Ok I think I may have found a solution, hope I don't get into trouble posting it.
Do not folow directions by Frank Van Alstine to reuse the original board as posted in his back issues. For some reason I could not get this simple circuit to work after no less than 10-20 times over 2 years. I decided to make a jig today with coathangers and do a logical build mimicking the schematic exactly as posted above. You should see my bench with this ugly thing. This point to point circuit looks exactly like the schematic above all point to point. I got 66 volts on cap 12 when I did this, and I also had lots of crapy solder conections, aligator clips on all pins of the fet and long runs of wire and coat hanger
. I also used caps that were 20 years old or better.
after I tighten things up with new caps and a small board I make I bet I will get 68-70 volts, 66 will run the amp though with no problems. The original supply was only putting out a little more on a good day anyway.
The problem I think lies with trying to use the existing board from the original supply. Now that I know it works I can put this one to bed. Man it has been a rough go with this one, glad it's over.
Do not folow directions by Frank Van Alstine to reuse the original board as posted in his back issues. For some reason I could not get this simple circuit to work after no less than 10-20 times over 2 years. I decided to make a jig today with coathangers and do a logical build mimicking the schematic exactly as posted above. You should see my bench with this ugly thing. This point to point circuit looks exactly like the schematic above all point to point. I got 66 volts on cap 12 when I did this, and I also had lots of crapy solder conections, aligator clips on all pins of the fet and long runs of wire and coat hanger
. I also used caps that were 20 years old or better. after I tighten things up with new caps and a small board I make I bet I will get 68-70 volts, 66 will run the amp though with no problems. The original supply was only putting out a little more on a good day anyway.
The problem I think lies with trying to use the existing board from the original supply. Now that I know it works I can put this one to bed. Man it has been a rough go with this one, glad it's over.
how did you make out with this??
i'm currently working on one as well and using the same mosfet as you did <IRF241>
whats the deal with the pinout? im assuming i need to wire differently than the instructions.....
which way should i wire it?
i'm kind of new at this and don't understand "drain" etc....
thanx
scott
i'm currently working on one as well and using the same mosfet as you did <IRF241>
whats the deal with the pinout? im assuming i need to wire differently than the instructions.....
which way should i wire it?
i'm kind of new at this and don't understand "drain" etc....
thanx
scott
the Sk135 is a Lateral FET.
The irf24x are Vertical FETs.
The plastic package To247 Lfet are always GSD from left to right.
Vfet are always GDS from left to right.
In To3 package the Middle pin becomes the case. That is the big change.
The Lfet will have a much lower Vgs at low output current. But at high output current the Vgs will be similar to the Vfet substitute, i.e. the output voltage will fall as the output current rises.
Where is the 475r gate resistor located?
It might not be on the PCB.
It could be soldered direct to the gate pin of the Lfet.
The irf24x are Vertical FETs.
The plastic package To247 Lfet are always GSD from left to right.
Vfet are always GDS from left to right.
In To3 package the Middle pin becomes the case. That is the big change.
The Lfet will have a much lower Vgs at low output current. But at high output current the Vgs will be similar to the Vfet substitute, i.e. the output voltage will fall as the output current rises.
Where is the 475r gate resistor located?
It might not be on the PCB.
It could be soldered direct to the gate pin of the Lfet.
ok thanx for the help both of you guys.........
according to the info i have the "gate" resistor is suspended BETWEEN the PCB and the heat sink
heres a audio basics issue in PDF that gives detailed instructions
http://www.davidreaton.com/Dyna120/Dyna_120.pdfDF
i havent even looked at mine in a few days as i have some other projects going on as well and we are getting into motorcycle season but when i do mine i believe i am going to "breadboard" it with point to point wiring to avoid any issues
scott
according to the info i have the "gate" resistor is suspended BETWEEN the PCB and the heat sink
heres a audio basics issue in PDF that gives detailed instructions
http://www.davidreaton.com/Dyna120/Dyna_120.pdfDF
i havent even looked at mine in a few days as i have some other projects going on as well and we are getting into motorcycle season but when i do mine i believe i am going to "breadboard" it with point to point wiring to avoid any issues
scott
I have tried all the tricks like short leads ect, ect. If it works for you I would be surprised. I wonder if board revisions might have changed some traces. I bet you get 58v on cap 12 when you are done, or 98v on cap 12 do tell please. Keep in mind the circuit is so simple, very easy to make your own board without all the clutter on the dyna board.
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