well , I had suspicion from the start ( of the thread ) that they (trimpots) are there exactly for purpose of trimming voltages
it seems you helped me to solve that suspicion
take care of reading entire start-up procedure over and over , until you're sure of grasping things ....... because you evidently had luck on your side , to this stage
when you have VFets in circ , there is no place for luck
it seems you helped me to solve that suspicion
take care of reading entire start-up procedure over and over , until you're sure of grasping things ....... because you evidently had luck on your side , to this stage
when you have VFets in circ , there is no place for luck
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well , I had suspicion from the start ( of the thread ) that they (trimpots) are there exactly for purpose of trimming voltages
it seems you helped me to solve that suspicion
take care of reading entire start-up procedure over and over , until you're sure of grasping things ....... because you evidently had luck on your side , to this stage
when you have VFets in circ , there is no place for luck
I'm following the guide 'within reason'. I won't put the VFETs in until everything is perfect in the guide up to that point. So far so good. All the resistances matched the guide so then I moved to step II where all the voltages (except the supply was 31VDC) matched within a certain range.
More tomorrow.............
Regards,
Dan
As Zen Mod has suggested,
Here's the details.
Both my boards passed the PART 1 TESTING THE RESISTORS with flying colors.
Now Part 2- APPLYING THE POWER TO THE FRONT END
Everything appeared to power up well with no smoke so I was happy. I went through all the initial voltage test points and everything looked good until I got to G-T19 and G-T20. They were 24V each. Also, G-T17 and G-T16 were 20V. After a little coaching from Zen Mod I found that I left all four pots fully CC instead of just P3 and P4. After tuning P1 and P2 my voltages returned to they should be.
Here's the latest measurements.
G-T6=31.43V G-T8=31.43V
G-T4=24V G-T2=24V
T6-T7=0V T8-T9=0V
T6-T11=5.76V T8-T13=5.69V
G-T18=0V
G-T14=15V G-T15=15V
G-T19=12V G-T20=12V
G-T17=9.9V G-T16=9.9V
Now herein lies my problem. P3 and P4 have no real effect on T6-T7 and T8-T9. Max I can get is .2V on each. G-T18 goes way up when I do this.
My first two guesses are that I damaged something by leaving P1 and P2 fully CC? Or, I may have to adjust some resistor values for higher than expect rail voltages?
Regards,
Dan
Here's the details.
Both my boards passed the PART 1 TESTING THE RESISTORS with flying colors.
Now Part 2- APPLYING THE POWER TO THE FRONT END
Everything appeared to power up well with no smoke so I was happy. I went through all the initial voltage test points and everything looked good until I got to G-T19 and G-T20. They were 24V each. Also, G-T17 and G-T16 were 20V. After a little coaching from Zen Mod I found that I left all four pots fully CC instead of just P3 and P4. After tuning P1 and P2 my voltages returned to they should be.
Here's the latest measurements.
G-T6=31.43V G-T8=31.43V
G-T4=24V G-T2=24V
T6-T7=0V T8-T9=0V
T6-T11=5.76V T8-T13=5.69V
G-T18=0V
G-T14=15V G-T15=15V
G-T19=12V G-T20=12V
G-T17=9.9V G-T16=9.9V
Now herein lies my problem. P3 and P4 have no real effect on T6-T7 and T8-T9. Max I can get is .2V on each. G-T18 goes way up when I do this.
My first two guesses are that I damaged something by leaving P1 and P2 fully CC? Or, I may have to adjust some resistor values for higher than expect rail voltages?
Regards,
Dan
can't help with that ..... my (bare) pcbs are 1km away from me and I'm lazy to stare at pcb pictures
No problem.
Hi Dan,
I think you can go by Papa's document:
http://www.firstwatt.com/pdf/art_diy_sony_vfet.pdf
Page 5 shows the silkscreen of the PCB.
Dennis
I think you can go by Papa's document:
http://www.firstwatt.com/pdf/art_diy_sony_vfet.pdf
Page 5 shows the silkscreen of the PCB.
Dennis
1V8/220R=appr. 8mA , which is good
now , be sure that you dial back both P3 and P4 , replace R34 and R35 with , say , 390R-430R and try biasing mosfets again
check for P3 : upper leg of R35 and T10 , ohmmeter must read 0
check for P4 : upper leg of R35 and T12 , ohmmeter must read 0
"upper leg" when looking at pcb as shown in post #755
now , be sure that you dial back both P3 and P4 , replace R34 and R35 with , say , 390R-430R and try biasing mosfets again
check for P3 : upper leg of R35 and T10 , ohmmeter must read 0
check for P4 : upper leg of R35 and T12 , ohmmeter must read 0
"upper leg" when looking at pcb as shown in post #755