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  #1  
Old 08-18-2009, 04:14 PM
benalford benalford is offline
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Default 880-107 1k static memory board

Grant:

I would like to purchase a second memory board. I noticed that pin 11 on ICB is not connected. The schematic shows this pin is connected to +5v.
I tried connecting this pin to +5v but it didn't make any difference in the operation of the kit, by the way the kit works great.

Thanks again

Ben
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  #2  
Old 08-18-2009, 04:20 PM
marty marty is offline
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Talking 1 K

Hi ;
You should connect the +5 thru a pull-up resistor like about 1K. Just in case...I would need to look at the schematic to see what it does...
THANK YOU Marty
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  #3  
Old 08-19-2009, 01:50 PM
marty marty is offline
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Talking 1 K

Hi;
I should have restated what I last said in my last post, When trying an unknown pin , then go thru a resistor, to protect the circuit and the power supply, such as connecting a line that goes to ground to a +5 , by going thru a resistor you find out what is happening without shorting to something else, without a limiting resistor....
On pin 11 of the 74L30 it is an input and with no connection it would float high , so connecting it to +5 would eliminate the possibility of it going low at any time... You could connect it to pin 12 next to it which is connected to pin 14 on the board... and this would eliminate any interference of any kind to the Ic...
THANK YOU Marty
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  #4  
Old 08-24-2009, 01:33 AM
benalford benalford is offline
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Default 880-107 1k static memory board

Marty:

Thanks for the advice. I did check the IC data sheet before I tried anything. I don't do a smoke test.

Since I found the error on the memory board I checked the CPU board and found ICK pin 12 to be tied to ground. The schematic shows pin 12 to be connected to ICK pin 11.

The collector of CS4410 is connected to +5 through R28 instead of being in series with R26.

I also found Jumper J1 on 8800 D/C Board dead ends at the bottom left corner. Was J1 for future use?

Thanks

Ben
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  #5  
Old 08-24-2009, 02:52 AM
marty marty is offline
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Talking 1K ststic

Hi Benalford;
I checked the Schematics, and you were right on one and wrong on the other, and the jumper I'll have to check on... On the Transistor you are right, and on IC K you are wrong, a closer inspection of the Schematic shows that pin 12 IS tied to ground, and pin 11 and pin 2 are tied together before being pulled up, by a resistor... I have an Origional Altair CPU Board and I compared the two for both IC K and the Transistor circuitry,,, they are the same... So I suspect that they changed the transistor circuitry when it didn't work and forgot to change the Schematic or they changed the schematic and never got around to doing the board...
THANK YOU Marty
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  #6  
Old 08-24-2009, 03:35 AM
marty marty is offline
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Talking 1 K

Hi Benalford;
I just got thru checking J1 on the Front Panel, that I have from Grant, it connects Ic S pin 11 to wire connection 39. And I also checked the Schematic, they are the same....
THANK YOU Marty
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  #7  
Old 08-24-2009, 01:59 PM
marty marty is offline
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Talking 1 K

Hi Ben;
I coppied out the how the Transistor circuit is from the Board lay-out, and I think that is what they intended to draw on the Schematic , where both resistors are pulled up, instead of one being pulled up thru the other...
THANK YOU Marty
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  #8  
Old 08-27-2009, 03:59 AM
benalford benalford is offline
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Default 8800 D/C Board

Marty:

My Bad, ICK is correct. I misread pin 2 for pin 12. As for J1 on 8800 D/C board the end opposite wire connection 39 dead ends. I looked through the board with a strong light. But Ic S is connected to wire connection 39 but not through J1.

Thanks once again.
Your Help Is Greatly Appreciated.

Ben
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  #9  
Old 08-27-2009, 04:20 AM
marty marty is offline
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Talking 1 K

Hi Ben;

THEN You have a different Front Panel Board, then I do. But as long as Ic S is connected to pin 39, That is all that counts... Then Don't worry about it... As on the Rev 0 boards it uses Jumper J1, Maybe on a later Rev. it is eliminated... As Long as your system works and you are Happy with it and it does what you want -- execute 8080 code, then I wouldn't worry about it...
THANK YOU Marty
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  #10  
Old 09-03-2009, 05:51 PM
benalford benalford is offline
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Default 880-107 1k static memory board

Marty:

You are right my D/C board is different. I have 2 boards from Grant and I will install one of them. These boards use J1.

Thanks once again

Ben
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