Well, I screwed up (details below, picts attached) and now I need another IRFP9140. The major electronics dealers list the IRFP9140PBF as a direct replacement, so unless ZM says otherwise, that’s what I will order.
Here’s what I think happened
Background: I am building mono blocks and have been trying to keep both chassis up to date with each step of the build. I finished the SissySIT R.3 boards a while ago and turned my attention to completing and testing the PSUs, and drilling the heat sinks for the SITs. With the right channel chassis on the bench, I cleaned up the left channel board, fixing a cold solder joint or two and wiped it down. Setting that aside, I moved the right channel board onto the bench, then walked away for a couple of days.
The Event: When I got back to it, I forgot I hadn’t given the right channel Sissy board a thorough inspection and went ahead with mounting, wiring and hookup. With the pots adjusted, the jumper out, and my DVMs set up, I thought it was ready to go, so I slowly powered up the right mono block on my variac. As I passed through 100v I smelled the magic smoke, then zzzzphf! and the MOSFET sizzled, cracked, and popped to its death.
Issues Found and Fixed: After a nights wrestles sleep, I took everything apart and found that there was a solder bridge across the gate and drain on M101. And I found 3 pins on OK101 weren’t soldered to the board.
Could either of these issues have caused the 9140 to fry? Do I have it mounted correctly? I’m concerned there might be something else looming. I did a fairly thorough check of the other comments on the board, and it seems the 9140 was the only component to take a hit.
Here’s what I think happened
Background: I am building mono blocks and have been trying to keep both chassis up to date with each step of the build. I finished the SissySIT R.3 boards a while ago and turned my attention to completing and testing the PSUs, and drilling the heat sinks for the SITs. With the right channel chassis on the bench, I cleaned up the left channel board, fixing a cold solder joint or two and wiped it down. Setting that aside, I moved the right channel board onto the bench, then walked away for a couple of days.
The Event: When I got back to it, I forgot I hadn’t given the right channel Sissy board a thorough inspection and went ahead with mounting, wiring and hookup. With the pots adjusted, the jumper out, and my DVMs set up, I thought it was ready to go, so I slowly powered up the right mono block on my variac. As I passed through 100v I smelled the magic smoke, then zzzzphf! and the MOSFET sizzled, cracked, and popped to its death.
Issues Found and Fixed: After a nights wrestles sleep, I took everything apart and found that there was a solder bridge across the gate and drain on M101. And I found 3 pins on OK101 weren’t soldered to the board.
Could either of these issues have caused the 9140 to fry? Do I have it mounted correctly? I’m concerned there might be something else looming. I did a fairly thorough check of the other comments on the board, and it seems the 9140 was the only component to take a hit.
there is clear as whistle how to mount M101 on pcb, white overlay is showing which side is back-tab of mosfet
now, in your place , I would replace zeners in OS, both around M101 and SIT and IRFP
whichever 9140 you find, it is OK, just ignore suffix
if you want to play safe, buy a pair and replace them in both channels, in case you can't get same manufacture
now, in your place , I would replace zeners in OS, both around M101 and SIT and IRFP
whichever 9140 you find, it is OK, just ignore suffix
if you want to play safe, buy a pair and replace them in both channels, in case you can't get same manufacture
Thanks for your help!
I mounted M101 correctly, I just had a solder bridge between the 2 pins. The part checked out ok in my tester. For M102, I asked as a sanity check - the metal back goes on the heat sink side.
I will replace the zeners. Here are the parts I found: 1N4734A (5v2) and 1N5237B (8v2)
I haven’t mounted the 9140 in the other channel yet, so I will buy 2 so they match on both channels.
I mounted M101 correctly, I just had a solder bridge between the 2 pins. The part checked out ok in my tester. For M102, I asked as a sanity check - the metal back goes on the heat sink side.
I will replace the zeners. Here are the parts I found: 1N4734A (5v2) and 1N5237B (8v2)
I haven’t mounted the 9140 in the other channel yet, so I will buy 2 so they match on both channels.
All of the self imposed issues have been resolved, and I am now happily in SissySIT R.3 listening mode.
Zen Mod, this amp is so good! Thanks for the kit, this modded Papa Pass design, and for your guidance in getting it up and running.
First listening impressions
It takes about 20 minutes after a cold start for the amp to fully warm up. Once it hits its stride, the sound stage is detailed and the music emerges sweetly from an impressively quiet background - it’s the most quiet amp I have bought or built. Much more quiet than my F6. I attribute this to the CLC PSU behind the SissySIT. I may have to build a CLC for the F6 to test that theory. Anyway, the SissySIT provides plenty of punch, tight bass and volume through my diy SBA 761 speakers.
I really like this amp!
Zen Mod, this amp is so good! Thanks for the kit, this modded Papa Pass design, and for your guidance in getting it up and running.
First listening impressions
It takes about 20 minutes after a cold start for the amp to fully warm up. Once it hits its stride, the sound stage is detailed and the music emerges sweetly from an impressively quiet background - it’s the most quiet amp I have bought or built. Much more quiet than my F6. I attribute this to the CLC PSU behind the SissySIT. I may have to build a CLC for the F6 to test that theory. Anyway, the SissySIT provides plenty of punch, tight bass and volume through my diy SBA 761 speakers.
I really like this amp!
Knowledge and power!well, I'm sure both Scull and Piston are immensely helping!
Fugly!
That's cool, you can surprise yourself every day without knowing of itI'm Omniwonder!!
Even if I'm not aware of fact, I made these too!!
Hi cwlo - I tried to pay attention to current paths, magnetic fields and other factors around EMI. That diligence and the chokes make this a very quiet amplifier. I wouldn’t change anything.
Sissyheat is a welcome side effect this time of year here in the Northeast of the USA!Piston still in shape, isn't melted from Sissyheat?
I read that self-shielding by twisting pairs with equal and opposite current reduces mutual inductance by 40dB. And they do look good! 👍Love the look of twisted wires.
I didn’t twist the black (-) and red (+) together because they both return to ground, not to each other. I thought that would mean their currents are not equal and opposite making the twist aesthetically pleasing but irrelevant to shielding. Maybe someone with a greater understanding of mutual inductance can weigh in on my thinking…