Ok so I am going to try the mosfet power supply mod to a scrap Dynaco st120. I know the amp is more or less garbage but it is cheap and fun to work with. I have tried many times with this power supply upgrade but keep falling short on regulated voltage. I have checked and re-checked a dozen times the circuit and have found small errors and fixed. My voltage is to low, about 58v on cap 12 when I should have about 70v or so. The control zenner is fine but I changed it just to be sure a couple times. I have also changed the FET a couple times with the same result. This is what I have that is not working, any advice would be nice. I am having problems finding a sub for a 2SK135 and that is why I used the IRF241 and it has a nice TO3 case that I like.
FET used IRF241 which should work right?
Now I admit I cheeped out on the rectifiers and used NTE components, could this be a cause?. They are NTE588 a 200v/3a ultra fast and should work perfect.
I think my entire problem lies with the FET being used which on paper should fit nice but in reality is not giving me the regulated voltage I need.
FET used IRF241 which should work right?
Now I admit I cheeped out on the rectifiers and used NTE components, could this be a cause?. They are NTE588 a 200v/3a ultra fast and should work perfect.
I think my entire problem lies with the FET being used which on paper should fit nice but in reality is not giving me the regulated voltage I need.
An externally hosted image should be here but it was not working when we last tested it.
SA-12 said:yeah, figured that out with destroyed fet number one , I think I have pinout right. I downloaded the spec for this fet and pinout was clearly shown. I had it wrong at first. When i had pins reversed I was getting 98vdc on cap 12.
In the 2SK135 the case is the source, In the IRF the case is the drain...
SA-12 said:ok so turns out the first way I had it was right, and I got 98v on cap 12, zenner is good. 1n4760. what am I doing wrong
The Mosfet is shorted (burned)...
Inspect again the pins layout.
The pins position is the same of this one:
http://pdf1.alldatasheet.com/datasheet-pdf/view/67474/INTERSIL/IRF244.html
The pins position is the same of this one:
http://pdf1.alldatasheet.com/datasheet-pdf/view/67474/INTERSIL/IRF244.html
yep that the pinout I used all along, still get 98v on cap 12. I have to check some other component values but I am sure it is all right. I might have to make my own pcb as I just can't trust the original pcb even though I checked it now about 5-6 times to make sure I got it right. To many traces not being used it is a little confusing.
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.
- Home
- Design & Build
- Parts
- fet help please 2SK135