A1200 Timing fix for my Escom Amiga?

[manic23]

I have an Escom Amiga A1200 with 3.1 Rom. I have just ordered an ACA 1232/33Mhz 128MB Accelerator from Amikit, but since then have read that some A1200's need a timing fix for this to work, How to I find out if my Amiga needs that? I understand that I need to find out the revision of my motherboard, is there a way of doing that without taking the computer to bits?

[fitzsteve]

The only way is to test it with your ACA1232, if everything works fine you don't need the fix. If you get lockups and general instability it's likely you need either the timing fixes and/or have the Capacitors replaced

Note. Sometimes the instabilities can be down to a dirty expansion connector or poorly/underpowered power supply.

[manic23]

OK, thanks very much, loving your blog by the way

[fitzsteve]

Originally Posted by manic23

OK, thanks very much, loving your blog by the way

Glad to hear that, I already approved your post & replied

[manic23]

Thanks mate. Makes my humble A1200 and monitor setup look feeble in comparison, but one day, I hope to get a 4000 just for the hell of it

[ShK]

I have Petro's Escom new-old-stock A1200 with ACA1231 Freezing issues. After freezing ACA1231 doesn't boot (only yellow or black screen).

I noticed that Escom's A1200 E123C and E125C capacitors are already missing.






(sorry for cell phone picture size and quality)

Is there nothing I can do?

[fitzsteve]

See here for timing fixes:

http://www.ianstedman.co.uk/Amiga/am..._mobo_fix.html

Also replacing capacitors might help, Amigakit offer kits of a replacement service:

http://amigakit.leamancomputing.com/...oducts_id=1137

Lastly, putting electronics on a Carpet like that is asking for more trouble

[ShK]

Thanx for fast reply! hmm.. even if it outdoor plastic carpet?

What about assembling E125C with a 22pF capacitor?
http://eab.abime.net/showpost.php?p=...postcount=2065

[manic23]

Not sure what you are telling me here, are you saying I probably will need the fix or I won't?

[fitzsteve]

Originally Posted by manic23

Not sure what you are telling me here, are you saying I probably will need the fix or I won't?

I was replying to ShK's question

Did you get your ACA yet? You can't tell if you need any fixes until your try the card. If it runs fine then no need for timing fixes, if it locks up and crashes then you either need timing fixes or capacitors replaced generally...

[ShK]

Originally Posted by manic23

Not sure what you are telling me here, are you saying I probably will need the fix or I won't?

I have a issue, but if your system works, don't fix it.

[manic23]

Ok thanks for clarifying, no not got the card yet. I will post my experience with the card when I get it. Here's hopping for a timing issue free motherboard lol

[FOL]

Originally Posted by fitzsteve

See here for timing fixes:

http://www.ianstedman.co.uk/Amiga/am..._mobo_fix.html

Also replacing capacitors might help, Amigakit offer kits of a replacement service:

http://amigakit.leamancomputing.com/...oducts_id=1137

Lastly, putting electronics on a Carpet like that is asking for more trouble

Ians fixes arent the same as the ones needed for the ACA cards.
You need to do the ones for the ACA cards only.

http://eab.abime.net/showpost.php?p=...postcount=2065

This one should be followed.

[manic23]

You know what, the more I read about the timing fix, the less I understand it! There is sooooo much discussion about on EAB, some say do this, some say no do that, others say don't do either, Aunt Bessie says...... Ahem yes well you get the message, honestly, my brain literally hurts! if it turns out that I need the fix, I think I will send it to AmigaKit, otherwise I think I'll end up in a secure unit

[Bamiga2002]

Don't forget to join the Happy group of ACA-owners (no pun intended)

[ShK]

Originally Posted by FOL

Ians fixes arent the same as the ones needed for the ACA cards.
You need to do the ones for the ACA cards only.

http://eab.abime.net/showpost.php?p=...postcount=2065

This one should be followed.

This guide says: "Remove resistors E121R and E122R and replace them with 0805 ferrite beads - something in the range of 60R@100MHz or more".

Is Murata NFM60R30T222 suitable to this?

[manic23]

Originally Posted by Bamiga2002

Don't forget to join the Happy group of ACA-owners (no pun intended)

LOL, thanks Bamiga, if all goes well I will

[Stedy]

@Shk,

Those parts are a little bit overkill for a signal line though they should work.

Finally got around to updating the website, I would recommend the following Ferrite beads:
Suitable parts from Farnell are:
Wurth Elektronik 7427922 (stock code 1635740)
Taiyo Yuden FBMJ3216HM600-T (stock code 1651732)
MEC Marcom MLB-321611-0060PQ (stock code 1308785)

Ian

[ShK]

Okay - it's done. Now after little period of time screen goes gray. Should I Change Ferrite beads back to the resistors?

(before / after images)

[Stedy]

@Shk,

Oops I missed the capacitance of those parts. They are actually a feed through LC filter with 2200pF (2.2nF) capacitor built in. This will severely distort the clock signals.

For now, remove them and re-fit the original resistors. The parts I posted earlier should work, I use the Wurth Elektronik devices in a number of my projects.

Ian