smoking yoke

[cfriberg]

Hi everyone I'm digging up my old mac classic with the hopes of reviving it. I know its gonna have lots of problems but i hope it ends up a happy mac story.

The first most important i think is on power up i get a screaming sound that i think originates from the analog board, hopefully just the speaker but it was followed by smoke coming from the yoke connector. I dont see any signs of burning though so i dont know what is extactly is smoking.

I need to exorcise this demon before i can start troubleshooting other issues. Any thoughts? Did a search for smoke and yoke connector and i dont see anyone else with this problem.

Thanks and happy classic mac-ing

 

[uniserver]

video?

 

[cfriberg]

The deflection yoke?  There are 7 pins at the butt end of the CRT past the yoke, attached to these pins is a plastic connector on a PCB.  The smoke was coming from somewhere on that little PCB.  I don't want to turn it on again and wait for more smoke to see exactly where it's coming from.  I was hoping someone had this issue before.

I did read something about people having problems with dry solder joints somewhere on the yoke, maybe this is the problem?  I'm not sure which joints commonly fail.

Anyways, thanks to anyone who can give me a clue.

 

[techknight]

if the smoke was coming from the neck board, the CRT is bad, or the output transistor is bad. 

The yoke is the coil that sits on the bell of the CRT. Not the same thing. 

 

[uniserver]

so it kinda looked something like this?

 

[cfriberg]

Ha ha uniserver, I think your analog board needs to be recapped.   Anyways, I tried to be respectable and figure out where the output transistor is on my own, but I give up.  I found a funny picture on the way though:

https://flic.kr/p/4F81tG

Also, what's the best way to detach the CRT from the analog board so I can do some more investigating on the board without being tied down to a possibly dead glass tube?

 

[techknight]

Ha ha uniserver, I think your analog board needs to be recapped.   Anyways, I tried to be respectable and figure out where the output transistor is on my own, but I give up.  I found a funny picture on the way though:

https://flic.kr/p/4F81tG

Also, what's the best way to detach the CRT from the analog board so I can do some more investigating on the board without being tied down to a possibly dead glass tube?

 

[cfriberg]

Wow, you guys are brutal.  OK, so I found a big problem and I hope I fixed it.  The board is cracked right at the "high voltage connector?"



This is where the neck board was caught smoking


Here's just some more pics to make this thread more "useful".

So what do you think?  Should I try powering it up again and see if that crack caused a short and was the source of the smoke or would it be the little black transistor on the neck board like you said earlier?

 

[MJ313]

hahaha! I can't help you at all... but you're a funny guy!

 

[techknight]

I love that last pic. And I like the cigarette pic. That was awesome. hahahahahaha.....

Anyway, The CRT Neck PCB has quite a few noticeable bad solder joints. Might want to attack that first. 

 

[uniserver]

haha where did you find that cig butt?

 

[uniserver]

https://youtu.be/gDg2jh-KZbk

https://youtu.be/gDg2jh-KZbk

poor MJ fox.  

 

[cfriberg]

Well, I tried a bunch of things and I think it is out of my scope of comfort.  I feel like I'm repairing a TV more than a Mac.  I haven't even gotten to the logic board issues and with no power it's really unrewarding.  I retraced some bad circuits.  I resoldered some bad joints. I would love to just see a scrambled screen and a chime of some type come out of the speaker at the very least. 

So I know better than to throw it in the dumpster.  I will post the sad little mac on the want ads.  Maybe someone with a bunch of spare parts lying around can frankenstein it.  Thanks for the laughs.  I enjoyed it while it lasted.

 

[uniserver]

is that a classic II?  if so i can atleast buy the MB from ya.  as i need some.

 

[Schmoburger]

This thread has delivered.