Do I have an Escom A1200 motherboard? or not?

[Sim085]

A couple of years ago my A1200 motherboard no longer worked and therefore I had to buy a new one. To replace it I bought another rev2B motherboard like the one I had.

Today I was testing the Floppy Drive using Amiga Test Kit and this reported "No READY Signal: PC or Escom drive?". When doing a Signal Test I can see the Index Pulses increase by the Ready Signal remains 1 (RDY1).

I opened the A1200 to get the Floppy Drive out. This is a Chinon drive and on the back has jumpers. One of these jumpers is to set the READY signal and it was correctly set.

I therefore decided to try the same Floppy Drive on an A500 I have. This time Amiga Test Kit reported "READY late (506.6ms): slow motor spin-up?". When doing a Signal Test again I can see the Index Pulses increase but this time I can see the READY signal go to 0 (RDY0).

So it would look like the Floppy Drive is reporting the READY signal (as the A500 picks this up) but the A1200 does not pick this up. Now I know Escom made use of PC Floppy Drives which did not had a ready signal but not that the motherboards did not read the READY signal.

I therefore did a search on the Internet and found that indeed it seems that the Escom A1200s did have a motherboard hack (source: http://www.amibay.com/showthread.php...l=1#post680969). So I dismantled it all to see the back of the motherboard. Being honest with myself I can see some touches of de-soldering on pin 2 and pin 34 of the floppy internal connector. However for the hack to be complete there also needs to be a wire between pin 34 of the floppy internal connector to pin 1 of the floppy external connector, but the soldering of pin 1 of the floppy external connector looks factory like. Sure enough, using a multi-meter I can confirm there is no continuity between pin 1 of the floppy external connector and pin 34 of the floppy internal connector.

Based on all the above I conclude that the motherboard is an Escom A1200 ... But ... the motherboard itself is labelled as "Commodore Electronics Ltd". Escom A1200 where not labelled as so (example: http://www.amibay.com/showthread.php...com-Amiga-1200). Now, I know for sure that unlike what stated on other threads, not all rev2Bs are Escom. The busted rev2B I had was not Escom, it came with an Amiga Floppy Drive and from photos can confirm it did not have any hacks on the floppy connectos. From reading other threads it also seems that Escom first used any stock left by Commodore (source: http://eab.abime.net/showthread.php?t=95829).

So is it possible that this was a Commodore rev2B motherboard mutilated by Escom to work with a PC Floppy Drive?

If yes then they must have cut the trace between pin 1 of the floppy external connector and pin 34 of the floppy internal connector. However as hard as I try to look I cannot see anything. I have checked amigapcb.com and there really isn't much where to do such a cut. When using the multi-meter I have continuity between pin 1 of the floppy external connector and pin 2 of resistor E581R. I can only imagine any such cut is under the floppy internal header itself and as curious as I am I do not have the heart to touch the internal floppy header just to check.

[demolition]

Originally Posted by Sim085

So is it possible that this was a Commodore rev2B motherboard mutilated by Escom to work with a PC Floppy Drive?

Very possible yes. Some Escom models have Amiga drives, some have PC drives, some motherboards are modified and some are not. When Escom took over, they obviously must have inherited a stock of parts which is why early Escoms are like C= machines just with another badge.

Did you try bridging ext pin 1 with int pin 34?
http://www.softpres.org/article:hard..._fdd_connector

[Sim085]

Originally Posted by demolition

Did you try bridging ext pin 1 with int pin 34?
http://www.softpres.org/article:hard..._fdd_connector

To be honest it did not even pass through my mind to try it. I am more after the "history" of it all. I am pretty sure it will work but will try it out. I do not play any games from Floppy Disks anymore so not really bothered as long as my Amiga Floppy drive works .

Something else I noticed is that this rev2B has some changes from my other (broken) rev2B. For example there is a resistor between pin 2 of the clockport to R151J. I have attached a photo. At first I thought this might be some timing fix done by the previous owner. However soldering looks like out of the factory and I cannot find a timing fix as documented on the A1200 motherboard fixes page (link) which match this one.

[demolition]

Yes, that is a factory fix. Not sure how common it is, but I have it on a Rev. 1D4 and you can also see it here:
https://www.the-liberator.net/site-f...otherboard.JPG

[Sim085]

Originally Posted by demolition

Yes, that is a factory fix. Not sure how common it is, but I have it on a Rev. 1D4 and you can also see it here:
https://www.the-liberator.net/site-f...otherboard.JPG

I guess then this confirms the rev2B I have is definitely an Escom as that in the photo is an Escom A1200 motherboard.

Are there any other documented changes Escom did to the A1200 and what they targeted to resolve with such fixes?

Also, from what I read it would look like when it was discovered some floppy disk games did not work there where two options;

One had to always cut pin 2 from pin 34 of the floppy internal connector and connect pin 34 of the floppy internal connector to the pin 1 of the floppy external connector.

Then, once this was done one could either (i) use an Amiga Floppy Drive or else (ii) keep the PC Floppy Drive but modify this as documented here: http://www.softpres.org/article:hard...u-257a605p_fdd.

Is this correct? and does the PC Floppy Drive also need to be modified some other way to read Amiga floppy disks?

[demolition]

I don't think it is an Escom fix since my 1D4 board is not an Escom board. My Escom 2B board does not have that particular fix so with so many other things C=, you can't really rely on revisions, fixes etc. as some fixes were done in some factories and not in others.
The floppy issue is only for Escom models as far as I know. They could no longer source Amiga drives so they had to come up with a solution so they could use standard PC drives instead. On some models they did some modifications to the MB, and in some machines they put a small adapter board between the drive and the MB. My Escom machine does not have this floppy change however and it contains a regular Amiga-type floppy drive so just because it is Escom, there is no guarantee that they did the change as it would depend on their stock and sourcing situation.

[Sim085]

Thanks demolition for all the information. It has been a nice history lesson for me