Macintosh TV not powering on (MLB issue)

[elemenoh]

I have a Macintosh TV that has power, but will not chime or boot with its MLB. With a known-good Color Classic MLB installed, it will chime and boot okay, though there is an intermittent fluttering sound coming from the speakers. That might just be an issue with the CC board though. I cleaned it up but it needs caps replaced too. 

 

There wasn't obvious cap leakage, but I cleaned the board and replaced the MLB caps anyway. The symptom remained the same. On flick of the power switch you can hear the display power on, but when the power key is pressed, no LED on the keyboard and no chime or boot on the computer.

 

I installed a new PRAM battery on the original board, but that didn't change the symptom. And the machine boots with the CC board without a PRAM battery installed.

 

The analog board also looks okay at first inspection. No obvious cap leaks.

 

So, what should be checked next?

 

Edited September 15, 2019 by elemenoh

[bibilit]

Bad trace or maybe the Egret chip, don’t know if is present  in Mac TV but was in many other LBs. 

 

Will prevent an overall good board from booting 

 

 

[68krazy]

I read about one case with the Macintosh TV where cap goo had shorted a reset switch on the board, and that was keeping the board from booting.  Not sure if yours has the switch or not, but that could be an easy thing to check.

[defor]

On many of my 5xx chassis AIO boards, I've had issues with battery goop having corroded the traces on or around the CUDA chip. Resoldering (or replacing this chip using a suitable similar donor mac) usually fixes the problem right away.

 

One of my MacTVs also had a trace corroded through UNDER the battery holder- so its worth desoldering and inspecting that as well.

[elemenoh]

Removing the CUDA and cleaning underneath did the trick! Now to find a hard drive adaptor for this thing. Anyone have a spare?

[elemenoh]

Found the adapter on eBay. It’s called a Macintosh LC HD adapter bridge.