FYI: TX-1 Temp Study

[Peter A Markavage]

My TX-1 had a fan in final compartment since day 1. Sucked air and fur
balls into the compartment  for years. Finally threw it out and installed
a fan in suck out position above the final compartment. Also installed
another fan in suck out position on a bracket, (I forget where I attached
the bracket) just above the moderator section. The combo of both fans
keeps the innards cool. Both fans are 24 volt DC. Since the power
supplies were solid-stated back in the 70's, I used the 5 volt filament
voltage to power a voltage quadrupler with a variable DC voltage output
control. Mounted all this stuff on a perf board which I stuffed and glued
into a discarded octal tube socket and plugged into the low voltage
rectifier socket. I can adjust the voltage control to vary the speed of
the fans to keep noise to a minimum. This Apache has been in active use
since 1959 when I built it.

Pete, wa2cwa

On Mon, 25 Jun 2007 20:26:02 -0700 "L.G. Robertson"
<digital-conjurers at ROADRUNNER.COM> writes:
> Thought the group might be interested in a recent test I did with a 
> TX-1  that was getting a little too hot for my taste, i.e. the 
> modulation 
> and HV transformers getting hot (110F @75F ambient room temp, 
> measured with 
> a thermocouple) after a couple of hours.  I had been hearing about 
> TX-1's 
> with blown modulation transformers and/or HV transformers...and I am 
> from 
> the old school of "if it's running close to or over 120F, it's too 
> hot". 
> [Tubes excepted, of course.]
> 
> There were two schools of thought:
> 
> 1. Running the TX-1 at a lower voltage via a 125/12V "bucking 
> transformer 
> would take care of the problem; my line voltage is 123-127.  Running 
> it off 
> 111-114 should do the trick.
> 
> 2. The problem was with the insufficient air flow in the TX-1 
> cabinet design.
> 
> Well, I spent 2 days building a 12A "bucking" transformer, tested it 
> out, 
> and guess what?
> 
> Running the TX-1 on 112 volts AC only _delays_ the problem; the heat 
> 
> build-up still occurs, the hot spots still get to 110F, it just 
> takes longer.
> 
> [Well, maybe I can use the "bucker" as a piece of gym equipment... 
> ;)  ]
> 
> Just thought you'd like to know; I should have invested in a small 
> fan, and 
> somehow parked it on top of the cabinet...maybe on felt feet, or 
> something, 
> and directed the air to be drawn _out_ of the cabinet .  It may 
> cause a bit 
> of frequency drift, but it should run cooler.  I'll try this 
> sometime.
> 
> Now, why Heathkit would use the SAME cabinet for the TX-1 (500 
> watts) as 
> the RX-1 (65 watts) I'll never know...marketing, cosmetics,...but it 
> was a 
> bad idea...now, putting that fan in the final cage helped the life 
> of the 
> finals (the original TX-1 had no fan), but blew the hot air out into 
> the 
> surrounding areas of the chassis.
> 
> Now, this is not to say that, in general, running vintage rigs on 
> 110-115VAC is not a good idea; it is.  Just in the case of the TX-1 
> it 
> didn't seem to help.
> 
> Just FYI for anyone else having troubles with this.
> 
> -Lin/KJ6EF

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