Corrections to the Tribbeck circuit diagram for the BBC B

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Coeus
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Re: Corrections to the Tribbeck circuit diagram for the BBC B

Post by Coeus » Sun Aug 02, 2020 2:41 pm

Thanks, Kazzie.

I have just re-read what I wrote and it is not as clear as it could be. When I said I had traced the signal to the capacitor with the red dot (applied with GIMP, not on the real capacitor) that was actually as far as it got before disappearing, not the first capacitor it reached so I wasn't claiming the one with the red dot was C35 - it is C31 as you rightly say. I'd also traced the signal through the yellow capacitor behind the socket which I can see marked as C35 on your board as well as on the circuit diagram.

Seeing the legends without the covering of dust makes everything clear and, seeing that, I now agree with you. I had been struggling previously because I had been trying to probe from the top of the board and found I could not see what I was doing well enough. Once I took the board out and checked the tracks on the bottom I was able to work out where the signal went but looking at your picture I maybe should have tried cleaning the top a bit first. What do people use for this kind of cleaning?

Anyway, the LM324 turned up yesterday but I was too busy listening to the excellent talks and discussions. I'll pop it in today and see if that solves the problem.

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1024MAK
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Re: Corrections to the Tribbeck circuit diagram for the BBC B

Post by 1024MAK » Sun Aug 02, 2020 7:38 pm

daveejhitchins wrote:
Sun Aug 02, 2020 9:01 am
TobyLobster wrote:
Sat Aug 01, 2020 11:08 pm
The legend next to D15 says "2xIN414148" in the user guide, but "2xIN4148" on the Tribbeck and original circuit diagrams.
Do please note that the part number is '1'N4148

Dave H.
For those that are not aware, excluding the markings used on surface mounting devices/components, the vast majority of part numbers for diodes and transistors conform to one of three standards. Although there are also manufacturers house codes.

If a part number starts with a 1N then that indicates ONE semiconductor P-N junction, meaning it's a diode, the remainder of the part number is the individual device number.

Transistors (which have two semiconductor P-N junctions) have part numbers that start 2N....

The part numbering system described above is the JEDEC system.
The other big systems are the European Pro Electron system and the Japanese JIS semiconductor designation system.

Mark

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Re: Corrections to the Tribbeck circuit diagram for the BBC B

Post by Kazzie » Sun Aug 02, 2020 8:57 pm

1024MAK wrote:
Sun Aug 02, 2020 7:38 pm
For those that are not aware, excluding the markings used on surface mounting devices/components, the vast majority of part numbers for diodes and transistors conform to one of three standards. Although there are also manufacturers house codes.

If a part number starts with a 1N then that indicates ONE semiconductor P-N junction, meaning it's a diode, the remainder of the part number is the individual device number.

Transistors (which have two semiconductor P-N junctions) have part numbers that start 2N....
That's another one of those little things that makes perfect sense when you think about it, but I'd never noticed it myself. Thanks! :)
BBC Model B 32K issue 7, Sidewise ROM board with 16K RAM
Archimedes 420/1 upgraded to 4MB RAM, ZIDEFS with 512MB CF card
RiscPC 600 under repair
Acorn System 1 home-made replica

Coeus
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Re: Corrections to the Tribbeck circuit diagram for the BBC B

Post by Coeus » Tue Aug 04, 2020 8:20 pm

I don't think this one has been reported, yet:
circuit.png
Look at IC15 - according to the labels this has two Pin 14s and no Pin 15.

Checking the data sheet it looks like the Q on the right should be 15.

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