[MRCA] GRR-5 Fun Facts

[wa6bbq at sdf.org]

Thanks Ray for the reminder about the dry battery operation!

I have one known working GRR-5 with a blown up power supply, (open
transformer winding, IIRC) and two sad looking parts units in condition
unknown.

I'll have at least one running very shortly, thanks!!

Jason WA6BBQ

> 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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