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Part Sourcing Assistance/Advice Thread


n_maher

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According to the Arctic silver website, ceramique "does not contain any metal or other electrically conductive materials. It is a pure electrical insulator, neither electrically conductive nor capacitive."  So it should be OK.

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Perfect, thanks everyone!

 

Next, a question about heatsinks. I've been comparing various Aavid models, and found three models with identical footprints:

 

http://www.aavid.com/products/standard/530002b02500g(2.5" height, 2.6 thermal resistance)

http://www.aavid.com/products/standard/529902b02500g(2.0" height, 4.5 thermal resistance)

http://www.aavid.com/products/standard/529802b02500g(1.5" height, 3.7 thermal resistance)

 

The largest sink has the best thermal resistance; seems reasonable. But the 1.5" has a better thermal resistance than the 2.0"? How can this be? They seem to be made of the same material and look otherwise the same.

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Is there a source for matched 2SK170 transistors other than AMB? AMB says those JFETs are all reserved for people buying his own boards (which I'm not). I don't fancy getting buying dozens from bdent just to get a handful of matched pairs. Do you trust eBay sellers who claim to have matched (like this or this)?  :unsure:

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Is there a source for matched 2SK170 transistors other than AMB? AMB says those JFETs are all reserved for people buying his own boards (which I'm not). I don't fancy getting buying dozens from bdent just to get a handful of matched pairs. Do you trust eBay sellers who claim to have matched (like this or this)?  :unsure:

FWIW I've bought from "alweit" and his parts look good to me. Service was good too.

 

//UFN

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He's referring to the 2SJ109, the dual J74.  Not that easy to find.  :)

 

Indeed. Need a few of the GR grade ones. Don't wish to pay $40-50 for a pair as I'll be damn broke for the amount I need. Also don't wish to go down the route of buying 100+ J74's and trying to match them to the tightest tolerance.

 

Wish there was a modern day equivalent.

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He's referring to the 2SJ109, the dual J74.  Not that easy to find.  :)

Ah - goddit.  Must have had brain fade.  Alternative way of doing it is to get matched pairs from Spencer and mount them in an isothermal housing.  Something like the old 2SJ75 package of two discrete matched J74 that predated the funky plastic packaged dual 2SJ109.  I just got four J74BL quads matched to 10mA.  Each quad is matched to the second decimal place, so easily good enough for a roll your own 2SJ109.

 

2SJ75GR available from the usual source, but at $32.

 

Or buy a bunch of LSJ74 and match.  Not cheap at $6 each.

 

Basically the cheapest way is to buy matched from Spencer at $9 each and then pair them to give a cost of $18 per pair.

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Just curious - has anyone been brave enough to try the new, V2.0 Khozmo attenuators?  I say that PE is now stocking them (in some values) and that more are available direct from Khozmo.  At ~$400 for a quad w/ upgraded resistors it would appear to be a pretty good value as long as it's not as fragile as the earlier ones.

 

http://khozmo.com/products_dale_shunt.html

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I've just sprung for an LDR passive attenuator, having looked at and tried various standard rotary (TKD etc), switched resistive attenuators, and flirted with tapped transformer attenuators without trying them.  We'll see once I get them boxed up.

Edited by Craig Sawyers
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