Unstable 60hz output from my A1200(T)

[woody.cool]

Hi all,

Recently, I've started to notice that my Amiga 1200 (in tower) has started to develop a strange video output problem that only affects 60hz output (or output using the NTSC monitor driver)
This happens no matter whether it's from a game (WHDLoad or NDOS booted floppy) or from a Workbench friendly app.

My A1200 is of the following spec:

Hardware


Commodore Amiga 1200 rev. 1D4 motherboard
Kickstart 3.1 ROMs
68040 accellerator: Magnum MKII '040. Unsure of speed (can't remember withuot running SysInfo or similar) & FPU
10GB IDE Hard Drive
16x IDE DVD ROM drive
IDEfix 4 way buffered IDE interface
Internal High Density 3.5" floppy drive (1.44MB PC/1.76MB Amiga/insanely close to 2MB with DiskSpare)
all in a nice EZ Z4 Tower (http://amigakit.leamancomputing.com/catalog/product_info.php?products_id=700)

Software


Workbench 3.1 (I changed hard drive recently and can't find my 3.9 CD or my 3.5 CD :()
WHDLoad 16.9
MCP (can't remember version, but it's quite an old ish one)
MUI 3.8
MagicWorkbench 2.?
NewIcons 4.6
ClassAct 2.8 (iirc)
all the usual unpackers (XPK, PowerPacker, LHA, LZX, DMS, ZIP/UNZIP, ARC, ZOO etc.)
Deluxe Paint V
PPaint 7.1 (for stuff that DPaint can't do)
Transdisk in C: (you know, the pants command line one that's part of WinUAE)
and that's about it

Like I say above, I've tried booting from floppy, booting with a minimal WB (so bypassing everything, doing a boot with no Startup-Sequence and typing LOADWB and ENDCLI at the prompt) and obviously a normal startup.

This is looking increasingly like a hardware problem tbh.
Any ideas?

All help/idea/whatever appreciated.

Thank you all in advance!

Cheers
woody.cool

[Harrison]

Could be a hardware issue. Only effecting one screen mode/resolution is a little odd, although grounding issues often effect things like this. What PSU are you using, and how old is it?

Might also be custom chipset issue.

[woody.cool]

Oh, the PSU is a 250W ATX PSU (can't remember the brand) which came with the EZ Z4 Tower case, so we're looking at approx 12 months old (if that) as I haven't had it all that long.
As for the Amiga 1200 .... well, it's the same A1200 motherboard (and 3.1 ROMs) that I've had for nearly 8 or 9 years, so that bit's getting old now!

[Phantom]

250W I think it's sufficient for what you have inside your tower.

[woody.cool]

250W I think it's sufficient for what you have inside your tower.
Same here!
I have ordered a 4GB CF card and a CF-IDE convertor, so will be 'loosing' the HDD when they arrive.