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Old 25th July 2012, 07:06 AM   #211
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Quote:
Originally Posted by spurlte View Post
If computers CPUs can use water cooling (I see r-tools.com program considers water cooling), why isn't it possible to cool off TO3s this way? I have seen whole working mother boards submerged in a fish tank with a circulating bath of some special liquid of some sort here in Chicago at a local computer shop I must get a picture of it for reference, but the liquid cooling type I am speaking of is are those attached directly to the computer CPU. What a mouthful.
That would be very VERY cool David! I've never seen a water cooled KSA before. It certainly could work, but I think you will have to fabricate some pieces to attach the watercooling and TO-3's to. I don't know if there are DIY TO-3 kits, never seen one.

Hmm when rethinking about the little heatsink you've mounted to the MJ15032/33's, Mark could have a point David. The heatsink I use stays pretty cool, but is not fully biassed right now and off course a lot larger. I would say my heatsink is even a bit to large. From the other hand.... I have not tried what temperature will do when fully biassed. When I check Wikipedia, I see temperatures in Chicago are a bit like here in Holland. You could always try what it will do. Tj is for MJ15032/3 150 degrees C (yes I am all into thermo related stuff right now ), so even at let say 60 degrees, there should not be a real problem but offcourse the cooler, the better.
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Old 25th July 2012, 07:40 AM   #212
neychi is offline neychi  Croatia
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Michael, I suggest that you borrow from someone thermometer and measure temperature on the heatsinks exactly. I was thinking that the temperature is too high on my amp when I touched with my fingers, than it really was. I measured with a thermometer. 50 degrees is pretty hot to the touch, and at 55 degrees you can hold your fingers only a few seconds.

To quote N. Pass: "Human skin has the remarkable characteristic that we think 40 is comfortable, 45 is hot, 50 is very hot, and 55 is untouchable"

About Dale resistors, I told you so...I'm not surprised, but you can now sleep peacefully
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Old 25th July 2012, 09:03 AM   #213
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I have at least one (maybe two) water cooled to3 plate(s), hard to call it a heatsink really, it has no fins, just a drilled plate and a water pipe soldered or brazed into the surface.

If it were something someone wanted to try I could probably be convinced to track it down...I'm visiting family in England atm, but I should be back at home at the end of august.
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Old 25th July 2012, 11:30 AM   #214
john65b is offline john65b  United States
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Quote:
I have seen whole working mother boards submerged in a fish tank with a circulating bath of some special liquid of some sort here in Chicago at a local computer shop.
Distilled / De-ionized water?

I have thought of dropping a simple F5 or Zen V5 into a vat of circulating Distilled / Deionized water to cool...it was to be used as a humidifier in the winter.
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Last edited by john65b; 25th July 2012 at 11:34 AM.
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Old 25th July 2012, 02:28 PM   #215
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The immersed PC display I saw used mineral oil, IIUC it's not hydroscopic and largely inert as far as other components are concerned. If you are going to immerse the whole motherboard you can probably just dispense with anything more than trivial heat-sinks with wide space fins, oil and water are much harder to pump between closely spaced fins.
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Old 25th July 2012, 02:58 PM   #216
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Water cooling is an excellent idea. Just be sure to use the proper type of coolant or you might end up with mold growing in the circulation system. I've seen this happen in a Series 1 Barco D-Cinema projector where the factory coolant was replaced with antifreeze from Wal-Mart. Newer Series 2 D-Cinema stuff are all sealed type of cooling system and this won't happen. If you can use copper for your heat sinks and silver solder copper tubing to that you can make up fairly inexpensive custom heat sinks from 1/4" copper sheet.

Mark
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Old 25th July 2012, 03:04 PM   #217
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Hahaha your comments always comforts me Dean Will do. Unfortunatelly lab @university is closed, so I can't borrow one at the moment :-(.

@John, you could use de-ionized water, water itself is not conductive, but electrolytes in it like Na+, Ca2+, CO32- and so on cause the conductive character from water. Another advantage of de-ionised water is that it almost does not cause corrosion. The more electrolytes water contains, the faster corrosion can occur (that is why boats have to be protected from corrosion by mounting zinc-blocs underneath because of RedOx processes). You can also use demineralized oil, which is not conductive either. But I would say water is more favored, it's heat capacity is higher, so it can absorb more heat (joules) per kg than oil when augmenting 1 degree in temperature (oil ~2KJ / kg * K, water ~4KJ /kg * K).

I have some news too, am afraid that it is not positive. Well start positive first; I have bought a very nice Audio Generator from Peaktech! I should have had this device far more earlier, this works so much better than using an computer, and I can do square wave tests.

Click the image to open in full size.

So I did some tests, used 8 ohm dummy load, did not connect a capacitor parallel, will do that later. I first want to verify if this results are OK. Results on my scope are exactely the same for both channels. Bias was 450mV. You can see VAC RMS on the right meter below the scope.

1. 400Hz, sine wave, max output (30 VAC RMS @8 ohm):
Click the image to open in full size.

2. 1000Hz, sine wave, max output (29.5 VAC RMS @8 ohm):
Click the image to open in full size.

3. 400Hz square wave, output 1VAC RMS
Click the image to open in full size.

4. 1000Hz square wave, output 1VAC RMS
Click the image to open in full size.

5. 10 kHz square wave, output 1VAC RMS
Click the image to open in full size.

So far so good, but at max power, there is a BIG overshoot, which worries me

6. 400Hz square wave, max output
Click the image to open in full size.

7. 1000Hz square wave, max output
Click the image to open in full size.

8. 10 kHz square wave, max output
Click the image to open in full size.

Fortunatelly I don't see any oscillation so far, just overshoot. Tried with and without zobel, but still overshoot at max output. I can think of a few causes:
- The amp clips at this amount of power (when switching to sine wave you can see it clips).
- The VAC meter which is connected to the scope it has a 100:1 devider inside, so when I measure 100VAC, it sends 1VAC to the scope.
- I've made a mistake, the amp is faulty.
- It is common and not a problem.
- I don't know what I am doing

Guys, need the expertise again. Can someone judge my results?
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Old 25th July 2012, 03:59 PM   #218
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I have to learn to check, check, double check before worrying haha. Yes friends, problem solved. I was allready surprised that my RMS VAC meter gave 30 VAC RMS, I've measured 40 VAC RMS before. Turns out that the measuring clips made a bad contact which caused the problems. I realy hate those clips, my next investment will be some relieable Hirschmann clips.

New picture, 10 kHz square wave:

Click the image to open in full size.

I think this is more like it
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Old 25th July 2012, 09:50 PM   #219
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Sorry for kicking the topic, but I could not edit the post above.

Well guys, I blamed the clips, because when changing them the problems were over. But, believe it or not, but 4 minutes after I sended the post above, my oscilloscope went blank and loads of smoke came out of it. It was pretty impressive . Pfew, that stinks. Took the oscilloscope outside. It kept smoking for a wile.

I had an earlier discussion with David (Spurtle) about the so called 'rattle capacitor'. These oscilloscopes have one too. They are from Rifa. Altough quality is not that bad, after 30 years they go short circuit (X2 capacitor my a**). Here is a picture of it, I would not even imagine what would have been happened if I don't was in my room:

Click the image to open in full size.

(blue one is the replacement)

Click the image to open in full size.

Unbelievable how much smoke can come out of such a little capacitor. Replaced it, cleaned the print and decided to clean the potentiometers and switches with some Tuner 600 spray. This is very good spray btw, leaves absolutely no residue. Prayed that it would work again, because Kaplaars is a bit broke nowadays And IT DID!!!

The oscilloscope had some stability problems earlier with triggering and al sorts of strange distortions. Thought that was due to the clips, but it turned out it was actually caused by the oscilloscope itselve! So another note to myself, when testing equipment NEVER leave the room.
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Old 25th July 2012, 10:11 PM   #220
spurlte is offline spurlte  United States
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Default Water cooling

Quote:
Originally Posted by Mark Allen View Post
Water cooling is an excellent idea. Just be sure to use the proper type of coolant or you might end up with mold growing in the circulation system. I've seen this happen in a Series 1 Barco D-Cinema projector where the factory coolant was replaced with antifreeze from Wal-Mart. Newer Series 2 D-Cinema stuff are all sealed type of cooling system and this won't happen. If you can use copper for your heat sinks and silver solder copper tubing to that you can make up fairly inexpensive custom heat sinks from 1/4" copper sheet.

Mark
Fantastic. I have a scrap metal yard near my home in Chicago that deals mostly with aluminum and copper (money makers). I wanted to use a car heater radiator (the heater core which is usually located below the dash and if the heater core can heat the interior of a car in dead winter, it should be perfect to dissipate the heat of the TO3s), with electric fans, parallel fluid lines attached to the copper plates holding TO3s and a temperature sensing circuitry that would control fan speed and circulating fluids--no different than that that is used in modern vehicles. Imaging, no need for filtering forced air into the amplifier's cabinet. Hey, it's just an idea and a project for the coming winter.
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