I have built four SSLV regs feeding one of my SEN i/v stages, unfortunately i did swap the IRF9610 with the MJE15031's on two of the regs.. the IRF's in the MEJ's position got hot as hell really fast (small sinks) - had it turned on for a few minutes.
I found the problem and swapped the transistors with each other.
When i tried the setup after swapping, the DC voltage seems fine (i only have multimeter here), but i have a little to no AC output from the SEN i/v stage on that channel (balanced setup, so both these regs are to same channel on each phase) - and i get more distortion also. The other channel works fine!
So, i swapped out the IRF's and the MJE's for new ones, but now i seem to have the same problem still! Is there anything else that could have been damaged in the reg because of this?
I found the problem and swapped the transistors with each other.
When i tried the setup after swapping, the DC voltage seems fine (i only have multimeter here), but i have a little to no AC output from the SEN i/v stage on that channel (balanced setup, so both these regs are to same channel on each phase) - and i get more distortion also. The other channel works fine!
So, i swapped out the IRF's and the MJE's for new ones, but now i seem to have the same problem still! Is there anything else that could have been damaged in the reg because of this?
What could have happened to your SEN if the rail voltage reached reg DCIN level during the error period? Was it connected as a load?
I tried to swap the PSU's, and the problem follows the PSU's.
Plus i have two SEN-boards - and tested both, which give same problem.
So i have gotten to the point where the problem has to be with the SSLV's.
When i measure the boards with multimeter it seems fine... but could any of the small fets in the shunt-part gotten any damage?
Plus i have two SEN-boards - and tested both, which give same problem.
So i have gotten to the point where the problem has to be with the SSLV's.
When i measure the boards with multimeter it seems fine... but could any of the small fets in the shunt-part gotten any damage?
The BC transistor and the two small fets around its circuit could. See for 0.6V vbe for the BC when powered on and no shorts across fets D-S when powered down.
Gos increases with Id.... So one way to speed the ccs Vref would be to use higher currents right ?
If the bias current is the same between JFET types and the filter capacitance across is the same, then the rate of climb is the same. Higher bias current means faster charging to a plateau. Lower Gos JFET translates to higher output impedance type. Such a JFET will have less drift until settling and will be faster to do that. Also running lower Id means less relative Gos. Some types have an optimum Id-Vgs zero tempco point. Those are usually the lower Gos and somewhat higher noise ones.
Changed the Q105/Q104 to new ones. One of the regs seems fine - the other gives ~15v vbe on the BC550. What can cause this? shouldn't be the transistor (thinking its a new one)?
I actually measured again, and double checked the pinout of the transistors, and found that i measured wrong pins. This is with homebrew pcb's, i actually think the problem may have been a bad isolator pads between the heatsink and the TO220 units. I have put them back now, measuring the resistance between the To220's and the sing (which is grounded to chassis) to make shure no shorts there.
If i have time tomorrow i'll take a listen to see if it works this time.
I'd like to try a high value resistor/foil capacitor for the Vref chain. Judging from the topic, it was done 5 years ago. For this, I have to decrease the current passing through the Vref chain in order to use, say 50k resistor and a 1uF capacitor.
For 8,5Vref, I need 170uA. I must tweak it with a resistor from the gate to the source of Q103, right?
I also replaced the 47uF elna silmic by a Zobel of 4,7uF and 1,5R... I had only 1,5R hanging around. 🙁
Also, could a LED only Vref work, without bypass capacitor? Any dangers of oscillations?
For 8,5Vref, I need 170uA. I must tweak it with a resistor from the gate to the source of Q103, right?
I also replaced the 47uF elna silmic by a Zobel of 4,7uF and 1,5R... I had only 1,5R hanging around. 🙁
Also, could a LED only Vref work, without bypass capacitor? Any dangers of oscillations?
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I'm very angry. The regulator has become somewhat unstable with my Vref resistive circuit. 😡
My first try was in the morning. I put a 100k trimer for Vref and another 100k between the gate and source of Q103. I set Vref to 60k4 because I had this value of fixed resistor. Then I set the Q103 trimmer until I got 8,5V output on the reg.
I then removed the trimer, measured its value and put a fixed resistor (approx 2,9k) it was, turned the regulator on and surprise! The output was no longer 8,5V, but 13V.
The trimer was faulty, I thought. I then tried to stack resistors until I got the output to 8,5V again. It was still unstable. Sometimes it jumped to 11V.
In the afternoon, I tried putting a 86k6 Vref resistor. I then increased the GS resistor to 6,4k to get 8,5V. It seemed stable after multiple turn ons and varying the dummy load. I then assembled my DAC and what to see? - 10,6V on the output. 😡
I don't have my oscilloscope and cannot observe waveforms, so my hands are tied. I can't understand what is happening. The Vref is bypassed by 1uF Philips MKC capacitor. The output is 4,7uF/1,5R Zobel.
My first try was in the morning. I put a 100k trimer for Vref and another 100k between the gate and source of Q103. I set Vref to 60k4 because I had this value of fixed resistor. Then I set the Q103 trimmer until I got 8,5V output on the reg.
I then removed the trimer, measured its value and put a fixed resistor (approx 2,9k) it was, turned the regulator on and surprise! The output was no longer 8,5V, but 13V.
The trimer was faulty, I thought. I then tried to stack resistors until I got the output to 8,5V again. It was still unstable. Sometimes it jumped to 11V.
In the afternoon, I tried putting a 86k6 Vref resistor. I then increased the GS resistor to 6,4k to get 8,5V. It seemed stable after multiple turn ons and varying the dummy load. I then assembled my DAC and what to see? - 10,6V on the output. 😡
I don't have my oscilloscope and cannot observe waveforms, so my hands are tied. I can't understand what is happening. The Vref is bypassed by 1uF Philips MKC capacitor. The output is 4,7uF/1,5R Zobel.
I had used up to 47K ref resistor in the past with no funny results. Do you ground the gate of Q103?
The Q103 is not removed from the board. Only the source leg is cut from the board and a resistor is soldered between it and the drain.
Do you recommend of lowering the Vref resistor value?
Do you recommend of lowering the Vref resistor value?
The Id control resistor must be between source pin and sense (0). The Vref array should be between drain and sense (+).
I recommend you lower the Rref value since Bib uses 117GR, not 170BL like in those older stable experiments, so you may used too little Id entering unstable territory.
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