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Old 4th Feb 2023, 6:45 pm   #49
3pinplug
Pentode
 
Join Date: Jun 2016
Location: Kent, UK.
Posts: 190
Default Re: Help needed with - Racal Dana 9081

Hi all
Right heres the readings / findings, hopefully I have done these correctly.

C11 - desoldered it and found it was just a lump of solder on the leg - see attached pic. There was only 6 tants on the divider & phase detector board so took the opportunity to replace them all!. All were pretty much to spec apart from"C1" which read as a resistor so was not working, so glad i did this afterall. Checked the resistor associated with C1 and it was ok.

Checked Pins 15, 17, 13 and 18 on the Logic board on my oscilloscope looking for pulses, assuming thats the correct way to do it?
Results were
Pin 15 - Pulse (waveform?)- pic attached
Pin 17 - nothing
Pin 13 - Nothing
Pin 18 - Brighter pulse (waveform?) than Pin 15 but looked the same waveform.pic attached.

Didn't change the pins round as 2 had nothing and one (Pin 18) was working as it should.

Tantalum Voltage on + leg of Tants on Divider and phase detector board after replacement:-
C6 = -5.07v
C22 = -5.51v
C1 = +12.32v
C4 = +12.29v
C13 = +7.36v
C11 = +12.30v (tant that was found to be dead)

I have tried the unit since replacing all the tants and still in exactly the same condition, hopefully the above gives the next pointers to look at?

Thanks again all

Mark
Attached Thumbnails
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