Maybe you got a 47R to parallel the 22R R1 with so to get something like 15R? That will give some decent headroom CCS for when it will fully work and hopefully Vin will remain adequate.
Change a Q5 to see what happens now. Dummy on output, +f +s to one side of the dummy, -f -s to its other side.
Change a Q5 to see what happens now. Dummy on output, +f +s to one side of the dummy, -f -s to its other side.
I think we're good now (or at least very close.) 🙂
Changed Q5
Vin 44 V, Vout adjustable with pot from 44 down. Set it at 28 V out.
New R1 = 16 ohm, got Vdrop 1.57 V = 100 mA
Put a big 50 ohm put in front of reg, and dialed down Vin to 38 volts
(about 35 ohms through pot.)
Voltage stayed at 28 volts even with drop of Vin from 44 to 38 V
Added another 47 ohm to R1, new R1 = 11.3 ohms. V drop now 1.52 V for about 130 mA. Could probably go back to original 10 ohm resistor now for R1.
Other readings:
Q1 G to S = 3.3 V
Q4 G to S = 2.5 V
Q3, Q6 and Q7 all give B to E = 0.6 V
Q2 G to D = 2.9 V
Q5 G to D = 0.6 V
R4 Vdrop = 44 V (when Vin was still 45 V)
R5 Vdrop = 0.6 2 V (when Vin was still 45 V)
Anything else I should do? Is a target of 150 mA reasonable for two channels?
My choke is rated 200 mA, and I don't really want to go there.
Thank you!
Doug
Changed Q5
Vin 44 V, Vout adjustable with pot from 44 down. Set it at 28 V out.
New R1 = 16 ohm, got Vdrop 1.57 V = 100 mA
Put a big 50 ohm put in front of reg, and dialed down Vin to 38 volts
(about 35 ohms through pot.)
Voltage stayed at 28 volts even with drop of Vin from 44 to 38 V
Added another 47 ohm to R1, new R1 = 11.3 ohms. V drop now 1.52 V for about 130 mA. Could probably go back to original 10 ohm resistor now for R1.
Other readings:
Q1 G to S = 3.3 V
Q4 G to S = 2.5 V
Q3, Q6 and Q7 all give B to E = 0.6 V
Q2 G to D = 2.9 V
Q5 G to D = 0.6 V
R4 Vdrop = 44 V (when Vin was still 45 V)
R5 Vdrop = 0.6 2 V (when Vin was still 45 V)
Anything else I should do? Is a target of 150 mA reasonable for two channels?
My choke is rated 200 mA, and I don't really want to go there.
Thank you!
Doug
Congratulations!Go to 150mA is a nice enough value given the choke's spec.
When you had the MOSFETS reversed, much current found its path from rail to ground through Q2,3,5 is likely. All restored and even better balanced now. Thumbs up! A photo with the DMM showing 28V on its output and the CCS Leds glowing is the debug glory and in order I suppose.🙂
P.S. If you got a scope, set it to AC input, 10mV & 50uS per division, probe x1, and check that the rail is a DC line without much noise fuss or riding oscillation waveforms.
Oops. Spoke too soon. LEDs aren't glowing. I probably got the first one too hot when I kept soldering around R1.
WIll replace them and change R1 back to 10 ohm.
Still holds 28 V though.
WIll replace them and change R1 back to 10 ohm.
Still holds 28 V though.
Output holds anyway if the first MOSFET passes current but is not regulating it. Check VdropR1/R1=CCS 150mA after that again.
I did recently get a scope, but haven't bought probes yet, and need ti learn how to use it.
I assume you are concerned about oscillation?
I assume you are concerned about oscillation?
I am not particularly suspicious with that class of 1.X regs, they are fairly layout indifferent, and been made many times along this phono, but is always good to check when had damages before final good test.
OK, had a bad thing happened. Reg slipped out of my hand and landed hard on the concrete, due to the weight of the heatsinks. Broke the perfboard, but I think it will be OK after some Crazy glue.
All three LEDs light up, and it is probably regulating, as they go out if I touch the R1 to read voltage, and then come back on after a second.
R1 seems VERY sensitive to current drawn. 10 ohms gave over 200 mA, spliced in a 1 ohm and then another 0.5 ohm, and am down to 188 mA (2.2 V/11.7 ohm)
So I will need to play around with that, and glue the board back together and clean up some messy work. Starting to look like a dead bug project. 🙂
I think its OK though. Will report back later or tomorrow.
Gracia Mr Salas!
Doug
All three LEDs light up, and it is probably regulating, as they go out if I touch the R1 to read voltage, and then come back on after a second.
R1 seems VERY sensitive to current drawn. 10 ohms gave over 200 mA, spliced in a 1 ohm and then another 0.5 ohm, and am down to 188 mA (2.2 V/11.7 ohm)
So I will need to play around with that, and glue the board back together and clean up some messy work. Starting to look like a dead bug project. 🙂
I think its OK though. Will report back later or tomorrow.
Gracia Mr Salas!
Doug
Here's an update:
I epoxied the board, and it is good enough.
Adjusted R1 to 15 ohms, got 150 mA with 39 V in, 28 V out.
Kept burning out the amber LEDs if my probe slipped while reading volts.
I thought maybe the red ones I have would be more reliable, so I put them in.
This changed the Vdrop from 1.7 V per amber LED to 1.5 V per red LED.
This changed the current to about 100 mA, so I need to go change R1 again.
Anyway, the LEDs are glowing and I think it will be OK after I lower R1 a bit.
Really appreciate all the support!
Doug
I epoxied the board, and it is good enough.
Adjusted R1 to 15 ohms, got 150 mA with 39 V in, 28 V out.
Kept burning out the amber LEDs if my probe slipped while reading volts.
I thought maybe the red ones I have would be more reliable, so I put them in.
This changed the Vdrop from 1.7 V per amber LED to 1.5 V per red LED.
This changed the current to about 100 mA, so I need to go change R1 again.
Anyway, the LEDs are glowing and I think it will be OK after I lower R1 a bit.
Really appreciate all the support!
Doug
Salas, the scope is 30 Mhz B & K.
I just got it last week and haven't ordered the probes yet.
I'll just get something off of eBay probably.
Doug
I just got it last week and haven't ordered the probes yet.
I'll just get something off of eBay probably.
Doug
Yes, those on Ebay that get advertized as 100MHZ are sufficient for your scope. Always remember that probes are nominally voltage rated at x10, and they lose much of that spec with frequency and/or x1. So make sure you will read their little leaflet. They also lose a drastic amount of bandwidth at x1 due to no self capacitance division. That voltage spec thing I remind you given the opportunity because you are a tubes builder and there will be HV. There is a US company named Cal Test Electronics that has a most thorough line of probing, clipping, connecting, everything in logical prices by the way. Maybe their spec would be more reliable despite of where they possibly OEM.
As for led colors and voltages and CCS current affected report, it all looks like going by the book. Photo time!🙂
As for led colors and voltages and CCS current affected report, it all looks like going by the book. Photo time!🙂
Salas,
Reduced R1 to 9.6 ohm; got 150 mA. Looks good. WIll get a photo in a bit.
Do these probe look OK?
Scope Probe Set with Isolated BNC | 100MHz | Selectable x1/x10
Reduced R1 to 9.6 ohm; got 150 mA. Looks good. WIll get a photo in a bit.
Do these probe look OK?
Scope Probe Set with Isolated BNC | 100MHz | Selectable x1/x10
This probe looks like the one in Rigol 1000 series, should be honest spec wise. Small and agile.
Cowboy Legs & Ammo Belts !!! ( mean lookin' hombres ! )
50 mean as hell, gunslingin' cowboys from the 'Toshiba Ranch' arrived today. 😱
This time 'Zhoufang' stylee ( the Singapore-Sling ! )...BOO JAH ! 😛
That enough bad-boy bandido's, to start a revolution !...
😎
...or even 33 & a 1/3rd of them !
Now we rockin' phono-freaks ! 😉
I'm outta here...
...where's that meter ? 😕
Cheers.
😀
Si.
50 mean as hell, gunslingin' cowboys from the 'Toshiba Ranch' arrived today. 😱
This time 'Zhoufang' stylee ( the Singapore-Sling ! )...BOO JAH ! 😛
That enough bad-boy bandido's, to start a revolution !...
😎 ...or even 33 & a 1/3rd of them !
Now we rockin' phono-freaks ! 😉
I'm outta here...
...where's that meter ? 😕
Cheers.
😀
Si.
