Does a Mediator graphics card replace AGA?

[Mizar]

In my A1200 the graphics output has been getting gradually weaker for some time, requiring ever increasing brightness adjustments on the monitor.  I'm wondering, when I upgrade to the Mediator PCI expansion and put in a modern graphics card, if that will fully replace the aging Alice and Lisa chips that seem to be wearing out?

[Mizar]

No. A gfx card in an Amiga acts like a second gfx card. Programs which support it (including Workbench but excluding most games) can be made to display on the gfx card. But the main output remains through AGA, like the early startup menu, the guru meditation and those games and programs which don't support gfx cards or switch off AmigaOS.

Yeah, that makes sense.  Bummer.  Just like how using a 31 kHz scan mode you still have to display those same things on a 15 kHz screen with anything that doesn't support the higher scan mode, or that can't be mode promoted.

A suspect a quick capacitor change would get your Amiga back nice and bright again....

Quick? Heh, I wish, but that sounds fairly involved.  It'd require knowing which capacitor, disassembling the system to gain access, acquiring an exact replacement component, doing the SMT desoldering and resoldering, and reassembling the system.  I've even done SMT work, but not for years, and there's no margin for error if you end up damaging something in the process (overheat or otherwise damage the board or pads while removing and installing).  Probably the diagnoses of the exact problem and which component to replace would be the trickiest thing of all.

[Mizar]

Agreed. If your chips were wearing out, I suspect you'd be seeing other symptoms. It's more likely that your monitor is getting old, especially if it's a CRT. If you don't have another monitor, you could try a different computer attached to that monitor to see if you get the same results.

Well, I am seeing other symptoms, actually.  I see weird flickering in certain parts of the display sometimes, and the picture has missing blocks in certain places when I drag screens up and down at other times.

My monitor is a CRT, but it's not that old really, and hasn't been used too awfully heavily.  Unfortunately, I don't think it's the monitor.  The other monitor I have is a 1084S, but it's under a bunch of boxes I'd have to dig it out from under, and try to find some space.  So, I was going to hook up another computer to the monitor.  That's what I forgot to do... I'll test it tomorrow.

I presume he's tested the monitor on another machine, right..?

Either way, you will need to change the capacitors at some point. They're the right way round (it's only the A3640 that's not), but they're just very cheap.

There are various people who can do it for you if you want - I'd offer myself but I'm across the pond in the UK.

Didn't test it yet... will tomorrow.  No, I can do the capacitor replacement myself actually.  I was basically just saying it'll be hard to find the time.  And I didn't know where to get the install info.  I think someone mentioned where to get it.  (I'll also have to get some fine pitch equipment.)

[Mizar]

I also think its the monitor.

The Indivision AGA MK2 will get you the best picture period...

It's not the monitor, as I suspected (see below).  It's either the AGA or the scan doubler maybe.  But I'm not sure the scan doubler would have those symptoms.  I forget, the Indivision AGA MK2 is a scan doubler, right?

have you tried with another monitor?

Ok, yes I checked the monitor now, with another computer.  As I figured, it's fine.  It's exceptionally bright, in fact, even when I turn the brightness way down it's still bright.  However I have to keep the brightness at the default, 50%, or it's hard to see detail in dimmer pics.  This is opposed to 75% for it to be marginally bright enough with the Amiga output, and I used to have it well below the default setting originally.

I'm skeptical the scan doubler could be at fault.  For one, it's normally in bypass mode as I'm using a 31 kHz mode, but there's no difference with the problem at whichever frequency, 31 or 15 kHz.  That is, unless it could be causing some issue even when it's supposed to just be bypassing... seems unlikely.  Also, the strange display anomalies are too specific to parts of the screen for the scan doubler to cause.  However, I'm not 100% sure because there is some toasting and very slight melting of the case.  As there had been some overheating going on with the scan doubler at certain times, it seems.

I will have to dig out the 1084S from the storage area to further test it.  Being as that doesn't require a scan doubler, it should indicate whether the problem is the scan doubler, or that it is in fact the AGA chips.