Embedded Files
1/22/2010
Ok, so my Pacman has been running pretty well since I got it. The screen has always been just a little blurry, especially the ghosts and pacman, maze isn't too bad. Thought I'd give it a Bob Roberts deluxe repair kit to see if that would help sharpen the image. Kit included new caps, flyback, HOT, and voltage regulator. I also picked up a filter cap 680uf 200V (not included with kit).
So far so good. Spent about an evening and part of the next day replacing all the caps and making notes of any discrepancies between the new parts going in and the old parts coming off the board. Here are the notes I made:
Header pins:
reflowed S1-S5 pins
reflowed J1/2/3 pins
reflowed E1-E6 pins
reflowed Q1-Q5 pins
B+ filter cap:
Installed new filter cap at C904 with 680uf 200V (replaced the original 600uf 200V). The 600uf 200V is not available, but Bob Roberts confirmed the 680uf 200V would work fine.
Neck board cap:
C107 10uf250V replaced with same.
Main board caps:
C504 1uf50V replaced with same.
C523 1uf250V replaced with same.
C412 pulled a 3.3uf 250V and replaced with same. BR parts list called for a 3.3uf160V but kit had 3.3uf250V.
C408 pulled a 4.7uf250V and replaced with 4.7uf 50V which is what the BR kit called for and came with.
C407 pulled a 4.7uf250V and replaced with 4.7uf 63V which is what the BR kit called for and came with.
C303 Did the mod. Removed C501 and tossed it. Removed C303 and installed it in C501. installed 10uf50V in C303, filling original hole farthest from the chassis edge with solder. Cleaned out and used the closer hole to install the longer positive lead going in the hole nearest the chassis edge and shorter negative lead going in newly cleaned out hole.
C905 pulled a 10uf35V and replaced with 10uf250V which is what the BR kit called for and came with.
C506 pulled a 33uf16V and replaced with 33uf25V which is what the BR kit called for and came with.
C511 pulled a 47uf250V and replaced with 47uf160V which is what the BR kit called for and came with.
C403 pulled a 100uf16V and replaced with 100uf25V which is what the BR kit called for and came with.
C517 pulled a 220uf16V and replaced with 100uf25V which is what the BR kit called for and came with. Later replaced with a 220uf25V after reading about this mod solving potential keystone issues with picture.
C701 pulled a 100uf 6.3V and replaced with 100uf25V which is what the BR kit called for and came with.
C411 pulled a 100uf160V and replaced with same.
C302 pulled a 220uf16V and replaced with 220uf25V which is what the BR kit called for and came with. NOTE: This cap's polarity is silkscreened backward on the solder side of the board.
C518 pulled a 100uf35V and replaced with 220uf25V which is what the BR kit called for and came with. Higher uf, but replaced as the kit called for.
C521 pulled a 2200uf25V and replaced with same.
High output transistor:
Pulled the original C1106 and replaced with same. Desoldered the wires connected to it, unscrewed the 2 screws, installed new one and reused the mica shim, with non-conducting thermal paste, resoldered wires and tested for continuity to ground. No continuity = good thing.
Voltage regulator:
Pulled 2SD870 and replaced with same. Same process as HOT and checked for continuity to ground and all was good. I didn't document the wiring and relied on memory. In retrospect, this was a bad idea. I connected the brown and red wires on the lead where the red wire was supposed to go. Found out later that I did it wrong. The brown wire should have been attached to other pin where the white wire was attached. Major OOPS.
Time to test it out 1/23/2010:
Ok, so all seemed well at this point, so it's time to hook it up and test it out on the Pacman machine. Hooked up all wires/connectors/grounds/etc. Turned on the game. Screen came on but didn't seem to be any different than before the rebuild except things were actually fuzzier. I adjusted the focus/brightness and brought the maze in pretty clear, but the ghosts and pacman well still a little fuzzy, looked much like it did before. After a few minutes and some more minor adjustments on the focus, it became very clear. I decided to test the B+ voltage and it was set at 110VDC. I adjusted the pot to bring it up to 120VDC and it made things very clear and looked to be a success at this point. Starting smelling something not right, but it wasn't too strong so didn't think much of it, but seemed to get stronger smelling like something burnt. I turned off the power to double check the cap orientation and see if there was anything else visibly wrong. Seemed fine, so turned it back on.
Tested B+ voltage and it was at +162 and the screen was briefly bright white and eventually turned off altogether. Removed board and inspected further but still didn't see anything wrong, so hooked it back up and turned it on, still dead and game plays blind. I removed the board again and starting going through the G07 flowchart. Followed it through until I found the part about removing the transistor x701 (overvoltage shutdown) and hooked it back up. Game would come up on the screen now, but very wavy on the sides left and right. B+ was about 158VDC at this point, so still way over voltage. Removed board and started going over it further. This is when I found the miswiring issue on the voltage regulator 2SD870. Wired it up correctly and replaced voltage regulator assuming that it burned up (something did, according to the smell). Hooked it back up with no change and still about +157 or so on the B+ voltage. Removed the board several more times and starting sifted through KLOV threads and testing components as suggested. No changes. Decided to order some of the replacement parts suggested on the KLOV threads from Bob Roberts.
1/28/2010
C511 pulled 47uf160V (previously installed during cap kit), replaced with same just in case it blew.
D905 Pulled original Zener RD6.8EV3, replaced with 1N4736 Zener diode 6.8V from BR
R908 47K 1/2W carbon film resistor pulled and replaced with 47K 1/2W resistor from BR
C301 3.3uf 50V non polarized capacitor pulled and replaced with same. Was not part of the BR deluxe kit so I ordered separately.
C520 3.3uf 50V non polarized capacitor pulled and replaced with same. Was not part of the BR deluxe kit so I ordered separately.
R902 tested O.K. - I don't have a replacement but will add it to next parts order or steal from donor chassis.
Hook the monitor chassis back up to Pacman. No dice, same issue with HV shutdown circuit engaging. Tested B+ at 166VDC. Tested the other side of the big white resistor and it was also 166VDC.
Suspect parts at this point: all 900's. x902, r902 in particular need to order or steal from donor chassis. Will probably replace x901 as well. Also T501 will steal from donor chassis since you can't buy them anymore.
Potential candidates for replacement at this point (below). I decided to focus on the 9xx transistors since the resistors all looked visually ok and was having trouble locating new parts for some of them.
x901
x902
d701
x701
r901
r902
r903
r904
r905
r910
fr901
t501
1/29/2010
Acquired a donor chassis (Thanks Troy!).
X901 replaced with same from donor chassis.
X902 replaced with same from donor chassis.
Reinstalled chassis in Pacman and fired it up. B+ voltage at 108VDC and screen came up. Adjusted the B+ pot to 119VDC, I couldn't quite get 120VDC as voltage started to drop when I got close to the end of the range on the pot. Probably a worn out pot, but left it at 119 VDC. Close enough.
Screen is absolutely crisp and clear, much improved from before the rebuild.
Fixed. Most likely part that failed was X902, but I replaced at the same time as X901 so no way to be 100% sure it wasn't X901.
Pacman AFTER G07 rebuild. The camera makes the ghosts look blurry, but they're crystal clear on the game.
Pacman B4 G07 rebuild. Overall picture is soft and ghosts/pacman are blurry.
This repair log written by Torin Newman (tng25) on 1/29/2010
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