VA7DVR via EV wrote:
I have mine apart presently, parts arrived but I have not had time to tackle it. http://divemaster.ca/kubvans/EV1/Controller%20mosfets%20sm.jpg I have been using this drawing, http://divemaster.ca/kubvans/EV1/curtis_1221b_schematic.pdf
This is the schematic for the Curtis 1221B, reverse-engineered by Otmar Ebenhoech and drawn by Rich Rudman back around 1995. The logic board is essentially the same as the 1231B.
The 1221C and 1231C logic boards had a number of part value changes. The 1231B and 1231C had a different power board, and a bigger case.
Regarding parts, I found a tube of IXTH50N20 on ebay to do my rebuild I have been unable to find a source for the diodes. I am planning on replacing the mosfets removing the damaged diodes.
If you replace any MOSFET or diode, you should replace *all* of them. Since they are directly in parallel, they all need to have the same on-state voltage drop. Otherwise, whichever one is lower will "hog" the current, run hotter, and burn up sooner.
Some one mentioned mounting the diodes externally not sure if that would provide the same protection.
That's a bad idea. You need the MOSFET-diode-capacitor loop to be as short as possible, or voltage spikes get worse.
Happy to hear from anyone else that found an available diode or an external solution.
Jay Summit found a Diotec diode that appears to be a correct replacement. See diotec.com and search for "tab mount" rectifiers. Their MR2406FR, DR3506FR, and DR7506FR appear to be drop-in replacements if you get the "R" reverse-lead option.
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