A4k Left Mouse Button issue

[skilgannon]

Hi folks, has anyone seen any issues with the Amiga 4000 Desktop and the left mouse button?  Mine stopped working tonight (hardware level too as I can't access the boot menu either).  Tried two different mice - one being pretty much brand new.  Amiga was on most of the evening so heat maybe???  

Anyhoo - any ideas as to what's wrong would be appreciated as I'm thinking of selling it or trading it for a fully specced minimig or something and would rather it not have issues!

Cheers all!

John

[save2600]

Cold solder joint on the connector of the 4000? You could try wriggling the connector as you hold the button in to check that.

Otherwise, hope you didn't blow a surface mounted CIA chip!

[skilgannon]

Thanks Save - can't think why I would have blown the surface mounted chip as I haven't plugged / unplugged the mouse with the power on.  Will try the cold solder idea.  I take it that overall system heat wouldn't do this - the machine eminates a lot of heat from the cybervision video card?

[Tension]

Caps.

[save2600]

Thanks Save - can't think why I would have blown the surface mounted chip as I haven't plugged / unplugged the mouse with the power on.  Will try the cold solder idea.  I take it that overall system heat wouldn't do this - the machine eminates a lot of heat from the cybervision video card?

The heating up and cooling down of the system *can* agitate a bad solder joint - effectively simulating the plugging/unplugging of a controller or mouse.

Too bad these systems were designed to be as cramped as they are. Cooling is a total joke. I wouldn't hesitate fastening some small heat sinks onto some of the typical problematic chips, including those on your video card.

@Tension: failing caps usually affect the CPU (3640) or sound circuitry. Are those leaky bastards near the CIA's too?

[Tension]

@Tension: failing caps usually affect the CPU (3640) or sound circuitry. Are those leaky bastards near the CIA's too?

Not sure, but my A4k has a problem with the right mouse button jamming on, even without a mouse in the port.  I also have bad audio and random crashes.  Plus the Parallel port causes a printer to start printing random nonsense.

I put it down to caps, but one of the CIAs is probably buggered as well

[skilgannon]

OK - I think it must surely be heat as it wasn't doing it today when I turned the machine on but after about 5 minutes - LMB failed again

[tokyoracer]

Yup caps can be an issue, got an A1200 that has a very similar problem to your A4k. I'd put money on saying its a fault with a cap.

[Castellen]

The capacitors which generally leak are the 22µF and 4.7µF ones, which aren't involved in AC decoupling of the 5V supply.  The positions they're in are unlikely to damage the left mouse button line due to localised corrosion.

CIA U350 does read the left mouse button, but an intermittent CIA failure like this is not common.

Measure between the left button pin (CN975 pin 6) and U350 pin 10.  Should be about 47 ohms if it's working normally.  If it's open circuit, then I'd start looking for a problem with a fractured pin in CN975 (which is fairly common), or a crack in resistor ER976.

To check for a cracked connector lead, heat the bottom side soldered connection of the pin.  If the pin moves very easily, or slides out when you pull it gently with tweesers, it's obvoiusly broken.  Easy enough to fault find/repair.

[Castellen]

Not sure, but my A4k has a problem with the right mouse button jamming on, even without a mouse in the port.

Had a job come in with this exact fault the other day.  The problem had started with leaking capacitors in the audio stage, the corrosion around op-amp U402 caused enough damage to the device so that the reference voltage of 2.3V was no longer present on the DAC output pins (U400 pins 33 and 34).  It was either at 0V or something much higher than it should have been, I forget now.  This caused the ADC channels to malfunction, hence the right mouse button would fail to operate and jam on.

I've written details of how to repair it all here.

[Tension]

Yup caps can be an issue, got an A1200 that has a very similar problem to your A4k. I'd put money on saying its a fault with a cap.

Just heard about the £30 capacitor replacement service by AmigaKit.  Might take them up on that offer because I wouldn't want to risk doing it myself.

The steaks are too high.

[save2600]

Man, those look good - but what the heck is that fungus growing in the upper left?  lol

[skilgannon]

Just heard about the £30 capacitor replacement service by AmigaKit.  Might take them up on that offer because I wouldn't want to risk doing it myself.

The steaks are too high.

I appreciate all the good advice folks and it does sound like something a bit more technical than I can do myself (rubbish at electronics).  Think I may send it off to Amikit as well unless someone wants to trade me for my machine as is of course!