Re: XT clone motherboard repair advice/help needed (KT 10 M/B)

Posted on 2019-04-24, 23:34

by

by HanJammer

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Hm. Just to confirm, this was tested with no CPU, no 8288 and no BIOS ROM? No CPU, no 8288 (just pin 4 and 7 resistors to GND), no BIOS ROM. There's something wrong still with bit 4. It's weird that you get 2.2V on U58 pin 15, and yet only 1.52V on U54 pin 13. These should be connected so why is it …

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Re: Looking for QT-102 V3.05.1 286 BIOS dumps

Posted on 2019-04-24, 23:07

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by HanJammer

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

How about this? http://minuszerodegrees.net/bios/BIOS_30MAR90_QUADTEL_ENHANCED_286_BIOS_3.05.01.zip I don't think it's known what board this was intended for but the version number is correct so it can't hurt to try (probably) Wow, that appears to be exactly what I needed. Curious thing - I didn't …

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Re: XT clone motherboard repair advice/help needed (KT 10 M/B)

Posted on 2019-04-24, 22:35

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by HanJammer

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

F and S are very close in terms of speed but I think F uses less power. In most cases F will work fine as S replacement. If replacing U58 doesn't cure the mobo, try with the resistors again and check the voltages - I'm curious if the bit 4 will still show different readings. In fact if you get odd …

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Re: XT clone motherboard repair advice/help needed (KT 10 M/B)

Posted on 2019-04-24, 22:06

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by HanJammer

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Congrats to your new solder sucker :) 74F should normally work fine. F means "fast", being near to S (Schottky) in speed, but nearer to LS (Low power Schottky) in consumption. Did you test the chips in U23 and U66 too? For now I didn't. Perhaps I will desolder them too and install sockets later, …

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Re: XT clone motherboard repair advice/help needed (KT 10 M/B)

Posted on 2019-04-24, 20:57

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by HanJammer

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

OK, back to work. I received my desoldering station today and desoldered U58 right away. I soldered in a DIP20 socket. Now, I forgot I have some old dammaged 286 motherboard for parts and I found a lot of 74 logic chips on it - 74F245Ns among others. The question - is it a direct replacement for …

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Re: Best Motherboard for my 90’s pc?

Posted on 2019-04-23, 12:16

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by HanJammer

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

That's funny.... I remember 2003/2008 as dark times in PC gaming. All games were more or less a ripoff of each other, and were they did not rip each other off, they just took and re-issued old ideas from the mid-90's. The FPS shooter genre died during that period Far Cry F.E.A.R. BioShock …

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Re: Best Motherboard for my 90’s pc?

Posted on 2019-04-23, 09:27

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by HanJammer

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

IMHO What you are asking for is not really a 90s PC... '99 well into 2004 were pretty dark times for both - PC hardware and games. On one hand - motherboard and graphics chipsets were still plentiful (some may find interesting how things were handled by early ATI/Matrox/S3 and other 3D graphics …

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Re: Best Motherboard for my 90’s pc?

Posted on 2019-04-22, 19:08

by

by HanJammer

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

IMHO What you are asking for is not really a 90s PC... '99 well into 2004 were pretty dark times for both - PC hardware and games. On one hand - motherboard and graphics chipsets were still plentiful (some may find interesting how things were handled by early ATI/Matrox/S3 and other 3D graphics …

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Re: XT clone motherboard repair advice/help needed (KT 10 M/B)

Posted on 2019-04-22, 18:48

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by HanJammer

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

I just tested the CPU from the broken motherboard on the 'new' working one and it works just fine. I will order parts today so I will get back with results once U58 is replaced...

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Re: Serial ports won't work on ASUS VX97

Posted on 2019-04-22, 18:34

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by HanJammer

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

I have VX97 complete with all original cables and brackets. Here's how it should be connected… DB9 for now… I can check DB25 too if needed… Filename pinout.png File size 169.93 KiB Views 350 views

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Re: Anyone know what this object is?

Posted on 2019-04-21, 21:46

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by HanJammer

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

UPDATE: Last night, my dad told me what this object is. It's actually a box that controls a light bulb. You connect a light bulb to a circuit that connects to this box, and you twist the knob to adjust the light's brightness and dimness. No actual name has been specified for this object, but at …

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Re: XT clone motherboard repair advice/help needed (KT 10 M/B)

Posted on 2019-04-21, 11:07

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by HanJammer

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

TL;DR: It all points out to bit 4 on U58, it has to be replaced to make sure, we cannot test it any better while in motherboard. But, if my theory as to the exact failure mode is correct, it might just be possible to boot the mobo by piggy-backing the faulty U58 with a working chip. Though this …

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Re: What's the best CRT monitor for DOS gaming?

Posted on 2019-04-21, 00:32

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by HanJammer

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

What's the best CRT for DOS gaming? I will tell you it's the one you have. You will always find better one than the one you have. Stop thinking about hardware. Start thinking about making the use of it and enjoying it. If your CRT is already some low-end crap then grab any decent CRT that is easly …

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Re: XT clone motherboard repair advice/help needed (KT 10 M/B)

Posted on 2019-04-20, 22:35

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by HanJammer

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

A few more tests - remove BIOS and measure voltage on the address and control pins of the socket. With both 8288 resistors. Let's see what byte is being addressed (should be ADR [19:0] = 0xfffff but due to the multiplexing of low address byte with data it's a bit wild without the '373 latching). …

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Re: DOS Music Creation Hardware

Posted on 2019-04-20, 21:02

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by HanJammer

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Would an SC-55 sound the same, have the same capability, and especially the same compatibility with DOS games? Even though the MT-32 looks better, there are more SC-55s available on Ebay, and they're significantly cheaper, generally speaking. SC-55 is supposed to be reverse compatible with MT-32 …

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Re: XT clone motherboard repair advice/help needed (KT 10 M/B)

Posted on 2019-04-20, 19:42

by

by HanJammer

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Oh, so you did have it in the socket back then. That might explain the different behaviour of the bit 4 then. Yes, I removed it since "2019-4-18 @ 11:01 " post where you asked to measure the resistance of the BIOS ROM data pins. Earlier it was in the socket. A few more tests - remove BIOS and …

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Re: Anyone know what this object is?

Posted on 2019-04-20, 16:56

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by HanJammer

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

It's a transformer for illuminator in Nikon microscope. edit: https://profcontrol.de/Nikon-Transformer-UN-Power-Supply-12V-100W-Lamphouse-Labophot-BH2-Microscope_1 If it still works then you can easly use it as universal transformer (for example to power LiPo charger for RC cars/aircraft as it has a …

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Re: DOS Music Creation Hardware

Posted on 2019-04-20, 16:50

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by HanJammer

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

I've been wanting to do more and more on DOS systems, and one of the things is music creation. The system I'll be using will most likely be a 486 DX2/66, and probably with a Soundblaster Awe32. Do I need/want an MT-32? I've seen several videos and reviews (LGR and 8-Bit Guy, for example) of the MT- …

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Re: XT clone motherboard repair advice/help needed (KT 10 M/B)

Posted on 2019-04-20, 15:12

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by HanJammer

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Second XT motherboard I bought last wednesday seems to work just fine! It's some sort of ERSO XT clone and it's overal layout and logic chip count is similar to the board we are trying to fix. Manual for this board contains some schematics, so maybe you will find them useful http://minuszerodegrees. …

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Re: XT clone motherboard repair advice/help needed (KT 10 M/B)

Posted on 2019-04-20, 14:01

by

by HanJammer

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Hm. So the test with the resistor has different result now than it had last time when you measured voltages on 3 of the '245 chips. And the only thing different is the voltages on B side were a bit higher now (you said those slowly go down so chances are last time it took you more time to measure …

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