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Author Topic: How hot does a Boat Anchor get?  (Read 40568 times)
KD0ILM
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Posts: 55




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« on: January 31, 2015, 04:06:54 PM »

There are a lot of small LCD digital temperature gauges with probes on them for sale. For my personal interest I want to measure the temperatures inside my Heathkit tube amplifiers and radios (101,102,200,220, 301,401) and how they vary with use. Does anyone know generally speaking what upper limit I should look for in a device? I realize that up to tube melting temperature is one answer but I am looking for the temperature of a radio that is in normal use. I am also guessing the most useful information might come from the finals cage of the transmitters.
Opinions please
Kevin
KD0ILM
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AA4HA
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Posts: 2630




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« Reply #1 on: January 31, 2015, 07:20:26 PM »

Generally most boat-anchors I have owned have not pushed much more than 120 F as an ambient internal temperature. There are always exceptions to that and as you can imagine, a tube amplifier can run quite a bit warmer. Not to the point where you are going to fry the fingerprints off of your fingers but right up the upper limits of comfort.

Surprisingly it ends up being some smaller devices that run hotter, things like a CV-591 (SSB adapter) that is chock-full of tubes in a very small package.

They try to limit temperatures because capacitors do not like it.
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Ms. Tisha Hayes, AA4HA
Lookout Mountain, Alabama
W4OP
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« Reply #2 on: January 31, 2015, 07:40:02 PM »

I find a good deal of difference when running my BA's of the AC socket (something I no longer do) as opposed to running through a bucking transformer to bring the voltage to 110VAC- where it was "back in the day".

Dale W4OP
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G3RZP
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Posts: 1280




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« Reply #3 on: February 01, 2015, 08:18:21 AM »

Depends on the rig. I have an Eddystone 888A ham bands rx: 8 tubes in the signal path, plus one in the crystal calibrator, a 5Z4G rectifier and a VR150 stabiliser. About 16 inches wide , 8 inches high and about 9 deep. It gets too hot to comfortably keep your hands on the pretty well ventilated case, so it must be around at least 55 degrees C (131 deg F) inside.

Generally, as you might expect, the greater the number of tubes and the smaller the box, the hotter it gets. Maritime radios for compulsory fitting had to meet full spec from -15degC (5 deg F) to + 55 degC  ambient. I'm not sure how the crew were supposed to function at the upper limit, though!

My Drake TR3 got warm, but not probably over a case temperature of 40 or so degrees in a 22 deg C ambient.
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KD8IIC
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« Reply #4 on: February 02, 2015, 08:33:52 AM »

 I think I can warm a sandwich or make toast on top of my Johnson TR Switch. The old heads report that it is normal for the device.  73
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WB4SPT
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Posts: 777




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« Reply #5 on: February 02, 2015, 09:23:09 AM »

I want to measure the temperatures inside my Heathkit tube amplifiers and radios (101,102,200,220, 301,401) and how they vary with use. I am also guessing the most useful information might come from the finals cage of the transmitters.
Opinions please
Kevin
KD0ILM


My opinion is to encase the probe cable in teflon tubing, including the end.  Shocked
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KD0ILM
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Posts: 55




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« Reply #6 on: February 02, 2015, 09:43:24 AM »

What is your thinking about the teflon tubing?
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G3RZP
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« Reply #7 on: February 02, 2015, 09:59:54 AM »

Stops you touching some high voltage point by mistake? Trouble is, it will act as a heat insulator....
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KD0REQ
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« Reply #8 on: February 02, 2015, 10:47:33 AM »

the old problems never go away.  heat kills components.  they didn't used to publish derating curves back in the tube days, but electrolytics were commonly rated to 140 Fahrenheit.  at that temp, the wax flowed near hot spots by tube sockets and the caps would short.  rubber wire insulation cracked to allow arcing.  resistors would slowly go into runaway and bake to high values.  the old grey engineers at the radio station said if it's comfortably warm, it's OK.  if it's raw hot water warm, you have a problem, send the talent into another studio and take this one down.
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KD0ILM
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Posts: 55




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« Reply #9 on: February 02, 2015, 10:56:33 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.
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WA4NJY
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Posts: 146




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« Reply #10 on: February 02, 2015, 12:43:06 PM »


 Does it really matter what the top cabinet temperature  is?  If heat is flowing upward out of the cabinet, should not cooler air be drawn up from above or below the chassis by this convection?

Any fans could be placed on a ventilated cabinet top to assist the upward flow of hot air.  Or am I the hot air?

Ed
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KD0ILM
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Posts: 55




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« Reply #11 on: February 02, 2015, 12:50:48 PM »

This is why I am doing the experiment.  Smiley
I don't have a clue!!
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W1BR
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Posts: 4189




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« Reply #12 on: February 02, 2015, 12:50:56 PM »

Heat is not good for filter caps, nor the organic insulation used in transformers. If I have a radio that runs hot, I'll take steps to reduce the AC voltage to 110 or 115 VAC.  That often makes a big difference.

Pete
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WB4SPT
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Posts: 777




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« Reply #13 on: February 02, 2015, 01:02:26 PM »

Stops you touching some high voltage point by mistake? Trouble is, it will act as a heat insulator....

OK, 2nd try.  I've solved that plus the electricity issue. 

http://www.omega.com/pptst/TL-10.html
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HFCRUSR
Member

Posts: 359




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« Reply #14 on: February 02, 2015, 01:06:54 PM »

For what it's worth, I run a 12v fan, airflow-out at the power supply side of my 20-tube boatanchor. This way, it draws in fresh air from the audio side and pulls the heat out the rear of the hot side. Even the transformer is cooler. Without that fan it gets hot enough that you cannot touch the hood on the power side. Plus I run it at 110v off a variac. Even though the hood is perforated, IMHO it does not dissipate enough heat.
Small drawback is having to vac dust from the audio side and rear of the variable cap house.
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Not a ham, but an avid hobbyist in HF world. All things, short of transmit happen in this shack.
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