[MRCA] GRR-5 Fun Facts

[Ray Fantini]

GRR-5 Fun Facts! another slow day at work.
Been a while that I have owned one or run one in the field but things I remember and I think may be unique to that radio.
The radio has two different audio output stages, one for low level output (LOW) that uses the BFO tube V7 and a completely different stage for high level output (HIGH) using V8 they both share the output transformer T14 but use different windings. No idea why, maybe so the level of the audio on the 600 Ohm output can be set to low as not to exceed driving external devices like intercom and telephone circuits, avoids the issue of having to use the AF gain control?
With the exception of using dry batteries the Filament vibrator (E102) is always active. When running the radio from 120 volts AC they still use the filament vibrator system to provide the filament voltage for the receiver. There is a flock of voltages provided to the receiver by the power supply, +90 (B+) +12 and +24 if you're in that mode along with 1.4 volts and -4.2 volts of bias.
You can bypass almost the entire power supply deck by using the Dry Battery input, pin A- B Battery + (90 volts), pin B- A Battery (1.5 volts), pin C- ground and pin D- B Battery - that's isolated from ground to develop the bias. I used one for a long time with just a D cell and an old 90 volt B battery installed in a box next to the radio.
When running the radio in the field from the dry batteries you can screw the antenna MS-116,117 and 118 directly into the top of the receiver, just don't think that would be a good idea in mobile operation.
Accessories, if you got the radio might just as well try going all the way with it!
Canvas cover, CW-211/U
Accessory Bag, CW-206/GR Never saw one, only in manual.
Accessory "Spares" box, Electron Tube Case, CY-1031/URR Lots of them around, no idea why.
Vehicle Mount, MT-768/URR They will often sell for as much as the receiver itself.
Think the least I have paid for one may be $20 and have seen them sell for more with the most common price being $75 the last couple that sold on eBay went for around $150.00

Ray F/KA3EKH



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