They have not pulled the crystal oscillator, it's on one of the boards, shown as a transistor heater stuck to a crystal (exactly as the diagram shows), the dashed lines show each board.
Ohhhhh...... thanks for that, you are right in deed ! Wow, I expected a biggish "can", not such a very compact arrangement that it can fit onto a sandwich of boards like that !
So there it is, yeah !!!
I have my 80 Euros worth, mood is improving fast !
I reworked the inside pic a bit, zooming on the required area and adding lots of light, we can see the OCXO much better now.
also attached the board layout of interest. No doubt this is it... transistor is on the right on the picture, crystal on the left.
Looking at the schematic I was wondering where the hell was the resistor/heater in this "oven", and what the hell was transistor doing in there ! ... only to come to the conclusion that yeah, as you said.... transistor IS the heating element, no resistor here !
I guess I learned something... I though a resistor was the easiest / most obvious way of heating a crystal oven.... looks like not ?
Maybe a power resistor would have too much thermal mass and the control loop would be too slow ? Using a transistor instead makes it more responsive ? No idea, just talking out of my arse...
Still with no can to cover the crystal and transistor completely, thermal coupling / regulation is not great is it ? Maybe they rely on the fact that the instrument is very compact / crowded, to consider that the temperature around the OCXO, though "open", is still stable enough for it to work. At least to get the accuracy they were targeting I guess...
Some other vintage counter use the 95H90 prescaler IC, or the Plessey SP630B for approx 500MHz.
Datasheet I got gives the 95H90 for 250MHs so 500MHz seems like quite a stretch ! Maybe if you pump up the signal before hand... but the datasheet does not give a graph showing bandwidth relative to input signal amplitude, so I don't know....
Please do not turn this into another clock, more than enough of those out there already using old stock Russian parts* and the last thing we need is people on here encouraging the destruction of more TE.
That would make you no better than the Tek murderer you were criticising yesterday.
*example of Russian tubes; https://www.ebay.co.uk/itm/334226281408
David
OK OK !!
Now that I know it does have an OCXO, I would not have taken it apart anyway, and again had I turnesd it into a clock it would have been implemented as an extra feature, counter would have kept its original counter ability.
Thanks for the link on the Russian things, so you can buy a set of 6 for only 25 quid (double that with shipping and import charges, but still, kinda reasonable), of Numitron displays... packages in a vacuum tube envelope ?!
Interesting... yes in this case it would be a waste and stupid to repurpose a nice and exotic counter just for its displays...
Also found these on Ebay :
https://www.ebay.co.uk/itm/194289930578Again Russian "tubes", this time using VFD 7 segments rather than Numitrons, and they look very large/tall at that. NOS, for a reasonable price...
OK OK.... I won't modify my little counter, will make my own clock with brand new displays of some kind...
Or maybe Robert can find me an old cheap piece of avionics gear that I can repurpose... something with a few digits and a knob or two ti set the time... I don't know, some auto-pilot control maybe, heading/altitude/vertical speed displays, something like that.... or an old FMS with a monochrome CRT and a cool keypad, for more options wrt to user interface and looks... yeah....