ALPHA MODIFICATIONS

[exxos]

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..

[PhilC]

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

[kodak80]

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?

[PhilC]

Hopefully you can see it on here.

It didn't sort my sync problem but will work on that.

[exxos]

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.

[PhilC]

Ok will put 9 back in, good point

[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).

bw1.jpg (278.2 KiB) Viewed 6380 times

[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)

f2.jpg (181.48 KiB) Viewed 6356 times

[troed]

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

I'm confused by this being connected to BR.

[exxos]

I'm confused by this being connected to BR.

Its a missing pull up resistor on BR & BGACK.