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Portable - two steps forward one back

at0z

Well-known member
Double-check your soldering work. 
Went back over any suspect joints and one step passed, no more Sad Mac error or chime. 
 

Now getting pointer in top left but no flashing question mark and my SCSI2HD external doesn’t show any signs of access nor does floppyemu. The striped display changes and clears. Looked for hotspots on the board but oddly the two sound chips are the warmest (sound left & right). 
 

I’ll have a look at the video vram side next but if you’re familiar with the pattern changes, please chime in...

3935BAC1-E9A1-425E-B67C-F1790911F61B.jpeg

C0A66CFE-41B3-4BE4-9D81-FE3092E8BE0C.jpeg



View attachment 93A678A8-D5F7-47D0-B798-0BED5EFF2EB0.MOV
 

techknight

Well-known member
Bad SWIM probably, and the line is a broken trace to the LCD from the controller, or potentially between the SRAM and controller IC. 

 

at0z

Well-known member
Bad SWIM probably, and the line is a broken trace to the LCD from the controller, or potentially between the SRAM and controller IC. 


Thanks!

I figured I would look at both the SWIM and SCSI packages. Which controller do you mean - the Video one ? I also see another Sony brand SRAM close by and I assume that's the VRAM. Will also look at that.

I'm not giving up on it yet :)

 

at0z

Well-known member
Well curiouser and curiouser said Alice...

Ran a soldering iron around the SWIM and SCSI and VIDEO packages just to see if there was a bridge or dry joint. Connected power and the voltage and current is all over the place and PMGR reset has no effect, Q16 gets hot. Not my bench supply as another gave the same results. 
 

Guess it’s one more demon to exorcise.



View attachment 4FC88E4D-5D56-4FEC-BACC-82E46748795C.MOV
 

techknight

Well-known member
Well curiouser and curiouser said Alice...

Ran a soldering iron around the SWIM and SCSI and VIDEO packages just to see if there was a bridge or dry joint. Connected power and the voltage and current is all over the place and PMGR reset has no effect, Q16 gets hot. Not my bench supply as another gave the same results. 
 

Guess it’s one more demon to exorcise.

View attachment 39566


Remove the SWIM. its bad. 

 

at0z

Well-known member
Hmmm so Q16 is getting warmer/hotter than I would expect (I saw it reach 150F) - does that suggest it may be faulty or it's just running hot trying to manage the voltage swings ?

Q14 and Q15 although I see swings on voltage there do not appear to be toasty...

It's fairly early on in the power schematic if I read it right...

467B7368-51BD-4963-9E6B-1A6B25F39937_1_105_c.jpeg

 
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techknight

Well-known member
with that image, I dont know what im looking at . 

and no, thats not normal. theres something upstream drawing an excessive amount of current. 

This happened after you reworked solder? Check to make sure you didnt bridge anything. 

 

at0z

Well-known member
with that image, I dont know what im looking at . 

and no, thats not normal. theres something upstream drawing an excessive amount of current. 

This happened after you reworked solder? Check to make sure you didnt bridge anything. 
that’s an infrared of Q16 showing the temperature after about a minute with power on. 
 

I didn’t do any rework around the power side of the board, just SWIM and SCSI packages. Of course as most things there could be multiple layers to the onion.

I pulled Q16 and the wild fluctuations went away which suggests to me nothing upstream is shorting but....

going to replace it and see...

 

techknight

Well-known member
well the fact that you just resoldered SWIM and SCSI, doenst mean you didnt form a short there. 

Same with the video chip. 

 

bibilit

Well-known member
Display issue can be related to the cable connecting the Logic board to the screen (faulty very often)

 

at0z

Well-known member
well the fact that you just resoldered SWIM and SCSI, doenst mean you didnt form a short there. 

Same with the video chip. 


Well replacing Q16 was interesting but ineffective at resolving the wild swings in power draw. Couldn't see any pin shorts on the video or SWIM or SCSI. As the SWIM was already off the board, I decided to pull the video chip which was fun. But it was worth it - underneath the chip out of sight were a couple of solder bridges. Unfortunately didn't note the pin numbers off hand, but cleaned up the pads and the board now draws an expected voltage and current.

Got the video chip reunited with the board (those overhangs are a challenge - do most folks use a curved tip on the iron or solder paste and a hot air gun ?).

Powered back up, normal power draw but Sad Mac chime instantly and a strange code on the display which looks like 0083 as the major but that seems way out of range. So one mystery solved, another awaits.

But at least no RAM error :)

 

techknight

Well-known member
and solder bridges now create a whole set of new unknowns that make troubleshooting that much more difficult. :-(  Because that's how one fries shit. (been there, done that).

 

at0z

Well-known member
and solder bridges now create a whole set of new unknowns that make troubleshooting that much more difficult. :-(  Because that's how one fries shit. (been there, done that).


I feel better knowing I'm in good company :)

Question on pin numbering - on some of the quad packages, it seems pin #1 is halfway down one side rather than the corner - I don't see anything in the schematics stating which chips do that - is there a listing somewhere of which ones play that game ? At least that might give me an idea whether the couple of bridges were in a major danger zone...

 
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techknight

Well-known member
all PLCCs follow the convention. Pin 1 is in the middle and it goes counter clockwise. 

QFP/TQFP is different. 

 

at0z

Well-known member
I think the VIA may be hosed - I'll try one from a donor board. Got to keep feeding the slot machine for a payout...

 

at0z

Well-known member
Would anybody care to share their top tip(s) for replacing the packages like the SWIM and VIA ? The curled under pins make it very easy to create a bridge that you can't see, at least from my examples.

I've seen YouTube videos where the pads are cleaned back completely, flux is added, the package is placed in position (much easier to do with no solder on pads) and then solder paste is applied and hot air used. Others appear to start with bare pads, add flux, tack a couple of pins to anchor the package then drag solder each side (that seems to be a prime risk for bridges though). Final strategy I saw was tin the pads, add more flux, place the package down as accurately as feasible, then use hot air to flow the solder and hope the package jiggles itself into the final accurate position....

So what's my best strategy to get things lined up, connected but not shorted...? Help me Obi Wan Kenobi....

 
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