trying to assemble the floppy disk controller

[guibrush]

HI, last week I finally assembled the Floppy disk controller (R7 is now mounted, I did the pic before, as I missed this component)


But something is not right: my friend took his oscilloscope and we tried to adjust both potentiometers, but nothing change. We have even a very strange ripple signal:

https://imgur.com/a/f8Mcpsl

Then we checked the voltage between TG43 and the ground, and we have 2.3V... We checked the board for short circuit, it looks good.

Any idea what can be the cause?
Thanks

[johnhalk]

Hello,

I have noticed one issue looking at your photo of the PCB. You need to solder a jumper on the BUSDIR PCB jumper pads per the manual.
There are no solder PCB jumpers whatsoever on the M1 pads.

https://exidysorcerer.net/?r=/download& ... YxLjMucGRm

BUSDIR.JPG (35.57 KiB) Viewed 37911 times

i.e The left PAD to the middle PAD.


Double check all the solder work on the bottom of the PCB with a magnifier - check for any solder bridges between PINS.

Also per the datasheet for the WD2793 IC.

https://exidysorcerer.net/?r=/download& ... dC5wZGY%3D

Check for +5V VCC on PIN 21 and GND PIN 20 on 2793 IC.
Then check that the crystal oscillator circuit is generating the 2 MHZ clock signal for the 2793 IC.
i.e. Check PIN 24 CLK on the 2793 IC for a 2 MHZ frequency.

Regards,
John

[guibrush]

ok, thanks. I will try and report later.