[Milsurplus] most Dangerous Transmitters

Wed Nov 20 14:35:54 EST 2019

   I owned one of these beasts for a few years. I have almost 40 years
experience in electronics, 30 in communications alone but no experience
working around high voltage like the 2400 vdc in the T-368. My T-368 was
purchased from an old timer who had gone through it as part of my
agreeing to purchase this beast. 

    I had lots of problems with this beast including more than a few
FLASH BANGS. I had to pull the 300 pound power supply shelf to replace
the plate relay. My T-368 had the military base with the outriggers and
metal caster wheels, I left it that way assuming the base was there for
a reason. It was easy to move around my garage on the metal casters. 

    I built a platform from 3/4" plywood that was mounted on 6 casters,
this was made to be just high and wide enough to straddle and clear the
outriggers on the military base and sit just below the bottom of the
power supply shelf. That made removing the power supply shelf easy and
it was not difficult to stand the shelf up on the end that has the iron.
I was able to work on it easily and also not hurt my back which was a
consideration. I have badly strained my back a few times and am very
cautious in that regards. 

     This beast scared the SH*T out of me a few times with the FLASH
BANGS, the last FLASH BANG was while dipping the plate while loading
into a dummy load. There was a flash over in the plate meter while I had
my head near by looking for the plate current dip. 

      That was the LAST STRAW, it was time to let this go. I sold it
with full disclosure to a ham friend, he had more experience working on
high voltage and was able to get it on the air and was happy with it. 

       Except for swapping tubes and the draws I don't see how this
beast could have been repaired easily in the field. There seems to have
been no thought given to field repair in the design. I would assume
there were repair jigs used at a repair depot for that purpose. 

                                                        Tom, W6TOM

On 2019-11-18 10:33, Ray Fantini wrote:

> My vote would be the T-368 transmitter. The first thing most Hams do is bypass all the interlocks. The stupid thing about that is in order for the HV distribution to work the drawers have to be all the way that sets the interlocks. Have had people tell me the interlocks become internment, so why not just fix them. 
> 
> I cannot think of any reason why you need to operate it outside the case, for it to work removed from the case you would also have to build up HV jumpers. The overload adjustments are all located on the front of the power supply, any diagnostics of the power supply can be done at low level or by isolation along with pushing the drawers back in but imagine most people don't want to do the additional work sliding the drawers in and out when trying to diagnose an overload issue. 
> 
> Second thing would be the Hot PA tank, the plate current meter and the band selector switch for the output tank are all at HV potential. Later series have an isolated PA current meter but the first generation had only a small amount of isolation and doing things while the transmitter is on like washing off the front of the transmitter including the plate meter with a wet rag have interesting results. The tube that is used as a shunt across the screen of the PA tube as part of the keying system can be fun also and although I am not certain of this would suspect that when the transmitter is in HV on standby and the shunt is full on it may produce X-Rays. Fortunately there are tons of shielding when the drawer is in place. 
> 
> And last but not least my favorite thing about the 368, unless the transmitter is secured to a wall or the floor it needs to be on a special dolly that has outriggers attached. Most Hams remove this first thing because they keep stubbing their toes on the outriggers. What's worse and I have seen this twice is that they will install wheels or casters under the four corners of the transmitter and when you do this if you pull out the top drawer to far or fast the transmitter will tip over and do its best to kill you! 
> 
> The manual states that never attempt to pull out more than one drawer at a time. If it starts to fall forward you will not be able to catch it. 
> 
> The T-368 is a great transmitter when used by the book, unfortunately most out there have been Ham Hacked in a great number of ways. There are volumes written about how to hack up the modulator. Maybe the only thing that's been Ham Hacked more would be the ARC-5 radios and the BC-348 
> 
> Well that's my rant, what's yours? 
> 
> Ray F/KA3EKH 
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