Silent, nothing visible

discuss both original and modern hardware for the bbc micro/electron
Colday
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Re: Silent, nothing visible

Post by Colday » Sun Aug 16, 2020 2:58 pm

I've tried replacing with a known good 6502. No change.
BBC B's... I now have 6!
I also have 1 boxed with manuals, unmolested model A.
And also an unmolested model B. (but not boxed sadly)
12x floppy drives (only 1x currently works I think)...
Learning to repair and refurb keyboards next! No more sticky keys!

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hoglet
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Re: Silent, nothing visible

Post by hoglet » Sun Aug 16, 2020 3:20 pm

Colday wrote:
Sun Aug 16, 2020 2:04 pm
Ok, finally found time to get these checks done.
It might be worth having another try at those measurements.

What you are trying to do is to use the rising edge of reset as a trigger, and capture a single trace from that event.

If you set up the triggering correctly, the scope should trigger once when the break key is released, and the rising edge of reset should be visible on the left of the display,

I think what's gone wrong is you left the scope on auto-trigger, so it's triggering continuously.

See if you can find a way to change the trigger setting from Auto to Normal.

Dave

Colday
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Re: Silent, nothing visible

Post by Colday » Sun Aug 16, 2020 3:33 pm

Yep. I can do that!

I'll go now!

Watch this space! Lol.

Edit:
IMG_4725.jpg
IMG_4726.jpg
BBC B's... I now have 6!
I also have 1 boxed with manuals, unmolested model A.
And also an unmolested model B. (but not boxed sadly)
12x floppy drives (only 1x currently works I think)...
Learning to repair and refurb keyboards next! No more sticky keys!

Colday
Posts: 402
Joined: Thu Jul 25, 2019 10:18 pm
Location: North Essex, UK
Contact:

Re: Silent, nothing visible

Post by Colday » Sun Aug 16, 2020 6:04 pm

hoglet wrote:
Sun Aug 16, 2020 3:20 pm
See if you can find a way to change the trigger setting from Auto to Normal.

Dave
I think that is what you were meaning?
BBC B's... I now have 6!
I also have 1 boxed with manuals, unmolested model A.
And also an unmolested model B. (but not boxed sadly)
12x floppy drives (only 1x currently works I think)...
Learning to repair and refurb keyboards next! No more sticky keys!

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hoglet
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Re: Silent, nothing visible

Post by hoglet » Sun Aug 16, 2020 7:02 pm

Colday wrote:
Sun Aug 16, 2020 6:04 pm
I think that is what you were meaning?
That's more like it.

But what you are seeing on the blue trace is switch bounce, which is causing it to trigger at the wrong point.

There might be ways around this...

Do you have a PDF version of the DOS1102 Manual you could post?

Dave

Colday
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Re: Silent, nothing visible

Post by Colday » Sun Aug 16, 2020 7:10 pm

I have no idea what that is.... so no.

Lol.
BBC B's... I now have 6!
I also have 1 boxed with manuals, unmolested model A.
And also an unmolested model B. (but not boxed sadly)
12x floppy drives (only 1x currently works I think)...
Learning to repair and refurb keyboards next! No more sticky keys!

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hoglet
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Re: Silent, nothing visible

Post by hoglet » Sun Aug 16, 2020 7:16 pm

Colday wrote:
Sun Aug 16, 2020 7:10 pm
I have no idea what that is.... so no.
I'm asking about the manual for your oscilloscope.

Sorry, I think I've taken this about as far as I can.

Maybe someone else has some ideas...

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1024MAK
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Re: Silent, nothing visible

Post by 1024MAK » Sun Aug 16, 2020 7:17 pm

hoglet wrote:
Sun Aug 16, 2020 7:02 pm

But what you are seeing on the blue trace is switch bounce, which is causing it to trigger at the wrong point.
The values used in the NE555 ‘reset’ circuitry should result in a minimum pulse width of about 0.1 seconds (assuming it’s working as designed and that the signal for the ‘scope is being picked up downstream of the NE555.

Mark

Colday
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Re: Silent, nothing visible

Post by Colday » Sun Aug 16, 2020 7:52 pm

hoglet wrote:
Sun Aug 16, 2020 7:16 pm
Colday wrote:
Sun Aug 16, 2020 7:10 pm
I have no idea what that is.... so no.
I'm asking about the manual for your oscilloscope.

Sorry, I think I've taken this about as far as I can.

Maybe someone else has some ideas...
Well, only just having bought it, I didn't remember the model number off the top of my head. My bad. I shall attempt to do better in future.

Thanks for your help.
BBC B's... I now have 6!
I also have 1 boxed with manuals, unmolested model A.
And also an unmolested model B. (but not boxed sadly)
12x floppy drives (only 1x currently works I think)...
Learning to repair and refurb keyboards next! No more sticky keys!

Colday
Posts: 402
Joined: Thu Jul 25, 2019 10:18 pm
Location: North Essex, UK
Contact:

Re: Silent, nothing visible

Post by Colday » Tue Aug 18, 2020 3:31 pm

So, does anyone else have some time to spare to help me out with this?

I'm doing my best to learn. I prefer to jump in with both feet as I find I learn better by 'doing' but guidance rather than going off and reading a book about it. (Unless the book tells me what to put where and what to expect from that testing location)
BBC B's... I now have 6!
I also have 1 boxed with manuals, unmolested model A.
And also an unmolested model B. (but not boxed sadly)
12x floppy drives (only 1x currently works I think)...
Learning to repair and refurb keyboards next! No more sticky keys!

Colday
Posts: 402
Joined: Thu Jul 25, 2019 10:18 pm
Location: North Essex, UK
Contact:

Re: Silent, nothing visible

Post by Colday » Sat Sep 12, 2020 2:58 pm

Well, through some trial and error.

I removed the UHF output bin, cleaned underneath and re soldered it all, I cleaned as best I could the traces on the bottom of the board with white vinegar, I checked and reseated several of the IC's.

Innumerable checks for continuity and a wee bit of soldering.... and it works.

So, as an announcement, you CAN put a BBC motherboard through the dishwasher on a hot cycle with Fairy Platinum dishwasher tab, then stick it in the oven at 60-70 deg for an hour or so without killing your motherboard.

I've no idea if I would have gotten the thing working WITHOUT washing it, but it was caked in rust and was a right mess.

I need to go and check, I do not think that I have a broken beeb anymore. That can't be right, can it?

7x beebs, all working?

I'll have a look later.
BBC B's... I now have 6!
I also have 1 boxed with manuals, unmolested model A.
And also an unmolested model B. (but not boxed sadly)
12x floppy drives (only 1x currently works I think)...
Learning to repair and refurb keyboards next! No more sticky keys!

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