[Premium-Rx] Racal RA6790GM questions

[Heinz Breuer]

Hello,
after a couple years in storage I got my RA6790GM out and on the bench again.
Upon power on I enjoyed fireworks from two tantalum capacitors, C106 on A4 board burst out in flames and C9 in the power supply let out the magic smoke. Well I finally replaced these and the receiver is working.

I have the older version incorporating light bulbs to illuminate the displays and noticed that all are burned out. The manual calls for a B25T miniature light bulb 28V, 0.24A with wire leads. Do these tiny tiny bulbs really burn 6.8W? Anyhow I cannot find these bulbs. I would appreciate any help in locating suitable light bulbs. I wonder if I should modify it and use LEDs.

I also noticed that on the back of the control board A9 LED DS3 is on. This indicates Reference out of lock but the receiver seems to work ok and the fault light on the the front panel is off. I am using the internal TCXO and switch S2 is switched to INT. Any help with this?

And finally my RA6790GM only has 3 filters installed, a Collins 526-8635-010 2.5kHz filter in position FL1, a 526-8693-10 500Hz filter in position FL2 and a 526-8695-010 6kHz filter in position FL3.
As far as I understood the manual a 3.2kHz symmetrical filter is recommended for position FL1 to receive LSB and USB. My receiver has a 2.5kHz symmetrical filter which gives USB with a wrong pitch. Anybody has this 3.2kHz filter for sale?
I wonder if I could use standard Collins FA case LSB and USB filters which have to be soldered in? Do I need any capacitors with these? There seem to be holes for these.

I want to upgrade my receiver with more filters. Also I am looking for the A5 ISB board and the A6A1 remote control board. 

vy 73 Heinz


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