FYI: TX-1 Temp Study

[john]

Another thought, is that there's significant IR energy emitted by the 
various tubes in the immediate vicinity of the power and mod 
transformers.  The black metal transformer shells do an excellent job of 
soaking this up. In the 32V2 I rebuilt (due to, you guessed it, a bad LV 
transformer) I attached an aluminum shield with a dot of double side foam 
tape, to reflect this energy from being deposited into the 
transformer.  Yes, it probably causes the rectifiers to run hotter, but 
they're more easily replaced than transformers!

John K5MO


At 11:26 PM 6/25/2007, L.G. Robertson wrote:
>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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