Looking at some schematics and I've just confused myself.
The Gtose/MJ cap mx has a BD139 and a 2sc5200 on the positive rail.
On the XRK SLB we see a BD139 but the 2SA1943 on the positive. Can anyone clarify that for me please.?! Seems strange to me that there is a transposition of device polarity.
The Gtose/MJ cap mx has a BD139 and a 2sc5200 on the positive rail.
On the XRK SLB we see a BD139 but the 2SA1943 on the positive. Can anyone clarify that for me please.?! Seems strange to me that there is a transposition of device polarity.
Thanks for that prompt reply X. I was referring to this Capmx schematic back in this thread.
https://www.diyaudio.com/community/...sy-capacitance-multiplier.297921/post-5510507
https://www.diyaudio.com/community/...sy-capacitance-multiplier.297921/post-5510507
That is an excellent Cap Mx. I'm using two in a M2 clone and it is dead quiet.
The Darlington version in post #497 is quite a bit more resistant to instability / undesired oscillation. And if you connect its intermediate bias resistor "R4" to the rail instead of the output, it responds a lot faster to an immediate step-down of output current (Iout switches from 95% to 5% of max load, in 2usec).
Neither do I, but thanks Mark - they work very well as Skylar88 says. I also use two of these for running my awesome sounding Alpha Nirvana amp dual mono.
The schematic in post 3497 is reproduced here. R4 connects the base to the Ground.
Can you please clarify your statement on R4?
T
I've built a couple up and tested this afternoon. One of the rails out of the 4 won't trim. It remains at the full available voltage despite manic twirling of the trimmer resistor. Only on this one. I've noticed the pot won't 'click' at either end of its travel so I assume I have a bad pot.?
Or are there other issues that would portray this behaviour?
Update....found a short on the bd140 soldering....my bad. All good now ! Didn't hurt anything...solder cleaned up and it works as it should .
Or are there other issues that would portray this behaviour?
Update....found a short on the bd140 soldering....my bad. All good now ! Didn't hurt anything...solder cleaned up and it works as it should .
Last edited:
Thanks jimk04 for the info, I do appreciate that!
I have five similar variants of Gtose/Johnson CapMxs and have today tested two of them on a couple 100W/22Ohm resistors. One of the rails couldn't trim too. Try to readjust other potentiometers because it seems that one of them is at the upper or lower limit.
I have tested them a bit harder at +/-36.2V until dummy load became too hot. Ripple was about 1.6VRMS. I intend to use two such separate power supplies for my AN.
Good luck
Last edited:
That circuit is not the subject of this thread. Maybe there is a dedicated thread elsewhere and you can ask there. Not sure how that Gtose/MJ circuit ended up here.
The point of a cap Mx is to minimize the need for bulk capacitance. 35,000uF is a very large one. You need to smooth the rectifier ripple to a certain extent but it depends on your load (current draw). Low ESR is not needed or desired. You want high ripple current rated caps there as low ESR will cause a high charging current and more than necessary heating of the cap.
The point of a cap Mx is to minimize the need for bulk capacitance. 35,000uF is a very large one. You need to smooth the rectifier ripple to a certain extent but it depends on your load (current draw). Low ESR is not needed or desired. You want high ripple current rated caps there as low ESR will cause a high charging current and more than necessary heating of the cap.
Can Use 42 -0-42 V Transformor for Gtose/ Johnson capMx,please suggest any parts changes.
Perhaps because you discussed it here, in this thread, when you copy/pasted the schematic into (post #49). Then later, member @gtose published his PCB layout for it here, in this thread, in post #477 .
Also of possible interest are posts # 35 and # 36 in this thread.
.
As a reminder , in these cap multiplier circuits , the large electrolytic cap before Bi polars or MOSFET takes the brunt of the ripple .
P = I^2 * ESR , so suggest selecting a cap that is designed with a low ESR , and can handle the ripple .
With the circuit Mark , Prasi and XrK971 have been discussing , Post #607 , this would be C2 and C6 = 35KuF .
For the darlington set up in post #607
Vout = Vin * ( voltage divider set up by R2 , the trimmer and R3 ) - Vbe1 - Vbe2
A softer start has been discussed . Increasing C4 and C8 will give the circuit a softer start .
As mentioned , suggest by passing C4 and C8 with something like 10nF .
IMO the Sprague Orange drop 716p is very good in this application.
.
As a reminder , in these cap multiplier circuits , the large electrolytic cap before Bi polars or MOSFET takes the brunt of the ripple .
P = I^2 * ESR , so suggest selecting a cap that is designed with a low ESR , and can handle the ripple .
With the circuit Mark , Prasi and XrK971 have been discussing , Post #607 , this would be C2 and C6 = 35KuF .
For the darlington set up in post #607
Vout = Vin * ( voltage divider set up by R2 , the trimmer and R3 ) - Vbe1 - Vbe2
A softer start has been discussed . Increasing C4 and C8 will give the circuit a softer start .
As mentioned , suggest by passing C4 and C8 with something like 10nF .
IMO the Sprague Orange drop 716p is very good in this application.
.