elemenoh Posted May 10, 2020 Report Share Posted May 10, 2020 This MLB doesn't chime or display any video. A working MLB in the same enclosure works okay. It was recapped and reworked by Uniserver last year but didn't work when I got it back. The following has been done so far: Swap tested with known good parts: ROM Processor (it's socketed on this board and I had another working one also socketed) PALs RAM Replaced: UE8 UD8 Tested power and ground pins at ROM, UD1, UI2, UI3, UI4, UJ2, UJ3, UJ4, UK8, UK11, UK12 Tested all other pins in the video interface. The transistors at D1/D2 had been reworked and I haven't touched them yet. Would anything in that area cause this symptom? Any other suggestions for what to try next? Quote Link to post Share on other sites
dochilli Posted May 11, 2020 Report Share Posted May 11, 2020 (edited) First I would check J12. Perhaps there are broken solderpoints. Reflow the solder of J12. Perhaps you can check if there are the right voltages at the connector. Have you tried to press the reset button after the mac was switched on? Edited May 11, 2020 by dochilli Quote Link to post Share on other sites
elemenoh Posted May 11, 2020 Author Report Share Posted May 11, 2020 Quote First I would check J12. Perhaps there are broken solderpoints. Reflow the solder of J12. Perhaps you can check if there are the right voltages at the connector. Have you tried to press the reset button after the mac was switched on? I will try reflowing J12, but I was probing to it when testing power and ground on the ICs. I did try hitting reset and could hear a very slight blip (not chime) from the speaker, but no other activity. I checked the traces under C2 in case the reset line was broken, but I think it's okay. If there are specific points I should test, please let me know. Quote Link to post Share on other sites
elemenoh Posted May 12, 2020 Author Report Share Posted May 12, 2020 Reflowing J12 did not change the symptom unfortunately. Quote Link to post Share on other sites
dochilli Posted May 12, 2020 Report Share Posted May 12, 2020 (edited) Did you check that you can measure the right voltages at J12? Here are the schematics: Edited May 12, 2020 by dochilli Quote Link to post Share on other sites
elemenoh Posted May 17, 2020 Author Report Share Posted May 17, 2020 (edited) Pin 6: -5.8V Pin 7: -13.38V Pin 9: 0.34V (Composite Video) Pin 10: 0.327 (HSYNC) Pin 11: 0.257 (VSYNC) Pin 12-13: 5.5V Pin 14: 13.8V Though the rails seem high, 5 other boards work okay attached to this analog board/PSU. EDIT: On a couple of working boards I get the following values: Pin 10 HSYNC: 3.9-4.0V Pin 11 VSYNC: 2.5-2.6V EDIT2: It has those low values at the PALs too: So far tested UE7 pin 3, UG6 pin 14, UG7 pin 13, UI6 pins 4,18. What would be a common culprit on the MLB for not getting good voltage on those pins? Edited May 17, 2020 by elemenoh Quote Link to post Share on other sites
elemenoh Posted May 17, 2020 Author Report Share Posted May 17, 2020 Also replaced UA8, UB8 and UC8, but the symptom didn't change. Quote Link to post Share on other sites
elemenoh Posted May 17, 2020 Author Report Share Posted May 17, 2020 Also tested on the bottom of the board: R20: 1.2kΩ R21: 48Ω R22: 48.6Ω R24: 73Ω C40 couldn't be read with my ESR meter, but the same goes on a known good board. Continuity is okay from the connector through the passives and UG6/UG7. Quote Link to post Share on other sites
Bolle Posted May 19, 2020 Report Share Posted May 19, 2020 Check the main reset line, it should be at 5V. Does your multimeter have a mode to measure frequencies or do you have a scope to check the Hsync and Vsync pins on J12? No sync output is often caused by a bad counter at UF8 and/or UG8. Quote Link to post Share on other sites
elemenoh Posted May 19, 2020 Author Report Share Posted May 19, 2020 (edited) Not sure I'm measuring correctly. I put the red probe on pin 10 or 11 and the other to ground. I get 0Hz on either pin when doing that. Edited May 19, 2020 by elemenoh Quote Link to post Share on other sites
elemenoh Posted May 19, 2020 Author Report Share Posted May 19, 2020 (edited) I replaced UF8 and UG8 and now get video! It's simasimac, so still more troubleshooting to go, but making progress. Thanks @Bolle!! BTW if it's helpful for others, I'm getting the following values at J12 after replacing those binary counters: Pin 10 (HSYNC): 22.24Hz / 2.7V Pin 11 (VSYNC): 59.80Hz / 4.28V Edited May 19, 2020 by elemenoh Quote Link to post Share on other sites
marcelv Posted May 20, 2020 Report Share Posted May 20, 2020 Know you already checked the connections in the video interface, but could you check these again? Quote Link to post Share on other sites
elemenoh Posted May 20, 2020 Author Report Share Posted May 20, 2020 @marcelv Thanks for the cheat sheet. I tested all of these again including their respective address lines at ROM, GLUE, VIA, SWIM Serial and Sound. All checked out okay. Last night I did the same for UA8 and UB8. I did just find that A11 was broken at UI3. I patched that but still get samasimac. All other connections for UC8 are okay. BTW, you have a typo in your sheet. UD8 Pin 7 goes to UC6 (not UC8) pin 17. Also FWIW, I checked reset at pin 7 of UI12 and got +5V. And the button seems to work okay. The screen will go blank when pressed and then back to samasimac when released. Quote Link to post Share on other sites
Bolle Posted May 21, 2020 Report Share Posted May 21, 2020 (edited) So just to recap, what’s happening exactly when you turn ob the board in the current state? No chime and static screen? Got a photo of what it’s displaying? This usually gives a hint about what’s wrong. Edited May 21, 2020 by Bolle Quote Link to post Share on other sites
elemenoh Posted May 21, 2020 Author Report Share Posted May 21, 2020 (edited) Quote So just to recap, what’s happening exactly when you turn ob the board in the current state? No chime and static screen? Got a photo of what it’s displaying? This usually gives a hint about what’s wrong. @Bolle The original symptom was no chime or video. I got video after replacing UF8 and UG8. Now I get no chime and just a static samasimac screen . A broken connection for A11 was patched, but the symptom did not change. I checked all the address lines again and couldn't find any other problems. I also rechecked all connections to UA8-UE8 and swap tested known-good PAL, RAM and ROM again. UA8,UB8,UC8,UD8,UE8,UF8,UG8 have all been replaced with new chips. Edited May 21, 2020 by elemenoh Quote Link to post Share on other sites
techknight Posted May 22, 2020 Report Share Posted May 22, 2020 Can you stick with the stock ROM please? Some SE/30 boards have trouble with those modern ROM SIMM replacements. Why I dont know, but it is a crapshoot. Quote Link to post Share on other sites
elemenoh Posted May 22, 2020 Author Report Share Posted May 22, 2020 Yep I did try with a known good stock ROM too but got the same result. Quote Link to post Share on other sites
techknight Posted May 22, 2020 Report Share Posted May 22, 2020 (edited) I figured you did, I just saw the picture and had a concern. Anyways the fact that you have no audio chime or anything legible on the screen tells me that system has a data/address bus issue somewhere. theres a break in a trace/via or there is a shorted over address or data line from the recap. Edited May 22, 2020 by techknight Quote Link to post Share on other sites
elemenoh Posted May 22, 2020 Author Report Share Posted May 22, 2020 I checked all of the data lines and did another inspection for solder blobs but didn't find anything wrong. After shuffling the socketed chips again it now gets a slow chime with samisimac pattern. All ram socket pins tested okay. So maybe I have one or more dead F258s? I ordered some from Mouser to be sure. If there's other stuff I should check, please let me know. Quote Link to post Share on other sites
techknight Posted May 22, 2020 Report Share Posted May 22, 2020 Make sure your RAM SIMMs are ok, and you have at least 4 matching SIMMS in stalled. Quote Link to post Share on other sites
elemenoh Posted May 22, 2020 Author Report Share Posted May 22, 2020 I triple checked and booted with another board OK. Moved its ROM and RAM to this board but get the same result. Slow chimes. Does replacing the F258's next make sense? Quote Link to post Share on other sites
Bolle Posted May 23, 2020 Report Share Posted May 23, 2020 (edited) Check all signals on the RAM sockets and trace them to their destination. Often you get broken traces around the resistor network next to C1. The RAS and CAS lines run through there - if one of those is broken you will get slow chimes. Sidenote: we should find and establish new names for the different faulty screen outputs. People use simasimac no matter what the screen is actually showing... no ROM stripes, broken data line grey screen with artifacts, different states of video logic failure... they are all different and usually give hints where to look first when hunting down the problem. Edited May 23, 2020 by Bolle Quote Link to post Share on other sites
desertrout Posted August 22, 2020 Report Share Posted August 22, 2020 On 5/22/2020 at 7:08 PM, elemenoh said: I triple checked and booted with another board OK. Moved its ROM and RAM to this board but get the same result. Slow chimes. Does replacing the F258's next make sense? @elemenoh Did you find a solution? Quote Link to post Share on other sites
elemenoh Posted October 29, 2020 Author Report Share Posted October 29, 2020 @desertroutI need to double check, but I think this one (and a bunch of other boards) recovered after an ultrasonic clean. I recently got a tank and it recovered 6 boards that were previously full of gremlins despite lots of manual washing. Totally worth it if you work on MLBs regularly! Quote Link to post Share on other sites
desertrout Posted October 29, 2020 Report Share Posted October 29, 2020 Cool. Which tank did you get? Quote Link to post Share on other sites
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