exxos's Atari, Amiga & retro forum

You have installed pull-ups on the 1772 data lines haven't you?

No I haven't because of the description of the fix:

The 1772 Has a set of inverters on its output which connect the floppy drive. The original Atari drives had internal pull-up resistors however, other compatible drives such as the MPF920 (and possibly others) do not have the resistors and should be fitted to the Atari directly.

I am only using an original Atari drive or a Gotek, which I understand both already have internal pull-up resistors.

If this is a potential issue, I'm 100% on board for trying it, just seemed like a recipe for trouble doubling up on the resistors if not needed.

Ok, so try this, use the /ce line from the right hand socket, when I connected mine to the left socket /ce like you have it wouldn't work for some odd reason.

Just another thought, when you remove the blitter patch you do reconnect the cut track under the cpu right?

Am away from home tonight, so not able to give a more complete answer

hmmm @coonsgm When you soldered the decoder wire to the ROM PCB.. did you remove the CE pin which is plugged into the socket ? As that pin needs to be removed when driving from a external decoder... It probably wont matter for TOS206, but it may screw up TOS104..

@exxos ive not removed the pin on any of mine but I have to use the other socket /ce

PhilC wrote: 02 Mar 2021 18:00 @exxos ive not removed the pin on any of mine but I have to use the other socket /ce

It shouldn't really be done that way, as GLUE and the TOS206 decoder would both be driving the CE pin.. and they won't be driving at exactly the same time they would short each other out for maybe 100ns or something.

For example, the decoder board would drive CE low pretty much within 10ns... But GLUE could still be driving it HI for some time, I've can't remember how fast GLUE decode, but for the sake of Argument, GLUE could be still driving HI up to 100ns... :fire: :fire: :fire:

Sweet, I'll try the other CE/ pad.

Yes I did connect the trace cut when the blitter patch was removed with a bodge wire under the board.

Your thoughts on the 1772 floppy failure fix? Do you think that could have an impact on this if I'm using either an original Atari drive or Gotek?

@coonsgm try the 1772 pullup fix as it's simple to do and may cure it.

Well, I'm calling a full retreat here. I'll live with the Mega as it is.

• I've added the 1772 pull ups and results are neither better nor worse.
  I've swapped to the "other" CE/ pad with the decoder input with both CE pins in the socket.
  I've swapped to the "other CE/pad with the decoder input with the CE pin attached to removed
  I've swapped to the "other CE/pad with the decoder input with both CE pins removed
  I've tried the original CE/pad with the decoder input with both CE pins removed
  I've tried the original CE/pad with the decoder input with the CE pin attached to removed

I like to be thorough...was a bit of an interesting task to remove the pin completely when attached to all the others and then add one back in at a time.

Super big thanks to everyone with ideas and suggestions. I fully understand when working with these computers these are the risks we take :)

@coonsgm can't fault you for your efforts. After all, I've still got one Mega that won't run with a TF536 and another that does but hates floppy drives.

Sometimes it's knowing when to quit is the wisest decision to make.