Another beeb start up problem.

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Lusciousthelock
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Another beeb start up problem.

Post by Lusciousthelock » Thu Feb 25, 2016 10:38 am

I decided to dig out my old bbc to see if the power supply would go pop... It did. This issue 7 beeb was in mint condition when put away ten years ago, so after repairing the blown capacitors, I thought it would fire straight up, but it won't. I know there are some standard clue's but mine doesn't appear to be producing them.

When I hit the power button I get the first beep (which sounds healthy) then I get both the caps lock light and the shift lock light illuminate. I can hear the usual noise from the speaker (kind of like the wind in the distance) that it's always made. I do not have it connected to a monitor as yet as I can't find the cable so can't tell what's on the screen. I've swapped the 6522 chips over and cleaned some white fluff from some of the pins on the board but cannot see any signs of damage.

Any ideas?

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danielj
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Re: Another beeb start up problem.

Post by danielj » Thu Feb 25, 2016 10:42 am

The first beep is just the sound chip un-initialised. If you don't get the second beep then the OS isn't starting. I think you need to get it plugged into a monitor to have more of an idea of what's going on there. The whistling is just noise around the sound circuit.

I find this a good place to start!

http://primrosebank.net/computers/bbc/d ... 0Micro.pdf

d.

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1024MAK
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Re: Another beeb start up problem.

Post by 1024MAK » Thu Feb 25, 2016 11:02 am

Err, depending on what ROMs and other expansions are fitted, you may not get the second beep. So remove all ROM chips except the OS and BASIC. Disconnect any expansions.

As Daniel says, you really do need to see what display the Beeb is producing.

Check to see if the keyboard links/DIP switches are fitted and if so, what they are set to.

Also see the Fault finding index.

Mark

Lusciousthelock
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Re: Another beeb start up problem.

Post by Lusciousthelock » Thu Feb 25, 2016 2:03 pm

Well, here's a weird thing...

I made a composite lead using a mixture of wire and gaffa tape to see what the display was showing. I had already removed all the Rom's to get a basic system working. The screen was blank and so after loading up the fault finding guide (Thank you) and deciding an afternoon of fiddling was in order, I went to make a cup of tea.

When I returned my 13month old daughter was typing on the keyboard of a fully working computer! Maybe it needed to warm up? It's working spot on now! Thanks for the pointers.

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leenew
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Re: Another beeb start up problem.

Post by leenew » Thu Feb 25, 2016 2:07 pm

The real test will be the first power-up from cold in the morning. .... fingers crossed. .....
Lee.

Lusciousthelock
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Re: Another beeb start up problem.

Post by Lusciousthelock » Thu Feb 25, 2016 2:12 pm

bugger,

It's an intermittent fault. After running for 20 minutes I decided to restart the machine and- beep. Blank screen with those two pesky LEDs illuminated again and no further action. A few resets and nothing again. Something must be playing up?

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1024MAK
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Re: Another beeb start up problem.

Post by 1024MAK » Thu Feb 25, 2016 2:14 pm

It's amazing how a cup of tea helps to fix things :lol:

Mark

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leenew
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Re: Another beeb start up problem.

Post by leenew » Thu Feb 25, 2016 2:17 pm

Try carefully pulling the keyboard connector off and re-fittng it. Do this half a dozen times at both ends. ..

Lusciousthelock
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Re: Another beeb start up problem.

Post by Lusciousthelock » Thu Feb 25, 2016 2:49 pm

Okay after some keyboard connector wiggling the computer suddenly started up in what looked like mode 0 with a searching for file message? The boarder's look off. A few hard reset's and its again working normally starting in mode 7?

Any ideas? I'm not not sure if the keyboard wiggling was a fluke or not?

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1024MAK
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Re: Another beeb start up problem.

Post by 1024MAK » Thu Feb 25, 2016 3:52 pm

This could be related to the settings affected by the keyboard links/DIP switches. Even if they are not fitted, the OS still reads the "settings". It's just that normally, with noting fitted, the result is the default value.

But if there is a poor connection on the connecting cable, the OS may see a value that is different to the default value.

See the section in the Advanced User Guide (page 246 in my copy) [ OSBYTE &FF (255) or *FX 255 ]
Start-up options
Screen mode (3 bits, bits 0 to 2)
Reverse action of SHIFT-BREAK (bit 3)
Sets FDD timings (bits 4 & 5)
Reserved (bits 6 & 7)

Also Appendix J (page 489).

Mark

zeem
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Re: Another beeb start up problem.

Post by zeem » Thu Feb 25, 2016 7:18 pm

Watch out for bad solder joints on the pin header on the keyboard. Years ago I had a similar problem that I thought was caused by a duff keyboard cable, until something on the motherboard broke. I paid a local computer shop to repair it, but I still had problems. It was only when I examined it more closely that I found that the problem was the soldering and not the cable. If I hadn't have found it, the repaired motherboard would probably have broken the same way.

Lusciousthelock
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Re: Another beeb start up problem.

Post by Lusciousthelock » Thu Feb 25, 2016 7:31 pm

I think your right about the keyboard connector. The pin header's look very tarnished but appear to be working fine now. I'll try some contact cleaner on it as the keyboard itself looks lovely. All good for now :D

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Re: Another beeb start up problem.

Post by Lusciousthelock » Sat Feb 27, 2016 4:18 pm

Just a final word on this. The computer is sorted now, but it turned out to be the Cassette Motor LED causing the problems. It's solder connection was broken and it's track actually pulled from the mother board. A big blob of solder later and all is well. I may well reinforce this connection with some hot glue later too as my children can be a little rough with this keyboard.

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