Recapping PowerBook AC Adapter M5140X 7.5V 2A - caps?

[Byrd]

Hi all,

I have four M5140 PowerBook AC adapters (7.5V 2A) - all have failed and I'd like to try my luck recapping these.  Checking the voltage of these, they read 7 - 8V initially plugged in but the voltage continually drops down to nothing.  None are able to power on a PowerBook.

Cracking open the case (and don't forget the tiny little screw which holds down the PCB), it has:

47uF 400V

1200uF 16V

180uF 16V

82uF 16V

47uF 50V

... some of these are odd uF ratings and no longer manufactured and difficult to source (the 82uF, 180uF of note).  I know you can substitute slightly higher voltage capacitors, but not sure on altering the farad rating - any tips please?

Thanks

JB

 

[Elfen]

Using electrolytic (Canned) Caps and can't find the replacements? Hmmmm....

If they exist in a higher voltage, like 20V, it should be fine.

But if they do not and you must go with a different farad rating, I would go with ±10%. So the 180µf could be as low as 160µf and as high as 200µf. The 82µf can be as low as 75µf and as high as 90µf. I would try to make it minimal as possible - the next rated µf would be best. If you can find an 85µf you can use it instead of the 82µf and 185µf for the 180µf for the high end; If you can find an 80µf you can use it instead of the 82µf and 175µf for the 180µf for the low end.

 

[Byrd]

Using electrolytic (Canned) Caps and can't find the replacements?

The 180uf, 82uf caps are no longer in production - well, they are around in single quantities online "somewhere" in the world but I'm hoping to order all the caps in one swoop from a local store or element14.  Thanks for your advice, I do notice two trim pots inside so assume they are for voltage/amp adjustment.

JB

 

[techknight]

depends on what part of the circuit those 2 caps are in, you can sub them. 

180 for a 220uf, and 82 for a 100uf. 

 

[Byrd]

Thanks teckknight, that's really my only option short of buying the discontinued caps separately (at a high cost too)

 

[Byrd]

I set about recapping five PowerBook 1x0 7.5V/2A power bricks - using the correct value caps (sourced from three different places on eBay), three bricks were in good condition two were rough looking.  None could power on a PowerBook (in this case a PowerBook 170).

Some comments:

- Un-opened and un-repaired, when plugged in the voltage of three of the five bricks had ~ 10V initially which crept down to almost nothing.  Two of the five displayed erratic almost non-existant voltages.

- Once cracked open on a vice, all bricks displayed cap leakage (not bulging, but leaking from the bottom) - one in particular had significant damage on the circuit board (cap goo was everywhere and had rusted) and was thrown out.

- All caps were replaced, three of the remaining four checked out well @ 7.5V with slight pot adjustment.

- One blew up and smoked when plugged in - thrown out.

All in all, three working power bricks out of five isn't too bad but I'm dangerously low on these now - they're all I have left

JB

 

[tanaquil]

Nice, thanks for reporting on the project!

I see these power adapters on ebay pretty often though, for reasonably low prices, so I guess this is a good time to stock up. Especially if they are rated "working".

(I have been stalking ebay for the higher 3A power supplies - those are not too uncommon either. Incidentally, is it safe to plug a 3A power supply meant for a 180c or similar into a lower-level PB 1xx that normally uses the 2A version?)

 

[techknight]

For battery charging reasons, not really a good idea. However the 2A supplies can be tweaked close to 3A by adjusting the current setting on the riser card inside the power supply. 

Trouble is, you need an electronic load to reliably set that pot. Or a good resistor. 

You will need to calculate the resistor based on the voltage, and desired current (3 Amps) and adjust the pot until you get 7.5V at 3A across the load. 

 

[butterburger]

Doctor Gough Lui very recently documented his repair of two M5140 (M5140X APS-20A) Macintosh PowerBook AC Adapters, with illustration.

Repair: Apple Macintosh PowerBook 100 AC Adapter (M5140X)

 

[bibilit]

I have repaired a few of those lately, all of them are working great, including a Macintosh Portable one.

Exactly the same brand found inside LC PSU's (Elna...not so long life  ) 

 

[Bunsen]

is it safe to plug a 3A power supply meant for a 180c or similar into a lower-level PB 1xx that normally uses the 2A version?)

For battery charging reasons, not really a good idea.

Really?  I always thought the device would only draw as much current as it needed from the supply.

 

[techknight]

The device does. The battery on the other hand, does not! 

Batteries will draw whatever it needs to charge. Even if the battery is small, if you provide it 10 amps, it will try and draw 10 amps on charge even though thats not correct. 

So unless the charge circuitry is regulated (most early stuff is not), then you'll likely damage something. Unless your not using the battery and its not inserted in. 

For example, the macintosh portable has piss poor charging circuits, Actually, it really doesnt have any at all! just a pass transistor that gets turned on and a parallel resistor used for measuring current consumption so the PMU can roughly guesstimate the state of charge while charging. 

This is why the Portable's adapter is 1.5A, its the exact current needed to charge the battery at the correct rate whilst keeping the unit running. 

 

[EvieSigma]

I figured this would be a good place to ask...a M5652 AC adapter is safe for a non-color PB180, correct? Apple's website says it is but I wanted a second opinion.

 

[flashedbios2012]

Do any of the old powerbooks still have functional batteries or a source of new ones? I would have guessed that by now anybody using one of these was doing so solely on AC Power.

 

[Carboy7]

Yep. But the batteries in the Portable (lead-acid) have to work, because I believe the power supply packaged with the computer had to work with the batteries IIRC. Otherwise, the computer won't work. That's why people used the PB100 power supply to get it to work.

 

[techknight]

 That's why people used the PB100 power supply to get it to work.

And it wont last long doing it that way either. At first I didnt see an issue, but over the years, and especially studying the schematic, Its dangerous. 

 

[EvieSigma]

Do the 100 series AC adapters need recapping too? Kind of confused by the concept of recapping an AC adapter, my old Sega and Nintendo ones still work great...

 

[bibilit]

Do the 100 series AC adapters need recapping too

Yes, capacitors are getting old and will leak...sooner or later.

 

[EvieSigma]

Great, I still don't know how I'm going to get my PB180 recapped and now I gotta find cap lists for the 180 and the M5652 AC adapter.