Recent content by bburley

It is possible that the TDA3653 Vertical IC could be going bad as it warms up. I used to use a can of "Freeze Spray" to cool down parts to see if the temperature change would affect the problem. https://www.crcindustries.ca/crc-freeze-spray-283g/

A good tip is that you can download datasheets for each I.C. number that the monitor uses. That will quickly explain the function of each I.C. Using the datasheet makes it obvious that pin 5 is the main output and that the vertical deflection yoke is the part marked as "Part of AT1201"

Looks like for testing power supplies (to get them to turn on). But not sure if the pins are in the right place.

I would think it would be ok to leave it set just high enough to be able to see what is on the screen for now. I am not sure if it is stable or if it will change again if additional repairs are done. It the raster collapses to a single horizontal line, that means that you are losing vertical...

Transistor 7512 seems to be functioning because if it wasn't driving the flyback you still wouldn't have the -27V. The G2 voltage is low, should be about 370V. Perhaps the G2 adjustment was fiddled with while it wasn't working. Turn it up to see if anything shows on the screen, if nothing...

I may look at that later. I will stick to decoding more tapes for now. As soon as it warms up a bit more my computer activity will reduce a lot until fall.

One more tip that I can add. Once the recording level and EQ settings are worked out, the single most important Tuning adjustment is the DC Offset. Using the "Debug" function should be avoided. Instead start a fresh run with each Tuning or DC Offset setting and check the end of the log for the...

I have been playing with every setting imaginable trying to decode TI-99/4A cassette tapes with CS1er with dismal results until I finally learned a few things and started to get excellent results. I thought I would share some of those tips here. For the initial recording, playback from a Mono...

This is the area that can have the most problems related to loss of drive for the flyback. You can carefully re-check components and connections/traces in this area. After that, you will be at a serious disadvantage without a scope.

This one? https://archive.org/details/MaintenanceManualForModel810Printer

If the 27V is missing because the flyback is not operating or is not being driven, you should also be missing the G2 voltage (370V) that appears on pin 7 of the CRT. Do you have any voltage there?

The waveform from pin 2 (Collector) looks low. It should look closer to this; I would have expected to see a smaller 31KHz waveform on the base of Q312 coming from the driver transformer, but it doesn't seem to be there or your scope probe connections are not right or something caused the...

After I thought of tossing it, I at least should look inside. I guess that blob (of epoxy?) is saying "so you want to reverse engineer it, do you?"

Reminded me that I had a stray dongle stashed for a long time. Now that I have dug it out, I don't see any reason to keep it. If anyone wants it for the cost of postage, let me know before I toss it.

I have converted MANUAL.EXE and REFMAN.EXE into PDF for the fun of it, although it doesn't look like there is any hardware manual on that CD.