HunterZero Posted May 4, 2014 Share Posted May 4, 2014 Hey people, My Intellivision has a slightly dark rolling bar that creeps down the screen. PSU voltages check ok. Sometimes the problem disappears after resetting. Wondering if I have a ground issue somewhere? The shielding isn't soldered on, it is just placed back on, but the bar is still there if I run it with the shield removed. Checked around the edge of the board for continuity to ground and it seems ok. Might replace the PSU caps. Any other ideas? Quote Link to comment Share on other sites More sharing options...
intvnut Posted May 4, 2014 Share Posted May 4, 2014 (edited) Does your +12v line check out OK? That's what provides power to the RF modulator, although the RF mod itself re-regulates that to +5v locally with a zener diode. In general, it could be a little too much supply ripple making its way into the circuit. As I recall, the resistor ladder that generates the RF comes off the main logic board's +5v rail, so it too could be the issue. Edited May 4, 2014 by intvnut Quote Link to comment Share on other sites More sharing options...
HunterZero Posted May 6, 2014 Author Share Posted May 6, 2014 Yes all voltages seemed to check out - can't remember the exact values. Can recheck if it's important. What are the best test points to use? I've been checking the 5 pins against the rear pin on the 2 pin connector. - James Quote Link to comment Share on other sites More sharing options...
intvnut Posted May 6, 2014 Share Posted May 6, 2014 I honestly don't know what would be an "optimal" point for checking the +5v. If there's any sort of ripple in the +5v, I doubt it would show on a DVM / DMM anyway. You'd need a scope to see it. The video signal itself is generated by the AY-3-8915, so checking its +5v input (on pins 13, 16, 17 if I read the schematic correctly) might be a good starting point. Also, the schematic scan I have suggests that the voltage on the DC input to the RF modulator should be about 6.3v. You can download the entire service manual I have scans for here: http://spatula-city.org/~im14u2c/intv/dl/intmasrv.zip Quote Link to comment Share on other sites More sharing options...
HunterZero Posted May 6, 2014 Author Share Posted May 6, 2014 I am still wondering if there's some sort of ground issue around the RF module. This is a PAL unit. Quote Link to comment Share on other sites More sharing options...
HunterZero Posted May 15, 2014 Author Share Posted May 15, 2014 Rebuilt it, did some panel beating on the logic board shroud, checked all the connections, powered it up - rolling bar gone, picture rock solid. I reckon there was some dodgy connection in there. - James 1 Quote Link to comment Share on other sites More sharing options...
+intvsteve Posted May 15, 2014 Share Posted May 15, 2014 Awesome! Quote Link to comment Share on other sites More sharing options...
HunterZero Posted May 20, 2014 Author Share Posted May 20, 2014 OK this console is possessed. It's cursed. Read, it has a problem. For history, this is the same problematic console from here: http://atariage.com/forums/topic/207602-because-we-all-love-troubleshooting-intellivisions/ For a while, it was working perfectly. Recently, the console has started blackscreening and won't start the game (even after pressing reset), or the title comes up then the game crashes to black screen within a second or two. Here's the weird bit. If I take the console apart and put it back together, then it usually works again. So I am thinking I have a bad joint or trace somewhere. At one point it was running, but AD&D crashed when starting the game, and in Thin Ice, the sprite collision wasn't working, implying bad STIC! I've already replaced the sound chip and SRAM chip in this thing... Plus the rolling bar tends to come and go, and sometimes the speed of the rolling slows down. Holding reset for a second or two longer can sometimes get rid of the rolling bar. Took some power supply readings: + 5 VDC --+ | |_| | 4.98V+ 12 VDC --+ | |_| | 12.30V+ 16 VDC --+ | |_| | 23.10V (23.54V) (unregulated)+ 0 VDC --+ | |_| | Falls quickly to about 1V then slowly to 0.1V- 2 VDC --+ |_|_|_| -2.166V (-2.143V) Although these look to be in tolerances, I am thinking about rebuilding the power supply board anyway, replacing the regulators and capacitors. I don't have another power supply board to swap in unfortunately. I've replaced the ribbon cable with pin headers and a proper cable. I do have an Intv System III, but it hasn't had the power supply header mod done. Checked the ground trace around the board and it seems to be fine. I have spares of all logic chips to swap in, except for STIC and SRAM. - James Quote Link to comment Share on other sites More sharing options...
HunterZero Posted May 20, 2014 Author Share Posted May 20, 2014 I am wondering if it's an issue with the blue wire that goes from the power board to just near the STIC - I might resolder that... Quote Link to comment Share on other sites More sharing options...
HunterZero Posted May 20, 2014 Author Share Posted May 20, 2014 And can someone pls confirm that's how the power supply is meant to behave? In particular, pins 3 and 4, the 16V and 0V lines. Quote Link to comment Share on other sites More sharing options...
HunterZero Posted May 21, 2014 Author Share Posted May 21, 2014 Awesome! Any tips? Quote Link to comment Share on other sites More sharing options...
HunterZero Posted May 27, 2014 Author Share Posted May 27, 2014 Bump. Anyone able to confirm how the voltages are meant to behave? Looks like the voltage regulators are fine. Quote Link to comment Share on other sites More sharing options...
HunterZero Posted June 16, 2014 Author Share Posted June 16, 2014 (edited) The console works again, the black screen and collision detection problem seems to have been due to a bad connection with the 2 pin single wire. However the rolling bar is still there. Can someone confirm the power voltages are right? Edited June 16, 2014 by HunterZero Quote Link to comment Share on other sites More sharing options...
fabulous_Muller Posted June 22, 2014 Share Posted June 22, 2014 H0, Checked my spare bad unit (but the psu is fine) and got almost the same voltages. Just 24,1V on pin 3 ( or whatever n. it takes) which is the unregulated + 16V and 0V on 0v pin. 0V and does not have any single variation. Remebering that all meausures were done with flat and blue STIC removed, pls confirm if you are removing them. This 1V variations on 0v pin seems a little strange... Quote Link to comment Share on other sites More sharing options...
HunterZero Posted June 23, 2014 Author Share Posted June 23, 2014 Thanks for the reply. Yes this is with the ribbon and blue cable disconnected. The weird bit is the 0v line. It looks like it is reading a capacitor discharging. Quote Link to comment Share on other sites More sharing options...
HunterZero Posted August 4, 2014 Author Share Posted August 4, 2014 Noticed that the 7812 regulator gets very hot, too hot to touch. Suspect that has an issue. I have all the parts to shotgun the power board, since the electronics are 30+ years old I may just go that route. Quote Link to comment Share on other sites More sharing options...
HunterZero Posted October 10, 2014 Author Share Posted October 10, 2014 (edited) Forgot to update this - Fixed it. Replaced the power supply electrolytics and regulators on the power supply board. It's now rock solid, rolling bar is gone. - James Edited October 10, 2014 by HunterZero 2 Quote Link to comment Share on other sites More sharing options...
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