Just fired it up minus the dac end chips. No chips in because I wanted to make sure everything was working first. I get all the LEDs lighting up but on the PS that go to the dac chip won't adjust enough to get +5 -5v Maxes out at 4.7vdc
I followed and compared the voltages on this two supply rails to the ones that I can adjust and everything seems the same until the VR.
These are regulated supplies so I'm not sure since the chip doesn't need to be in to draw power.
I followed and compared the voltages on this two supply rails to the ones that I can adjust and everything seems the same until the VR.
These are regulated supplies so I'm not sure since the chip doesn't need to be in to draw power.
I had a similar problem, except only one the six regulator circuits was working properly to start with. The tolerences of the transistors are important. I had to switch them around into different spots to "match" them. I actually had to order more 2sk170's, and while I was at it I got a couple extra bc550 and a bc560. I was using lower grade 2sk170's from digikey though, some guys here are using the BL grade. Check lil'knight's post #197.
Hopefully just changing them around will sort it out, just make sure they have some headroom. (of course leave the regulator circuits alone that are working)
On post #3 of this tread, check the Salas Shunt for Dac-Ash diagram, it shows where you should be measuring 3-4 volt to check for headroom on the circuit. Measure between the regulator output and the gate of the IRF9540 (IRF540 on the negative rail)
This is the Salas shunt for the Dac End. There isn't any 33R or 27R. Am I missing something?
Ok, I just did a lot of measuring with a DMM (no scope here)
Starting with final SK170 etc before the last reg. This is measured from the problem supplies moving across to the 4 good supplies. All measurements are in ohms.
1.05 .57 | 1.06 .46 | .83 .44 | .86 .43 | .85 .46 | .84 .44
Next set
46 48 41 42 42 42
Next set
43 47 42 44 43 42
Main regs measuring outside pin to outside
1.3 for both problem supplies. 1.1 for all working supplies
Final regs
276 265 262 263 265 263
Ok, I just did a lot of measuring with a DMM (no scope here)
Starting with final SK170 etc before the last reg. This is measured from the problem supplies moving across to the 4 good supplies. All measurements are in ohms.
1.05 .57 | 1.06 .46 | .83 .44 | .86 .43 | .85 .46 | .84 .44
Next set
46 48 41 42 42 42
Next set
43 47 42 44 43 42
Main regs measuring outside pin to outside
1.3 for both problem supplies. 1.1 for all working supplies
Final regs
276 265 262 263 265 263
Since you have a couple extra 2sk170's, I would use them to replace ones you have in your board, one at a time and see what happens to your voltage output. Just focus on one rail at a time. Try replacing Q3 and check, then Q6 and check, ect...
I am assuming your having the same problem I did. Did you get you 2sk170's from mouser? part #757-2sk170GRF .
Sucks as I planned on doing just that and took a break to do it and --- with everything laid out carefully and cutting out the old SK's because I was worried about damaging the solder pads -- I put them in the wrong rail!! Arrrgh. I will try and carefully remove those and swap them for the others I should have replaced. Thanks. I really want to find this out. I was so proud the board looks perfect then...
I replaced Q3 and the voltage came right uo. 
So if I didn't waste those two spares I might have it working now.
Since I have order more I see there's comments about the BL which draw more current. Is there any advantage to these? I wouldn't mix and match but if I'm doing all this anyway I wondered if there's any serious sonic benefit to switching them all out?
So if I didn't waste those two spares I might have it working now.Since I have order more I see there's comments about the BL which draw more current. Is there any advantage to these? I wouldn't mix and match but if I'm doing all this anyway I wondered if there's any serious sonic benefit to switching them all out?
Why don't you try swapping out some of the 2sk170's in the one rail that you have left to sort out. Even try the 2sk170's that were elsewhere in the board, before you order more.
If you ise for tube 6h6 or 6h30, it is no good!
For 6dj8, it is ok!
because : 6h30 and 6h6 need 800mA one filament tube, and 20mA 1/2 tube!
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