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Author Topic: Marpet Deveopments M1207  (Read 2747 times)

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Offline nicholasTopic starter

Marpet Deveopments M1207
« on: May 16, 2011, 03:28:36 PM »
I have one of these with 4MB RAM and I also have an MC68882FN25A.

The card works perfectly without the 68882, but when I fit the PLCC my A1200 just stays on a grey screen when I switch it on.

Any ideas chaps?
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Offline Franko

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Re: Marpet Deveopments M1207
« Reply #1 on: May 16, 2011, 03:31:31 PM »
I know this might sound obvious but are you sure both the crystal and the FPU are in the right way round... :)
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Offline nicholasTopic starter

Re: Marpet Deveopments M1207
« Reply #2 on: May 16, 2011, 03:55:45 PM »
Quote from: Franko;638138
I know this might sound obvious but are you sure both the crystal and the FPU are in the right way round... :)

Chip is, but dozy me didn't think to buy a crystal! lol

Any particular one I need?
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Offline Franko

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Re: Marpet Deveopments M1207
« Reply #3 on: May 16, 2011, 04:26:21 PM »
Dug out an old one I have in me box off accelerators & RAM boards... :)

Make sure the crystal is orientated like in the picture I've taken... NOTE: don't use a 50MHz crystal, I only used this for the photo as my 28Mhz crystal has no printing on It... :)

As far as I remember this board can only take a 33Mhz FPU at most (I only have a 25Mhz FPU for it but it runs fine on a 28Mhz crystal)... :)

The FPU chip you have is a 25Mhz one so 24 or 28Mhz crystal will run it fine... :)





If you don't have a crystal yet just make sure the Jumper is set to INT and it will run at 14Mhz from the Amiga's on board one... :)

AmigaKit sells the crystal you need (14 Pin DIL Type)... :)

AmigaKit FPU Crystal (14 PIN DIL)
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Offline nicholasTopic starter

Re: Marpet Deveopments M1207
« Reply #4 on: May 16, 2011, 04:44:53 PM »
Thanks Franko, much appreciated.

I'll buy that crystal later.

Jumper is currently set to INT.  Which way round is the correct way for the PLCC chip to be fitted?
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Offline Franko

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Re: Marpet Deveopments M1207
« Reply #5 on: May 16, 2011, 05:24:11 PM »
In the close up picture above, the FPU should be keyed to the bottom left corner of the socket (where the round hole is just above the word CPU) but it should only be able to fit in one way, hope you haven't forced it in the wrong way... :)

PS:any luck with the RetroBright yet... :)
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Offline nicholasTopic starter

Re: Marpet Deveopments M1207
« Reply #6 on: May 16, 2011, 05:34:33 PM »
Quote from: Franko;638164
In the close up picture above, the FPU should be keyed to the bottom left corner of the socket (where the round hole is just above the word CPU) but it should only be able to fit in one way, hope you haven't forced it in the wrong way... :)

PS:any luck with the RetroBright yet... :)

I've got it fitted that way but still stuck on a grey screen. :(

RE: Retrobright, on my third attempt at i left it under a proper UV bulb for 10 hours without checking on it.  Went back at the 10th hour to find out the fuse had blown in the plug!

4th attempt tonight! :)
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Offline Franko

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Re: Marpet Deveopments M1207
« Reply #7 on: May 16, 2011, 05:51:00 PM »
Hmm... it should run fine set up that way, if the FPU's clockspeed was actually wrong then you would get stuck at a yellow screen instead... :(

If everything is working fine when the FPU is removed then I'd try using a sewing needle or pin to gently pry the FPU's socket connectors gently inwards a wee bit to make sure everything is making contact... :)

I'd also check the actual FPU's legs/Connectors with a magnifying glass just to make sure they are clean and not covered in anything that might make a bad contact... :)

Of course the board or the FPU itself could be faulty (hope not) but other than having a spare FPU handy there's no way to check really... :(

To me it sounds like it could just be a bad connection on the FPU as I say you would normally get a Yellow screen if the FPU's crystal was at the wrong speed... :)
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