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Show all reviews of the Racal RA1772
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of the Racal RA1772.
May 8, 2013 07:51
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Power Supply mod
Time owned: more than 12 months
The RA177X 'family' of receivers are excellent but in the years that I've owned mine, I've had to repair two power supply faults to date. This of course is to be expected with ageing equipment.
Due to it's compact design, the RA1772 power supply generates quite a bit of heat which leads to brittle wiring in the power supply area over time.
If your RA177X family receiver suddenly stops working, the PSU is the obvious place to start looking for problems. Check for missing insulation and short circuits on the wiring loom connected to the power supply PCB. I've even seen wires desolder themselves in the power supply area!
Remember that the receiver has a handy voltmeter with which to (quickly) check voltages, if your radio quits. You don't want to 'cook' anything so any voltage checks made should be very swiftly made.
For some reason, RACAL decided to place bridge rectifier D2 on the power supply PCB rather than on some metal surface that would conduct the heat elsewhere. In normal use, this rectifier runs really warm.
A far better solution, is to remove D2 to the card cage which is of course ventilated. This simple mod will dramatically lower the temperatures in the PSU area of the receiver, while only making the card cage slightly warmer. Use some heatsink compound applied to the bridge rectifier to aid heat transfer. The 'wet' electrolytics in the power supply will thank you for this mod by lasting longer than they otherwise would.
You can read about my power supply mod at..
Because these receivers are now quite old, it makes sense to replace the large electrolytic capacitors on the power supply panel. These will all be well past their 'sell by' date. It's a simple job and worth the effort.
Moving the rectifier and replacing those tired old electrolytics will go a long way to getting years more service from a great receiver.
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