Reviving a Master

for bbc micro/electron hardware, peripherals & programming issues (NOT emulators!)
vannystick
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Reviving a Master

Postby vannystick » Sat Feb 04, 2017 6:23 pm

As my daughter reaches 2.5yo I think its about time that she learns about proper computers and not some touch screen 'smartphone' monstrosity.

Simple enough, I have a BBC Master in a wardrobe which worked fine when i challenged my cousin to Chuckie Egg in Christmas 2015. Its got a Turbo MMC which would boot and give all the games a 2.5yo could ever need. It is an Iss 1 board, the first computer my father ever bought and probably the first computer I ever saw and used!

Image

Plugged it in to the telly, and it boots (CMOS battery is flat, must have forgotten to unplug it for storage) but Turbo MMC is no where to be seen!

I did briefly see 'Turbo MMC' as the language (?) but it was a one time only affair. A bit of tinkering, moving the ROM out to make sure it was detected and following some tips from StarDot and it would seem that either the card is corrupt or the user port isn't working right.

Image

So next steps are to check the MMC in a PC, rebuild the CMOS battery, recap the PSU as its on original components are 30+ years and figure out why the scart lead I made up isn't working what so ever.

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danielj
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Re: Reviving a Master

Postby danielj » Sat Feb 04, 2017 6:38 pm

If the CMOS is toast, it could well have changed the TurboMMC ROM to "unplugged" - type *ROMS and see what it says!

d.

vannystick
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Re: Reviving a Master

Postby vannystick » Sat Feb 04, 2017 9:27 pm

I think it is seeing the ROM, and seems to respond to the *MMC and *CARD commands.

Image

I believe ROM 8 - DFS 5A is the TURBO MMC rom, if i pull the physical eprom out (observing anti static precautions) then it is no longer in the list.
Last edited by vannystick on Sat Feb 11, 2017 9:52 pm, edited 1 time in total.

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1024MAK
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Re: Reviving a Master

Postby 1024MAK » Sat Feb 04, 2017 11:22 pm

Your picture in your last post is not working :(

Mark
For a "Complete BBC Games Archive" visit www.bbcmicro.co.uk NOW!
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richardtoohey
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Re: Reviving a Master

Postby richardtoohey » Sun Feb 05, 2017 1:19 am

1024MAK wrote:Your picture in your last post is not working :(

Mark

It is (and still is) for me ... but have downloaded & in-lined a copy ...
master.jpg

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MartinB
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Re: Reviving a Master

Postby MartinB » Sun Feb 05, 2017 8:30 am

For me, the 'missing' picture doesn't show on Android or IOS mobile devices but is fine on a Win 7 netbook. (?)

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tricky
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Re: Reviving a Master

Postby tricky » Sun Feb 05, 2017 9:16 am

As it's a Google h hosted image, I thought it might be chrome related, but it doesn't work on my phone in chrome or default browser.

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richardtoohey
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Re: Reviving a Master

Postby richardtoohey » Sun Feb 05, 2017 10:32 pm

... and it's just disappeared for me on the same machine & browser as when it used to be working ... (A bit off-topic ...)

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fordp
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Re: Reviving a Master

Postby fordp » Sun Feb 05, 2017 10:39 pm

The pictures do not show your MMC/SD Card plugged in anywhere?

With the power off try pulling the adapter in and out of the user port a couple of times to clean the connector.

Then power on and check if it works.
FordP (Simon Ellwood)
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richardtoohey
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Re: Reviving a Master

Postby richardtoohey » Sun Feb 05, 2017 10:41 pm

Might not be relevant to this case, but I did have the same issue on a BBC with a failed 6522. So if you've got another machine you can try the MMC on, that's another thing to try/eliminate.

mw0uzo
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Re: Reviving a Master

Postby mw0uzo » Mon Feb 06, 2017 9:52 am

If you have to desolder the 6522, I'd recommend preheating the board with a hair dryer/hot air station and using good quality 2mm wide desoldering braid, surface mount rework flux and an iron at a hot temperature - i use my cheapo variable iron at 3/4 temperature - with a wide chisel bit. You'll have to go along each pin top and bottom 2 or 3 times, then free the pins with the tip of the iron from underneath. Then revisit the stubborn ones. It's a bit annoying, but if you don't press too hard with the iron, you should be able to get it out with zero damage. You'll know when you've got the amount of heat right because you'll get lucky and several pins in a row will completely desolder easily, and from the top you'll get a little 'snap' when a pin is done. At the end, grip the IC hard between your fingers and move it hard up/down/left/right, this will snap the tiny bits of solder left and the IC will lift out without force. Don't lever the IC out, as any pin left partially soldered will pull out a through hole, which would be a disaster.

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fordp
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Re: Reviving a Master

Postby fordp » Mon Feb 06, 2017 9:14 pm

If the 6522 is broken for sure the I would cut it out (Side cut each pin one at a time) and then desolder the pins one by one (with small long nose pliers) before taking the solder out of the holes with a desolder pump and braid.
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vannystick
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Re: Reviving a Master

Postby vannystick » Sat Feb 11, 2017 9:52 pm

Success!

I've replaced the PSU capacitors (thanks to RetroClinic) which definitely needed doing. I then made up a SCART lead, then realised the instructions I was following where from the socket not the plug and inverted. I've rebuilt a battery pack (using Energiser Lithium batteries from Amazon) and reset all the configuration settings, which still didnt help. I've then taken the MMC ROM out, and in, and out, and in . . .

and now . . .

Acorn_TurboMMC.jpg

Turns out I can still manage Chuckie Egg, setting myself a new personal best for the second level. I'm sure those grey cells that have memorised the path of the birds could have been better put to use!

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fordp
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Re: Reviving a Master

Postby fordp » Sat Feb 11, 2017 10:57 pm

Well done another Acorn computer saved :)
FordP (Simon Ellwood)
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