ChrisS is trying to build a H5C1

[PhilC]

@Oldskool you don’t need to solder a socket in, you can use the pads on the pcb to test with and still use the PLCC CPU as all lines are connected, well, except for the 3.3V ones which go through level shifters.

[Oldskool]

So soundchip is not inserted the wrong way.
When measuring pin 17 and 18 on the io port 1 I see that both measure the same.
So both are high after startup and when pressing reset go low and high again.
So cpu is not halted..

[PhilC]

@Oldskool ok, still check the address and data lines as mentioned before but don’t be surprised if you need a diagnosis cart to diagnose a ram fault

[Oldskool]

All measured from power on to white screen

D0 - D15 seems to show activity ( maybe d11 is looking a bit different)
A1 - A23 All start with activity
A6 and A7 the signal drop
A9 A12 A13 A18 A19 A20 A21 A22 A23 go to a constant high

[PhilC]

All measured from power on to white screen

D0 - D15 seems to show activity ( maybe d11 is looking a bit different)
A1 - A23 All start with activity
A6 and A7 the signal drop
A9 A12 A13 A18 A19 A20 A21 A22 A23 go to a constant high

So using the H5 schematic I'd check D11 for bad or shorted connections and A6 & A7 for poor connections, IIRC all the address lines should pull up when the CPU is halted. Best bet is to remove the CPU and meter A1-A23 to check they are all pulled up to 5V when switched on with the CPU out.

[Oldskool]

Hi @PhilC ,

Thanks again for the help.
Just tested without any CPU.
All D’s and A’s are 5V when the cpu is removed.

Also had the look at the board again. This pin seems a bid strange (Glue). Should this pin be ground?

gnd.JPG

[Oldskool]

Carefully removed the piece of metal.
No longer measured as GND now.
(There are multiple tiny damages on the pcb near this area.)

And:

IMG_2486.jpeg

[exxos]

:bravo:

I looked and that would be LDS shorted to GND!

Capture.PNG

Sorry you had the problem in the first place, if it is any consolation, I have stopped using that PCB company!

[PhilC]

@Oldskool really happy to see you got there in the end and it was just something silly like that short, well done.

BTW, some of those pins look to need a bit more solder on the Glue.

[Oldskool]

Thanks. Really happy that it works. The floppy also works and I can load stuff.
Yes indeed need to check those soldering joints as well. I only focussed on my own soldering and the parts used.

The audio is still all wrong (fading only a few channels or nothing at all) but I assume that’s normal without the audio fixes applied.

Very nice picture quality never saw this before out of a ST!!