I noticed only two thermistors at the transformer primaries. Since it is dual mono, each transformer should have its own set of thermistors. Each transformer should also have its own fuse. So AC power into chassis, then one fuse to each channel's power transformer, then each channel's transformer has their own two thermistors. The only thing shared by the two channels is the AC power into the chassis and switch. Some people have even provided a switch to each channel.
It is then best to work on one channel and get that working. Connect the AC in, fuse, thermistors, transformer primaries. and bridge rectifiers . Double and even triple check all connections. If you have a variac or dim bulb tester, use that for the first power up. Connect your meter, or if you have two meters, connect them to the DC plus and minus of the two bridge rectifiers and measure the voltage. If everything is connected properly, the voltage should be somewhere around 25V when fully powered up. If no DC voltage is measured, then there is something not correctly wired.
Power supply schematic attached. Antek transformer primary winding colours added.
Connect the power supply board only after the correct DC voltage is at the two bridge rectifiers.
It is then best to work on one channel and get that working. Connect the AC in, fuse, thermistors, transformer primaries. and bridge rectifiers . Double and even triple check all connections. If you have a variac or dim bulb tester, use that for the first power up. Connect your meter, or if you have two meters, connect them to the DC plus and minus of the two bridge rectifiers and measure the voltage. If everything is connected properly, the voltage should be somewhere around 25V when fully powered up. If no DC voltage is measured, then there is something not correctly wired.
Power supply schematic attached. Antek transformer primary winding colours added.
Connect the power supply board only after the correct DC voltage is at the two bridge rectifiers.
Attachments
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Thank you all. I'll work on making the changes outlined and see where that gets me. Looking through my leftover bits and pieces to find needed parts. I'll report back when I'm able to get some of the changes made. Appreciate the help!
Hi, while I was testing Aleph J with cervin vega at100, the board with the jfets supplied with the kit broke quickly. R7 is at 0 volts again. R8 is ok. The other board works with my jfets. Perhaps too much electrostatic charge comes out of my body 🙂 I also brought with me ACA first version with mod and my friends and I we were impressed by how the giant cervin vega drove. Now I have to buy lsj74 again but digikey doesn't sell version B (5/6 mA). Can you recommend a reliable seller?
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This is great - you make it so easy.
I have a question on front stage for this amp - will Burning Amplifier 3 Gain Stage Board (BAGS-N) work well, as it is also a designated pre amp? If yes, what design considerations should I take care of?
(p.s. I have seen the BA3 Preamp build guide at https://www.diyaudio.com/community/threads/the-ba-3-as-preamp-build-guide.258022/#post3968063 - wondering if its just that, for using with Aleph J)
I have a question on front stage for this amp - will Burning Amplifier 3 Gain Stage Board (BAGS-N) work well, as it is also a designated pre amp? If yes, what design considerations should I take care of?
(p.s. I have seen the BA3 Preamp build guide at https://www.diyaudio.com/community/threads/the-ba-3-as-preamp-build-guide.258022/#post3968063 - wondering if its just that, for using with Aleph J)
again, that is irrelevant when having bridge dedicated for each secondary
if by "pairing" you mean phasing
nope. pairing. Making sure you have the correct leads paired together.
which I believe are correct judging by the heatshrinked pairs but I always check.
which I believe are correct judging by the heatshrinked pairs but I always check.
Amp was warmed for about 30 minutes
Yes - cap removed and link soldered in
JFETs are matched LS quad from DIY store. I think the grade was B.
Left channel has needed the + and - reversed or speakers are out of phase.
Ho BA3 e B1. Se hai sorgenti ad alto rendimento, il B1 va bene con qualsiasi amplificatore. BA3 ho provato con Aleph J e dava un suono meno lineare, ma si poteva adattare con il suo trimmer centrale.
Just starting to build out my Aleph J boards and came to this thread (9391 posts!). So much for a concise guide 🙂. Starting from post #1 I came upon post #4 which contains a bunch of links to helpful links within this thread. The links don't seem to take you to the relevant post. Perhaps post #4 should be deleted as it just creates confusion for new builders (me), or is there something I'm missing? Thanks.
The links work just fine (for me). Read the post numbers and navigate there directly and/or change your number of posts displayed per page to 10 and use the links. IMO, the post should not be deleted, it is quite useful.
Also, I'd strongly recommend reviewing this blog, if you haven't already.
https://diyalephj.blogspot.com/
Edited to add - Congrats on starting the Aleph J!
Also, I'd strongly recommend reviewing this blog, if you haven't already.
https://diyalephj.blogspot.com/
Edited to add - Congrats on starting the Aleph J!
Thanks ItsAllinMyHead. Resetting the posts/page back to 10 seems to do the trick. And thanks for the link!
Hi, I matching irfp 140 for J, I would like to know what is the minimum Vgs Q7 and Q8 to work.
irrelevant
just match them for upper group, and for lower group
no need to match lower to upper
just match them for upper group, and for lower group
no need to match lower to upper
I was digging through old posts old posts and found that this amp is not supposed to invert signal. On the left channel, I have to swap the + and - around, the right channel is normal. Any thoughts as to why one channel is inverted and the other isn't?
What measurements would be helpful? Iq tends to drop as the amp warms up.c After about an hour it stabilizes.