As part of a prep to create a 9V external supply for this head amp, I thought I'd take a deeper look and see if the circuit could be exposed.
The little pot is just a cover and was glued to the sides of the inner tray. The board was also attached via a sticky pad to the base of the tray and the adhesive had worn out -
Here's a closer look at the board -
For copyright (?) reasons, any printing has been removed from the transistors, but hopefully the pics can tell someone the values of the very close tolerance (for the period) transistors used.
As for the caps, the outer tantalums are 6.3V 47 (uF?), the inner ones are 16V 10 (uF?), the two purple topped flat caps are n22's and the three little flat red ones have black and orange dots on (black at top, orange bottom right).
Am I right in thinking that the tants might be the cause od the slight "solid state brightness" this unit exhibits (and has always done from memory?). I don't know enough to know..
I've fitted a PP3 socket to the existing plug, which I've repaired, and taken the leads out through one of the screw holes (screw wrapped and placed in battery tray for posterity). This should make things possible to put back to original easily.
By the way, I've measured the voltage of the extra long life Alkaline PP3 I fitted and on my digital volt-meter it measures 9.14V. This makes me think that the regulator output shouldn't be set to more than 9.5V I think, unless anyone recommends differently