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Re: ALPHA MODIFICATIONS
Posted: 17 Sep 2018 20:36
by exxos
Realloy wrote: 17 Sep 2018 20:33
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.. :)
Re: ALPHA MODIFICATIONS
Posted: 18 Sep 2018 10:45
by PhilC
For the sync fix I pulled both pins 8 and 9 out of the U51 socket and then jumpered the socket.
Re: ALPHA MODIFICATIONS
Posted: 18 Sep 2018 11:07
by kodak80
Forgottenmyname wrote: 18 Sep 2018 10:45
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?
Re: ALPHA MODIFICATIONS
Posted: 18 Sep 2018 11:13
by PhilC
Hopefully you can see it on here.
It didn't sort my sync problem but will work on that.
- 20180918_111006.jpg (3.78 MiB) Viewed 6512 times
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Re: ALPHA MODIFICATIONS
Posted: 18 Sep 2018 11:28
by exxos
Forgottenmyname wrote: 18 Sep 2018 10:45
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.
Re: ALPHA MODIFICATIONS
Posted: 18 Sep 2018 11:30
by PhilC
Ok will put 9 back in, good point
Re: ALPHA MODIFICATIONS
Posted: 18 Sep 2018 18:15
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).
- bw1.jpg (278.2 KiB) Viewed 6481 times
Re: ALPHA MODIFICATIONS
Posted: 18 Sep 2018 18:23
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)
- f2.jpg (181.48 KiB) Viewed 6457 times
Re: ALPHA MODIFICATIONS
Posted: 18 Sep 2018 18:29
by troed
exxos wrote: 18 Sep 2018 18:23
Bodge resistor 1..... 2.2K between the 2 circled points on back of CPU socket...
I'm confused by this being connected to BR.
Re: ALPHA MODIFICATIONS
Posted: 18 Sep 2018 18:32
by exxos
troed wrote: 18 Sep 2018 18:29
I'm confused by this being connected to BR.
Its a missing pull up resistor on BR & BGACK.