View Profile: modem7 - Vintage Computer Forum

February 26th, 2021, 03:37 PM

modem7 replied to a thread IBM 5150 Parity Error in PCs and Clones

Good work. Looking at the circuit diagram and POST source code, I suspect that the failure mode of the bank-0 bit-0 chip was: the RAM chip was...

13 replies | 195 view(s)

February 23rd, 2021, 02:07 PM

modem7 replied to a thread How to enter the BIOS for a PC’s Limited 286 (Dell clone) in PCs and Clones

I wonder if the computer's motherboard has an RTC module that contains a nearly depleted battery/cell. We have sometimes seen odd boot/SETUP...

4 replies | 106 view(s)

February 23rd, 2021, 01:57 PM

modem7 replied to a thread unstacking a stacker compressed drive in Vintage Computer Hardware

Long standing advice has been to never smoke whilst using your computer. :-)

7 replies | 156 view(s)

February 20th, 2021, 12:18 PM

Exceter replied to a thread Flyback Transformer for the IBM 5151 - part # 74730102538 in Vintage Computer Items For Sale or Trade

I'll take all 3. I have 3 IBM 5151's and only 1 on them works. Not sure if the flyback transformer is what's wrong with them but, at you say, it...

4 replies | 117 view(s)

February 16th, 2021, 03:07 PM

marcampion started a thread Apple IIGs Keyboard Reboot? in Early Apple (I, ][, ///, etc.)

Hi! Does anyone know how to re-boot an Apple IIGS with keyboard commands? Using contro + reset button just gets me to a ] prompt. I know on my...

2 replies | 89 view(s)

February 15th, 2021, 01:01 PM

modem7 replied to a thread IBM 5150 with DB37 External Floppy in PCs and Clones

How is power supplied to the drive ? Note that the stock floppy controller in an IBM 5150 does not supply drive power on its external 37-pin...

9 replies | 181 view(s)

February 14th, 2021, 03:09 PM

modem7 replied to a thread IBM 5151 Jittery Row? in PCs and Clones

Welcome to these forums. A pity. A 'known working' video card would have allowed you to very quickly isolate the problem to either...

2 replies | 81 view(s)

February 14th, 2021, 02:11 PM

modem7 replied to a thread IBM 5170 issue in PCs and Clones

The D82284 has dual functionality, described by Intel as a 'clock generator and ready interface'. Per here], in the IBM 5170, for 12/16 MHz clock...

19 replies | 665 view(s)

February 14th, 2021, 09:44 AM

tonata replied to a thread Repairing Oliveti M24 monitor in PCs and Clones

So thanks again everyone! I added an extra cable for the H-SYNC it worked perfectly in the end. An Olivetti M24 monitor can be opened and...

45 replies | 2033 view(s)

February 13th, 2021, 01:58 PM

modem7 replied to a thread ESR Meter Suggestions in Vintage Computer Tools

That sounds like the one described in the construction manual at here]. Circuit diagram and description included. When published, I built some from...

28 replies | 625 view(s)

February 12th, 2021, 02:27 PM

modem7 replied to a thread IBM 5170 issue in PCs and Clones

I have added the IBM 5170's startup sequence to here]. I will enhance that later. We know that the OP is not seeing any codes on a POST card (OP...

19 replies | 665 view(s)

February 12th, 2021, 03:18 AM

modem7 replied to a thread Picked up an IBM 5150. Keeping it original or upgrade ? in PCs and Clones

No. One reason is that the controller, the 'IBM 5.25 diskette drive adapter', does not support a 300 Kbits/second data rate, the rate used when a...

25 replies | 1273 view(s)

February 12th, 2021, 03:06 AM

modem7 replied to a thread IBM 5170 issue in PCs and Clones

The OP has a POST card. Previous experience reveals that if the only problem is a completely faulty MC146818 (or it being ineffective, for whatever...

19 replies | 665 view(s)

February 11th, 2021, 11:11 PM

modem7 replied to a thread IBM 5170 issue in PCs and Clones

Careful with "continuity". For example, if I use the 'continuity' setting of my multimeter to measure a good 56 ohm resistor from my spares box, my...

19 replies | 665 view(s)

February 11th, 2021, 01:14 PM

modem7 replied to a thread IBM 5170 issue in PCs and Clones

So, when you earlier wrote, "NEW PSU is outputting proper voltages", the motherboard was not connected to the PSU. (Otherwise the motherboard would...

19 replies | 665 view(s)

February 10th, 2021, 08:02 PM

modem7 replied to a thread IBM 5170 issue in PCs and Clones

Which means that there is no short circuited capacitor. If there was, it would overload the new PSU, resulting in the new PSU shutting down. To...

19 replies | 665 view(s)

February 10th, 2021, 01:23 PM

modem7 replied to a thread Strange floppy drive behavior from Zenith Z-386SX/20 in Vintage Computer Hardware

All I can do is provide a possible workaround (not fix) - see here].

5 replies | 219 view(s)

February 10th, 2021, 01:15 PM

modem7 replied to a thread IBM PC 5150 ROM failures (and substitutes) in PCs and Clones

To give you some kind of idea, for the IBM PC family, I have recorded some motherboard BIOS ROM failures at here]. That page excludes Cassette BASIC...

2 replies | 169 view(s)

February 9th, 2021, 01:23 PM

modem7 replied to a thread Wanted: Toshiba T3200 "Reference" and "First Time" Manuals in Vintage Computer Items Wanted

In case you are unaware, a copy of the maintenance manual is at here].

6 replies | 460 view(s)

February 8th, 2021, 08:38 PM

modem7 replied to a thread Help ID this combo LPT/128k card (with 256kb upgrade card) in PCs and Clones

I see now that I have taken a closer look at the photos in the first post. Oki MSM37S64 used on the parent board; Oki MSM3764 (no "S") used on the...

10 replies | 332 view(s)

February 8th, 2021, 01:26 PM

modem7 replied to a thread Help ID this combo LPT/128k card (with 256kb upgrade card) in PCs and Clones

I see 64 KB (one bank of 64Kbit chips).

10 replies | 332 view(s)

February 7th, 2021, 06:53 AM

tonata replied to a thread Repairing Oliveti M24 monitor in PCs and Clones

Hi guys, Thank you for all you help so far! I might have break trough ... I found a problem! The f***** cable has only pin 1 not connected - H...

45 replies | 2033 view(s)

February 5th, 2021, 01:37 PM

modem7 replied to a thread Alternative Font for IBM 5150 with MDA? in PCs and Clones

Do you have any references (books, magazine articles, etc.) to support that single reason for a year and a half delay ? Surely, a part of that...

19 replies | 829 view(s)

February 5th, 2021, 01:15 PM

modem7 replied to a thread Is it possible to use XT-IDE on a IBM 5170 computer? in PCs and Clones

The Award BIOS. What exactly is the error message ? All that you should need to do is set the hard drive type number in 'CMOS SETUP' to...

8 replies | 337 view(s)

February 4th, 2021, 08:45 PM

modem7 replied to a thread Is it possible to use XT-IDE on a IBM 5170 computer? in PCs and Clones

Quite a standard configuration. What I would expect to work is: 1. Exchange the motherboard's IBM BIOS ROM set for the Award set at here], then...

8 replies | 337 view(s)

February 4th, 2021, 02:09 PM

modem7 replied to a thread Is it possible to use XT-IDE on a IBM 5170 computer? in PCs and Clones

So you are using an XT-IDE card that is known to work. These days, "XT-IDE" is used to describe many different cards. Exactly, what card do you...

8 replies | 337 view(s)

February 2nd, 2021, 06:37 AM

tonata replied to a thread Repairing Oliveti M24 monitor in PCs and Clones

Only if you have already the experience. If you have already seen a similar IC. Maybe I should inspect some the components: diodes, resistance and...

45 replies | 2033 view(s)

February 2nd, 2021, 02:35 AM

tonata replied to a thread Repairing Oliveti M24 monitor in PCs and Clones

There is also a switch "normal" => "service mode".

45 replies | 2033 view(s)

February 2nd, 2021, 01:05 AM

tonata replied to a thread Repairing Oliveti M24 monitor in PCs and Clones

Thank you! The problem is that I can not find the datasheet for the TA7634AP ... So no documentation for the monitor and no datasheet for this IC.

45 replies | 2033 view(s)

February 1st, 2021, 11:27 AM

tonata replied to a thread Repairing Oliveti M24 monitor in PCs and Clones

Please have a look. Here is the photo again: From what I see horizontal and vertical sync are connected here and then after a series of diodes...

45 replies | 2033 view(s)

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