[MRCA] GRC-19 power supply

[D. Platt]

On 10/7/2012 6:31 PM, Robert Newberry wrote:
>
> I'm possibly looking to purchase a GRC-19. I've heard people use two 
> 12v batteries hooked together.
>
> Then I read some post on QRZ.com about the batteries do not provide 
> enough voltage to auto tune and for current in rush in TX.
>
> What is the groups thoughts?
>
>
>
> -
Robert,

Good luck on your GRC-19 project.  Those radio sets can be a nice 
experience.  A couple of items from my research and direct experience.  
If you end up with a non-lettered T-195, one with all dynamotors, the 
inrush current will be about 70 amps.  Invariably, power supplies like 
the PP-4763 (especially the "A" model) will trip out, every time.  One 
can replace the fast-acting circuit breaker with SB fuses and it may 
work better.  That said, if you have a T-195A* or one modified with the 
high voltage inverter/dynamotor replacement, the inrush current will 
quite manageable.  The ones I use have all solid-state replacement 
dynamotors and the operating current is about 31 amps at 29 volts.  If 
the multi-voltage dynamotor is still there, but with a solid-state high 
voltage dynamotor replacement the inrush minimal.  I'll also add that 
power relay K2 gets a horrible hit every time its activated owing to the 
inrush current to the HV dynamotor.  Before I converted the T-195's,  I 
have had to burnish that item regularly to keep it from burning out.

Regarding the solid-state dynamotor replacements, they are getting 
scarce to unobtanium.  They were made by Victoreen and use germanium 
power transistors and custom toroid transformers.  In essence, Victoreen 
put 15 lbs of electronics in an 8lb enclosure... so to speak.  What I 
have helped others do when these HV replacement supplies go bad is to 
build up an external 1000vdc supply and feed it in via the rear of the 
cabinet.  K2 provides the "keying" of the supply.  No more HV issues.

You mentioned the required DC input voltage, and you are correct.  The 
T-195's, over time, require a bit more voltage to operate the servo 
circuits, reliably.  One issue is that the matched germanium diodes in 
the servo discriminator circuits/require regular replacement/, according 
to the TM.  If the servo circuits don't work, it will, of course, never 
tune up!

Working through all this, if you get a good one, they are a fine rig and 
sound excellent if used with a good quality carbon mic.

*  Look for the tel-tale yellow painted function switch knob.  However, 
be sure and look inside to see if the SS dynamotors are there!

Jeep - K3HVG

PS:  I have some servo choppers, in stock.
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