Sony vFET Illustrated build guide

[ernesternest]

big cables for small pcb holes.

Dave, Rush,

thanks a lot for your answer. Dave, also thank you for the pics!!
Since I have no other solution, this is exactly, what I have done several times before - not as beautiful as you - and it does not really satisfy my lets say - aesthetics. If there is no better solution and this is what all guys are doing here, I'll try to make ist as beautiful as you did.

Btw, interesting resistor composition 🙂

Cheers, Ernst

 

[Rodeodave]

You can see more details of the resistors in post #2630 in the Sony VFET Amplifier Part 2 thread:
https://www.diyaudio.com/forums/pass-labs/276711-sony-vfet-amplifier-2-a-53.html#post4975031
The fat ones are RN65E.

I don't like having to clip the litz wires either, but tight routing and a little heatshrink makes the wiring easier on the eyes 😉

 

[Stanney2017]

I’ve started to power up the front end. All semiconductors/ no VFETs.
Reading some strange voltages. Bench psu at 28v

G- T6. 14.16. G- T8. -13.38
G- T4. -12.87. G- T2. 13.59
T6-T7 0. T8-T9. 0
T6-T11 -12.89. T8-T13 12.84
G- T18. 7mv. G-T15. -0.526
G -T14. 1.25. G-T20 -10.61
G-T19. 11.24. G-T-16. 9.30
G- T17. -8.7

 

[Ben Mah]

Your G-T6, G-T8, G-T4, G-T2 are approximately half of what they should be. You said that "Bench psu at 28v". The board takes +28V 0 -28V. Are you providing that?

 

[Stanney2017]

I believe so.

+- 28v through bench Psu.

They are roughly half.
The PSU is new. I’ll check it:

 

[Ben Mah]

T6-T11 and T8-T13 too high. Are pots P3 and P4 set fully counterclockwise?

G-T14 and G-T15 too low.

Something is not right at the front end at Q1, Q2, Q3, Q4.

Something is drawing down the voltage - short or damaged component?

 

[Stanney2017]

The Psu is measuring + 14 - 13

 

[Stanney2017]

I have a Psu for an F6. I can try that.

 

[Stanney2017]

Actually not sure I can.

 

[Ben Mah]

The Psu is measuring + 14 - 13 .

Is that with it connected or not connected to the board?

If it is +28 -28 unconnected and +14 -13 connected then the board is probably drawing too much current. I don't know what the current draw is for the front end but I would think that it should only in the region of tens of milliamps.

You probably shouldn't try another power supply until you figure out why you are getting these readings. You don't want to inadvertently toast some parts.

 

[Ben Mah]

Your T14-G and T15-G are very low, indicating very little current through Q3 and Q4. Defective or incorrectly placed?

 

[Stanney2017]

With it connected.
Both boards read the same.
I’ll have to double check all components.

 

[Stanney2017]

Q3 and Q4 are correctly placed.

 

[Zen Mod]

check PSU , do you have proper rails , when not connected to amp pcbs

then connect PSU to pcbs and check rails again

if you don't have proper rails , you're just wasting time

 

[Stanney2017]

I checked q1 and q4. Seems I placed them as the wrong sort of pairs. Pair of sk170 on one board. Pair of j74 on the other.
Process of correcting this.

Checking the Psu now. A cheap one. So just might be a dud.

 

[Zen Mod]

with cheap - usually means unreliable - PSU , you're risking great damage, when dealing with circuit having rare parts

deal with that first , then proceed with testing

think of final money value of amp , you'll see that investment in proper testing equipment is clever ........ also count on fact that once you started with building , it's logical that you'll proceed 🙂

 

[Stanney2017]

I agree.

 

[Stanney2017]

Hooked up to a UPS. +-28v on both rails.
Only long enough to take a reading.

Voltages out are.
T6 -T11. -12.9.
G - T19. 23.7
G - T17. 19.5
T8 -T13. 12.76
G - T20. -23.4
G - T16. 19.3

All other voltages are +- 1 volt to what you’d expect.

Andrew

 

[Dennis Hui]

Are you using 1K pots for P3 and P4? Also are P1 and P2 at mid-position? If not, what happens if you set them to mid-position?

 

[Stanney2017]

Using 1k pots for P3 and P4. Fairchild mosfets.

I’ll check again this evening with pots set to middle.

Best,

Andrew