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Old 12th Nov 2017, 4:12 pm   #1
__i4cy__
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Default Racal Dana 9084 signal generator

Hello,

After acquiring a copy of the 9084 manual, I have been able to establish a faulty 24v supply rail. This has been tracked down to a short circuit tantalum capacitor, C3. I have now replaced C3 and the 24v supply works again.

Any tantalum capacitor experiencing high in-rush current is eventually going to fail. The 9084 is full of tantalum caps. Does anyone know which caps on the 9084 often fail or suspect, so I can change them before putting the 9084 back together?

Thanks.
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Old 17th Nov 2017, 1:24 am   #2
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Default Re: Racal Dana 9084 signal generator

So far I have replaced 22 tantalum capacitors that failed after successive power cycling the 9084. The following caps have been changed.

PSU board C16
19-0896 board C8, C30, C28
19-0892 board C36, C16
19-0904 board C9
19-0900 board C11
19-0897 board C4, C28,C36, C45, C1, C20, C38, C30, C? (PCB mod)
19-0903 board C43, C1, C39, C33, C30

At least now there is no bellowing smoke coming out of shorted tantalums, the 2A fuse does not blow, and the power supply rails (-5V, +24V, +5V, +15V and -15V) all appear stable.

Unfortunately the unit is far from working (see photo). The frequency display flashes, while not showing the right frequency. None of the buttons seem to function, and the rotary encoder doesn't seem to do anything when spun. Could this be faulty "Instrument control logic system"?

Does anyone have any experience repairing the 9084, and could possibly point me in the right direction? Any ideas would be very much welcomed. The service manual PDF I have, many of the pages are unreadable. Does anyone happen to have a decent scanned copy of the 9084 service manual?

Thanks.
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Old 17th Nov 2017, 9:43 am   #3
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Default Re: Racal Dana 9084 signal generator

I have a 9087 and it spends more time being repaired than it does being used.

Displays not lighting up can often be cured by reseating the displays, or perhaps it's the driver chips, in their sockets.

Flashing displays indicate an error. Possibly the SG is out of lock? There may be diagnostics you can run as described in the manual.

Have you tried the Racal yahoo group?

https://groups.yahoo.com/neo/groups/...E1MTA4NzgyODU-
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Old 17th Nov 2017, 12:31 pm   #4
__i4cy__
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Join Date: Mar 2015
Location: London, UK.
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Default Re: Racal Dana 9084 signal generator

9087 the flagship model, very nice if it works.

Thanks Graham for the tips. Hopefully as you say it could be a bad connection somewhere. I wouldn't be at all surprised as it apparently has been stored in a garage for who only knows how many years.

I did actually source a copy of the service manual from the Racal yahoo group. Maybe someone there has prior experience with the 9084.

Thanks.
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