Falcon floppy problems

[Acsi]

No it ins't it is the original Wizztronics PSU

12v measures 12.1v
5v measures 5.08v

[exxos]

I would suggest you recap the PSU or at the least get a 4700uF on the 5V near the PSU and floppy drive and see if it helps.

[Acsi]

OK I have tried an ATX PSU and get the same result.

Swapped the old 4700uF cap with one of your replacement kits and get the same result.

Thinking this is now beyond my feeble repair abilities. :x

[exxos]

Can you turn off afterburner if you can't remove it ? Do you have a clock buffer patch ?

[rubber_jonnie]

I know this works for a semi dead ST, but are you able to connect a serial cable to the Falcon, and the other end to a serial terminal on a PC?

If so, do you get any output on the terminal screen when booting with the diag cart?

[Acsi]

Here is where the clock buffer would be.

IMG_4902_zps1p7vlmyw.jpg

I do have one of your patches but haven't installed it as I'm a bit confused by the connection currently at R221 which goes here

IMG_4900_zpsiytdfvxk.jpg

I think it's where the original owner separated the DSP and System clocks?

[exxos]

I think it's where the original owner separated the DSP and System clocks?

Is that the "termination resistor" as mentioned on the CT60 site ? If so, remove it.. my Falcon wouldn't even power up with that resistor, it squashed the signal to half a volt!

It just looks like a wire has been run bypassing the PCB track. I've seen that done before.. There's no need with my new buffer boards, you can remove the wire (assuming the PCB track is actually OK) .

[Acsi]

So looking at this it seems the following instructions were used as L102 was removed and the crystal is hooked up as shown

Remove inductor L102 (directly above U65) and feed the output from
the FREE pin on the oscillator to the LEFT solder pad of L102. This pad
is the dock input to the Combel chip, where almost all other clock
frequencies are derived through division

One amendment to the Nemesis instructions concerns the DMA signal patch (pages 16 & 17). We have found that
with Rev. 1 Nemesis boards an inductor soldered to the cut track, followed by a series 100 ohm resistor should be
tried as a replacement. A suitable inductor is L102 which can be removed from the Falcon motherboard and replaced
with a wire link. Take great care when soldering the series inductor/resistor onto the PCB track as it can tear very
easily! Please also solder one end of the inductor onto the cut track then the resistor, leading to pin 14 of U20.
With Rev. 2 Nemesis boards do not use any component between the cut track and pin 14 of U20..

IMG_4901_zpsiiyaab46.jpg

I think I'm going to go down the path of removing the AB and trying to reinstate it to run on the 68030 (unfortunately I do not know the status of the 030).
The track between pin 16 of the CPU and the VIA is damaged I believe so I will need to run a patch to somewhere from pin16 of the 030?

[exxos]

Pin 16 is bus grant which is part of the DMA system.. As you have problems with DMA , I would say you found your problem.

[Acsi]

Currently Pin 16 of the 030 isn't connected to anything and pin 17 which is also lifted is connected to the Afterburners wiring loom.

I believe pad 16 connects directly to one of the pins on the falcons expansion port pin3 which I may use as a temporary connection for testing until I can find a better connection point. Whoever had this board before me had or had tried to install an 030/040 switch as described here https://atari.joska.no/ab/ as the afterburner board has the track cut (Which has been patched) on it as described.

Tomorrow I will pull the board out of the case and solder the cut tracks, remove the 40 and 50MHz Oscillators and reinstate the 32MHz Oscillator and the 030. Unless work gets in the way of course (currently in lock down working from home). I highly suspect the outcome will be the same however but it's worth it to narrow down the fault.