Mac Plus Clicking

[Dennis Nedry]

You can probably skip the solder-sucking step and go straight to resoldering (with fresh solder).

It has always been my understanding that removal of the old solder is a necessary first step because any oxidation or carbon that has accumulated in any cracks will remain even after heating and adding new solder, resulting in a fairly weak repair.

If you have the tools and want to make the best repair, I recommend to heat, remove the old solder, and add new solder, all of that, one point at a time.

 

[tomlee59]

It depends very much on the skills of the operator. An unskilled tech is likely to cause more damage, so that's the basis for my recommendation.

Btw, carbon is not the usual problem. It's a simple cleaving along grain boundaries in the solder, plus a bit of oxidation at the interfaces. Resoldering fixes that very well, thanks to the miraculous action of flux.

Skip the sucking step unless a) you are skilled and B) the joint looks like it's crud-filled.

 

[Dennis Nedry]

^

^

Yes I agree, this is good advice.

 

[imagineer]

I have finally been able to get onto some soldering. I resoldered the yoke joints (if I understand correctly the blue, red, yellow and green wires where they join the power board -outside of board - J1?), went round redoing any flat solders to brighten them up, also the little square transformer joints (LF1?) and it's 4 adjacent electrolytic caps. ( I did that since the first time the fuse blew it was after finger tapping that transformer).

Results? Blew new fuses twice. Where do I go from here? Test the little first transformer in the powerline? How to do that? Take it out? Ohm test it?

I have checked each joint carefully for "bridging", all OK.

 

[techknight]

you probably got a solder bridge by accident? or shorted something to something? Without pictures of your work and the board, this thread is going to go nowhere fast....

 

[tomlee59]

Before plugging the thing into the wall again, perform a few simple checks with an ohmmeter first. It sounds as if you have a short circuit somewhere. Those are usually very easy to find (unless they're intermittent).

If you do find that a short exists, you can narrow down the possibilities by selectively disconnecting parts of the circuit. For example, if a resistance measurement shows, say 10 ohms of resistance between the power leads, try pulling out the common-mode choke near the power input. If the resistance goes way up, then the problem lies with the choke or points downstream of it.

Since you have a schematic of the power supply, it shouldn't be too hard or time-consuming to devise and execute your own troubleshooting strategy.

And, once again, it's impossible to overestimate the value of a thorough, careful visual inspection. Use a magnifying lens and a bright light and look at both sides of the circuit board. Especially in cases like this where tapping affects things, a visual inspection will frequently reveal your problem.

Don't power up your Mac again until it passes the ohmmeter test, unless you like buying fuses.

 

[imagineer]

Thanks Tom, I thought I'd better go and buy a fuse or 10!