[Collins] [CCAECollins] Questions about a 51S-1

[Jacques Fortin]

Hello Heinz,

Thank you for your answers.
I cannot tell if the front panel was changed/swapped with another unit, but
if it is so, it was done following the Collins standards.
All the screw threads are sealed with the same bluish lacquer, so all the
assembly looks original to me.
Reading more of what is available about the 51S-1, it seems that they were
made by "batches" and some kept in semi-assembled state until an order came.
The unit was then "finished" and sent to the buyer.
That can explain why it was made in 1967 but have a "transition period"
front panel.

But this is not the problem I have with that unit for now.
It is obvious that only the first schematic revision change (the capacitors
around the filters) is applied to it, but not the ones that followed.
The BFO stage is completely different from the manual rev. 11 schematic,
same for the calibration oscillator.
There is a 200µF, 30V capacitor connected at the junction of R52, 54, 55, 56
to GND that does not appear in the latest schematic (and this one is
defective, BTW).

If somebody can provide me with the earlier version of the schematic (which
was the one used for the 1967 production ?) it will be a great help.
What did you recommend ? Updating the circuit to the latest schematic or
leave it as-is ?
All the electrolytics need to be changed within anyways !

For the tuning tool, it is made of white nylon but I cannot tell if it is an
original or not.

What did you mean with " not the ex-Israel military metal scrap" ?
Did you mean that there is Collins-made 51S-1s and cheap "copies" ??
I've seen a 51S-1 on the web with different knobs than the genuine Collins:
is that an Israel military one ?

73, Jacques, VE2JFE