(Topic ID: 200569)

SOLVED: Genesis sys80b display issue

By jmountjoy111

6 years ago


Topic Heartbeat

Topic Stats

You

Linked Games

Topic Gallery

View topic image gallery

2017-10-19_07h20_00 (resized).png
E561C8BE-7B4C-4A2C-8352-E03984ABC7E3 (resized).jpeg
7C5B1CD8-F2F5-407C-8120-2D29966AB705 (resized).jpeg
B5808FE7-341C-4159-A15C-8D9C8FC9349B (resized).jpeg
0375CFB8-3093-4700-8E90-5877A6DC05F4 (resized).jpeg

You're currently viewing posts by Pinsider noflip95.
Click here to go back to viewing the entire thread.

#5 6 years ago

Hello,

About the manual : read your PM
It's weird, but I do not see how the connection to the back of the A24-P2 (TC1) connector could burn something related to the SYS80B display.

In general, it is not necessary to reconnect the small RESET card because it generate more problems than it solves. The pinball can work very well without, and for a particular, this card has no use. It was only used in operation, to force a RESET of the pinball when the CPU card was hanged. Disconnecting this card while solving the problem, it is absolutely not necessary.

In SYSTEM 80B, the display works with commands and datas sent by the CPU (8-bit commands, read directly by the circuits 10939/10941). As a result, compared to a SYSTEM 80 / 80A the display circuit is much simpler.

2017-10-19_07h20_00 (resized).png2017-10-19_07h20_00 (resized).png

The data / commands are sent by the RIOT 6532 (U5 - not shown, on left of the picture). They pass through a buffer 7404 (Z16) and then into two latches 74175 (Z18 and Z20). The reset signal also passes through buffer 7404 (Z17) and this IC serves only for this purpose (not shared with matrix or decoding).

Maybe one of these circuits is roasted, but diagnosing which is difficult without a test bench or logic analyzer.
As you can see, there is no connection with the display and the TC1 connector, so I do not understand what could have been broken. If the decoding of circuit U5 (6532) is burned out, the CPU board will not work at all.

A trick also to try: invert the EPROM with the other Genesis that works. To be sure that the problem does not come from a partially erased EPROM.

#8 6 years ago
Quoted from jmountjoy111:

...
I then went ahead and replaced Z16, 18, and 20 also no difference. Could the 6532 be bad and the game still boot?

Yes it could. To boot, the CPU need that full amount of RAM (384 bytes) be present (the RAM is located 1/3 in each 6532 - 128 bytes).
The RAM can be good, and also the registers/timers, but one or more output-buffer can be damaged. In this case, the chip works but not the I/O.

I've seen all types of failure on the 6532: sometimes, a divider/timer doesn't work but others are fine. In this case, the chip work fine at U4 location and not if placed at U5 (because the CPU doesn't use the same divider for U4 and U5). Sometimes, the RAM is defective but I/O works. This a complex component and not all elements fail at the same time.

Note that the issue with the display comes mandatory from this area - there no other parts involved in the display system. As you replace Z16, 18 and 20, nothing remains but U5 (6532) or Z17 (7404). Another possibility is that there is a cut track somewhere (you have to search with an ohmmeter).

Promoted items from the Pinside Marketplace
$ 15.00
Cabinet - Sound/Speakers
Gweem's Mods
Sound/Speakers
$ 83.00
Electronics
PinballReplacementParts
Electronics
$ 5.95
Playfield - Protection
The Pinball Scientist
Protection
Wanted
From: $ 2.99
$ 16.99
Cabinet - Other
Maine Home Recreation
Other
$ 259.99
Cabinet - Toppers
Lighted Pinball Mods
Toppers

You're currently viewing posts by Pinsider noflip95.
Click here to go back to viewing the entire thread.

Reply

Wanna join the discussion? Please sign in to reply to this topic.

Hey there! Welcome to Pinside!

Donate to Pinside

Great to see you're enjoying Pinside! Did you know Pinside is able to run without any 3rd-party banners or ads, thanks to the support from our visitors? Please consider a donation to Pinside and get anext to your username to show for it! Or better yet, subscribe to Pinside+!


This page was printed from https://pinside.com/pinball/forum/topic/genesis-sys80b-display-issue?tu=noflip95 and we tried optimising it for printing. Some page elements may have been deliberately hidden.

Scan the QR code on the left to jump to the URL this document was printed from.