Studio display - bad caps?

[Mikeyy00]

Hi,

Had a working 17 inch LCD Studio Display which I move between a Cube and Dual CPU G4.. been working fine for years. Now, if the monitor is connected to either the Cube or the G4 Tower, both computers won't power on. I can hear an electronic "chirp" from the power supply area on the G4 tower that repeats every couple of seconds. Soon as I unplug the monitor the sound goes away and the desktops will power on again.

Tried plugging the monitor into one of those ADC-DVI adapters with the giant power brick.. same issue, it emits a chirp/pulsing sound every few seconds until I disconnect monitor.

Opening it up, nothing was obviously shorted. No caps are blown/leaking (that I can see). I found another monitor locally (but the seller hadn't tested it in years), another 17inch LCD. Took it home, connected it and it's doing the same thing.

So, any chance it's just bad capacitors inside? They're both approaching 20 years old.. Anyone ever see similar behaviour on one of their monitors?

Thanks!

 

[alectrona2988]

Perhaps when it does utilize the graphics chip on the G4 tower, the power supply might be under load. You definitely want to check your caps on that one. LCD Studio Displays aren't really part of a bad cap issue.... yet.

 

[CircuitBored]

This is a really odd issue - thanks for sharing!

How cold is the room you're trying to use these machines in? The G4-era power supplies really struggle when booting cold. The ADC power circuitry in G4 power supplies is notoriously weak and often the first thing to die when a PSU is on its way out. As an experiment, use a hairdrier set to its lowest heat setting to warm up the power supply of your G4 tower before booting and then try the monitor again. Don't hold the hairdrier too close, just close enough to the PSU's exhaust warm it up about 10C above room temperature. Make sure you pin the fan with something to stop it over-spinning. The "hairdrier trick" is how I had to boot my Quicksilver every time back when it was my daily driver. I did eventually replace the PSU with the much better AcBel model.

That said, it's odd that this is happening on both of your G4s as well as an ADC-DVI adapter so a bad PSU seems like an unlikely culprit in this scenario.

However, there is an important question to be asked: did you first test the monitors on the same machine each time? If so, it's entirely possible that a bad PSU in one of your machines has tanked the monitors. I've seen it happen and if you have a Quicksilver with a Delta-brand PSU it's especially likely. IIRC (this was a decade ago now) there is a set of fuses near where the ADC cable is soldered into the monitor's circuit board. Grab a multimeter and test for continuity across all the components in that area. It was either a fuse or a small capacitor that I replaced to bring my 17" Studio back to life.

The next thing I'd suspect is the ADC cable itself. A lot of pressure gets exerted on the part of the cable where it joins the back of the monitor and I've seen quite a few Studio LCDs with cables that are broken there both internally and externally. Again though, this is somewhat unlikely to be affecting both monitors in the same way at the same time.

Lastly, check your earth connection on the mains circuit you're powering these devices on.

It is very, very unlikely that bad caps are to blame but I am interested to hear what you uncover as you troubleshoot this rather strange issue.

 

[Mikeyy00]

Thanks for the suggestions, couple of thoughts;

With two monitors doing the same thing (and they were known to work previously), we can probably rule out the ADC cable.
Similar thought to the PSU/Temperature since there's 2 desktops + adapter all exhibiting the same issue

I did teardown the monitor, and disconnected everything past the board where the power portion of the ADC cable connects into (see picture). Everything aside from the red section was disconnected and still doing the same behaviour.

I did order some caps from Digikey today.. so we'll see if that changes anything in a couple of days. I'll keep y'all posted.

 

[CircuitBored]

However, there is an important question to be asked: did you first test the monitors on the same machine each time?

@Mikeyy00 Please answer! I'm especially interested to hear if there's a Delta PSU'd Quicksilver in the mix. As I said, it's entirely possible that one of your machines has fried the monitors.

 

[Mikeyy00]

Hey.. so quick update. Cap replacement did squat. Same "pulsing" sound.

Quicksilver had an AC Bel? PSU inside. I did plug the "new" monitor into the QS first.. so, I guess possible that it broke something? You'd think it'd be some sort of cap/resistor/diode that I could change out on the monitor though if it fried something.

Not really sure where to go from here.

 

[Byrd]

Does the power light blink at all? These 17" displays were not known for their reliability even when new - Apple had a class action lawsuit from owners in the day to repair or replace, usually related to a failed inverter board.

Dim Apple Studio Display 17" LCD

Apple's 17-inch Studio Displays have a common problem, in which the upper or lower part of the monitor goes dim, and the power light flashes. Apple has not acknowledged this as a known problem, and charges an exorbitant fee for out-of-warranty repairs.

wysz.com

I'd perhaps look into the other common failure points of the monitor - as you've said diode/vreg/resistor

 

[alectrona2988]

I still have a working one of these from 2003 and the only issue is the display has some pressure marks.
Not sure what type of connector the panel uses.