Aleph J illustrated build guide

[Zen Mod]

same thing

 

[chelg2012]

same thing

Dear Zen Mod,
Thank You for the answer.Just more question.What a modern output mosfet's from a good manufacturer would be used instead of 244?
Regards,Chelg

 

[grimberg]

The IRFP240 MOSFET is a perfect fit for the Aleph amplifiers, is in current production and available at an affordable price. Why complicate things trying to find alternate devices?

 

[Zen Mod]

@chelg

as Grimberg wrote - IRFP240

and , as I said numerous times - feel free to use one IRFP150 instead of two pcs of IRFP240 , as long you keep it cold enough (50C at sinks and decent thermal interface - read -mica and goop or better) and as long you keep dissipation under 50W/piece

 

[chelg2012]

Dear Grinberg,
Thank You for the answer. Do all regimes of output cascade remain the same as in the original Pass circuit?
Regards,Chelg

 

[grimberg]

The Aleph 3 uses two pairs of MOSFETs, each pair matched within .01V. One pair is driven by the differential input (first stage), while the other pair provides the bias current. I am not sure about the meaning of "output cascade".
You can use IRFP240 to replace the IRFP244 devices without making any changes to the other components.

 

[chelg2012]

Dear Grimberg,
Thank You.I made an inaccurate definition.
Regards,Chelg

 

[grimberg]

If you are planning to build an Aleph 3, you might want to read this thread:

http://www.diyaudio.com/forums/pass-labs/267857-aleph-design-reloaded.html

You may be especially interested in post #9.

 

[chelg2012]

Thanks.Go to post #9.
Regards,Chelg

 

[rif]

@chelg

as Grimberg wrote - IRFP240

and , as I said numerous times - feel free to use one IRFP150 instead of two pcs of IRFP240 , as long you keep it cold enough (50C at sinks and decent thermal interface - read -mica and goop or better) and as long you keep dissipation under 50W/piece

Could you get a little crazy and use 2 pcs irfp150?

 

[Zen Mod]

Could you get a little crazy and use 2 pcs irfp150?

you mean - two pairs of IRFP150 ?

of course, and of course they need to be matched

issue/possibility pretty much covered in this thread

 

[ABest]

blowing fuses

I am troubleshooting the PSU of my Aleph J. The PSU has two toroidal transformers of 250VA each with two separate PSU boards from the diyaudiostore. I am using 4 monolithic bridge rectifiers and a total of 264,000 microfarads across the two PSU boards. Upon power up, the LEDs on the PSU boards light up and I can very briefly measure the expected positive and negative voltages. But, then the CL-60 thermistors which connect PSU ground to chassis (and the IEC safety earth terminal) get hot enough to smoke and the fuses blow. I am using a pair of 2.5A slow blow fuses. Reading this forum has shown me that I should be using a pair of 5 Amp slow blow fuses which I intend to order. But, would fuses which are not sufficient lead to the thermistors smoking? This all occurs without the amplifier circuits attached.
Any suggestions will be greatly appreciated?

 

[rif]

you mean - two pairs of IRFP150 ?

of course, and of course they need to be matched

issue/possibility pretty much covered in this thread

Yes, of course, meant 4 per side, 8 total for stereo.

Thanks for the link, it's a good read. Apparently I read it once since I posted in it

 

[Zen Mod]

I am troubleshooting the PSU ........

pictures , please

also - find here what's bulb tester and prepare one

 

[ABest]

Please see attached photos.

I will look up how to build a bulb tester.

Thank you

 

[ABest]

I built a bulb tester and found 5A slow blow fuses. When I turn on the power, the bulb lights up indicating a short somewhere. So, I tested each PSU separately by de-soldering the primaries. When tested in separation each PSU turns on the bulb. I see many millions of Ohms between PSU ground and the rails. I am not sure what to do next.

Aaron

 

[Zen Mod]

I'm not familiar with these PSU pcbs ... I mean - I can't see markings on pads

please take some better pics - so we can see details - how you wired that

 

[ABest]

Please see the attached photo of a PSU PCB as requested. Though, I am beginning to think I may only have had a fuse issue. I have stepped through the components from transformer to PSU PCB (on the left side) adding back and testing. The transformer appears normal as do the bridge rectifiers. When I solder the PSU PCBs back into the circuit I do see the bulb tester turn on briefly on power up but I suspect what I am seeing is the supply caps charging. I think previously I assumed that any light from the bulb tester indicated a short. After I regained my confidence in the circuit, I turned the power on without the bulb tester in place but with the 5 Amp slow blow fuses and all appears fine now. I still am unsure why the thermistors between PSU ground and chassis/IEC earth got so hot when the 2.5 Amp fuses blew. Perhaps I fixed a problem when I de-soldered and re-soldered the components. Any thoughts?

Thank you,
Aaron

 

[ABest]

I am waiting for the chassis to warm up before rechecking the bias and offset for both channels. All seems fine!

Thanks,
Aaron

 

[noSmoking]

might try a variac to power up with, your amp might be showing a short because your caps are not charged up yet , you're cl 60/fuse can't handle the load and smoked.
A slow start up is best ,check the store for a soft start!
A speaker cutoff is good to have also


NS