Audiophilenoob said:
Yes. Comes down to YOUR comfort level.
You have seen firsthand the effects of a short between the HS and the chip. If you butt them together, and smear a bit of your insulating paste (assuming it really is electrically non-conductive) around, it should be ok. Not as good as a one-piece insulator, but a lot easier and quicker to get hold of.
It's a pity Peter and Brian don't include insulators with those kits, it's tripped a few people up, and there are no off-the-shelf solutions. Anyone going the silpad route has to buy enough for multiple amps. In the US, you can get a silpad sample though...
Michael
maf_au said:
Since we started selling those kits, nobody really asked for insulators, I might have less than 5 requests altogether.
If anybody needs such insulators, they are free, and can be included with any order (untill my supplies last though), just ask
Audiophilenoob,
If you need them, e-mail me, and I'll send you a set of pads.
The LM4780 is certainly *NOT* in a TO-220 case. The MUR860 diodes you have on the rectifier board ARE (although the TO-220 more commonly has three pins).
You're looking for something like Sil-Pads or a roll of Kapton tape. The Arctic Silver Ceramique, while an insulator, is not meant to insulate. It should be put on as THIN as possible, which means that certain parts of the chip will touch the heat sink on a microscopic scale. The more of this touching, the better the heat transfer (which is why sometimes lapping your parts and heatsinks is beneficial).
I'm assuming at this point that your 4780s are in TA cases; I think there is a TF version that is already insulated (I will be using LM3886TFs for my own amp, Kapton is expensive..
Hmm... The National Datasheet shows only the TA version of that chip... And it actually says it's in a 27-lead TO-220 case. That's really wierd.
A PAIR of TO-220 insulators would *probably* work. You'd want to be very careful doing this, though -- they would have to be exactly side-by side. I suppose another option would be COMPLETELY ISOLATING the heatsink (from ground) and using it as-is -- but I wouldn't consider that very safe.
If this were my project, I would order a roll of Kapton tape (usually about $25 depending on width) that was big enough to cut a pad without "stitching". Don't forget also to use insulated washers if appropriate.
Here's what it should look like with a Sil-Pad:
According to the measurements in datasheet, you want a pad which is about .75 x 1.25" -- with holes only where you need 'em (you can usually punch them with a hole punch or similar).
[Hmm -- reading]
Okay, take a look at this catalogue page from Digikey: http://dkc3.digikey.com/PDF/T053/0714.pdf
It looks to me that one of the "Figure 5" or "Figure 7" pads would fit -- but you can't use "Figure 7" pads because they are Q-Pads, not Sil-Pads, and Q-Pads are CONDUCTIVE.
Digikey #s BER106-ND, BER179-ND, and BER117-ND all look like passable choices. Unfortunately, I have no idea what the differences between them are besides thickness (but ranging between 94 and 176 cents each, it's not like it'll break the bank to find out).
Best of luck!
Wes
You're looking for something like Sil-Pads or a roll of Kapton tape. The Arctic Silver Ceramique, while an insulator, is not meant to insulate. It should be put on as THIN as possible, which means that certain parts of the chip will touch the heat sink on a microscopic scale. The more of this touching, the better the heat transfer (which is why sometimes lapping your parts and heatsinks is beneficial).
I'm assuming at this point that your 4780s are in TA cases; I think there is a TF version that is already insulated (I will be using LM3886TFs for my own amp, Kapton is expensive.
.Hmm... The National Datasheet shows only the TA version of that chip... And it actually says it's in a 27-lead TO-220 case. That's really wierd.
A PAIR of TO-220 insulators would *probably* work. You'd want to be very careful doing this, though -- they would have to be exactly side-by side. I suppose another option would be COMPLETELY ISOLATING the heatsink (from ground) and using it as-is -- but I wouldn't consider that very safe.
If this were my project, I would order a roll of Kapton tape (usually about $25 depending on width) that was big enough to cut a pad without "stitching". Don't forget also to use insulated washers if appropriate.
Here's what it should look like with a Sil-Pad:
According to the measurements in datasheet, you want a pad which is about .75 x 1.25" -- with holes only where you need 'em (you can usually punch them with a hole punch or similar).
[Hmm -- reading]
Okay, take a look at this catalogue page from Digikey: http://dkc3.digikey.com/PDF/T053/0714.pdf
It looks to me that one of the "Figure 5" or "Figure 7" pads would fit -- but you can't use "Figure 7" pads because they are Q-Pads, not Sil-Pads, and Q-Pads are CONDUCTIVE.
Digikey #s BER106-ND, BER179-ND, and BER117-ND all look like passable choices. Unfortunately, I have no idea what the differences between them are besides thickness (but ranging between 94 and 176 cents each, it's not like it'll break the bank to find out).
Best of luck!
Wes
I ordered a roll of that mica from mcmaster in a 0.004" thickness
and also fired an email off to peter and requested some... this way I can see which one works best...
thanks peter for the offer BTW
I actually was doing forum speak on this one... adding the cermaqiue is what someone here did.... I didn't even know it required more than that
then again instructions for the LM4780 would always be a great addition
3 chips are now in chip heaven
and also fired an email off to peter and requested some... this way I can see which one works best...
thanks peter for the offer BTW
I actually was doing forum speak on this one... adding the cermaqiue is what someone here did.... I didn't even know it required more than that
then again instructions for the LM4780 would always be a great addition
3 chips are now in chip heaven
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