Jump to content
techknight

SE/30 video issue that has ME stumped!

Recommended Posts

Quote

I think I changed the PAL set already. But I cannot honestly remember. 

 

You changed the PAL set, was said on one of your earlier post.


 

 

 

 

As i am lazy, tried to piggyback the PALs first... hoping it will help troubleshooting the board, and worked.
 

Share this post


Link to post
Share on other sites

Yea its been to long. I bought some new ICs for it and I sat it all on the shelf and I havent looked back yet. been way too busy with my standard day job. I cant wait until we get enough capital in where we an hire dev teams and customer service people so I aint gotta do it. ;-)

Share this post


Link to post
Share on other sites

@techknight

 

The SE/30 has two different sets (revisions) of PALs... i was lucky as apparently the one i changed is common in the two revisions.

 

For troubleshooting purposes, can i use one set instead of the other ?

 

 

Share this post


Link to post
Share on other sites

Even the ones from the early board revision that has the patch wire installed?

Or does that wire make the routing the same as on the later boards?

Never had to work in depth on one of the early boards yet.

Share this post


Link to post
Share on other sites

I swapped the PAL (all of them) and cleaned the pins, I swapped the  PAL sockets, I swapped all the 8 bit shift registers, I swapped the ROM SIM socket and I swapped the memory SIM sockets.

I replaced the capacitors and some of the resistors underneath the PAL chips.

Share this post


Link to post
Share on other sites

Well, if you've swapped every suspect chip on that board, the only things that could be bad are traces... I know that's kind of a stupid suggestion, but I would go bad trace hunting with a schematic if I were you. 

https://www.macintoshrepository.org/875-macintosh-se-30-schematics-and-repair

Edited by BadGoldEagle

Share this post


Link to post
Share on other sites

I think I found it Pin 5 on the ls166 (vid3) to UC7 pin 23 is OL. Pin 5 to via on the ls266 is OL. via to pin 23 on UC7 is .3ohm

a closer look reveals that the pad is disconnected from the Via

IMG_4273.thumb.JPG.eaaee88b9dd58ba8f8f4958fc460f7ab.JPG

thank you for the help  techknight

 

Share this post


Link to post
Share on other sites

Sorry to dig up a dead thread.
Techknight, did you ever find anything on this?  I have precisely the same video bug, but cant seem to figure it out.  Both VRAM's and UE8 have been replaced.  Tested all traces to and from VRAM.  I still get vertical stripes with a slightly abnormal disk icon.  Looks identical to your screenshot.

Share this post


Link to post
Share on other sites

ISSUE RESOLVED!  Techknight, you may want to add this to your notes.

It appears that Texas Instruments SN74HC166DRG4 is NOT a valid replacement for the the 166 shift register @ UE8.  It causes the discussed artifacts.
I swapped it out again, but this time with a Toshiba 74HC166D, and the issue completely resolved!

Share this post


Link to post
Share on other sites

I would always use the appropriate 74LS166 instead of a 74HC. It’s supposed to act the same but as you see it might not always do.

Edited by Bolle

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

×