[Drakelist] R4C deaf and TR7 questions AGC, tx all band mod

[ian parkinson]

Greetings from over the Pond, oddly I have had a R4C stored in a damp area, and 
years later when I fired up it still works..though I have only run it short 
periods. The 2nd R4C is rather deaf both with normal rx and with the xtal 
calibrater..if its not the valve and I have both 6ej7 and the uk version EF 184 
to replace it with. There doesn't seem any exccessive drift, so I wouldn't 
think voltages are down.

 2nd subjest is about the TR7 are there any mods to change the agc speed to 
something like fast attack with either fast or slow delay for the CW position 
etc ..

 I saw a Mod for the TR 7 which involves cutting some pcb tracks for all band 
tx option..it certainly would be great to operate on the 30 metre WARC band. 
Any thoughts over this mod is it too risky ??

 I got my first R4C about 1978 it took all my college holidays working night 
shifts, ten tec came along and I forgot just how good Drfake euipment is, hence 
the recent purchase of the TR7 and A/C psu. I haven't the uers handbook fot the 
TR7 but a service manual..now figured out what the up/down buttons are for.

 73 de ian G3YRQ..best bent wires to 1 and all..
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Re: [Drakelist] R4C deaf and TR7 questions AGC, tx all band mod

[Jim Shorney]

On Tue, 27 Sep 2011 07:41:03 -0400, ian parkinson wrote:

I saw a Mod for the TR 7 which involves cutting some pcb tracks for all band 
tx option..it certainly would be great to operate on the 30 metre WARC band. 
Any thoughts over this mod is it too risky ??


The only real risk, per se, is that you may accidentally transmit somewhere
that you shouldn't and the communications authorities will notice. However
There is a right way and a wrong way to do this mod. Surprisingly, the
published method from Drake is the wrong way to do it. It does give you all
band allband transmit as described, but the method for doing so has the side
effect of disabling the out-of-lock (OOL) transmit inhibit signal from the PLL.
This could allow you to accidentally transmit out of band if the PLL happens to
unlock for some reason, and also prevents G4ALG's mod to eliminate the TX spike
when power is turned on from working. 

I have published a method that preserves the OOL signal and involves two trace
cuts on the old version Digital Control board. I haven't worked it out for the
newer version board yet, not having one at my disposal, and there seeming to be
no interest. Most people seem to go with the bad method, despite explanations
as to why it is not a good idea 

73

-Jim


--
Ham Radio NU0C
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HyGain 3750, IBM PS/2 - all vintage, all the time!

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