Done. Here are the measurements.
Right channel board (SA1930 and SC5171; 3300 and 2200 pF comp caps):
On the +18V rail: +1.3V DC with 2V triangular spikes at 3.5 us period (300 kHz).
On the -18V rail: -1.3V DC with .5V noise/HF bursts coincident with triangular spikes on +18V rail above.
Left channel board (D45H11 and D44H11; 680 and 3300 pF comp caps):
On the +18V rail: +1.3V DC with 80mV ripple at 0.2 us period (5 MHz)
On the -18V rail: -1.3V DC with 40 mV ripple at same frequency as +18V rail.
Looks like my problem is in the CVS/CCS part of the supply...
Pierre
Looks like it, would you please redo the test but with one supply attached to the raw supply at a time. I would like to know if it is one oscillating and contaminating the others, or is multiple supplies have the same problem, also have a look at the input voltage/signal coming from the raw supply. Sorry to drag this out...
Looks like it, would you please redo the test but with one supply attached to the raw supply at a time. I would like to know if it is one oscillating and contaminating the others, or is multiple supplies have the same problem, also have a look at the input voltage/signal coming from the raw supply. Sorry to drag this out...
Thank you. Please don't be worry. You are not dragging this out. You are helping me troubleshoot step by step...
Let me add the new measurements to the previous ones.
Right channel board (SA1930 and SC5171; 3300 and 2200 pF comp caps)
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(A) Both rails tested at the same time with 10 ohm loads...
On the +18V rail: +1.3V DC with 2V triangular spikes at 3.5 us period (300 kHz).
On the -18V rail: -1.3V DC with .5V noise/HF bursts coincident with triangular spikes on +18V rail above.
(B) Only the + raw supply hooked up...
On the +18V rail: same as in (A) above
On the + raw supply: .25 V ripple synchronized with triangular spikes
(C) Only the - raw supply hooked up...
On the -18V rail: -1.3V DC with 100 mV ripple at freq > 100 MHz
On the - raw supply: same, i.e. 100 mV ripple at freq > 100 MHz
Left channel board (D45H11 and D44H11; 680 and 3300 pF comp caps)
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(A) Both rails tested at the same time with 10 ohm loads...
On the +18V rail: +1.3V DC with 80 mV ripple at 0.2 us period (5 MHz)
On the -18V rail: -1.3V DC with 40 mV ripple at same frequency as +18V rail.
(B) Only the + raw supply hooked up...
On the +18V rail: 80 mV ripple (same as in (A) above)
On the + raw supply: .6 V ripple synchronized with +18V rail ripple
(C) Only the - raw supply hooked up...
On the -18V rail: 10 mV ripple at 0.2 us period (5 MHz)
On the - raw supply: 100 mV ripple
Since my scope has 100 MHz bw, measurements above that frequency are questionable.
It seems the CVS/CCSs have various problems and the oscillations are shaking the raw supplies...
Thanks - Pierre
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Pierre,
It seems that both positive supplies have the same problem, and I do not know what/why. Did you earlier also replace the small-signal devices in these supplies? if not then you need to do it. (for now do not worry about the 100mV problem in the negative supplies, they are not designed to run as 1.3V current sources
).My problem now is that I am running out of time, from next Friday (tomorrow) on I will not be able to post in this forum (for about 2 weeks), lets hope you get the problem solved before I'm back.
Regards,
Frans.
P.s. I will send you a PM.
Hi, I'm trying to find an issue with my first pair of boards. I have one fully working board, and this one which I've not been able to find the cause for. Symptoms are:
-ve reg - output voltage OK (18.2V), L110 lit only very dimly, has only 0.7v across it
+ve reg - L210 bightly lit, L211/212 not lit. Around 0.25V output
BCE volgates are:
Q103: (pin 1,2,3): 24.4, 24.1, 24.4v
Q101: 23.6, 1.94, 24.2v
Q106: 0.19, 0, 0.26v
Q206: -14.3, 0, -18.2v
Q201: -18.3, -18.3, -1.71v
Q203: -24.2, -24.9, -24.9v
I can see I have an issue around Q101 on the -ve reg, but I have removed all transistors, re-tested with a transistor tester and re-fitted (several times). All six power transistors are correctly insulated from the heatsink. I am using 2SK170 as the FET and have double-checked the connections. I have replaced all LEDs and BC337's on the -ve reg.
Any idea where my issue might be please? The only issue I have found is that Q201 collector measures 10 ohms to ground, but I can't see any shorts anywhere and am using 7.5 ohm CCS resistor, there isn't 10 ohms anywhere on the regulator (!). It also messures 10 ohms after I removed the heat-sink.
-ve reg - output voltage OK (18.2V), L110 lit only very dimly, has only 0.7v across it
+ve reg - L210 bightly lit, L211/212 not lit. Around 0.25V output
BCE volgates are:
Q103: (pin 1,2,3): 24.4, 24.1, 24.4v
Q101: 23.6, 1.94, 24.2v
Q106: 0.19, 0, 0.26v
Q206: -14.3, 0, -18.2v
Q201: -18.3, -18.3, -1.71v
Q203: -24.2, -24.9, -24.9v
I can see I have an issue around Q101 on the -ve reg, but I have removed all transistors, re-tested with a transistor tester and re-fitted (several times). All six power transistors are correctly insulated from the heatsink. I am using 2SK170 as the FET and have double-checked the connections. I have replaced all LEDs and BC337's on the -ve reg.
Any idea where my issue might be please? The only issue I have found is that Q201 collector measures 10 ohms to ground, but I can't see any shorts anywhere and am using 7.5 ohm CCS resistor, there isn't 10 ohms anywhere on the regulator (!). It also messures 10 ohms after I removed the heat-sink.
Hi df_genius,
sorry I do not have access to the schematics right now (traveling, and google drive doesnt work), which is a shame as I painted the plans and put them online ...... whatever.....
All the LEDs should be lit up at roughly the same brightness (if they all are the same LEDs, that is), so if some of them are not lit up it may indicate they are assembled the wrong way, would you mind checking the LED polarity especially on those that are not shining? It might be that the second stage of the CCS is not working due to this.
sorry I do not have access to the schematics right now (traveling, and google drive doesnt work), which is a shame as I painted the plans and put them online ...... whatever.....
All the LEDs should be lit up at roughly the same brightness (if they all are the same LEDs, that is), so if some of them are not lit up it may indicate they are assembled the wrong way, would you mind checking the LED polarity especially on those that are not shining? It might be that the second stage of the CCS is not working due to this.
Thanks very much for the offer, I've sorted it today. Turned out to be two of the through-hole connections that have tracks on both sides had gone o/c when removing and re-fitting the power transistors (I initially went off the markings on the PCB and assumed the FETs needed insulating and not the bipolars). I might take you up on the offer to see what you think when I have finished. I still have the Calvin buffer boards to complete and fit. I'd like to think I've used a decent version of the config where I can, op-amps are OPA627, regulator FETs are 2sk170. I have also fitted compensation caps as I spotted some mild oscillation at a few Mhz, this first pair of boards are R2. When I've checked the currents are Ok on the input devices they will be thermally bonded with a piece of metal. DC offset on both boards is around 0.3v and is reasonably stable so far.
I have measured the drops across the 33 ohm resistors and both channels measure 115mV +/-2mV. Which I hope is regarded as decent matching. However one channel has 3V on the output of the op amp and the other has 15V. If not the input stages (and I am reasonably confident the rest of the groups of bipolars are matched) what are the usual suspects for high offset - the J310 and K170's? Both supplies are steady at +/-18.2V with no oscillation.