Reed relays for Racal Dana 1991 or 1992 counter timer

[David C. Partridge]

My Racal 1992 is bringing up error 52 on the Channel A relay test (Relay C,
50 Ohm/1Meg switching), and error 56 on the Channel B relay test (Relay G,
x1, x10 switching).

Racal part numbers 23-7529 and 23-7528.

Can anyone help (if you have a dead 1991/1992 perhaps)?

Based in UK.

 

[carneyke]

Hook up some AC from a function generator across the coil and rattle
the contacts. That may help if the coil isn't open. Take Care, Kevin

 

[Achim Metzen]

My Racal 1992 is bringing up error 52 on the Channel A relay test (Relay C,
50 Ohm/1Meg switching), and error 56 on the Channel B relay test (Relay G,
x1, x10 switching).

Racal part numbers 23-7529 and 23-7528.

Can anyone help (if you have a dead 1991/1992 perhaps)?

Based in UK.

David, please allow one question: Did You connect the SDT OUTPUT to the
right inputs for the test (to A for SF 77, to B for SF 78)?

Achim

 

[David C. Partridge]

I understand why you ask, and yes, I did connect the reference out to input
A for test 77 and input B for test 78. I used a piece of coax 90cm in
length.

Dave

 

[Achim Metzen]

Did You try [email protected]? I found them very helpfull
some years ago. But I'm not sure, if they are still alive...
I ordered some parts from racalinst Germany, which took a lot of time.
The parts itself were not very expensive, but they had a minimum order
of 25 or 50¤. UK was a lot easier, but I was foced to order in Germany...

Achim

 

[David C. Partridge]

It's not the Channel A 50 Ohm/1M relay whatever SF77 tells me. All the
channel A relays are switching and doing what they should when driven with
the front panel controls.

Unfortunately, the manual doesn't say exactly what SF77 actually does -
clearly it is more than just exercise the relays. What is notable is that
the only relays that appear to be switching are the 50Ohm and x10 relays,
but the other relays that are supposed to be switching in this test mode
(DC, FILTER and COM A) do not appear to be being driven.

The STD out is 3.5Vpp with the baseline sat at 0V (i.e. varying DC, not
strictly AC). Will count with 1M input / AC coupling

Switching in 50 Ohm termination drops this to about 1.3V pp and will still
count.

Switching to DC coupling - stops counting.

Switching back to 1M termination - will count again but somewhat
erratically.

SF78 for channel B doesn't seem to be doing much in terms of driving relays,
though the front panel controls DO seem to work to actuate the channel B
relays???

Dave

 

[David C. Partridge]

I've been doing some further checking - definitely something is sick around
the A/B amp or the DAC (TEC) on the H2 hybrid.

Here's what I see:

SF76 (trigger DAC exerciser) gives sawtooth between 0 and -10V on channel A
trigger level output, and pretty close to 0V on channel B trigger level
output. It should be a sawtooth between +5.1 and -5.1V on both.

DC trigger levels:

For channel A using TRIG Level control for +5 seems to be at -9.3V, and
for -5V drifting between -8.8V and -9.3V (where it eventually settles).

For channel B voltage does change but not very far from 0V (small number of
mV).

D.

 

[Achim Metzen]

I've been doing some further checking - definitely something is sick around
the A/B amp or the DAC (TEC) on the H2 hybrid.

Here's what I see:

SF76 (trigger DAC exerciser) gives sawtooth between 0 and -10V on channel A
trigger level output, and pretty close to 0V on channel B trigger level
output. It should be a sawtooth between +5.1 and -5.1V on both.

Checked: both are here at +5 and -5 sawtooth.

DC trigger levels:

For channel A using TRIG Level control for +5 seems to be at -9.3V, and
for -5V drifting between -8.8V and -9.3V (where it eventually settles).

For channel B voltage does change but not very far from 0V (small number of
mV).

D.

Strange...

some ideas:
check D.A.C +-11.2V (7,8 against 3,11)
Check Powerless Resistance of D.A.C. 1,2 against ground... Check
C84,C14,C108 (short?)
What about IC25?

Achim

 

[David C. Partridge]

+/-11.2V rails are good.
DAC pins 1 and 2 are 1.55M to ground.
Caps are good.
IC25 seems alive at least as far as putting a logic clip on it is concerned.

I think that I've got a sick H2 hybrid here. I'd like to think it was
something else of course, as no doubt this is either unobtainable or very
expensive.

D.