- The LaST Upgrade -

PART 30 - STFM VIDEO SYNC FIX

Last updated March 21, 2019

 

It seems to be a common problem in recent years of the STFM not being able to sync correctly on a TV or monitor. I have seen several machines over the past couple of years suffering with this problem and it took a while to track down. A example of this sync issue normally arises upon boot where the white background is flashing all sorts of crazy black, but this can also happen on the desktop but seems less common. A example of this video sync issues can be found HERE. Some discussion about this was also done on the forum HERE.

There seems to be 2 issues at work here. First that the electrolytic capacitors have finally failed causing a lot of issues, but also modern TV's do not like the "not very standard" voltages and timings the STFM puts out. It has been found that even the tolerances on some resistors in the video circuit can make or break a machine. So here is my current research on this video issue and what seems to have solved the issue.

If anyone has this issue, please take a video, try the fix and let me know if it solves your problem.

 

There are a few capacitor values, 10uF x3 ,1uF (replace with 2.2uf) , 33uF (replaced with 47uf) , 100uF x3, 470uF. These should be updated with low ESR values

Once that is done, its possible the sync may not be perfect or result in a black flashing bar at the top of the screen. In this case solder a 2.7K resistor between pins 8 & 15. This may increase the brightness a fraction on the colours also.

STORE LINK

https://www.exxoshost.co.uk/atari/last/storenew/#0068

 

INSTALL INFO

Values are pretty much the same as before (I used values I already had in stock so no huge reason why some values differ).

KIT CONTAINS

10uf x3
2.2uf x 1 (replaces 1uf) NOTE 1uF may be supplied in some kits.
47uF x1 (replaces 33uf)
100uF x3
470uf x1
2.7K resistor x1

 

 

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