FYI: TX-1 Temp Study

[L.G. Robertson]

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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