Macintosh TV sound/TV tuner problems

[techknight]

I've actually read that the humongous electrolytic caps are very rarely the problem and they're expensive, so I'm not going to replace them unless I absolutely have to.
Many (most?) of the smaller ones will definitely be getting replaced though, especially any that show a high ESR.

As I work in the repair industry, its those humongous caps that when they DO fail, they do the most devastating damage. Blowing up transformers, etc...

 

[dougg3]

Heh, I can only imagine how ugly it would be when the big ones fail!

I removed all the analog board capacitors except for the very biggest one today, so they are all being replaced aside from that one. Really glad I got that vacuum desoldering gun; it saved a TON of time. I started smelling that fishy smell when I removed a few of them...so yeah, some of them definitely had some leakage. None of them showed anything too crazy for ESR, but the fishy smell is a dead giveaway that they need replacement. I'll leave the logic board and TV tuner caps alone at first to see if the analog board ends up fixing the sound problem, but after that everything else is getting replaced too

 

[olePigeon]

What kind of capacitor? I can check my local parts store. Might have big, new ones for cheap.

 

[dougg3]

Hey thanks for the offer! I'm actually not planning on replacing it, so no biggie. Thanks for offering to check though

It's a 330uF, 400V capacitor. Looks like it can be had on Digi-Key for about $5 or so. It won't be a huge deal to get it on Digi-Key if I do end up having to replace it. Thanks again though!

 

[dougg3]

The fan was filthy before I cleaned it, but the awful sound when it first powers on (and off) is the hard drive. It's the original 160 MB Quantum, the same type that is prone to having the "spins up, then spins down and doesn't work" problem like techknight described on his YouTube channel. As of now it still works, but judging by what I've seen, I can't rely on that hard drive to last much longer

 

[dougg3]

Well, analog board recap didn't fix the faint sound. Logic board and TV tuner board coming next.

Luckily, my analog board recap doesn't appear to have hurt anything. The picture *might* be a little blurrier than it used to be, not totally sure. Does the analog board typically need adjustments after a recap?

 

[onlyonemac]

I can't see why it wouldn't need adjustments (essentially the new capacitors have a different capacitance to the old, failing ones, so most likely it will need adjusting).

BTW I would not say I would have ever described the sound of my late Quantam 160MB drive as "awful".

 

[dougg3]

Yeah, this is a weird sound I've never heard on other Quantums before.

Unfortunately I lifted some pads on the logic board last night when removing the old capacitors. One completely broke off. Fixable, but ugh. I think cutting the can off, removing the black insulator thing, and then removing each lead separately is the way to go on those things--NOT heating and lifting the sides alternately.

 

[uniserver]

Yeah I'm a twist off man my self. works like a champ.

If you would rather I take care of that for you, let me know.

i wouldn't mind earning some of that money I'v paid you back.

I'm Fast, and reasonably priced.

Charles

 

[dougg3]

Thanks man, I would like to finish this mistake up myself though I have several ideas and I found a place to hook onto to replace the missing pad.

 

[dougg3]

Update: I found where the lost pad was supposed to connect and ran a patch wire to a ceramic capacitor on the bottom of the board that connects to the same rail. I also just carefully re-soldered a new cap onto the lifted pads that were still connected. Probably should have epoxied them down first, but I'm too anxious to get this working!

The sound is nice and loud again. So yes, leaky caps on the logic board were causing the faint sound on this Mac TV.

Next up: recapping the TV tuner board to see if I can get TV tuning working again.

 

[dougg3]

I was able to recap the TV tuner board itself without problems (eww! ALL of the capacitors had leaked badly), but there's a little Sony daughterboard on it (covered with small electrolytic capacitors) that gave me some troubles and I lost a few pads on it -- my guess is the leaky caps didn't help matters. Luckily the Sony daughterboard is a part commonly used in many TVs, so I can just buy a new one if I can't salvage the existing one. If I can, I plan on adding a header so replacing it in the future won't require soldering.

The Sony board is an SBX1637A-01 and appears to be for the TV audio.

Right now I'm running the newly-recapped TV tuner board without the Sony daughterboard, and the TV tuner works perfectly after being recapped! Woohoo! I'm thinking as soon as I have the Sony board recapped and back in, the TV will have sound too. Can't wait to complete this! I'm super excited to be restoring this broken Macintosh TV to its former glory

 

[dougg3]

Haha, hope these updates aren't getting too annoying! I was able to repair the sony sound board's missing pads and recap it. The TV sound is there now, but very very faint. I probably screwed something up along the way. My plan is to just buy a new sound board. That board has a TON of capacitors on it; it was really difficult to recap. I'm sad that it didn't work But I'm not overly upset about it. Other sources online for TV repair said to just buy a new module and don't bother recapping it. I see why -- it's so jam-packed!

 

[dougg3]

Replaced the Sony sound board, and added a socket (found some 0.070" pitch headers on Digi-Key) so if it has to be replaced in the future, no desoldering will be necessary.

The TV sound is alive again! Woohoo! Haven't tested the floppy or CD drive, but everything else is perfect aside from the nasty hard drive sound when it first spins up (and when it spins down). Anyway, awesome! Mission accomplished before analog cable is completely gone.

 

[markyb86]

When they make the switch you can still get OTA local channels with a $20 digital converter box.

Some of my local channels look as good (or better than) HD on cable when we had it.

 

[dougg3]

That's true...also, bbraun told me there are devices that take composite and s-video inputs and turn them into analog TV channels. That would be interesting to try too.

Here's a video of the Mac TV in action:

 

[onlyonemac]

That's a cool TV! Just a few questions though:

Why did it show the happy Mac twice?

Why was the clock not set (I assume there's no PRAM battery, but am I correct)?

Is the TV flicker due to changing channels, or is that how it looks when on one channel (I'm not talking about the strobing effect on all screens)?

Why are you using that remote, not the original (I guess that's not the original)?

 

[dougg3]

Thanks!

Your first and second questions are actually related. Both happen because I don't have a PRAM battery installed. When a Mac with uninitialized PRAM first boots up, it's in 24-bit addressing mode. If you try to boot into System 7.6 with 24-bit addressing, it will chime and show the Happy Mac, and then it will put the Mac into 32-bit mode and reboot. So that's why you hear the second chime -- it's System 7.6 changing to 32-bit addressing. The clock was also not set because there's no PRAM battery. I don't know why the "clock not set" message immediately dismisses itself. Maybe it's special behavior in the Mac TV? Or do other computers do that too?

The flickering is definitely due to the CRT being filmed by my phone. I don't notice any blinking when I watch with my eyes.

The remote I'm using is the original remote. Newer systems with TV cards had a different style of remote which is also compatible with the Mac TV's remote, but the remote I have was the type Apple originally included with the Mac TV.

 

[Macdrone]

Clock not set happens on my 5400 series also. Sometimes its fast, sometimes not. I think sometimes its a disc access issue kinda like it had not loaded the control panel at the same rate during boot. Like the G3 accelerator changed the behavior even more.

 

[onlyonemac]

I don't know why the "clock not set" message immediately dismisses itself. Maybe it's special behavior in the Mac TV? Or do other computers do that too?

Mine does that as well! I've often wondered why... :?: :?:

The flickering is definitely due to the CRT being filmed by my phone. I don't notice any blinking when I watch with my eyes.

I'm not refering to the general flicker. There's a much slower "sweep" effect, repeating about once every 2 seconds, during the TV tuner demonstration. I couldn't quite tell if you were changing channels there or not.

The remote I'm using is the original remote.

Then that's a very modern-looking remote! It looked out-of-place with the Mac TV, so I assumed it was not the original.