[MRCA] T-195A

mac w7qho at aol.com
Sat Jun 8 18:37:14 EDT 2013


Robert,

How much documentation do you have.  Complicated rig and undocumented  
modifications make it worse.

Blowers and filaments lighting off, good!

For the high and low voltage relays to energize a time delay relay  
down on the modulator chassis will have to heat up and  close and, of  
course, the safety interlock will have to be closed (or maybe wired  
around in your case).  In PHONE the high and low voltage relays should  
then energize when either the PTT switch on the mic is pressed or the  
KEY switch on the front of the set is engaged (rotated).

No light or other indication when the time delay relay (see above)  
closes, the rig just won't key until it does.

The safety interlock switch should be located on the back of the  
antenna inductor compartment.  If it has been removed you should be  
able to find a small hole (approx. 3/16 D) where it used to be.   
Normally wired to pins 3 and 13 on the inductor connector (P 1101).   
You should see continuity between these two pins only if the switch is  
closed or, of course, if it has been jumpered out.  Circuit could be  
jumpered out elsewhere in the radio too, of course.

Hope this helps.

Dennis D.  W7QHO
Glendale, CA

******************
On Jun 8, 2013, at 9:09 AM, Robert Newberry wrote:

> Well i went to install the HV supply and noticed someones pencil  
> marks contradict the schematic. Essentially telling me to put a  
> ground where 24vdc is supposed to be.
>
> I instead powered up the set to see what is at the terminals where  
> the HV supply is supposed to go.
>
> Problem one:
>
> Someone removed the safety interlock. I tried to find convenient  
> spots to check for a path on both sides of the switch. I went from  
> pin one of the LV relay to pin eight in J606-8. I'm assuming that if  
> I got continuity that I should be good to go?
>
> Problem two
> The HV and LV relays are not energizing and I do not have 24vdc at  
> f603 or f602.
>
> That seems to me that my safety interlock is not engaged? The safety  
> switch is missing and I cant find any trace of it.
>
> The blowers do spool up and the set lights up when power is applied.
>
> Any thoughts from the group would be appreciated.
>
> Apparare Scientior
> Paratus Communicare
> -N1XBM
>
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