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Author Topic: How hot does a Boat Anchor get?  (Read 40553 times)
W1BR
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Posts: 4189




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« Reply #60 on: February 21, 2015, 09:12:27 AM »

I have found some in expensive , quiet portable, controllable (simple switch on the fan) computer fans. I want to get some baseline figures. If I think any of them are running too hot for me I want to experiment by just putting the fans on the top of the cases (HK thoughtfully provides cases full of holes), and blow air over the tubes on a parallel axis. The fans are really quiet and I don't want to hack up the radios. I am particularly  interested in running an SB-301 and SB-401 (transmitter and receiver) on top of each other which may present heat problems.

Blowing cold air on a tube tends to shorten tube life. Use the fan to exhaust the heat. Blow cold air on a semiconductor; suck hot air off a tube.

I guess Heathkit, Ten Tec, and many others had it wrong....
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KM1H
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« Reply #61 on: February 24, 2015, 02:38:18 PM »

Try something that dumb on an 8877, 4-400A, 4-1000A, etc. Even some big pre WW2 TX tubes used a fan on the envelopes blowing room air.
Using a muffin fan on a pair of T4XC's extended 6jJB6 tube life from 6 months of serious DXing/contesting to several years.

After I reduced the AC line to my BA's to 108-113V the heat was no longer an issue.

Carl
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KC2QYM
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« Reply #62 on: February 27, 2015, 09:56:44 AM »

Isn't the air drawing action of a top mounted fan over the tube doing the same thing as blowing air towards the tube?  The ambiant air still passes by the tube envelop at the same rate of speed. What's the difference?
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W1BR
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« Reply #63 on: February 27, 2015, 11:42:42 AM »

Isn't the air drawing action of a top mounted fan over the tube doing the same thing as blowing air towards the tube?  The ambiant air still passes by the tube envelop at the same rate of speed. What's the difference?

No, not really... you have to remember that the pin seals also have to be cooled.  For example, many rigs running 3-500 tubes have the fans blowing across the tubes, which was designed adequate airflow over the base seals... otherwise the pins will melt, and also the socket fingers will overheat and weaken. I don't disagree that drawing air away from the capacitor banks and bleeders is a bad idea, however. 

Pete
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KM1H
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« Reply #64 on: February 27, 2015, 04:14:52 PM »

The usual muffin fan blade design works best by pushing air; automotive fans excel at pulling air thru the radiator.

A fan in a radio with poor mechanical stability will be frequency modulated by the fans vibration.....many boatanchors are not very mechanically stable.

Ive added a small PC CPU fan under the chassis in several 12-16 tube console radios that ran extremely hot and even melted wax out of the various multiband coils. These radios all came wit several decent size chassis hole for the air to exit as well as move some hot tube air out of the cabinet. Since all these radios are for AM only there was no noticeable instability.

Carl
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KA4LFP
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Posts: 273




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« Reply #65 on: March 06, 2015, 07:36:46 PM »


Kevin, I'm going to walk away from all the arguing on here about MTBF and heat....

Instead, I'm going to propose a way to do what you want to do, not argue about whether you should replace half the parts in your BA, and spend hours debating the MTBF of those parts.

There is a temperature sensor known as a DS18B20.
It's a little TO-3 (or TO-220) digital chip, with a Vcc (5v) and Gnd and Data pin.

Not sure how computer interested you are, but lots of us IT people use them for measuring temperatures inside servers or other cabinets, when we want to go DIY with it.

Here's a piece of Windows software that will use multiple DS18B20 devices, and graph the results over time - just like what you were asking for (and no one actually answered, unless it got lost in all the arguing)
http://www.mrsoft.fi/ohj01en.htm

Alternatively, if you want to go a bit more DIY, you can run a Raspberry PI with  Linux combined with an open source tool called MRTG (or RRDTool) that does a good job of reading temp sensors.
There are a lot of projects for doing that -- I've got  a Raspberry PI reading temp sensors
and graphing the results - total investment < $50 for 10 sensors and the PI.
Graphs show on a webpage delivered onto my network by the PI.
It requires some investment in learning, but what real ham doesn't want to learn!
(I'm sure I'll get flamed for saying that, since I'm sure there's an exception and he/she will loudly complain...)

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