That diode at 702 was just bent really sloppy. I haven’t had much time to do much with it this week but I did remove the 4 diodes at the bridge and test with a meter and they all appeared fine. Straightened that bent one and put them back on. The print on them was really faint and not much to...
Thanks Andy for more suggestions. I appreciate your interest. I didn’t have time to mess with it today but I have to resolder the Vhold pot back on and re-assemble everything, and first thing I’ll do is turn the brightness up until I see raster and I’ll let you know if there are variations in...
Thanks for your reply Andy. I haven’t touched the B+. The rheostat says 502 on it so that’s 5K. I have some different style 502s here that all test 4.8, 4.9. When I test the one on the board in circuit it starts at .25 and slowly keeps rising. It will clearly have to be removed to be tested...
I looked at the Vhold pot and the contrast and brightness pots as well. They have the values printed on them and they are all different, so borrowing from Peter is out. The contrast is 1K, brightness is 100K and Vhold is 50K. I tested them in circuit with a multimeter and the contrast and...
Here's a pic if the main board and the neck board. As I said in my original post, I have replaced the electrolytic capacitors on both the main board as well as the one on the neck board. ALL transistors were removed and tested including the two on the neck board and all tested good.. The only...
I came into possession of a really nice BMC monochrome monitor model BM-1200SU (circa 1981) that has some issues. I've looked extensively for any documentation on this monitor and not a mention of this model anywhere. The issue is the video has a constant vertical scroll that the VHOLD won't...
Thanks for your reply Patrick. I should have looked at the other side of the tube before I buttoned it up. These are the others pictures I took. I do get video and I took a short video of what it was doing but I can’t seem to upload the video file.
Good evening fellow enthusiasts,
I recently took possession of a 1981 BMC international monochrome monitor model BM-1200SU. Could anyone direct me to where I can find any schematic or servicing manual for this monitor. I’d post a pic of the monitor but the cover is off at the moment.
Thanks in...
The drive only cost me $25 so not a great loss there. lesson learned. Stay away from Mitsumi. Wish I read that a week earlier. Oh well move forward.
Thanks again for the replies and help.
I just tested the coils on the head and I get no reading on anything I coil to the red wire. Labeled 5. The other 3 show good readings between them. Only the red #5 is dead. The head is clearly bad. So it looks like this problem is very common with these Mitsumi drives and why people say stay...
Thanks everyone for your responses. I did hear to stay away from the Mitsumi drives. only after the fact of buying this one. I will test the coils on the head today. I connected the drive to a C64 last night and the drive wasn't able to read a good disk. I was able to load "1541 Diagnostics"...