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Got the filaments all burning at about the same brightness on the new 813 amp by changing out one 813, so I guess the one it replaced had a filament with lower resistance and made that side burn brighter. But now it appears there is another issue. I ran the amp for several hours this morning and it just kept sounding better and better, but remembering all the resistors under the hood I decided to see how hot things were getting. After several hours of playing the top plate was too warm to keep your hand on comfortably for more than a few seconds. It has not caused any apparent problems so far, but it makes me wonder; what is the maximum temp the other components under the hood can handle longer term? I did some spot checks of the top plate with my laser thermometer, and it varied from about 110 to 125 degrees F. Definitely hotter than any other amp I have ever built, but I don't know if I have ever seen any numbers on max temps. Anyone out there have data? I don't want to install a fan unless I have to because of the noise. The amp will be only a few feet from my listening position.
Edits: 06/02/17 06/02/17Follow Ups:
for an ingenious solution to the heat problem. I put washers that are about 1/16" thick under the top plate by each screw hole. The end result is it appears to have lowered the temps by 10 to 15 degrees F overall. The highest reading I got this evening after playing it for about 45 minutes was 115 degrees, with most readings being between 105 and 110 F. The top plate sticks up a tiny bit but not really bad.
The next time I go to Lowes I may try to pick up some that are just a tad thicker. I think that would really do the trick. Anyway, if your amp is getting hot under the collar you might want to give it a try. Thanks Ray!
If you have enough washers, you could just double up and be 1/8" thick.
Thanks for the compliment but we all are the beneficiary of useful ideas on this forum.
ray
Now Ray, two stacked washers would be approaching tacky looking wouldn't it? : ) Got to keep some semblance of fashion here. I have thought of maybe finding or making little rectangular pieces that would be a bit thicker but would have more of a "belong here" look to them, i.e. build spacers that are part of the design rather than an add on. Still a great idea you had there. Can't help myself, I just love good, simple, effective design. Long live KISS!
Edits: 06/04/17 06/04/17 06/04/17 06/04/17 06/04/17
I adore tacky, preferably really ugly, so you can see where I come from.
ray
nt
"it varied from about 110 to 125 degrees F. "
I'm not sure that's too hot, or why it would be difficult to touch. I've been in 110° temperatures, and although it's miserable, it's not painful. That aside, do you know which components are responsible for heating the chassis? That's critical to determining whether this is excessive. For example, let's say a component operating at 100°C - but rated for 150°C - is conducting its heat directly to the panel. In that case, as long as nothing else attached to the panel can be be damaged by 125°F temps (the measurement), everything is fine. OTOH, if something under the plate is heating the air to 100° C, and that's the cause of the elevated panel temperature, you might have trouble. Certain other components under the plate might not be able to withstand that for long. Again, the issue relates to how the plate is being heated, and how hot the sources and nearby components are.
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Buy Chinese. Bury freedom.
That's the $64000 question isn't it? I am pretty sure it's the resistors I had to use to control the voltage on the switchers and for other items that are heating things up, but it would be tough to measure the temps around all the different components and compare that to their rated maximums. I think my best best is to try and lower the whole thing as much as I can without too much trouble and see what happens.
Not pretty but they are typically 30mm high
I think I have enough clearance, I just need more air flow.
A way to use a fan, with minimal noise, is by employing a cheap, large diameter, "230" VAC fan on "115" VAC. The fan will turn slowly, being under voltage, and that generates little noise. OTOH, even when turning slowly, large blades move quite a bit of air.
Eli D.
80mm 12V computer fans (rescued from the tip) run from a variable LM317 based PSU at approx 5V are silent in my set up. At least until they age, and then I replace them. Set the lowest voltage at which they start.
I went a different way with a fan.
I'm using a 5" AC-to-DC pancake fan, that is of decent quality with ball bearings.
Pretty quiet, and it does a good job of keeping my old Triad USA power transformer nice-n'-cool.
Steve
Antec has a line of fans designed for computers. I have a few of their 120mm fans, which, on their slow setting, are almost silent. At the price, I find them hard to beat.
WW
"A man need merely light the filaments of his receiving set and the world's greatest artists will perform for him." Alfred N. Goldsmith, RCA, 1922
Do you happen to know what voltage they run on? Believe it or not it's not in the spec sheet.
Ah. They are 12 VDC, which is often available on various plugs in Wintel PCs. The ones I got years ago had the standard PC 4-pin power connector, like the larger end of the adapter in the attachment. You can google the standard for those connectors to see what's on which wire, or just use a DC voltmeter to figure out which wires to use.
Make sure your wall wart will handle the combined amperage of the fans you're installing. Then strip the wire ends, connect them with twists, and cover with electrical tape of shrink wrap. Solder them if you want to. Connect multiple fans in parallel, so every fan gets 12V. Add an on/off switch if needed.
As always, there is no free lunch. The fans I have do not move a lot of air on low, but are so quiet I can't hear them unless I'm within a foot or so. On high, I can hear them at arm's reach, but just barely. The more air you move, the more noise you'll have to deal with. Pick your poison.
Cheers,
WW
"A man need merely light the filaments of his receiving set and the world's greatest artists will perform for him." Alfred N. Goldsmith, RCA, 1922
It's a thought. Are they easy to find?
Edits: 06/03/17
The usual (industrial?) safety rule is surface temperature no more than 140F (60C) - basically, you have enough time to perceive the heat and take your hand away before getting a burn.
Inside it is probably hotter. Each component will have a max temperature rating in the spec sheet. For reliable operation, you must have a margin. In my experience that margin is larger than you think. For example, I try to keep silicon solid-state junction temperatures at 100C or less, though the spec is 150C. Some resistors at max spec temperature are hot enough to melt the solder that holds them in place. It's a judgement call for each component - a lot of work!
Thanks Paul, that tells me I am not likely over the top yet at least. I will still try "simple" ways of getting the temp down.
110 should definitely not be too hot to keep your hand on. You might want to check your measurements.
Caps are rated at typically 85 degrees to 105 degrees Celsius, which would be +185 degrees Fahrenheit, though it is at a 1000 hour life typically. Keep the caps under 150 degrees.
Drill some vent holes.
Been there done that. Don't think it will be enough though, and I am running out of room with all that stuff underneath to punch too many more holes in the to plate. Might be able to do some through the wood sides though. That could help.
I can tell you you won't keep your hand on 125 degrees very long. As I said, the temps vary, the whole top isn't the same. I spot checked it several times, but it isn't a lab grad unit. I use it for my wood fired oven.
Edits: 06/02/17 06/02/17
Another way to make vents is the use a hacksaw and cut several slots on one angle of the bottom, then on the opposite side at the top.
The cross flow will certainly cool it down.
I did this on a headphone amp using (3) 6SN7GT.. IT was much cooler afterwards.
Cutting across the angle makes it easy to do.
The bottom is open and the chassis is on 1/2" high feet. I think the only place left for more vents are the side panels.
When I build amps these days I raise the top plate off the side panels with a washer at each screw, enough for air to escape. It's a bit hard to tell from your photo, but you might be able to raise your top plate a tiny little bit, either with washers on the screws or some other mechanism. If you can get some air moving through the small gap then the total for all four sides would be considerable and it will be virtually invisible.
ray
I like the sound of that Ray. Simple, but possibly quite effective. I will see what I can do. Thanks!
Edits: 06/03/17
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