Sad news! My most recent purchase on eBay was an Asus P5A-B (for parts)! This board was missing both NFETs for the low voltage. See pic...

It seemed odd that someone would salvage the FETs off a working board. It had some signs of wear but was otherwise clean. Maybe this board was undesirable and ended up a parts board at some time in the past...? Anyway, after finding only a few leaky caps, I decided to swap in some replacement FETs I had that were "close" IRFZ44N, the originals being PBYL1025B as far as I can find.

To my surprise, the board came to life!

I decided to order some replacements that were a better fit as well as some fresh caps. UNFORTUNATELY, I ordered something that would spell DOOM for this board that was saved from the dumpster. I mistakenly order these, IXTA100N04T2 being a 100A continuous vs 10A from the originals. The originals have a 100A peak current rating, but this was an obvious mistake on my part. After the recap, I did a quick thermal check to see if everything was okay and I noticed the buck chip near the RAM running nearly 70C after a few minutes. The IRFZ44N was close enough to get the board running, but that high temp made me think that FET was a bit out of spec from the original. The other near the CPU was just fine. At this point, the board was still functional and posted fine. So... I decided to swap in one of the IXTA100N04T2 and see if that would run cooler.

Here's a thermal pic of the HIP6013CB chip near the RAM. It did hit 70C while in the BIOS screen. I don't know if that's normal for these, but the datasheet lists 70C as an upper limit operating temp.

Had I double-checked my purchase I might have given this move a second thought, and maybe if I wasn't in a hurry I would have just asked if that was a suitable replacement. Of course, this board could have had a deeper issue lurking that didn't manifest until this moment, but at this point, I'm blaming myself for this one.

I decided to power up the board with no RAM or CPU and test the voltage. I wasn't even able to reach for my meter when I heard a loud pop and crackle! 😞😞😭😭😭 The damage is subtle but fatal in this case!

I should have left well enough alone... I consider myself lucky to have gotten one of these boards for under $60 and it looks like a working replacement is going to cost far more as the prices keep going up... 😡😡

I'm feeling a little depressed so I think I'll just go to bed for now.

Question for anyone who reads this...?

I see many postings for the IC that blew up, "M1543C" on eBay for about $12 from China. What are the chances those chips are "genuine" for a replacement and that everything downstream of Q10 NMOS on the board wasn't also cooked?

Given the high price of these boards and the possibility of chasing many dead chips, what would you do? The board was powered on for about 5 seconds before the M1543C chip popped with a little smoke. I see no burns anywhere, but that doesn't mean much.

I guess I'm looking for encouragement or assurance that it's simply a fool's errand... 🤷‍♂️

Oh... Made a mistake on the post. I gave the part number for the double diode instead of the original FET which is a HUF76121S.

Only you can answer that question! It comes down to what your time is worth, and/or if you have a strong desire to have a go at fixing it, and if the $12 part is an inconsequential extra cost. If it ends up needing more replacement parts then it's a case of how far down that road do you go...

Weigh all that up against the cost and avavailbility of a working board and go from there.

I guess I'd feel better if I had a boardview file or schematic... Something that would show where on the board Q10 was touching. That's probably impossible I'm guessing...

Got super impulsive and bought another P5A-B. I had my heart set on that board and... I'm sorry, everyone! I'm now partially responsible for raising the prices of these on eBay. I did order a replacement Southbridge chip and will try to fix the old board though.

This is the setup so far:

P5A-B 1.04
AMD K6-2+ 570mhz modded to 256k L2
ATI Rage Fury AGP main graphics
2 x Voodoo 2 12MB accelerators
ESS-1868F + wavetable MT-32 Pi

And it's going to fit into this. The goal is to make a "portable" rig that's kind of all-in-one. Mainly because after the nostalgia of retro gaming wares off I can easily store this in my closet and forget about it until I remember all the time and effort I put in and decide to pull it back out. 😄🤪

The sound card portion ESS 1868F + wavetable MT-32 Pi has been a fun side project! I only recently found the MT-32 Pi project and based on a YT vid - Wavetable Pi - https://www.youtube.com/watch?v=xC-qhcPUeRs, I decided to try and replicate it. I had to order the Pi Zero 2 but was able to assemble a working prototype quickly. I'm happy to say it all worked the first try and it sounds super cool. So much different from the card onboard synth and especially Windows GM.

The emulator also allows for sound fonts! I don't have a favorite yet, but I really wanted to try the SC-55 or SC-88 on DOS games without actually having to buy one. It all works pretty transparently and I'm grateful for the folks who put in the time and effort to make the MT-32 Pi project happen.

Beyond my prototype, I'm going to try my hand at a genuine PCB version that takes the Pi Zero 2 similar to the Wavetable Pi in the YT vid. His footprint was very optimized for size having the Pi on the reverse side of the PCB. I'm going to make one that's a bit more friendly to a wider variety of sound cards that have components around that area making it difficult or impossible to attach a card in that way. Case in point, I have an OPTi 82C925 card with a wavetable header, but they decided to place 10mm high capacitors in that area making it impossible for even a single-sided PCB to fit.

Many cards also have audio headers directly above the wavetable header limiting how high the PCB can be above that area. After looking at several Sound Blaster cards, I think a left-justified arrangement would fit most cards. Although the outliers would need a right-justified arrangement. Especially those with wavetable headers in the vertical orientation.

Anyway, I'll still post the plans on github for anyone interested. I'm also aware of the Rasp Pi compute module version, but that's a bit expensive! I was able to make this prototype for under $50 so I consider that a win!

Who does this!!!

Tevian wrote on 2024-04-21, 08:53:

And it's going to fit into this. The goal is to make a "portable" rig that's kind of all-in-one. Mainly because after the nostalgia of retro gaming wares off I can easily store this in my closet and forget about it until I remember all the time and effort I put in and decide to pull it back out. 😄🤪

20240420_234313.jpg
20240420_234332.jpg

Now that "case" is kinda a stroke of genius. That's gonna inspire me in my test bench endeavors ...

Well... It's mostly put together. The wiring management is a bit clumsy and I need a proper cage for the drives. This setup actually needs a 6 socket powerstrip internal! I need to rearrange a bit but I'd like to be able to store a keyboard, mouse, and controllers inside.

A few inclusions are a Rasp Pi as portable network storage, my Mister FPGA, and a 5 port network switch. The Mister is a fun bonus for playing the older console stuff and I was having a hard time finding a good place for it to live. I'll need to get a monitor switch though... My Dell LCD only has one VGA input. Or I might look for a 17" 4:3 that has VGA + DVI.

It's rather heavy but the idea of being mostly self-contained is coming together nicely.

Tevian wrote on Yesterday, 11:14:

Well... It's mostly put together. The wiring management is a bit clumsy and I need a proper cage for the drives. This setup actually needs a 6 socket powerstrip internal! I need to rearrange a bit but I'd like to be able to store a keyboard, mouse, and controllers inside.

A few inclusions are a Rasp Pi as portable network storage, my Mister FPGA, and a 5 port network switch. The Mister is a fun bonus for playing the older console stuff and I was having a hard time finding a good place for it to live. I'll need to get a monitor switch though... My Dell LCD only has one VGA input. Or I might look for a 17" 4:3 that has VGA + DVI.

It's rather heavy but the idea of being mostly self-contained is coming together nicely.

This is awe inspiring!
Can't wait to see the finished product!