Juno First Boot Leg

[NivagSwerdna]

Oh dear... I seem to have angered the philmurr gods.... better fix it quick...




Normally I would put some UV cure superglue over the top but it seems reasonably safe. Almost as good as a bought one.

I do have some life from the board...


The image is very intermittent... and obviously not right... but I guess it might not go in the bin just yet.
I recently bought my next board to fix.... so need to get this one done!

 

[NivagSwerdna]

To stop going around in circles I figured I should properly document some of this...

So marking up a grid on the board for reference in removeable white pen....



Partial schematic of video section...

The fact the image above is squeezed in the vertical direction by 4-ish should be a big clue to the problem and normally I would just suspect E18, D18 and D17 since that's where 128V flows... but it seems more subtle than that... Let me re-socket the chips and make sure I haven't broken too many traces and then re-think. All the removed devices test good so they may as well go back.

 

[NivagSwerdna]

OK... time to give this another go...

I rather rashly decided to remove and test all the DRAM... (if I had bothered to read the log above I probably would not have done this since quite a lot of the frame buffer obviously works)... anyway I was ****ed off with all the DRAM that made my recent Tutankham repair so annoying so I don't feel too bad...

Before... 16x 4116...



Now this is quite fun...
After...


The PCB markings are quite interesting.... 8116 not 4116... I've never come across 8116 (and still haven't!)

Seems a 8116 is a single rail 5V version of 4116... (Some 8116 are 5V, some are not... Check the exact model and datasheet!)

There actually seem to be some on EBAY.... "[20pcs] MB8116E 16KBit DRAM DIP16C"

It's almost tempting to get some just for fun.

Anyway...



So mostly good... 4 duds...

Now do I replace with my static equivalent board... socket and replace the 12 working and use 4 spares... or go rogue and order some 8116s!

 

[NivagSwerdna]

Well you learn something every day...

Those 8116 chips on EBay are not single rail!
Some 8116 are just 5V but some have the same power requirements as a 4116.
However the 8116 is a drop in replacement for a 4116 and consumes approx 50% of the power.

Not a bad price either... Just ordered 20 off to play with

 

[NivagSwerdna]

Well there's an afternoon of my life I'll never get back... oh man these things take so much time...







Don't ask me if those are all the original chips... because I might scream and start sobbing.
Need to clear some space and then restart the repair... (have to put my original K084 back in another board because I extracted it for comparison recently)...

 

[bones]

No comment but fingers crossed for you