Worked! Best position for the single remaining bridge is farthest away from tranny. Tried both positions. Single bridge close to tranny made the most noise, even more than original bridging. No (zero, zilch) noise in right channel now, barely perceptible hum in left channel (ear pressed close to speaker). What a relief!
Attachments
For future reference, wondering if that metal can covering the tranny was even helpful at all at reducing noise. It was the reason I had to separate the PSU cap boards to get them to fit.
next time get proper Modushop box
that 4U/300 is for Weaklingsesssssssss
Would have preferred a deeper Modushop 4U, but took what I could easily get. More a matter of lazy than weak, maybe...Plenty of sink for these boards. Bias is at 0.8V, heatsinks are 49C at hottest point. Q1 pin 2 65C, Q2 pin 2 66C.
Space is of importance, same as heatsink capability
especially in case of amps having signal xformer, you need to cheer every inch you gain between those and big Donut(s)
in any case, one's wallet, one's decision
I'm just mocking around, while highlighting importance of these factors
especially in case of amps having signal xformer, you need to cheer every inch you gain between those and big Donut(s)
in any case, one's wallet, one's decision
I'm just mocking around, while highlighting importance of these factors
Wow, I am at .650 and 65 degrees on pin 2 with my 4u 300mm chassis. Are you sure that your way of measuring temperature is accurate?
I have this multimeter with the little temperature probe that comes with it:
https://www.amazon.com/gp/product/B07FDBW1PT/ref=ppx_yo_dt_b_asin_title_o03_s00?ie=UTF8&psc=1
And then I have an interred thermometer. Some IR guns have an adjustment for emissivity
I have this multimeter with the little temperature probe that comes with it:
https://www.amazon.com/gp/product/B07FDBW1PT/ref=ppx_yo_dt_b_asin_title_o03_s00?ie=UTF8&psc=1
And then I have an interred thermometer. Some IR guns have an adjustment for emissivity
Using both an infrared thermometer and a temp probe on two different DMMs, a Fluke and a Klein. Temps on the left channel are a couple of degrees higher than the right channel with both biased the same.
800mv is across the R47 source resistor? That is crazy. Maybe I am doing something wrong. I built out the rectification section of the power supply board which does put off a lot of heat. I wonder if that has anything to do with my bias capabilities.
Yes, across R2, source resistor for Q2. Just checked again. Now at 47C after playing music for hours. Could the IRFP150s you're using run hotter?
as always, Papatable is handy
regarding temp of mosfets itself - you're good with them if thermal interface is good
mosfet case up to 10deg higher than heatsink measured close to mosfet
IR guns are tricky - you can't trust them due to surface emissivity problems
best to have decent DMM with temp probe in form of small blob NTC; use small blob of thermal goo on it and you're in much better situation than with contact-less methods
regarding temp of mosfets itself - you're good with them if thermal interface is good
mosfet case up to 10deg higher than heatsink measured close to mosfet
IR guns are tricky - you can't trust them due to surface emissivity problems
best to have decent DMM with temp probe in form of small blob NTC; use small blob of thermal goo on it and you're in much better situation than with contact-less methods
Putting Klein DMM temp probe, which has some sort of cloth cover on it, right on pin 2 (now at 67C) and Fluke temp probe, which is bare metal, in-between heat sink fins across from where Q2 is bolted. Measuring bias on Q2 now and it's a little lower than it was yesterday, now at 762mV. DC offset is 0.0mV.
nodough, They are about the same as the IRFP240s. I also changed to ceramic insulators from the insulators from the DIYstore. I will mess around with reading temps the next time I pull it apart to screw something up.
Zen Mod, thank you for the tips. The idea of a blob of thermal paste on the tip of the probe is pretty slick. I wouldn't have thought of that.
Zen Mod, thank you for the tips. The idea of a blob of thermal paste on the tip of the probe is pretty slick. I wouldn't have thought of that.
Temp on MOSFETs case (between washer and pins) stabilizes out at 63C+0.2. Temp on metal sink right next to MOSFET is 48C. Temp on outside of heatsink between fins directly across from MOSFET case is 47C.