In the 2001 follow up http://www.stereophile.com/content/simaudio-moon-p-5-preamplifier-w-5-power-amplifier-follow-may-200 it says "Finally, the output stage now uses 10 (vs 8) Motorola bipolar output transistors per channel."
Ya, I read another article that mentioned it was a class AB no feedback design. I also saw a picture where the two toroids were mounted flat against the front panel.
Regards,
Dan
I'm troubleshooting my front-end board and was wondering if I could get some help. I tested all the components before installation, but it's my PCB so errors are definitely possible 🙂
SW = open
R20 (2.2K from output to GND) is populated
input = open
Values on schematic. First is nominal, second is measured:
-28V = -28.17V and 270mV across 10 ohm R40 = 27mA draw
-13.7 = -13.7V (output of regulator)
4.0V = 4.03V (adjustable with trimmer)
1.8V = 0.5mV (output stage current)
-13V = -6.9V (Q12, Q14 junction)
28V = 28.1V and 35mV across 10 ohm R39 = 3.5mA draw
4.0V = 0.2mV (not adjustable with trimmer)
13.7V = 11.27V (very odd, resistors are correct as best as I can tell)
13V = .184V (obviously wrong)
1.8V = 0.05mV (basically zero)
It seems something on the positive half isn't working, which is influencing the later values in the negative half. I'm assuming the components are good (tested before) and nothing is damaged (almost no current drawn, tough to kill stuff), so looking for places there could be a board error.
SW = open
R20 (2.2K from output to GND) is populated
input = open
Values on schematic. First is nominal, second is measured:
-28V = -28.17V and 270mV across 10 ohm R40 = 27mA draw
-13.7 = -13.7V (output of regulator)
4.0V = 4.03V (adjustable with trimmer)
1.8V = 0.5mV (output stage current)
-13V = -6.9V (Q12, Q14 junction)
28V = 28.1V and 35mV across 10 ohm R39 = 3.5mA draw
4.0V = 0.2mV (not adjustable with trimmer)
13.7V = 11.27V (very odd, resistors are correct as best as I can tell)
13V = .184V (obviously wrong)
1.8V = 0.05mV (basically zero)
It seems something on the positive half isn't working, which is influencing the later values in the negative half. I'm assuming the components are good (tested before) and nothing is damaged (almost no current drawn, tough to kill stuff), so looking for places there could be a board error.
edit: found the problem - BJTs are all messed up.. I would need a BCE NPN and a EBC PNP to make the board work as is :/
Did I miss a post where the source was listed for the Toshiba 2SJ313 and 2SK2013's?
Regards,
Dan 🙁
Regards,
Dan 🙁
ok, board surgery and I get:
V(R39) = 0.521 VDC
V(R40) = 0.508 VDC
4V(+) = 3.993 VDC
4V(-) = 4.009 VDC
1.8V(+) = 1.904 VDC
1.8V(-) = 1.821 VDC
13.7V(+) = 13.66 VDC
13.7V(-) = 13.70 VDC
13V(+) = 13.02 VDC
13V(-) = 13.05 VDC
The heatsinks are appropriately sized, I can stick my finger on for 5 seconds or so.
Anyone want some busticated boards? 🙁
Also, anyone know of similar heatsinks that take a M4 (presumably) screw? I had to enlarge the transistor holes to get a #6-32 screw into the threaded heatsink, which is less than ideal
Are there any resistors on the final version that aren't 1/4W?
AL_Nelson_mods-CB_mods_VFET-2_3 - My Photo Gallery
Regards,
Dan 😉
AL_Nelson_mods-CB_mods_VFET-2_3 - My Photo Gallery
Regards,
Dan 😉
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The 0.1 ohm current sense resistor is 3w. You can use other values, as
long as they are low - this is only a means of being able to measure bias.
The rest are your standard 1/4 watt types.
😎
BTW, the standard circuit uses +/-28V for the supply. You can go as low
as 25 or so, and as high as 30.
long as they are low - this is only a means of being able to measure bias.
The rest are your standard 1/4 watt types.
😎
BTW, the standard circuit uses +/-28V for the supply. You can go as low
as 25 or so, and as high as 30.
Father Pass,
Referring the the link in my post with all the final revisions. It appears R45 (the current sense resistor) has been left out. Also, it appears it's been left out on TeaBag's boards, the ones I'm using. 😕
Regards,
Dan
The sense resistor can be the R in the CRC of the power supply so the .1 is redundant. What Nelson said....
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I have a set of TeaBag's boards so I'm going to start posting my Mouser BOMs to see if there's any suggested improvements or if anyone spots any errors.
Passive Parts so far,
20 ea. TL431 511-TL431ACZ-AP
10 ea. BC550C 512-BC550CTA
10 ea. BC560C 512-BC560CTA
4 ea. P3 and P4 652-3296Y-1-501LF
4 ea. P1 and P2 652-3296W-1-502LF
10 ea. 1N4004 512-1N4004
10 ea. Zener 512-BZX79C9V1
20 ea. PCB Pins 575-3128100150000
4 ea. Heatsinks 567-637-10ABP
4 ea. TO-220 Kits 532-4880
Regards,
Dan
Passive Parts so far,
20 ea. TL431 511-TL431ACZ-AP
10 ea. BC550C 512-BC550CTA
10 ea. BC560C 512-BC560CTA
4 ea. P3 and P4 652-3296Y-1-501LF
4 ea. P1 and P2 652-3296W-1-502LF
10 ea. 1N4004 512-1N4004
10 ea. Zener 512-BZX79C9V1
20 ea. PCB Pins 575-3128100150000
4 ea. Heatsinks 567-637-10ABP
4 ea. TO-220 Kits 532-4880
Regards,
Dan
Dan, I assume the TO-220 kits are for the Q15, Q16 mosfets. If you plan
to use 2sj313/2sk2013 you probably won't need them since those mosfets are
insulated.
Cheers,
Dennis
to use 2sj313/2sk2013 you probably won't need them since those mosfets are
insulated.
Cheers,
Dennis
You can put a resistor in series with the DC power supply wire temporarily
while adjusting the amp. It doesn't perform any function after adjustment.
😎