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Old 17th March 2019, 02:34 AM   #21
Zen Mod is offline Zen Mod  Serbia
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small NTCs are there for temperature compensation of Iq

more shorties

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Old 17th March 2019, 02:44 AM   #22
6L6 is offline 6L6  United States
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Heck - Sometimes I need to read Zen's stuff a few times to figure out his Wile E. Coyote (genius) shorthand.

The little thermistors touching the black part of the Mosfet instead of the washer is a belt & suspenders thing - if (somehow) the paint on the end of the NTC becomes worn through and touching the metal, it may ground out, but if touching the plastic, no worries.

Those thermistors, by the way, are there to adjust the Current through the Mosfet (Iq) as the amp warms up.
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Old 17th March 2019, 08:36 AM   #23
Kosst Amojan is offline Kosst Amojan  United States
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The only thing I see that could be problematic is those ,47R 3W resistors. Usually you don't want those tight to the board because they get fairly warm and having some longer leads and big bends makes it easier to clip probes to.
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Old 17th March 2019, 11:38 PM   #24
Trismos is offline Trismos  Canada
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Originally Posted by Kosst Amojan View Post
The only thing I see that could be problematic is those ,47R 3W resistors. Usually you don't want those tight to the board because they get fairly warm and having some longer leads and big bends makes it easier to clip probes to.
I do recall reading something about that somewhere but it slipped my mind which ones they were referring to while putting it together. I've had quite a few pics open along with several different threads (plus the build guide pdf) and it gets a tad confusing keeping it straight sometimes.
Thanks for pointing it out so that any others doing their build and perhaps looking here might learn that.

D
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Old 18th March 2019, 03:48 AM   #25
Trismos is offline Trismos  Canada
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Well, finished pretty much. I have a set of feet coming but other than that, she's all soldered up and all I have left is to do the biasing tomorrow. I haven't plugged it in yet mind you since testing the PSU.

18-20190317_161515.jpg

19-20190317_202540.jpg

20-20190317_202532.jpg

21-20190317_202456.jpg

22-20190317_202449.jpg

Thanks to ZM for some final pointers and everyone else that chimed in!
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Old 18th March 2019, 02:16 PM   #26
Dennis Hui is online now Dennis Hui  Canada
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Looking good. I guess you're ready for powering up.

Just a reminder to set P1 and P2 to min value so that the resistance
measured across R5 and R6 are low, to ensure low bias at your initial start up.

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Last edited by Dennis Hui; 18th March 2019 at 02:28 PM.
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Old 18th March 2019, 02:17 PM   #27
6L6 is offline 6L6  United States
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And disconnect one amp channel on initial power-up so if you have a symmetrical fatal error you don't kill both sides.
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Old 18th March 2019, 07:24 PM   #28
Trismos is offline Trismos  Canada
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Originally Posted by Dennis Hui View Post
Looking good. I guess you're ready for powering up.

Just a reminder to set P1 and P2 to min value so that the resistance
measured across R5 and R6 are low, to ensure low bias at your initial start up.

Dennis
Thanks Dennis - lefty loosey, righty tighty? CCW to turn to minimum?
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Old 18th March 2019, 07:29 PM   #29
Trismos is offline Trismos  Canada
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And disconnect one amp channel on initial power-up so if you have a symmetrical fatal error you don't kill both sides.
Symmetrical Fatal Error. Sounds like a death metal song. I may use it. Not that we play death metal....

So testing my power supply and coming up with 25V on both sides - give or take point something something - doesn't clear me yet? Was tempted to plug it in this morning before going to work just to see if the LEDs on the amps light up. Glad I didn't I guess.

Last edited by Trismos; 18th March 2019 at 07:30 PM. Reason: spelling
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Old 18th March 2019, 07:44 PM   #30
Dennis Hui is online now Dennis Hui  Canada
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Quote:
Originally Posted by Trismos View Post
Thanks Dennis - lefty loosey, righty tighty? CCW to turn to minimum?
Dunno. It depends on the pot and the direction it was installed in.
So best to just turn the pota and measure. Since the pots are in parallel with R5 and R6,
by adjusting the pots you should be able to get the measured resistance
across them down to a few ohms.
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