To Recapp, or Not to Recapp... That is the question

[Canby Fat Mac]

I found a Macintosh Portable 5126 south side of London from the original owner. Got it back to the states today, put in a new battery and was surprised to find it works flawless (even the clock was set powered with 9v dated 9/94). Took it apart to remove the British invasion of dust bunnies and was even more surprised to find all the original caps are installed. Inspected them and see zero signs of leaks.

Now should I stick to the side of "Preventive Maintenance" and have the board recapped?

Or the side of the purest and leave it "Original as designed by Apple" and "Dont fix whats not broken"

 

[poobah]

I'd leave them if they aren't showing signs of problems.

Always try to avoid the engineer's credo: "If it isn't broke, fix it till it is"

 

[techknight]

poobah: Bad advice, think before you type! That statement may be true on certain things, but it is an absolute no-no with the macintosh portable. 

CHANGE THEM ALL. They leak and causes trace rot on the portables, I get more dead boards across my doorstep from capacitor electrolyte damage than any other machine. 

Oh, Canby: Your inspection is flawed. they are leaking, trust me. It may not always be apparently evident. 

 

[poobah]

poobah: Bad advice, think before you type! That statement may be true on certain things, but it is an absolute no-no with the macintosh portable. 

Hmmm, well, imho, I'd suggest that it is always true.

The mac portable may be more prone to cap issues and electrolyte damage (I haven't repaired any of those), which certianly could tilt the decision, but I'd be loathe to repair a machine that is working properly with no signs of leakage. That said, in this instance I'll defer to your experience with these particular machines.

Have a great day

 

[Unknown_K]

It is easy to see leakage on old machines just look at the dust around the caps. If the machine works reliably and there is no leakage you can leave it be as long as you are willing to check on it every 6 months or so. If there is leakage now replace all the aluminum electrolytics.

 

[Juror22]

I agree with technight - if you have been lucky enough to catch the caps before they leak on one of these machines, the time to replace them is now, before they leak (they will - that is a certainty for 25 year old caps) and harm the boards.

I have had much better luck with boards that have been proactively replaced (SE/30's, II's, Cx's, Ci's, Classics, Portable and and numerous powerbooks).

If you are concerned with originality of the board, replace with like caps.

 

[gsteemso]

I agree with technight - if you have been lucky enough to catch the caps before they leak on one of these machines, the time to replace them is now, before they leak (they will - that is a certainty for 25 year old caps) and harm the boards.

What he said. It’s pretty much a no-brainer. You WILL need to recap it at some point, most likely quite soon, and better to do so while it is still intact. I did this proactive maintenance for my Quadra 840av, and was astonished to find that several caps actually HAD leaked, damaging the pads underneath, without any outward sign of such being apparent before the caps were pulled.

 

[uniserver]

With any 68k machine, with SMT can caps.... Change them now.  Wether you do it your self... or have a buddy do it... or Mike ... or ME...   OR at the very least just remove them all and clean up the corrosive/conductive goo, and remove or clip-off the pram battery and throw that away for most machines.  Clip the pram battery off for the SE / IIgs.  Then at least your board will be protected from any farther damage.  

Right now in the Ham radio field... lots of those dudes have the same MOTTO...  ( if it aint broke don't fix it ) 

Witch is great... because by the time their 80's 90's ham radio dies ... its really dead...  and talk about even more complex to recover

from fried traces / fried pads/ fried I/C's  Ham radios are way more complex then these 68k macs...

I have a KENWOOD TC-50 on my bench right now... man its screwed...   Tin cans everywhere... 47uf's 22uf's 10 uf's

granted i got the thing for cheap, I really thought I could make it work and it mostly does work now... except for there is still something wrong

because occasionally it goes into protection and the red led's on the mb light up... and if i bang what looks like a tuner in a metal box the red light will go off or a while, and all will work, only to come back on... so that is telling me cracked or rotted trace some where still.

but once it does work, it works great.  I blasted my EZ military Vertical with 100 watts from this rig, and 

JT65 receive sites lit up all over the place!

 

[uniserver]

i just got the darn thing to work good now…  i found a rotted up trace UNDER the pcb.  Ripping the main board out of this radio is a pain!

in the middle of listening to radio China Radio international with a make shift 2ft x 2ft half-wave dipole in my office right now. 

http://www.short-wave.info/index.php?station=CHINA%20RADIO%20INTERNATIONAL

9580 CHINA RADIO INTERNATIONAL 01:00 01:57 1234567 English 250 10 CUB
La Habana

 

[unity]

The Portable is the worst offender. Second being the SE/30. I had a NOS portable board with signs of leakage! A first for me as I have a few NOS boards that never showed a problem. And once they leak, they are a pain to fix. As for looking as dust - the portable has no fan so the boards stay very clean. Makes is a little harder to spot cap goo.

 

[EvilCapitalist]

Add another to the chorus of those saying "Recap now!"

I had a number of different machines that were working great and showed no outward signs of leaking (that I could see) and I kept thinking that I really should get them recapped just to stay on the safe side.  A few I managed to catch before they were toast, others worked great right up until they suddenly didn't power up anymore and the boards were in really bad shape at that point.  With these machines it's ALWAYS better to err on the side of caution, especially with the number of folks here who are really great at preventing these from biting the dust, and in some cases bringing them back from the dead.

 

[techknight]

Well, considering I now have the apple official portable schematics in my hand, Judging by the design, I would say yea, recap those bastards. 

 

[uniserver]

well its about freaking time....  i would assume HAP helped this one along?

 

[techknight]

Nope, and its a hard copy. Came from an ex-engineer from back in the day who designed peripherals for these beasts. 

Hopefully from this, I can design replacement Hybrid ICs which are needed, because they are failing at an alarming rate. You know when they do because one day it works, then all of a sudden battery charging/levels go intermittent, and eventually it doesnt power on. 

Also if you remove 1 of the 2 wires going to the 4 pin battery plug, it removes the reference and blows up ICs including the SWIM. because the 5.2V regulator goes out of regulation.

The reason why this happens, is there is a single 1.2v voltage reference in the Hybrid, and it provides the reference signal for ALL of the voltage regulators across the board. And guess what: It is powered by the battery sense line which is the top left corner of that 4 pin plug. So if you remove that voltage, while leaving the voltage present on the top right corner (2 wires for voltage), it loses the reference voltage. The loss of this causes the 5.2V to spike to your battery or worse, your AC adapter input which is 7.5V. This then in turn blows all the ICs that are the most sensitive to it. 1st being the SWIM. 

Bad design. 

 

[uniserver]

wow what a great explanation...  i was wondering why those SWIMS were so crispy!

 

[Elfen]

Took it apart to remove the British invasion of dust bunnies and was even more surprised to find all the original caps are installed. Inspected them and see zero signs of leaks.

Now should I stick to the side of "Preventive Maintenance" and have the board recapped?

I had LC Mac that was Dust Bunny Invaded while in storage, but it tuned on fine. Or so it seemed. The Caps did leaked, but the Dust Bunnies soaked up the electrolyte before it went further on the board to do damage. Cleaned it up, replaced the caps, and it worked better than before the recap.

When I washed the board, it looked fine, but the damage was minimal. It was when I removed the caps did I see the traces begin to rot on the pads the caps were on. No doubt you will see the same thing when you recap the board. Doing this, you are not doing "preventative measures" but an actual repair.

So RECAP THAT BOARD NOW!!!