OBSERVATIONS FROM SCOTLAND                            13 March 2007                                GM1SXX

After all the shenanigans with my RA1772... now fixed and working 100%, my RACAL RA117E has thrown in the towel. I'm sure somebody 'up there' has it in for me!

The RA117 has a faulty first VFO. I've started work on the RA117 to fix it.  It works normally for a while then starts crackling through the speaker before it quits.  When it does work, The VFO delivers RF at 40-69.5Mhz as it should do.  I unplugged the 1st mixer valve and 'stole' RF from the grid pin (pin 2) straight into the DFM to monitor the VFO output. It showed a healthy stable RF carrier until it chucked in the towel.  The fault is repeatable, in that it happens every time from a cold start. The radio usually works OK from cold for 10 minutes b4 it goes AWOL. Sounds like a leaky cap or cracked resistor to me.

To get at the first osc, you have to remove the front panel, the second VFO, the BFO and other bits before you even reach the first VFO module.  In fact, it's about as bad as it can be for access to this module.  Were it any other piece of kit, I'd dump it in the nearest midden but the RA117 is actually a great radio, when it's working properly, so I'll make a serious attempt at fixing it.

The RA117E chassis minus most of the really important  gubbins.

The first and second VFO's fit in the large empty space in the front of the chassis. The IF strip is to the left, The filters to the left-side rear, the audio chain is in front of the transformers and chokes  while the PSU to the rear right-hand side.

This radio hardly owes me anything... I've owned it since 1986 so I've had 20 years of use out of it.
What a pity though that I didn't get a component failure somewhere a bit more accessible.

The Crystal calibrator... two screws, one BNC and unplug it.  Easy!

I now have a shoebox full of hardware for it. What a pity Haynes don't do a 'car manual' for RA117's!

The first VFO.... has to be removed after the second one! Wires to unsolder and mark plus lots of fixings. (sorry about the poor photo)

The Second VFO, has to be ripped out before you can get at the First VFO.   Note the 35MM film scale and good quality gearing.

These receivers are heavy metal. Even with the calibrator, both VFO's and the front panel removed, It's still a heavy chassis.  You have to be brave to do this sort of butchery on a top grade RX, but it's simply not possible to reach the first VFO in any other way.

More as it happens.
 

73 Al.

GM1SXX

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