Author Topic: Racal Dana 1992 teardown  (Read 31639 times)

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Offline slburris

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Re: Racal Dana 1992 teardown
« Reply #25 on: October 06, 2012, 05:09:35 pm »
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
 

Offline grumpydoc

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Re: Racal Dana 1992 teardown
« Reply #26 on: October 06, 2012, 05:15:43 pm »
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?
 

Offline slburris

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Re: Racal Dana 1992 teardown
« Reply #27 on: October 06, 2012, 05:41:25 pm »
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
 

Offline muvideoTopic starter

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Re: Racal Dana 1992 teardown
« Reply #28 on: October 06, 2012, 05:44:32 pm »
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.
Fabio Eboli.
 

Offline slburris

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Re: Racal Dana 1992 teardown
« Reply #29 on: October 07, 2012, 12:36:41 am »
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
 

Offline Smokey

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Re: Racal Dana 1992 teardown
« Reply #30 on: August 30, 2024, 05:02:55 am »
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?
 


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