ang728

did you check 2N3904 and 24V Zener ? they also could gone with faulty GRHV

tried to build it last year . mine kinda works but put them away due to output dc sometimes would trigger protection circuit.Likely having oscillation .still looking for any solution/workaround

had similar experience before.I feel like the ROHM parts are prone to blow up when the inrush current is too much and it's not my first time. Recently I built a BH earlier with accidentally installed one wrong resistor on one channel causing it drawing too much current,showing -V is constantly pulled low. at first I thought maybe the neg rail is oscillating (I was using Microchip SiC on this build) so I swapped back to ROHM SiC thinking that should work fine since I use it alot during the time that Cree part is constantly out of stock.then it blew up as HV kicked-in and almost shot my face :( .pics related https://imgur.com/z5IHdpx I fixed the issue after doing a full check on both amp, psu side and swapped the blown / incorrect parts . as i said , it's not my first time had the ROHM parts blown, although the root causes are different but they did easier to blow up when something is wrong.

Same Here,also uses MJL21193/94 on other builds

LT1021-5 won't work in shunt mode,add 1 wire for pre-reg to Vin of 1021 will do fine.I used it in my 8.4VDC supply

Here to bump the thread up. Does anybody knows the spec of SRM-007T transformer? I am currently working on a SRM-007T repair and the transformer showing signs of leakage on one secondary HV rail. Measured about 160VAC w/o load and showing some magic smokes... also DCR on corrupted rail is lower than normal ones (79ohms vs 50ohms).so I feel theres some insulation breakdown in the sec side. I ask some workshop to see if they can rewind the transformer.they ask me detail about specs of all the rails. from schematics KG kindly provided me.I am sure HV should be two 270VAC ,filament is 12.6V CT (6.3-0-6.3).but I still need: AC Voltage on LV side (I assumed 30VAC CT) current rating on all secondary side rails thanks!

yeah that's for ZF/SS switch and protector hat PCB ,but can do better placement on next revision

so after some fiddling around , now my CFA3 working perfectly.I replaced all my old stock BC546/556 to newer parts with roughly matching,offset still 40mV w/o Servo but no big difference switching back to 300ohm maybe my problem comes from some crooked old BC parts...? I dunno but fixed anyway lol

Yes , I solve this problem from this post , a big help.but still need more fiddling to find out and that's why I like HC more than HF 😭

yes that's usually what I do but maybe not on my case this time.hope to see others experience about it.

Finished building CFA3 Ver1.21 recently.But offset reading seems off ,about 0.8V relative to gnd and 0.2V after solving oscillating issue ,VO+ to VO- also high as 0.2V and bias went huge bump when switching ss to zf with oscillation on scope.I was quickly solving the problem by pulling 600pf,20pf caps form the mentions in this thread. After some wild goose chase then I noticed a slight difference between schematic and board silkscreen.R211,R222,161,R262 value at current mirror is 680ohms but showing 300ohm on PCB. now I have about 40mV offset w/o servo at each side with 680ohm resistor,haven't done any further test but I think I can have a good sleep tonight Scrolling through the thread and it seems nobody mentioned .Not sure if that's a issue but just a heads up

I used 22AWG before,they worked fine.

the pin header I use is 127-1-4010-8002-310 made by Nextron. Or you can search "Nextron 2.54mm round pin" on Ebay

But I have different results here do you have other changes on the board like zener diode that KG mentioned ?

maybe try WAGO 294?