ALPHA MODIFICATIONS

All information relating to the Alpha plus all the WIP threads etc.
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exxos
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Re: ALPHA MODIFICATIONS

Post by exxos »

Realloy wrote: Mon Sep 17, 2018 8:33 pm i can see all the chips have a decoupling capacitor,,, but what about BAD DMA ? is there one and where? or is it not necessary?
Theres 4 caps around the DMA already.. no need to add a 5th.. :)
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Re: ALPHA MODIFICATIONS

Post by PhilC »

For the sync fix I pulled both pins 8 and 9 out of the U51 socket and then jumpered the socket.
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Re: ALPHA MODIFICATIONS

Post by kodak80 »

Forgottenmyname wrote: Tue Sep 18, 2018 10:45 am For the sync fix I pulled both pins 8 and 9 out of the U51 socket and then jumpered the socket.
Do you have a photos of the change for us less technical builders? And did this resolve the sync problem?
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PhilC
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Re: ALPHA MODIFICATIONS

Post by PhilC »

Hopefully you can see it on here.

It didn't sort my sync problem but will work on that.
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Re: ALPHA MODIFICATIONS

Post by exxos »

Forgottenmyname wrote: Tue Sep 18, 2018 10:45 am For the sync fix I pulled both pins 8 and 9 out of the U51 socket and then jumpered the socket.
You shouldn't pull pin 9 because you will have 2 floating gates in the chip then due to disconnected inputs.
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viewtopic.php?f=17&t=1585 Have you done the Mandatory Fixes ?
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Re: ALPHA MODIFICATIONS

Post by PhilC »

Ok will put 9 back in, good point
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Re: ALPHA MODIFICATIONS

Post by exxos »

BR PULL UP FIX

Bodge wire 1... Wire the thick yellow drawn wire as shown on the back of the pcb...

(Fixing missing pull up resistor on BR).

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viewtopic.php?f=17&t=1585 Have you done the Mandatory Fixes ?
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Re: ALPHA MODIFICATIONS

Post by exxos »

BGACK PULL UP FIX

Bodge resistor 1..... 2.2K between the 2 circled points on back of CPU socket...

(fixes missing pull up on BGACK)

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viewtopic.php?f=17&t=1585 Have you done the Mandatory Fixes ?
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Re: ALPHA MODIFICATIONS

Post by troed »

exxos wrote: Tue Sep 18, 2018 6:23 pm Bodge resistor 1..... 2.2K between the 2 circled points on back of CPU socket...
I'm confused by this being connected to BR.
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Re: ALPHA MODIFICATIONS

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troed wrote: Tue Sep 18, 2018 6:29 pm I'm confused by this being connected to BR.
Its a missing pull up resistor on BR & BGACK.
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viewtopic.php?f=17&t=1585 Have you done the Mandatory Fixes ?
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People should find solutions to problems, not find problems with solutions.
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