
Outputs are 1 pair 2SC2774/2SA1170

Diff pair tail has a diode that is probably a current regulator type.

 

[JMFahey]

I told you it´s a version of early 70´s "Motorola High Power Complementary Amplifiers", with protection circuit chopped off and output Zobel and inductor mounted offboard, probably straight on output connectors.
Way back then I read and reread it so much that I must have worn some ink off the pages

 

[academia50]

Yes, with some minor modifications (use of zener diodes to stabilize DC in the Motorola) it is very similar to the classic RCA universally adopted by many manufacturers.

Pacson used it here in its maximum power versions.

Fundamental:

Pair with HFE the pair in input Darlington configuration.

 

[academia50]

Ops, it is after the RCA, it uses complementary output transistors.

"There are people who talk a lot and think little, and others who talk little and think a lot"

That is my dilemma ....

 

[PB2]

It is not like that MOT design.
It is more like the RCA reference design but complementary output with modern devices.
Current source on the VAS rather than bootstrap.

Just curious to know where the boards came from.