This thread's purpose is to assist builders with their Aleph Jzm kits.
For general discussion, customization, parts substitutions, or anything unrelated to the kits, The Aleph Jzm thread is perfect.
The goal is to have this thread be a quick source for relevant information for kit builders. It will also be used as a source of information to update the Aleph Jzm Build Guide. At this time, comments are not active in the build guide.
For builders specifically needing help with their power supply, please search for a thread supporting your specific power supply, create a separate thread as needed, or post your question in the The Aleph Jzm thread.
For those needing assistance with their amplifier boards or overall assembly and wiring, please post the following:
1) The current step # from the AJzm build guide.
2) Well-lit, in-focus photos of the build in its current state.
3) A description of the issue or question.
For general discussion, customization, parts substitutions, or anything unrelated to the kits, The Aleph Jzm thread is perfect.
The goal is to have this thread be a quick source for relevant information for kit builders. It will also be used as a source of information to update the Aleph Jzm Build Guide. At this time, comments are not active in the build guide.
For builders specifically needing help with their power supply, please search for a thread supporting your specific power supply, create a separate thread as needed, or post your question in the The Aleph Jzm thread.
- For those using ThatcherDIYAudio PSU boards like those used in the guide, their build guide is excellent. Attached below. If there are updates, I'll be sure to re-post.
- For those building a PSU with the Universal PSU boards from the diyAudio store, the PSU section in the DIY Aleph J: A Build Guide blog is an excellent resource in addition to many threads in this forum.
1) The current step # from the AJzm build guide.
2) Well-lit, in-focus photos of the build in its current state.
3) A description of the issue or question.
Last edited:
Power up and problem
I had a built an ACA, working happily. So now I tried the JZM board/kit.
For the power supply I took a shortcut, 2 Meanwell 24-600. Connect One plus and one minus side to GND, should give me 18-24V V++;GND;V--
Set to 18V, turned current all the way down (still 13A per datasheet).
Turned on (one channel only), no magic smoke, both LEDs on, 520mV across R29, turned Iq CCW to 480mV. Fets get very hot, maybe heat transfer to cooling sink not optimal, hard to say, what is very hot? Using a"standard" transparent thermal insulation and heatsink from Logitech SUB/Sat combo.
Turned PS to 24V, current still down, turned Iq CCW to get toward 450mV, V++ side LED goes out, pull power.
Took PS off, both fine, deliver between 18 and 24V each
measured path for LED, it's ok (even lights up on diode testing), assume there is now a short, measure across FET (on V++ side) 260 Ohm, around 260 on V-- side. (Drain-Source, Drain-Gate)
Was that the end of the FETS, I would then need new ones, can I order anywhere or is matching required?
What to do next?
Cheers and thank you,
Brxl
I had a built an ACA, working happily. So now I tried the JZM board/kit.
For the power supply I took a shortcut, 2 Meanwell 24-600. Connect One plus and one minus side to GND, should give me 18-24V V++;GND;V--
Set to 18V, turned current all the way down (still 13A per datasheet).
Turned on (one channel only), no magic smoke, both LEDs on, 520mV across R29, turned Iq CCW to 480mV. Fets get very hot, maybe heat transfer to cooling sink not optimal, hard to say, what is very hot? Using a"standard" transparent thermal insulation and heatsink from Logitech SUB/Sat combo.
Turned PS to 24V, current still down, turned Iq CCW to get toward 450mV, V++ side LED goes out, pull power.
Took PS off, both fine, deliver between 18 and 24V each
measured path for LED, it's ok (even lights up on diode testing), assume there is now a short, measure across FET (on V++ side) 260 Ohm, around 260 on V-- side. (Drain-Source, Drain-Gate)
Was that the end of the FETS, I would then need new ones, can I order anywhere or is matching required?
What to do next?
Cheers and thank you,
Brxl
Hi brxl -
Perfect, so no issues up until #63, correct? I should assume, you followed the guide, correct?
So, each channel powered up separately/correctly in step 62 with no issues, correct?
If that is the situation, the symptoms you describe point toward an issue with your PSU being able to supply full current to both boards simultaneously. There could be other issues, but that's the only obvious one. I'm not familiar with that unit, and power supplies are out of scope for this thread.
I'd recommend running your PSU / testing it continuously loaded to about 3A. If you're unfamiliar with how to do that, perhaps seek out a thread with that specific power supply or ask over in the AJzm General Discussion Thread for some help. Once you are confident your PSU is perfect, re-do steps 62 and 63 and report any new findings.
Cheers,
Patrick
Perfect, so no issues up until #63, correct? I should assume, you followed the guide, correct?
So, each channel powered up separately/correctly in step 62 with no issues, correct?
If that is the situation, the symptoms you describe point toward an issue with your PSU being able to supply full current to both boards simultaneously. There could be other issues, but that's the only obvious one. I'm not familiar with that unit, and power supplies are out of scope for this thread.
I'd recommend running your PSU / testing it continuously loaded to about 3A. If you're unfamiliar with how to do that, perhaps seek out a thread with that specific power supply or ask over in the AJzm General Discussion Thread for some help. Once you are confident your PSU is perfect, re-do steps 62 and 63 and report any new findings.
Cheers,
Patrick
that confirmed with ohmmeter?
it needs to be unmeasurable in MOhm range, showing OL or whatever on your DMM
you can check that even if everything wired, under condition to temporary disconnect audio GND and chassis/heatsinks
besides - I see no washers on mosfets - neither big one nor split washer; that's Bad Juju!
Patrick,
currently just working one board at a time, so can only report on the first one.
Is the resistance of 260 Ohm on the FETs vs "open" on the not yet used other channel not of concern? The Meanwell 600-24
https://www.meanwell-web.com/content/files/pdfs/productPdfs/MW/HEP-600/HEP-600-spec.pdf
is able to supply up to 25A, since that pot is currently turned lowest, still around 13A.
BTW, my kit came with only one BD140, I am currently waiting for it to be sent. In theory, I could solder the BD140 from the board where I am suspecting problems to the second one and check.
In general, if I were to replace the IRFP150, just order (my usual sites are digikey and mouser)?
Cheers
Brxl
currently just working one board at a time, so can only report on the first one.
Is the resistance of 260 Ohm on the FETs vs "open" on the not yet used other channel not of concern? The Meanwell 600-24
https://www.meanwell-web.com/content/files/pdfs/productPdfs/MW/HEP-600/HEP-600-spec.pdf
is able to supply up to 25A, since that pot is currently turned lowest, still around 13A.
BTW, my kit came with only one BD140, I am currently waiting for it to be sent. In theory, I could solder the BD140 from the board where I am suspecting problems to the second one and check.
In general, if I were to replace the IRFP150, just order (my usual sites are digikey and mouser)?
Cheers
Brxl
yes no connection from drain, or any of the G,S,D toward the sink.
Yes, no washers.
Gotcha... so you're on Step 62.
Follow ZM's wise guidance. I'll chime in when a dodo is called for.
Edited to add below... sent before finishing...
So sorry about that (the missing 140). Let me know if I can help in any way for that.
Yep any 150 will do. PM me if you need a 150 and/or a BD140. Not sure if you're in the States or elsewhere, but I can help if needed.
Cheers!
I can't see anything from that one pic
Few more words - besides having DVM across 0R27 source resistor to observe Iq, there needs to be DVM at output (ref. to GND) to observe output DC Offset
What DC offset you have/had?
Iq needs to be anything between 1A5 to 1A8 (by choice) so giving 400mV to 490mV across 0R27
Few more words - besides having DVM across 0R27 source resistor to observe Iq, there needs to be DVM at output (ref. to GND) to observe output DC Offset
What DC offset you have/had?
Iq needs to be anything between 1A5 to 1A8 (by choice) so giving 400mV to 490mV across 0R27
Cool, thanks for the help already.
Patrick, are you the one emailing about sending one BD140 on my way? Yes, If you don't mind, I would really appreciate a pair of IRFP150s to the same address (PO Box in Clayton NY), let me know what I owe you, but it would really save me some time.
Now that our only phone has returned home from the day's errands run by my partner, the requested and hopefully sufficient pictures.
I did run a 2nd DMM on the outputs and it appeared not register any offset (it is an Auto-ranging FLUKE T6-600) for the short moment that I looked on it, was more into the voltage across R129.
Patrick, are you the one emailing about sending one BD140 on my way? Yes, If you don't mind, I would really appreciate a pair of IRFP150s to the same address (PO Box in Clayton NY), let me know what I owe you, but it would really save me some time.
Now that our only phone has returned home from the day's errands run by my partner, the requested and hopefully sufficient pictures.
I did run a 2nd DMM on the outputs and it appeared not register any offset (it is an Auto-ranging FLUKE T6-600) for the short moment that I looked on it, was more into the voltage across R129.
Yep, that was me.... sadly, your package went out on Monday and is already in Syracuse according to tracking and will be there tomorrow. I can't fly that fast to catch it. Wings are tired.
Shout if you need a part number for an order. Happy to help any way I can.
Hello again,
for the 2nd board, since the BD140 is shortly awaited here (should fit in an envelope)...if I first started only with 18V, should any thermal problem arise, it would take a bit longer. I do not have an adjustable transformer, but could provide 3s LiPo batteries (11.1V), valid alternative?
Thanks for the measurement points. I did only short pin 2 to 3 from the XLR input (but will now connect GND as well). Will report back when 2nd board testing.
for the 2nd board, since the BD140 is shortly awaited here (should fit in an envelope)...if I first started only with 18V, should any thermal problem arise, it would take a bit longer. I do not have an adjustable transformer, but could provide 3s LiPo batteries (11.1V), valid alternative?
Thanks for the measurement points. I did only short pin 2 to 3 from the XLR input (but will now connect GND as well). Will report back when 2nd board testing.
no use of squeezing the oak, using some smaller PSU voltage instead of variac
be sure that you have all parts in place, put temporary T2A5 fuses in both rails, pray and flip the switch
if you don't have enough heatsinking, arrange proper fans with heatsinks you have........ though, arranging permanent solution is issue per se
be sure that you have all parts in place, put temporary T2A5 fuses in both rails, pray and flip the switch
if you don't have enough heatsinking, arrange proper fans with heatsinks you have........ though, arranging permanent solution is issue per se
Excellent advice! On the fuse, remember that I once was told to put a protective resistor in series PS to board to counterbalance thermal runaway on a kit (Medium Power Amp, elektor, 1991)
Question; I put the pots in set at their halfway points, would I be somewhat safer if I dialed Iq all the way down (CCW) and work my way up, checking output offset of course?
Directions towards cooling acknowledged, let's see what I can come up with from my parts supplies here.
Question; I put the pots in set at their halfway points, would I be somewhat safer if I dialed Iq all the way down (CCW) and work my way up, checking output offset of course?
Directions towards cooling acknowledged, let's see what I can come up with from my parts supplies here.