Macintosh TV in need of repair - need advice

[krye]

I just picked up a Macintosh TV. It doesn't power on. When I plug it in and turn on the mains in the back, I hear a short buzz/chirp.

It doesn't turn on by pressing the power button on the keyboard. To rule out the obvious, I tried the keyboard and mouse on my Color Classic. It works. So it's not a dead keyboard.

Next step is to identify if it's the logicboard or the analog board. Correct me if I'm wrong, but isn't the Macintosh TV basically a black LC 520 with a LC 550 board? Can I just get my hands on a LC 550 board and swap over the TV tuner card? Can I just take the analog board out of a 520 and use that? (If need be)

Another silly question, can I put my Color Classic board in the Macintosh TV just to see if it powers on? They look very similar. Are the pin outs the same? I just want to see if I can use that board to figure out if it's the analog board that's dead, but I don't want to put my Color Classic board in the Macintosh TV if it's not pin-compatible and risk killing it.

Thanks.

[jsarchibald]

Could be many things, but I sometimes find this era of macs won't start without a good PRAM battery. Worth a shot?

[LCGuy]

I can't find a pic, but the slot that the TV tuner goes into is certainly not a standard LC PDS. Theoretically the pinouts should be similar, but they would not be identical - where the CC. LC520 et al have a microphone, the Mac TV has an IR sensor for the remote.

[FlyingToaster]

I would take it completely apart using the online pdf service manual. Maybe re-connecting head to toe might coax it to life?

[krye]

I tried a new PRAM battery. Still nothing.

[maceffects]

Any oily residue under any of the capcitiors?

[Dennis Nedry]

Yes, it sounds like bad logic board capacitors to me too.

You can narrow it down between the logic board and the rest of the Mac if you follow these steps:

Unplug Mac
Remove Logic Board
Plug in Mac
Turn on power switch near plug

If the non-logic-board part of the Mac (aka shell) can turn on, it will. The green light will turn on on the front of the Mac. (Same trick works on 5xxx PowerMacs)

I wouldn't attempt inserting the logic board in this state though. That would have zero chance of helping and a non-zero chance of wrecking something.

[Byrd]

Try cleaning the long edge connector, and the motherboard connector itself with electronic cleaning solvent

[krye]

Thanks for the tips. I'll try those and report back.

[krye]

Hummm. No power-on LED. I guess that means the analog/power supply board is dead?

[Dennis Nedry]

There's a switch right next to where the power cord goes in, did you make absolutely sure to turn that on? It's probably not good news otherwise.

[krye]

Yes, the mains is on. Still nothing. Just a slight buzz from the back when I flick the switch.

Also, I don't think this is a good sign either. Look at the underside of the logicboard. Is that leakage from the caps? Looks like all of them have leaked. The board is covered in a white residue.

[bibilit]

A good bath is required !

[Dennis Nedry]

Other than the logic board, the Mac TV has identical innards as a Mac LC 520. Probably any other 5xx (except 580) would work too. I got my Mac TV with a good logic board, plastic case, and nothing else, but after some parts from a spare 520, it was up and running.

So if your logic board is okay, it's just a matter of finding a donor 5xx for parts.

[krye]

I just scooped up an analog board from a 520 on eBay for only $20. Hopefully it works. I'll try and clean the logicboard, but I expect the worst.

[krye]

Even when I get the new analog board that I just ordered (providing that it even works), I don't think there's any hope for the logicboard. I dusted it off and removed the tuner card.

Look at the corrosion under the tuner card:



Also, I tried to clean the white stuff from the underside of the board and it just doesn't come off.

To make matters worse, look at the daughter board on the tuner card. It looks fried.

[Dennis Nedry]

It doesn't look too bad to me. It actually looks like cigarette smoke and dust to me, I doubt that's rust / corrosion. I don't know about the tuner card, but if those parts are burnt, they look to be replaceable.

Just clean it up really really well with soap, water, and a toothbrush, rinse the heck out of it to get the soap off, get as much water out as you can, and let it dry for a few days. I bet it's just fine.

[madmax_2069]

After you do clean everything off with soap and water, you can buy a can of compressed air to spray around any chips that might hold water under them. It makes the drying process a lot better. It still needs to sit a few days to make sure it's dry, chips that can trap water under them can be a pain because even after a few days if there is water trapped under any chips can still contain moisture.

[uniserver]

yeah its cooked, it was probably hit by lightning or some kind of surge… came in from the coax, i used to work for comcast, peoples tv's would fry all the time after storms. Technically if the Ground block was installed right, and grounded right… this wouldn't happen, but most of the time a contractor didn't install the cable properly. so your tv or computer is great way to ground

[maceffects]

Yes, if the Analog board doesn't fix the issue the main board needs replaced, and uniserver is right thats most likely what happened there.

[Bunsen]

Look at the corrosion under the tuner card:

That doesn't look too bad - it looks like mostly surface rust & deposits. It may still come up good after a clean. NB: board washing technique is something you may want to search on here if you've not attempted it before.

look at the daughter board on the tuner card. It looks fried.

Yeah, that's toast. Still, give it a clean and see how it looks afterwards. As Dennis says, you may be able to replace the individual components if the PCB itself is OK - and if you can work out or find out values for all the components

[krye]

OK, I got my hands on a new analog board. The seller couldn't test to see if it worked. He said it's been sitting on a spare parts shelf for years.

I popped it in and powered it on. Still, no green light on the front. I tried to insert the logic board, then remove it and power on. Still nothing. No green LED on the front. Is it possible that this board too is dead? Or am I doing something wrong?

[spiceyokooko]

That buzzing, chirping sound you hear when you switch it on suggests to me it's the power supply that isn't working.

Have you checked the voltage outputs from the psu with a multimeter for the correct voltages?

[Dennis Nedry]

The analog board is also the power supply if I'm not mistaken.

I guess I'm down to maybe 95% sure that the green light should turn on without a logic board... Could somebody verify this? I don't have a 5xx handy.

Have you double-checked the connection to the board containing the power LED? These noises you describe sound like a good sign to me, they kind of squeak and chirp a little, but I'm not completely sure without hearing it myself.

Also, there is a large edge connector on the analog board, is this clean and pushed in all the way? If you take some pictures of the inside and post them here, someone might notice something wrong.

Even something as simple as your power cord, a turned off power strip, or a loose power cord connection could cause this strangeness. I would never put myself above something like that, often times it's the dumbest thing wrong.

[krye]

I managed to score a LC 520 for $5. What a deal. I was hoping I'd be able to swap the guts out of it. The seller couldn't verify it works since he didn't have a keyboard. I took my chances for the $5 bucks.

Anyway, I got it home and plugged in my keyboard. Same thing as the Macintosh TV. There's a chirp sound when I turn it on from the mains in the back, but it does not power on with a keyboard. I have 4 different keyboards and nothing works. I've tightened all connections. Both machines do not have green LEDs on the front. I opened up the LC 520 and the analog and logic board look like they are in great shape. It's just a mystery. These machines will power on with a Keyboard II, right? It's not that I'm using the wrong keyboard?