HP 35470A SCSI 2/4GB tape drive attempted repair

Posted on 2024-03-25, 22:13

by

by mita

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Hi, I am trying to repair a HP35470a scsi tape drive. I got the drive in the following condition: - adaptec controller recognized correctly the drive - was able to feed with cleaning cartridge and eject using Tapemate backup sw I feed with a normal tape and tried to initialize the tape but the drive …

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Re: 486 SocketBlaster building experiment - Oh my God, a difficult beast to build

Posted on 2024-03-25, 21:35

by

by mita

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

I have just read Vpp (peak to peak I assume) on the scope. It was changing periodically but the max was about 70mV.

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Re: Tiny 486 build - SBC with ISA backplane

Posted on 2024-03-25, 21:22

by

by mita

in Marvin \ System Specs

in Marvin \ System Specs

CPU cooler fan now mounted: IMG_20240325_170543_(1200_x_900_pixel).jpg Now comes the fun/tedious/skin-shredding part of trying to (neatly) fit all of the cables inside the case as I finally put it all together! It's going to be very tight.... That is a nice project, congratualtions. You are lucky …

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Re: 486 SocketBlaster building experiment - Oh my God, a difficult beast to build

Posted on 2024-03-25, 16:31

by

by mita

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

I am going to build one more socketblaster using the remaining pins and boards. I will try a different aproach for pin alignment this time. Try to use existing free prin headers to stabilize and keep perpendicular position of the soldareable pin headers. The first inner rows of the male headers are …

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Re: 486 SocketBlaster building experiment - Oh my God, a difficult beast to build

Posted on 2024-03-25, 16:17

by

by mita

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

The ripple voltage can be a lot higher than you think. This is the highest Output LOW voltages acceptable for a DX4-100 3.3V CPU: IOL = 4.0 mA (Address, Data, BEn) ... 0.45V IOL = 5.0 mA (Definition, Control) ... 0.45V IOL = 2.0 mA ... 0.40V IOL = 100 µA ... 0.20V Lowest Output HIGH voltage: IOH = …

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Re: 486 SocketBlaster building experiment - Oh my God, a difficult beast to build

Posted on 2024-03-25, 16:14

by

by mita

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

It would also allow you to have the buck converter exposed so you can make changes without removing the CPU. thats how Sphere478 designed it https://www.vogons.org/viewtopic.php?p=1176382#p1176382 Well if somebody thinks he has a complicated project than it is worth to check Sphere478's project …

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Re: 486 SocketBlaster building experiment - Oh my God, a difficult beast to build

Posted on 2024-03-25, 16:09

by

by mita

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

- Check the DC-DC converter before soldering in to the socket. Use an 2 ohm/10W resistor to simulate the load and measure the ripple with the scope. Check the thermal condition of the converter. Please note the converter will be in a much hotter place next to the bottom of the CPU. Use high …

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Re: 486 SocketBlaster building experiment - Oh my God, a difficult beast to build

Posted on 2024-03-25, 16:04

by

by mita

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

feipoa went over picking best LDO for 486 https://www.vogons.org/viewtopic.php?f=46&t=54953 I would very much like to build a version with the sockets next to each other as opposed to on top of each other, like in this one you linked. It would make the whole process much easier in cases where you …

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Re: 486 SocketBlaster building experiment - Oh my God, a difficult beast to build

Posted on 2024-03-25, 15:56

by

by mita

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

- Check the DC-DC converter before soldering in to the socket. Use an 2 ohm/10W resistor to simulate the load and measure the ripple with the scope. Check the thermal condition of the converter. Please note the converter will be in a much hotter place next to the bottom of the CPU. Use high …

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Re: Looking for ALI M1429 datasheet

Posted on 2024-03-18, 20:27

by

by mita

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Sorry to hear it, but thank you anyway.

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486 SocketBlaster building experiment - Oh my God, a difficult beast to build

Posted on 2024-03-18, 19:19

by

by mita

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

I am going to share my experiment building this project, see the following links. In short: how to use non 5V CPU like AMD 5x133 in a 486 5V ONLY MB. https://github.com/scrapcomputing/486SocketBlaster?tab=readme-ov-file https://www.youtube.com/watch?v=vEpAoVE4KjU I drew the following build …

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Looking for ALI M1429 datasheet

Posted on 2024-03-18, 07:59

by

by mita

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Hi, I found interesting was not able to find datasheet about the Ali M1429 chip. Checked the VOGONS posts and it seems users tried to ask for it from 2015 but still not available. If you have it or you know a source please share with us to help hw debugging the boards with this chip. Thank you!

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Re: Anybody know if this BIOS supports hard drives over 540MB?

Posted on 2024-03-07, 18:40

by

by mita

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Hi thevdm! Would you mind to make picture of the CN1, CN9, CN10 connectos with cables attached? Unfortuantely these connectors are not documented. I have the same board, disassembled for testing. I made pictures about this part of the board before disconencted the power led, the ide led and the …

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Re: Looking for Toshiba 4800 datasheet

Posted on 2024-03-06, 01:13

by

by mita

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Thank you your post! Lot of things to consider. An important update! I found a freaking schematic of a 486 PC DIY. I do not know wether this porject is finished or not but a lot of effort were made to kick it on. FInally have a canche to study the whole system imcluding the chipset's co-operation …

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Re: Looking for Toshiba 4800 datasheet

Posted on 2024-03-05, 17:00

by

by mita

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

My bad.... The BIOS has two pins for enable: chip select and output enable. This particular circuit use only one control not two. FInally the board came to life. Conclusion: In case of battery damage board the precise and full cleaning is mandatory. Use dremmel with rubber tip or fiber glass pen to …

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Re: Looking for Toshiba 4800 datasheet

Posted on 2024-03-04, 10:44

by

by mita

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Thank you your reply! The problem is shorting low the OE results the 8 bit data bus of the BIOS drives the data bus lines all the time. It will conflict with the controller when the controller wants to drive the data lines. If the OE will be put high all the time than the BIOS data lines will be in …

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Re: Socket 7 MB starting problem

Posted on 2024-03-04, 03:27

by

by mita

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Recap did not changed the situation. Tricking the startup with the double switch described above the system is able to boot from floppy. Interestingly it can not boot from a tested ide disk, froze in the disk controller initialization phase. Next I will try to measure the IDE cable pins for stucked …

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Looking for Toshiba 4800 datasheet

Posted on 2024-03-04, 03:15

by

by mita

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Hi, Try to revive a GNB-486UNL V1.1 board. Powers are OK, clock is ok, reset ok but no sign of code execution on the post diag card. Checked the bios and found the CE - output enable pin short to ground. It seems this pin is connected on the internal layer there is no trace on top or bottom layer on …

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Re: Socket 7 MB starting problem

Posted on 2024-02-23, 09:01

by

by mita

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Did you put CR2032 battery into place? Some motherboards don't post when it is missing. My bad I missed it. Placing the battery resulted the reset state went away after switching on. Unfortunately the situation is the same, but one small step forward clearing the reset signal with the battery …

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Re: Zortech C++ 3.1 - request for information

Posted on 2024-02-23, 08:40

by

by mita

in Marvin \ Software

in Marvin \ Software

These days a cross compiler tool chain really is the way to go, and then you get to retain your modern version control toolset, your fancy multi-window, syntax highlighting, auto-completing editor... And not have your silly null pointer dereferencing mistake take down your editor as well. Much has …

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