4mb MMU upgrade STFM RAM test fail

[russellnash]

There is no error shown after I select R, nothing more happens. I did a cut and paste because you can see much better than with a photo. the information I showed is everything I get.

[DoG]

There is no error shown after I select R, nothing more happens. I did a cut and paste because you can see much better than with a photo. the information I showed is everything I get.

Do you press R, then RETURN?

[rubber_jonnie]

There is no error shown after I select R, nothing more happens. I did a cut and paste because you can see much better than with a photo. the information I showed is everything I get.

Do you press R, then RETURN?

What DoG said.....:)

[exxos]

I installed the MMU upgrade to an STFM board Action F C070789-001 Rev.F, TOS 1.04.. The board already had no RAM on it, it was in this state when I received., so thought that made a good candidate for the upgrade.

So the machine could may well have been faulty from the start ? Sounds like your are trying to diagnose a memory problem when the machine could have any number of faults even before actually getting to testing the memory..

[russellnash]

Yes R and Return from the PC keyboard, no reaction.Yes, of course the board could have all sorts of other problems.I cannot know what. I tried the upgrade on another known to be working board and it didn't work at all, just a black screen. I would be more than happy when sticking it in another board solves the problem and I think it is obvious even to me that trying that is a good idea. I think it says on your shop page something along the lines that you cant offer guarantees because the upgrades are going in 30 year old machines with many variables that cant be known beforehand or controlled?

[exxos]

Generally RAM upgrades cause no problems by themselves, other than I think majority of people managed to badly solder the shifter board causing problems.

There have been other similar people to yourself how try and fix a bad machine with a new memory upgrade and I don't think anyone has been successful in trying that get. The problem being you are trying to diagnose a new upgrade on the machine which is malfunctioning to start with it is very difficult to do.

There should be no problems fitting the upgrade to a otherwise working machine, if it does not work, then I would check your soldering work on the shifter adapter as this is generally where people have problems.

[russellnash]

I am sure that it is correct. I will try it another board with it when I get a good candidate i.e.not what are described as silly boards in the guide. It is my first time using the cartridge and I am sure I will need it in future so at least I now have a small amount of experience in using it instead of none.

[exxos]

Have you tried just doing basic things like removing the MMU & GLUE cleaning the contacts with IPA and putting them back in ?

MMU will cause various memory problems..
GLUE can cause various other problems and indeed problems with the keyboard...

[rubber_jonnie]

Honestly, I've been able to repair all but 2 of my STs and whilst it's rewarding it is also a huge time suck. Any STF/M type boards that has a problem for me become donors for either H4/H5 or simply for spare parts.

Megas I will spend the time as there is no other replacement currently.

See if the RAM will work in another machine that is known good, and if you are going to check the shifter board soldering. make sure you use good magnification as it doesn't take much to make a bridge.

[rubber_jonnie]

Have you tried just doing basic things like removing the MMU & GLUE cleaning the contacts with IPA and putting them back in ?

MMU will cause various memory problems..
GLUE can cause various other problems and indeed problems with the keyboard...

A faulty glue in the 520ST I got from you gave me FDD problems.