mumek
Member
lol If you have that power, yes, it should be pretty simple. Otherwise, I’ll give ya the part numbers for the ones I went with, when I get home.It would be reasonably simple to wind a new transformer, I guess?
lol If you have that power, yes, it should be pretty simple. Otherwise, I’ll give ya the part numbers for the ones I went with, when I get home.It would be reasonably simple to wind a new transformer, I guess?
First off, download a copy of the service manual and schematics, refer to the page on the power supply circuit, read up on VFD driver circuits. Replace all the electrolytic capacitors in the entire power supply. Next, remove the ceramic capacitor between the 35v windings of the small display transformer, it's marked C9 on the board. Next, if your display transformer is not visibly torched to death and crumbling apart, test the windings with a multimeter on continuity. If any of the windings don't pass the beep test, or if the ohm reading for either secondary winding is higher than 100ohms, your transformer is toast. If all the windings test good, replace C9 with a solid quality ceramic or film capacitor with a voltage rating of at least 100v. If one of the windings tests bad, you will have to replace the transformer with two transformers, unless you can wind your own from scratch or rewind the original on new bobbins. I used a Triad Magnetics F36-65 for the center-tapped 36VAC winding, and a Triad Magnetics FS12-090 with the primary winding wired in series to produce as close to 6VAC as I could get. It would up being just under 5VAC. This is not ideal, but I couldn't find any other transformer in my country that would fit inside the 300, alongside another transformer, that produced the right voltage. Do not excede 7VAC for filament winding or you might burn out the VFD. You may want to change diodes CR8 and CR9 in the path of the 35v winding to a diode with a lower voltage drop to get closer to 35VDC. Do not hook the wiring header that feeds the display board from the power supply board to the display board first time you power your 300 back on. Test the voltages coming from whatever solution you try before hooking the display wiring back up to make sure you're getting at least 30VDC and 4.5VAC respectively. The original .06A fuse feeding into the display power circuit should still be fine for this new solution, but if it blows, replace it with no higher than a .1A fuse.I would like to have these instructions too please!
Hell yeah, looks great Was the original x4mr completely Kentucky fried?Hera are some pictures
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