VOGONS


First post, by maniacminer

User metadata
Rank Newbie
Rank
Newbie

I bought a Compaq Deskpro 386s/20 from eBay for parts salvage. I am in need of a few parts for an existing Deskpro 386s/20 - this is an earlier revision of the PCB and doesn't have 30 pin SIMM slots and no SVGA. It didn't start well, the seller low-balled the postage and I was left with a "ransom note" from the courier, as it's close to Xmas, I paid the ransom and got the package. Yeah, it was the Compaq and it was quite beaten up. I asked the seller for a refund of the postage and got nowhere, as it was so heavily damaged I asked for a return, silence... So I went through eBay and their customer service said that the seller must provide me with a returns label. No action for a week or so and then out of the blue eBay refunded me the auction and told me to dispose of the machine as I choose.

I hammered out the worst dents, thankfully the front panel was intact, the first spare part I am looking for (it will be going to the TNMoC) the second part was rattling around inside the case, the drive rails for the non-existent 3.5" floppy, I need those to put a CD-ROM into my Deskpro/M machine. I also need a spare PSU for the TNMoC exhibit. I completely dismantled the machine and cleaned it thoroughly, then went through the PSU and noticed the characteristic smell of blown tantalum and leaking electrolyte. I removed all the capacitors, checked and measured each one (except the blown tantalum he blew his head clean off) Once I had done all that, I went over the main board to check the three banks of DIP switches and noted that a graphics card had been removed as the onboard graphics were disabled, also the memory board had been removed as the DIP switches were set for another 4MB of RAM. I put the PSU back into the case and switched it on. Success, a booting machine with no floppy drive, hard drive or keyboard - I don't need the mainboard or the case, it's just there if someone wants a parts machine.

If you've got one of these machines, it will definitely be in need of a recap, I caught this one just as it started to digest the PCB traces next to the worst leaking capacitors (3 x Nichicon 1000uF/10V)

The attachment 1 - Dusty.jpg is no longer available
The attachment 2 - Overview.jpg is no longer available
The attachment 3 - Found the blown tantalum.jpg is no longer available
The attachment 4 - Leaking electrolytics.jpg is no longer available
The attachment 5 - Tantalum removed.jpg is no longer available

Reply 1 of 2, by maniacminer

User metadata
Rank Newbie
Rank
Newbie

Flipping the PSU PCB over it was clear there was another problem, dry solder joints. The two transformers had stress fractures around the solder, I removed and resoldered those. I noticed the main switching transistor had broken away from the PCB, I removed and replaced the solder here too. Once reassembled and "modified" to take an SVGA cable, it booted - doesn't take long to count to 1024K vs. 64M in the Deskpro/M 😋 There's no CMOS battery and I've got no intention of fitting one. I have put a list of what the capacitors are and what I replaced them with (I do a lot of SMPS repairs and have a kind of "favourite" selection of caps)

The attachment 6 - MOSFET no longer connected.jpg is no longer available
The attachment 7 - Working now.jpg is no longer available
The attachment Capacitor Replacment Table for Compaq Deskpro 386s20 PSU.png is no longer available

Reply 2 of 2, by maniacminer

User metadata
Rank Newbie
Rank
Newbie

I was disposing of the packaging this morning and discovered this machine was sold to someone else before me. They had returned it, no doubt after plugging it in and the "bang" from the PSU decided to back out of the deal 😝 Oddly, the weight was 12.5kg on its return trip that time and somehow went on a crash diet to 9.9kg when it was sent to me. The machine was wrapped in two layers of, mostly popped, bubble wrap, useless. That explains the significant damage, d'oh! 💩 A quick eBay search and yup, the very same machine was sold a month earlier by the same seller.