Racal Dana 1992 teardown

[slburris]

And now I've acquired a 1992 to go with my 1998. 

The seller said powers on unable to test.  Which we all know
Is code for "I powered it up and something's wrong with it"

I expected to get a counter with a bunch of bad switches but that
doesn't appear to be the case here.  It does seem to have issues though.

I applied the output of a signal generator to the A input and oddly
the trigger lights for both A & B flash.  The counter displays
The correct frequency.  But I can't seem switch the mode of the counter
And none of the freq/period/total/phase etc LEDs are lit.  The resolution
buttons work fine.

So it's sort of working.  Do these symptoms sound familiar to anyone?
I may see if there's an EPROM image out there to check if I have bit rot.

Otherwise time to break open the service manual.

Scott

[grumpydoc]

The B channel trigger LED flashing with a signal applied to the A channel seems to be normal - with no input the AGC is wound to max gain and it's either noise or possibly coupling from the A channel.

Not being able to change the mode is probably bad tactile switches on the two buttons in question, have you tried all the other buttons.

Where are you located?

[slburris]

I'd expect the FREQ A LED to be lit at power on, at least based on experience with my 1998 counter.

I pressed all of the buttons.  None seem to have the squishy feel of failed buttons but I suppose it could be another kind of switch failure other than the rubber dome problem.

I'm in the US.

Scott

[muvideo]

Can be noise, and there is also the COM A button that connects B input to A input,
maybe that is engaged in some way? Also I would check the buttons with a dmm,
maybe some is stuck closed.

My roms are here:
http://www.ko4bb.com/manuals/index.php?dir=04)_ROM_Images_and_Drivers

Fabio.

[slburris]

Well this is most peculiar.  After power cycling a few times all of the issues seem to have magically cleared up.  I hate it when problems mysteriously go away.  Maybe some marginal electrolytic capacitors inside?

Still I wasn't expecting a working unit for $100.  I connected the output of a Trimble Thunderbolt to it and after warming up for 30 minutes it reads 10MHz +- 2 digits. 

I have an OCXO in my 1998.  I think I'll move it to the 1992 ( and look for any bulging caps while I'm at it).

Scott

[Smokey]

I made a silly ebay "make an offer" on a 1992 and the dude accepted it.  Didn't expect that

After replacing all the switches I noticed the reference was surprisingly good.  Turns out it's a "04E High-Stability" oven.  Cool.

Option 04E High Stability Ovened Oscillator
Frequency: 10 MHz
Aging Rate: ≤ 5 x 10^-10/day at shipment averaged over 10 days
Temperature Stability: ≤ 7 x 10^-9 over the range 0°C to 50°C
Line Voltage Stability: ≤ 5 x 10^-10 two minutes after a 10% line voltage change

How good is that relative to modern references?