Bull Micral 65 information ?

Pour tout ce qui touche au PC d'IBM et ses nombreux descendants. Attention tout de même, au delà de quelques MHz la discussion devient vite hors sujet.

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Systeman79
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Bull Micral 65 information ?

Message par Systeman79 »

So I found out I had a Bull Micral 65 case (which someone started modding but not too bad luckily) and I also found a motherboard.
The motherboard was missing its power supply headers (hmmm) and cpu.
So ordered the headers and a fellow collector had a 80286-12 for me so yesterday I soldered the headers back and today received the CPU.

Just now tried it and it works, whooohoooo :)

But now I am wondering, does anyone know what the two swiches do ?
And is it correct that the motherboard has SCSI onboard ?
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fneck
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Re: Bull Micral 65 information ?

Message par fneck »

I have almost no information on the BULL Micral 65 but the subject is interesting and I will try to search. Could you take a picture of the motherboard as well as the switches you are talking about?
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Re: Bull Micral 65 information ?

Message par Systeman79 »

Certainly, I actually have two systems but I am not sure which of the two is original so will take photo's of both systems.
Will probably be this weekend at the soonest though.
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xmamat
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Re: Bull Micral 65 information ?

Message par xmamat »

Hello,

I'm also very interested in this. The Bull Micral serie holds a special place in my heart :wink:

I recently got an untested Micral 60 (the first Bull IBM AT clone) which I haven't tried to restore yet. It's on my shortlist of coming projects.
I'd be curious to compare it in details with the 65.
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Re: Bull Micral 65 information ?

Message par Systeman79 »

Some pictures can be found here : https://flic.kr/s/aHsmUFxbdW

What I know is that P14 is battery, P12 is for the leds on the front and P16 is the speaker

If you want any specific pictures let me know and I will make some.
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fneck
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Re: Bull Micral 65 information ?

Message par fneck »

Thank you for the pictures 8)

The 65 model is an evolution of the 60 model. If it uses the same case, the motherboard is very different (SIMM support, many connectors onboard).

The controller card is interesting, it seems to be MFM and SCSI compatible. Unless the 50-pin connector that we see connected to the motherboard is an extension of the bus? with external connector? or the SCSI controller is on the motherboard? I had never seen a card like this.

[edit] It seems that the SCSI controller is on the motherboard, it is the NCR 53C80 that we see on one of the pictures near the 50 pins connector.
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fneck
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Re: Bull Micral 65 information ?

Message par fneck »

Then to find the correspondences of the switches without the documentation it will be complicated. Perhaps you can take inspiration from the switches on the Micral 45 here, there are the same formats, but with precautions:

https://forum.system-cfg.com/viewtopic. ... 62#p149762
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Re: Bull Micral 65 information ?

Message par Systeman79 »

The 45 and 65 were released around the same time and as the Bull Micral series seem to reuse things a lot it might make sense if the switches are the same too. I will check it out when I have some time.
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Re: Bull Micral 65 information ?

Message par Systeman79 »

This is the battery that is in the 65. I need to replace it.
Image
Image
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Re: Bull Micral 65 information ?

Message par Systeman79 »

So this battery goes to P14 and on P14 pin 2 is + and pin 4 is -
Also inside the battery box there is a resistor of, if I am not mistaken, 47k Ohms on +

Image
Image
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Re: Bull Micral 65 information ?

Message par Systeman79 »

I am not so good with electronics but what would the resulting voltage be with this resistor in place ?
Because 6,2 volts seems a bit too much for the BIOS battery backup power.
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Re: Bull Micral 65 information ?

Message par fneck »

It is the same référence than the battery in the Micral 35 ou 45 but not the same case:
Image

Inside:
Image

The role of this resistor is to protect the battery in the event of destruction of the diode which prevents its recharging. But the consumption is so low that it does not influence the voltage sufficiently.

I find the answer here :
https://forum.system-cfg.com/viewtopic. ... 02#p177002

And the tuto for rebuilt this battery:
https://forum.system-cfg.com/viewtopic.php?f=27&t=9780
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Re: Bull Micral 65 information ?

Message par Systeman79 »

You don't know if anyone tried with just 3,6V ? Because I could just use standard CMOS battery complete with wires and all.
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fneck
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Re: Bull Micral 65 information ?

Message par fneck »

The real time clock is the MC146818 (on the top right of the motherboard picture), you can look at the datasheet for specifications.

It seems to me that 3,6 V would be a little weak. It should not be forgotten that there is also one or two diodes on the circuit so a voltage drop of 0,5 to 1V.
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Re: Bull Micral 65 information ?

Message par Systeman79 »

Aah yes I see, 3V - 6V and indeed, if you loose 1V then it will not work and now I understand why 6,2V is not too much :)

Will order two AA sized with solder lips and the 47k resistor and then I can reuse the holder :)
It will look 100% original :)
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