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

Posted on 2019-03-11, 17:59

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

27J is +/- 5% tolerance, better than K which is 10%. Both LEDs being lit all but guarantee the clock is present, but check pin 21 on RTC as well. Did you check if the boot code is still 01/02 when you remove 8042 from the socket? Both the keyboard controller and RTC are on the same bus so either one …

Re: Olivetti PCS86 won't start - PSU?

Posted on 2019-03-11, 11:41

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Desolder the bridge rectifier and T3 transistor and check for shorts. Usually both will require replacing. There is a small chance it's actually one of those 2 grey capacitors near the ones you've replaced, so maybe start with those. And rather than waste fuses (and risk further PCB damage) just …

Re: Help me fix my Schneider Euro XT?

Posted on 2019-03-10, 18:55

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

If this thing has built-in CGA there might be address conflict with any ISA-based video card for both BIOS and video RAM decoding. Remove that card and try again. Any beeping or FDD/HDD activity would be a positive sign it actually works.

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

Posted on 2019-03-10, 13:27

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Hm, that pretty much covers all RTC pins. But just to be sure test that clock again, and pins I mentioned with the probe once you repair C82. In case the value is unreadable, it should be 27pF according to schematics. One more thing, test voltage on RTC pins 18 and 22 as well - but with a meter, not …

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

Posted on 2019-03-10, 11:34

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

So ISA is all OK now, good. Let's get back to that RTC then. Did you restore the connection to R13? You said you removed it afterwards and I'm not sure if the RTC chip will respond to I/O properly if it has no clock. Check with the probe again if you have to, on the last movie you've made you had …

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

Posted on 2019-03-10, 10:07

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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 …

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