Aleph J illustrated build guide

[avitkauskas]

Good to know, @joaoranito, that your Aleph J is holding fine with the new jfets!
I'm also enjoying my Aleph J (the ZM modification at the moment) so much.
And I have the diyStore boards waiting for jfet replacement too.

 

[andynor]

Have are you finding ZM’s iteration? It is in my pipeline too

Regards,
Andy

 

[joaoranito]

I'm interested too! I was planning to build an F4 after this (I have some good preamps that can swing enough volts for a buffer) but the Aleph J sounds so good direct from my DAC that I am hesitating...

 

[NightFlight]

Hi guys (any gals?), I'm seeing ~5-7C difference on a couple IRFP140 packages. Two are hitting 59-60C while the rest are at 53-55C. I'm about to take apart and re-apply thermal paste, as I suspect I was too skimpy on it. Both are on the one side, so it seems possible that was the first amp board I assembled. I became more comfortable and liberal with the paste on the 2nd board assembly

Or... do we expect this sort of delta between units?

 

[Zen Mod]

compare currents through them, measuring voltages across source resistors

 

[NightFlight]

Is this what you mean?


Right Side
Q6 59C R17 .410
Q5 52C R16 .380
Q8 60C R19 .399
Q7 52C R18 .390

Left Side
Q6 53C R17 .373
Q5 55C R16 .389
Q8 53C R19 .375
Q7 55C R18 .393

During the build I did notice a couple of the .47ohm resistors were out by the high side of their 10% tolerance. But I tossed them in anyhow. At this point I'm wishing I had made note of where they were placed. I'm fairly certain they ended up the R20-R23 parallel network.

 

[Zen Mod]

well, re-goop those you want, and it'll be handy to torque them all with torque-thingie, 0.9Nm

if not, try to be same gentle on all of them

Pa spoiled me, insisting, so I realized that having torque thingies for both M3 and M4 is very good for my OCD

 

[NightFlight]

Meh, I got lazy, so I threw a fan on it for now. But the numbers are interesting.

 

[Zen Mod]

currents - you're in 8%, which is better than 10% of resistors

so, chill - think just of goop and temperatures and torque

 

[peppennino]

Only 0,9Nm, ZM? My torque wrench is quite imprecise under 2Nm (min value)

 

[Monk55]

Here

 

[Zen Mod]

Only 0,9Nm, ZM? My torque wrench is quite imprecise under 2Nm (min value)

Here

Pa sez - M3 - 0.9Nm

Ok, he wrote in Yank measures, so I converted to adequate for my tool

Peppe - use that for Fiat and Moto Guzzi, not for mosfets

 

[Dennis Hui]

The mounting torque limit of many of our favourite parts (IRFP240, IRFP150, IRFP9240, etc)
is quoted as 1.1 N.m on the datasheets, so 0.9 seems like a good value to use.

 

[Zen Mod]

with mica&goop and AluOxide pads, I would dare and use more than 0.9

with soft pads (keratherm) everything above is showing more squeeze in area of mosfet hole, less squeeze in pin area

OCD is easiest to beat with proper tool

 

[andynor]

IRFPs are specced at 1-1.1Nm torque I think. I plan to buy a mini torgue wrench. One that can do lower than 1Nm.

Regards,
Andy

 

[Monk55]

The mounting torque limit of many of our favourite parts (IRFP240, IRFP150, IRFP9240, etc)
is quoted as 1.1 N.m on the datasheets, so 0.9 seems like a good value to use.

I now see that on data sheets…thx Dennis

 

[andynor]

Momentskrutrekker Micro Click MC2 0,4-2Nm PROXXON | Elektroimportøren AS

Something like that. Expensive little bugger.

 

[Monk55]

I’ve always taken into account the thermal expansion of metals when torquing dissimilar metals…aluminum generally speaking expands twice that of steel…so yes it makes perfect sense to use very slight pressure when sucking down transistors. The key is getting all the same pressure in any case.

 

[peppennino]

Peppe - use that for Fiat and Moto Guzzi, not for mosfets

Ok, please suggest a wrench!
I'm going to use mica+goop, so 1.?

 

[Zen Mod]

0.9

can't suggest a wrench, I was lucky - bought first one new for 1/4 of regular price, recalibrated it from 1.2 to 0.9

bought second one SH for 15E, recalibrated it from 1.5 to 1.2

now I have first for M3, second for M4

M4- handy to think less while dealing with pucks