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Main channel: Repairing a completely dead IBM PC 5150 motherboard (Patreon)

Published:
2023-06-26 21:06:18
Imported:
2024-05

Content

Hello my patrons! I hope everyone in the northern hemisphere is enjoying long warm summer days! (It's been especially nice here in Portland the last couple months.) For the next main channel video I'm going to go outside my comfort zone a little and try to diagnose and repair a completely dead IBM PC 5150 motherboard. If you aren't totally familiar with the IBM PC line this motherboard comes from the very first PC ever released. This is the machine that all the PC clones we still use today are based on. 

Back then, all the parts IBM used on this motherboard are off the shelf (so obtainable) and full schematics are available. The only thing that might stymie me is the IBM PC is substantially more complicated than something like a C64, so watch to find out if I am stumped!

Thanks for all your support!

Direct link: https://youtu.be/W7LJDmuHOlw

Files

Completely dead IBM PC 5150 motherboard #repair

In a recent second channel video I tested four PC motherboards. This IBM PC 5150 motherboard was in that lot and I found it to not be working. Let's troubleshoot the problem and try to get this 1983 IBM PC motherboard working again. Part 1: This part! Part 2: Coming soon --- Video Links My initial testing of this IBM PC 5150 motherboard: https://youtu.be/noRZC9y9Uz0 Great resource for IBM PC information: minuszerodegrees.net IBM PC 5150 Switch settings: https://www.minuszerodegrees.net/5150/misc/5150_motherboard_switch_settings.htm IBM PC 5150 Technical Manual: (64-256k) https://www.minuszerodegrees.net/manuals/IBM_5150_Technical_Reference_6322507_APR84.pdf RGB2HDMI: (What I'm using to capture CGA) https://github.com/IanSB/RGBtoHDMI Adrian's Digital Basement Merch store: https://my-store-c82bd2-2.creator-spring.com/ Adrian's Digital Basement ][ (Second Channel) https://www.youtube.com/channel/UCbtwi4wK1YXd9AyV_4UcE6g Support the channel on Patreon: https://www.patreon.com/adriansdigitalbasement -- Tools Deoxit D5: https://amzn.to/2VvOKy1 http://store.caig.com/s.nl/it.A/id.1602/.f O-Ring Pick Set: (I use these to lift chips off boards) https://amzn.to/3a9x54J Elenco Electronics LP-560 Logic Probe: https://amzn.to/2VrT5lW Hakko FR301 Desoldering Iron: https://amzn.to/2ye6xC0 Rigol DS1054Z Four Channel Oscilloscope: https://www.rigolna.com/products/digital-oscilloscopes/1000z/ Head Worn Magnifying Goggles / Dual Lens Flip-In Head Magnifier: https://amzn.to/3adRbuy TL866II Plus Chip Tester and EPROM programmer: (The MiniPro) https://amzn.to/2wG4tlP https://www.aliexpress.com/item/33000308958.html TS100 Soldering Iron: https://amzn.to/2K36dJ5 https://www.ebay.com/itm/TS100-65W-MINI-Digital-OLED-Programmable-Soldering-Iron-Anti-static-Structure/113382669853 EEVBlog 121GW Multimeter: https://www.eevblog.com/product/121gw/ DSLogic Basic Logic Analyzer: https://amzn.to/2RDSDQw https://www.ebay.com/itm/USB-Logic-DSLogic-Basic-Analyzer-16Ch-100MHz-4Ch-400MHz-Xilinx-Spartan-6-FPGA/202543965672 Magnetic Screw Holder: https://amzn.to/3b8LOhG https://www.harborfreight.com/4-inch-magnetic-parts-tray-90566.html Universal ZIP sockets: (clones, used on my ZIF-64 test machine) https://www.ebay.com/itm/14-16-18-20-24-28-32-40-pin-IC-Test-Universal-ZIF-Socket-Fs/303206721971 RetroTink 2X Upconverter: (to hook up something like a C64 to HDMI) http://www.retrotink.com/ Plato (Clone) Side Cutters: (order five) https://www.ebay.com/itm/1-2-5-10PCS-Micro-Scissor-125mm-PLATO-170-Electronics-Cutter-Side-Cutting-Pliers/163458746184 Heat Sinks: https://www.aliexpress.com/item/32537183709.html Little squeezy bottles: (available elsewhere too) https://amzn.to/3b8LOOI --- Links My GitHub repository: https://github.com/misterblack1?tab=repositories Commodore Computer Club / Vancouver, WA – Portland, OR – PDX Commodore Users Group https://www.commodorecomputerclub.com/ --- Instructional videos My video on damage-free chip removal: https://www.youtube.com/watch?v=XQVjwPsVFd8 --- Music Intro music and other tracks by: Nathan Divino @itsnathandivino

Comments

OzRetrocomp

I keep wanting to call the IBM PC 5150 the IBM Van Halen. 😂

Euro Micelli

19:40 and the S4 and S3 lines: It can be weird if you are not familiar with 8088 assembler. It doesn’t matter for the repair, but here it is: As you know the 8088 supports 1 MB of address space, but that requires 20-bits and the CPU is 16-bit - so something’s gotta give. The 8088 solution is to merge two 16-bit values to come up with physical addresses. One of the 16-bit values is called a Segment and it picks a specific 64K-wide block; the other one is a computed offset inside that block. The CPU has exactly four dedicated 16-bit segment registers, used to keep track of which 64K block contains the currently-executing Code (CS), the system Stack (SS), and two independent general-purpose blocks called Data (DS) and Extra/Alternate (ES). Every memory address is computed using exactly one of those segment registers; for example, a code fetch always uses the Code (CS) segment register. The S4 and S3 lines then must report externally which of the four segment registers was used to come up with the full 20-bit address of whatever the CPU is accessing. I presume “None” is there because unlike the 6502, the 8088 has an additional separate 64K address space and instructions intended for I/O ports, and those don’t use segment registers. But I have no idea why anything would care about which segment register was used for address calculations. Maybe the 8087 needs it?

adriansdigitalbasement
>>111762935

You know I knew about segments but I never put 2 and 2 together on how it would work in the physical world. And yeah as for why -- exactly maybe it's the 8087 or something. Not sure!