SE FDHD 820-0250A / neither Arrow pointer and Floppy icon

[flowers]

Hi there,

 I'm trying to let restart a board 820-0250A that won't start; regular chime and the video appear as normal but the arrow pointer and the floppy do not comes on. I red already the ref to RP2 Filter, i desoldered it; put a socket and tried with a substitution but the problem remain.

 Any suggestion to put my attention and control over ? ^_^

thank you

 

[Compgeke]

I'm not sure if the 4 MB labels on the RAM are 4 MB/stick or 4 MB as a set. If the former that's quite possibly your problem, the SE will only do 4x 1 MB.

If it's labeled 4 MB for a 4 MB set then make sure you have the RAM jumper either cut or the jumper set to the 1M position instead of 256K, depending on which your board has.

 

[techknight]

Those sticks arnt a matched set either. I remember that being critical back in the day. 

 

[Compgeke]

Sometimes you can get away without matched sets but you'll need to have them installed in horizontal rows rather than vertical like they are now. I didn't notice that myself until you pointed it out. I've a couple SEs with 4 megs and mismatched pairs.

 

[flowers]

uh.. i didn't get a look on that   .. but unfortunately this doesn't solve the problem; i tried 4 working 256K ram (M5M256J  -15) and i get the same result.

(just to confirm your feedback, the ram present before where left chip M5M41000BJ -7

and right one  USA  U 9138 1024 M8; and yes was not been rightly followed the Row but it doesn't help, i even didn't focus that until you do not make me point over )

The jumper is setted in 2/4Mb as is visible in the picture i got.

 

[flowers]

I add this info, in RP2 that i socket, checking continuity with the ground i get signal in pin 3 and 4, the bourn filter was not culprit as it give the same even with it changed. I get some picture measuring the opposite pins as curiosity with both new filter (MDP1603 471G) and past (115-0002 5s8) that is also working.

 

[flowers]

Setting the jumper at 1Mb, i tried 4 sticks i have by 256K

... is the below images telling me there is a men sticks problem .. isn't it ? 

 

[flowers]

i use another couple of SIMM putting 2 sticks 256K in the row 2 ( SIMM 3 and 4) with the 2/4 jumper as is required for this SE mainboard;  but the ram are not the culprit i tested all in a working board, ... now with this step instead of the vertical BARS as above ( same setting) i get finally a first signal... 

and reading around papers this seems to be a problem on SIMM 3 of this board 820-0250A... but the SIMM 3 is working in another working board.... hmmm.. . ok something that go to SIMM 3 can be where i've to go. the SIMM socket for me is all fine i checked it twice... any suggestion out there ?

 

[techknight]

SEs are cheap. find another logic board and toss that one. 

Keep your ROMs, and SWIM because the 800k boards are alot more plentiful than the 1.4MB boards. 

find an 800K boards, and swap those 3 chips over so you can retain the FDHD support. 

 

[flowers]

uh, thank you for the reply... that sound as a conclusion of the understanding road ..

.. but maybe i can try to check some of the other IC's like F257... the resistors, capacitors, transistor, burns and adb filter are all fine; i've not problem in soldering and socketing what ever is needed to try... in real my doubt is that are involved some bad connection between the SIMM and the rest of the board.

Technight have you ever found a relation between these signals and the broken part? I think it can be something repetitive and maybe useful to save even a today common mainboard, i red more people that get a similar problem. 

As last information i found out that the resistance that exit in pin 3 and 4 for the RP2/UB2 for this board are normal and are not linked to a problem... even if i remember also from your work that the check in the burns filter has to give continuity ... but i think that that was for the SE30 board and not for this one. isn't it ?

 

[flowers]

.. for now a first Understanding. I did some test with different RAM STICKS,  -12 (120ns) and -15 (150ns). I found finally theSticks that was the culprit of the error 00nn and 0003 (SIMM3) into this board. Changing position i get the relative mistake for the other position.

To get the Stick back fine i simply clean it with a the rubber of a Pencil Eraser, over the contact; i also payed a dry-cleaner for contact and the image above of the black vertical BAR disappear. So that BARS are linked definitively to bad contact between good RAM stick and the RAM Socket

Now i'm back at the start of this post... the mac start, BONG! (correctly).. then appear this screen.. but it stop and do not go to the rounded corner screen and the ARROW pointer... the mainboard is blocking there... something is not making the conclusion.. the screen now is again this :

so... now i think there can be a road to follow... the CPU is working, the ROM are all fine, the memory too... the UB2/RP2 burns filter is fine and even the resistance i measured in pin3 and 4 are correct... maybe i can try to socket something else but i need to see where to go to look in... really any idea ? i would like to see the solution for a NO ARROW for these boards.. i'm sure there is a common culprit for... 

 

[techknight]

the SWIM not being detected or bad can cause this as well. 

 

[flowers]

thank you techknight i try following your last thought but the SWIM chip its working fine in another working board and same for Hi and LOW ones; clean contacts and checked the continuity with the sockets too. This problem seems to be resident evil of another place.

Al errors code tells me to go to look in SIMM3 or around the hooks to it. 

 

[techknight]

Well if you ruled the SWIM out, and you keep having funky issues with memory, its entirely possible that one of the RAM muxes has gone bad. it happens all the time in the SE/30. 

 

[flowers]

.. i go to get some look into the multiplexers and let here know the feedback, thank you technight for the suggestion.