Re: Old KEnitec 286 Plus (suntac) Rescue, will need help.

Posted on 2019-03-10, 10:07

by

by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Well that motherboard has certainly turned into a big project. It is fun though. Those chips rarely fail so replacing them is last resort I think. I mean, CPU is socketed, right? So if you can get a cheap replacement then maybe it's worth try but I would not spend any money unless necessary. So …

---

Re: 386DX-40 Himem.sys problem

Posted on 2019-03-09, 10:39

by

by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

So the board has 8+1 cache IC sockets? That's good, common wisdom says that the cache is less strained in dual bank operation than when there's only one bank (4 chips) on board - and I lately experienced the same while experimenting with various 486 boards. Not op but my board does have 8+1 cache …

---

Re: 386DX-40 Himem.sys problem

Posted on 2019-03-09, 00:46

by

by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Yup, cache issues will manifest as random RAM errors, among other things. I have the same problem with an otherwise pretty nice mainboard based on OPTi 82C495SLC chipset - I'm forced to use more relaxed timings of 3-1-1-1 instead of 2-1-1-1. Just like in your case NSSI benchmark reduces my score to …

---

Re: Looking for an ID/manual/jumpers and more info on this 386 AMD 40MHz board

Posted on 2019-03-08, 14:32

by

by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Yes, they do: - Ye olde true TTL bipolar stuff (old, obsolete, not manufactured for years now): 74nn - old crap, do not use unless speed is not an issue (some special gates like 30V tolerant 7406 are only made like this) 74S - S is for speed, but power hungry and hot 74AS - improved S, still …

---

Re: 5.25 Floppy Not Reading

Posted on 2019-03-08, 12:28

by

by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

You can try and format 1.2 HD floppy as 360k if you want. At least you'll know if it's usable at all in a PC. In general HD floppy will behave as a very good quality DD disk. The other way around is not always so easy, some FDDs are hardwired for HD mode and will refuse working with DD/QD media, or …

---

Re: Looking for an ID/manual/jumpers and more info on this 386 AMD 40MHz board

Posted on 2019-03-08, 12:22

by

by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Just a quick note, HC and LS series might be a tad bit too slow for this task, if it's cache memory related. Mouser should carry FCT but you can try substitutes too. I'd pick ACT for FCT replacement. If you can't find ACT, try AC first, then HC/HCT, then ALS and LS as last resort.

---

Re: 5.25 Floppy Not Reading

Posted on 2019-03-08, 08:26

by

by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Huh, weird that it has DS1-DS4 selection, not DS0-DS3. But in this case DS2 is correct setting for B drive, and probably won't work otherwise anyway - having 4 selections mean it's a Shugart too. It's set to DC so might just work, try it as a 360k drive as it seems not to have HD mode either but I …

---

Re: 5.25 Floppy Not Reading

Posted on 2019-03-07, 23:30

by

by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Yeah, that's a Shugart FDD, there's a pinout in this datasheet that confirms it: http://v1050.classiccmp.org/chipset/fd55.pdf And a bit weird one too. See that jumper below that shiny black box? It's set to RY, which means the pin 34 is /READY and not /DSKCHG like PCs expect. That would be the DC …

---

Re: 5.25 Floppy Not Reading

Posted on 2019-03-07, 19:54

by

by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Again, Shugart drive. It will not work in DOS, Windows, or any PC for that matter unless modded. Which can be as easy as rejumpering or might require soldering. Might have READY or DSKCHG, or both, at wrong pins. Might lack the HD detection switch/LED barrier. Might be locked to 300 or 360 RPM. I …

---

Re: Old KEnitec 286 Plus (suntac) Rescue, will need help.

Posted on 2019-03-07, 17:14

by

by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

The data bus is 16-bit wide D0-D15. It's split into 2 bytes, D0-D7 and D8-D15. The ISA slots have all the lines connected but most if not all the mobo chips are just 8-bit and only need the lower byte so D0-D7. Now, the actual routing of the data bus is a bit complicated, so I'm skipping things here …

---

Re: 5.25 Floppy Not Reading

Posted on 2019-03-07, 14:07

by

by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Some photos would help. The drive itself could be configured for Shugart interface rather than PC.

---

Re: 386DX-40 Himem.sys problem

Posted on 2019-03-06, 21:30

by

by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

It could be some dirt in the SIMM socket or on the memory modules, brush both to make sure. There is an old version of memtest86 that works on 386 but it's pain to get it to boot if you don't have a floppy drive. So try GoldMemory: http://www.goldmemory.cz/ (If that version doesn't work use older …

---

Re: Old KEnitec 286 Plus (suntac) Rescue, will need help.

Posted on 2019-03-06, 19:22

by

by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Pin 46 of the 002 is fine I think. The scan is a bit hazy here so it could be 45 or 46, I think it's OK. But there are 3 pins missing. Before you desolder the '245 though, since you tested and it does connect to ISA bus, it's actually easy to figure out the rest. So just add 3 wires from '245 to ISA …

---

Re: Old KEnitec 286 Plus (suntac) Rescue, will need help.

Posted on 2019-03-05, 19:24

by

by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Well if there is no connection between R13 and pins 2-3 of the 4069 then yes, the bypass is still needed. Measure the voltage on pin 12 again, if you see 0 or 5 volts then the circuit is not working. It has to be something in the middle - although remember that it might start oscillating even …

---

Re: Old KEnitec 286 Plus (suntac) Rescue, will need help.

Posted on 2019-03-05, 17:09

by

by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Thanks. Those batteries are a menace on all older boards. Also I just noticed I messed up the probe description. I made a simplified "schematic" with just one LED but the explanation on how to use it is for two LED version. So, rather than swap the wires around, which is a pain during testing, just …

---

Re: Old KEnitec 286 Plus (suntac) Rescue, will need help.

Posted on 2019-03-05, 16:01

by

by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Whoa, schematics! What a find. Is there any more than this page, just in case? I will have a closer look at this in the evening, but for now I'd suggest building the probe I mentioned earlier to test if the RTC is getting clock now. This will allow us to cross that out of the list. Actually with the …

---

Re: Olivetti PCS86 won't start - PSU?

Posted on 2019-03-05, 12:20

by

by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

That white stuff might be a side effect of the factory solder flux cleaning process, or it could be a spill from one of the electrolytic caps. One or more - sometimes an old capacitor will appear to work when powered after a long time being unused but then it will quickly fail after that. In any …

---

Re: Old KEnitec 286 Plus (suntac) Rescue, will need help.

Posted on 2019-03-04, 20:12

by

by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Pin 6 is output from gate 5-6. So clearly it is driving something but shorting it out like that is not good for the chip. However according to the measurements you've made pin 5 is at about 0.2V, so the gate is working OK. The problem is why pin is low and what it is connected to. It can't be …

---

Re: Old KEnitec 286 Plus (suntac) Rescue, will need help.

Posted on 2019-03-04, 19:50

by

by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

I'm sorry but I can't view that video, says it's not available. Wrong link maybe?

---

Re: Old KEnitec 286 Plus (suntac) Rescue, will need help.

Posted on 2019-03-04, 18:39

by

by Deunan

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

2.5V so about half the VCC on pins 1,2,3,4,12,13 is good. It probably means the clock is now running (even if the system is not working still). Without a scope you can confirm that with a LED indicator. Solder a probe like this: wire -> 1k resistor -> LED kathode (-) -> LED anode (+) -> wire So …

---