kodak80 H4 build (x2)

[exxos]

Do you have a scope that you can start checking signals out with as Derkim has been doing and as in my fix it guide ?

[kodak80]

Yes, I have a 2 channel scope which I can use so will look to work through your guide over the next few nights.

[kodak80]

@exxos Any reason FC2 has a pull up on both RP5 and RP8? Pin 9 on both SILs.

[kodak80]

@exxos sorry, another question.

We have been working through you testing guide and AS and DTACK are both going high as expected but my board is still only showing white screen and no floppy access. All pull-ups are fine, and cpu puns check out as per testing guide so need some further pointers.

The BGACK PULL-UP FIX is my question as JP16 is already connecting R150 4.7k resistor as a pull-up. Adding a 2.2k resistor with JP16 jumpered is in parallel. JP 16 would need to be removed for the 2.2k fix to work correctly.

[Icky]

Good spot @kodak80. So thats a 1K1 pull-up on FC2

[derkom]

Good spot @kodak80. So thats a 1K1 pull-up on FC2

Agh, no wonder. That one weird pull-up has bugged me every time I've been checking those!

[kodak80]

My address being read from ROM is

0000000000001110

Which is wrong so just checking the soldering on the TOS ROM pins.

[kodak80]

Good spot @kodak80. So thats a 1K1 pull-up on FC2

I just bent up one of the SIL pins to remove the double-up.

[exxos]

@exxos Any reason FC2 has a pull up on both RP5 and RP8? Pin 9 on both SILs.

oops

[exxos]

The BGACK PULL-UP FIX is my question as JP16 is already connecting R150 4.7k resistor as a pull-up. Adding a 2.2k resistor with JP16 jumpered is in parallel. JP 16 would need to be removed for the 2.2k fix to work correctly.

Its the same on the original..

Yes there are 2 resistors in parallel, but when the jumper is removed, you then need 2 resistors to pull up each side of the now broken signal. Its probably how I missed the resistor off in the first place as I assumed it was connected anyway.

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