Hello, I’m stumped on this one. Replaced drivers, buffers, zeners and output fets and a few 4r7 resistors.
Inductors appear fine and output filter caps are in spec
Amp comes on and plays, has good drive waves with no dc offset, however, the output fets heat up quickly.
I suspect the drive frequency is too high? It’s 122khz. Anyone happen to have come across this issue and or know if this drive frequency is too high?
Inductors appear fine and output filter caps are in spec
Amp comes on and plays, has good drive waves with no dc offset, however, the output fets heat up quickly.
I suspect the drive frequency is too high? It’s 122khz. Anyone happen to have come across this issue and or know if this drive frequency is too high?
IRS20957 driver ICs?
From notes for a similar amp, 120k is normal.
Are the output FETs the original part number and from a reputable distributor?
From notes for a similar amp, 120k is normal.
Are the output FETs the original part number and from a reputable distributor?
Yes irs20957s both of which are new.
Drive buffers were (Texas Instruments) UCC27511a, I did replace those with an exact replacement from (Infineon)1EDN7511BXUSA1.
Outputs are new oem part number IRFB4127.
I used LL4148 and zmm5245b diodes.
All parts are from Mouser and Arrow.
Drive buffers were (Texas Instruments) UCC27511a, I did replace those with an exact replacement from (Infineon)1EDN7511BXUSA1.
Outputs are new oem part number IRFB4127.
I used LL4148 and zmm5245b diodes.
All parts are from Mouser and Arrow.
How fast do they heat up and how hot do they get in that time?
How does that change when clamped to the heatsink?
Did enough of any of the original parts survive to all you to drop them back in to see if there was a difference in heating?
Does the amp draw excessive current at idle?
How does that change when clamped to the heatsink?
Did enough of any of the original parts survive to all you to drop them back in to see if there was a difference in heating?
Does the amp draw excessive current at idle?
They start heating up instantly, after 48 seconds they are uncomfortable to the touch but can still be held.
Idle current is 3.4 amps.
Clamped to the heatsink, the heatsink around the fets has heated up 5 degrees F after 10 min. 93 degrees at the hottest point. Ambient temp was 88 when I started.
Idle current is 3.4 amps.
Clamped to the heatsink, the heatsink around the fets has heated up 5 degrees F after 10 min. 93 degrees at the hottest point. Ambient temp was 88 when I started.
After being on for an hour mostly idling, the output side of the heatsink is up to 116F while the power supply side is up to only 110F. Going to load test it tomorrow to see how it does under stress. Ran it for awhile at 400 watts earlier and it did fine.
I emailed someone who works on these to see what was normal (haven't heard back, yet) but what you described didn't seem excessive (completely normal for some amps).
According to the Taramps website, the smart 5 should idle at 3.6 amps.
This one is operating within that spec, but I sure don’t like when fets heat up at idle like that.
This one is operating within that spec, but I sure don’t like when fets heat up at idle like that.