High res picture of area around composite video out

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aferenbach
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High res picture of area around composite video out

Post by aferenbach » Mon Jul 29, 2019 2:34 pm

Hi guys

I just revived an old bbc master 128 and when I opened the case I was treated to the lovely surprise that there was a 2nd processor board fitted.

I am wanting to do the modification to add a 470pf capacitor so as to make composite video into colour.

As the board is perilously close to the area I can't really see the pcb markings so well. Can someone take a high resolution image of that area in one of your machines?

I am gonna attach the capacitor to a pair of flying leads to avoid removing the board or risking a soldering iron there

Thanks in advance

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Re: High res picture of area around composite video out

Post by MadeGray » Mon Jul 29, 2019 3:47 pm

Give me a few minutes I’ll take a few
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Re: High res picture of area around composite video out

Post by MadeGray » Mon Jul 29, 2019 3:53 pm

Here you go.

Can’t really see the numbering though.

Let me know if need any more.

John
Attachments
9DF02CF2-C18A-4A6D-B067-22384716F74E.jpeg
AF6B7121-888C-4045-A89D-05D4A93E4173.png
2651C3DC-3ED3-40BA-BE11-81A189B58581.jpeg
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Re: High res picture of area around composite video out

Post by MadeGray » Mon Jul 29, 2019 3:55 pm

However check revision of 128 board

If an issue 2 then you only need to add link to LK11 mod only needs doing to an issue 1 master 128
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Re: High res picture of area around composite video out

Post by MadeGray » Mon Jul 29, 2019 6:18 pm

Although rumour is there was only one issue Master board? I’m sure others will be able to provide more info.
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Re: High res picture of area around composite video out

Post by AndyF » Mon Jul 29, 2019 6:41 pm

MadeGray wrote:
Mon Jul 29, 2019 6:18 pm
Although rumour is there was only one issue Master board? I’m sure others will be able to provide more info.
I'd always (assumed) a few Iss2 did appear, and usually they have that membrane type keyboard fitted aka "the silent type" well, squishy and quieter would be more appropriate I guess.

My memory could well be playing tricks on me here though :oops: , plus the kbd is not a good way to ID it anyway given its seconds to swap...
Last edited by AndyF on Mon Jul 29, 2019 6:42 pm, edited 1 time in total.
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Re: High res picture of area around composite video out

Post by MadeGray » Mon Jul 29, 2019 7:55 pm

thanks Andy - I was a little confused myself thought there was just one. Service guide says the caps don’t need fitting on an issue 2. Surprised that the master didn’t come with a link like the later BBC B’s
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Re: High res picture of area around composite video out

Post by AndyF » Mon Jul 29, 2019 8:02 pm

MadeGray wrote:
Mon Jul 29, 2019 7:55 pm
thanks Andy - I was a little confused myself thought there was just one. Service guide says the caps don’t need fitting on an issue 2. Surprised that the master didn’t come with a link like the later BBC B’s
No problem. As I say please don't take my above post as Gospel though! It could well be my memory playing tricks.

Pretty (99%) sure that the Iss2 just needs the link, Iss1 needs the 'tweak' as above.

I suspect the reasoning for this was those who needed colour out would likely use the RGB socket, as most colour monitors would of had such an input, I can't remember seeing many 'for computer use' colour rather than mono (green/amber/black+white/other) just having say a BNC input and being colour. They would of existed but I can't offhand think of one. No doubt they were listed in the magazines back then too.

I think you do lose a fraction of clarity/crispness with a 'B at least if you modify it for colour out, the mono out is clearer but that could be a human-eye thing rather than electronic the same way as (years back, before LCD and LED televisions) a B+W one would usually look clearer than a colour.
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Re: High res picture of area around composite video out

Post by Kazzie » Mon Jul 29, 2019 8:34 pm

AndyF wrote:
Mon Jul 29, 2019 8:02 pm
I think you do lose a fraction of clarity/crispness with a 'B at least if you modify it for colour out, the mono out is clearer but that could be a human-eye thing rather than electronic the same way as (years back, before LCD and LED televisions) a B+W one would usually look clearer than a colour.
There is definite noise in the composite output of my Model B when fitting the colour link (as seen on my CM8833 monitor wit the colour knob turned all the way down so it still displays in black & white): the chroma dots are clearly visible.

(Composite colour is still useful for me with my Beeb though, as I usually have the Archimedes plugged into the monitor's RGB input.)
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Re: High res picture of area around composite video out

Post by 1024MAK » Mon Jul 29, 2019 9:18 pm

There are definitely issue 2 Master 128 machines with real keyswitch® keyboards. I know, I have a number of them... :D

Mark

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Re: High res picture of area around composite video out

Post by AndyF » Mon Jul 29, 2019 9:27 pm

1024MAK wrote:
Mon Jul 29, 2019 9:18 pm
There are definitely issue 2 Master 128 machines with real keyswitch® keyboards. I know, I have a number of them... :D

Mark
You're not suggesting that the membrane based keyboard is inferior are you ;) :D
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Re: High res picture of area around composite video out

Post by 1024MAK » Mon Jul 29, 2019 9:31 pm

With regards to colour composite video vs. monochrome composite video, keep in mind that the original video system WAS monochrome. Colour is an add-on. With a direct wire connection, you can get a very good monochrome video signal.
When you add the colour carrier (PAL), some of the monochrome picture information area of the signal overlaps with the colour carrier signal. Because the filter used in analogue sets is not perfect, the display can’t always differentiate which is which. Plus home computers, including the Beeb don’t have full broadcast quality circuitry.

If you really want to see the difference, use the high resolution MODE 0 and then compare the picture in monochrome before enabling the colour output (obviously this is easier if you have an issue 2 board with the link/jumper shunt...)

Mark

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Re: High res picture of area around composite video out

Post by 1024MAK » Mon Jul 29, 2019 9:37 pm

AndyF wrote:
Mon Jul 29, 2019 9:27 pm
1024MAK wrote:
Mon Jul 29, 2019 9:18 pm
There are definitely issue 2 Master 128 machines with real keyswitch® keyboards. I know, I have a number of them... :D

Mark
You're not suggesting that the membrane based keyboard is inferior are you ;) :D
Who? Me? :shock: 8-[ [-X

Actually, I don’t think I have a Master 128 with a membrane keyboard... so I wouldn’t actually know...

I do have some Master Compacts, they have a membrane keyboard. I can’t honestly remember what the keyboard feels like, as I don’t use them that much :oops:

Mark

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Re: High res picture of area around composite video out

Post by aferenbach » Mon Jul 29, 2019 11:02 pm

Hi guys

Okay, has anyone done the modification on a master issue 1 and can send me a picture of where the capacitor is connected to.

I was struggling to see the area in question in the photos

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Re: High res picture of area around composite video out

Post by MadeGray » Tue Jul 30, 2019 7:03 am

As per the pics mine isn’t modified, I always use RGB I’m afraid.

As per the others I’m really surprised this wasn’t a standard link option. Maybe most had moved towards RgB screens then perhaps?

I can look more closely this evening if that helps and see if can get better shots of numbers.
John Gray

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Re: High res picture of area around composite video out

Post by johnkenyon » Tue Jul 30, 2019 9:00 am

aferenbach wrote:
Mon Jul 29, 2019 2:34 pm
Hi guys

I just revived an old bbc master 128 and when I opened the case I was treated to the lovely surprise that there was a 2nd processor board fitted.

I am wanting to do the modification to add a 470pf capacitor so as to make composite video into colour.

As the board is perilously close to the area I can't really see the pcb markings so well. Can someone take a high resolution image of that area in one of your machines?

I am gonna attach the capacitor to a pair of flying leads to avoid removing the board or risking a soldering iron there

Thanks in advance
You shouldn't have to remove the main board from the case to do this - for issue 1 boards, solder the resistor to the component side of the board as detailed in http://chrisacorns.computinghistory.org ... AN/001.pdf
For issue 2 boards, you will probably have to clear the holes with a solder sucker, and then make a wire link by cropping a resistor and bending it to the right pitch and length. Then solder the link from the top of the board.

Using flying leads on the capacitor will probably result in you doing the job again, sans flying leads, when you are disappointed by the picture quality...

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Re: High res picture of area around composite video out

Post by aferenbach » Tue Jul 30, 2019 12:27 pm

Multiwizard wrote:
Tue Jul 30, 2019 8:48 am
Hi,

will this help?:

http://beebmaster.co.uk/CompColour.html


Greetings, Wim... :-)
That looks good - I guess these connections are the other end of the link going to the two resistors mentioned. I am gonna have to buy the right kind of capacitor to test it out.

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Re: High res picture of area around composite video out

Post by AndyF » Tue Jul 30, 2019 1:44 pm

1024MAK wrote:
Mon Jul 29, 2019 9:37 pm
Who? Me? :shock: 8-[ [-X
Apologies Mark if my post read in any way a bit erm 'off' :oops: :oops: It was intended in good humour/jest rather than anything at all negative. :)
Last edited by AndyF on Tue Jul 30, 2019 1:45 pm, edited 1 time in total.
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Re: High res picture of area around composite video out

Post by 1024MAK » Tue Jul 30, 2019 6:26 pm

AndyF wrote:
Tue Jul 30, 2019 1:44 pm
1024MAK wrote:
Mon Jul 29, 2019 9:37 pm
Who? Me? :shock: 8-[ [-X
Apologies Mark if my post read in any way a bit erm 'off' :oops: :oops: It was intended in good humour/jest rather than anything at all negative. :)
No apologies needed, I took it in good jest :lol:

Mark
Last edited by 1024MAK on Tue Jul 30, 2019 6:26 pm, edited 1 time in total.

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