Help needed with Apollo 1240 missing capacitor.

Amigafanboi

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This capacitor is missing on an apollo 1240@40 i picked up.

What value tantalum cap can i replace it with and be gentle...i have little or no electronics knowledge.
 

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rkauer

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This little capacitor is a 47uF x 16V unit. You can replace it with an ordinary though-hole counterpart. It is used to filter the power line.

So by any chance replace it with a tantalum unit! This kind of capacitor is not advisable for filtering power supplies.

The very low ESR of the tantalum units may cause a flash effect, ruining the accelerator.

More here.

Wikipedia said:
Higher cost than aluminum electrolytic capacitors. Voltage limited to about 50 volts. Explodes quite violently when voltage rating, current rating, or slew rates are exceeded, or when a polarized version is subjected to reverse voltage.

Slew rate refers to how quickly a capacitor has to go from charged to discharged state, or vice versa.

It's a fairly dangerous game, to replace them without knowing the hardware intimately, as you may unwillingly set yourself up for future fireworks and I would ask the question, if you're still going to replace the through hole ones with more through hole ones, then you will still have to change them the next time too.

I can't easily get the proper SMD types of tantalums, what I was going to suggest was to cut the legs short and bend them to form a U shape the size of the pad. Only thing with that is, if you accidently strike the capacitor, with an expansion board for instance, then you run the risk of ripping the SMD pads off the board.
 

stachu100

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@rkauer,

Sorry to say, but some inormations in Wikipedia are not correct!
Don't trust Wikipedia too much.

Look on phase5 Blizzard PPC (or any phase5 turbo) and tell me what kind of capacitors were used.
Open ANY good professional equipment (servers, high-end working stations, LAN routers, industrial controllers) produced by IBM, Sun, Apple, Cisco, Sony, ... a and tell me what capacitors are used.

Do you think all these companies (and engineers working in R&D) don't know what they are doing?

Of course tantalum capacitor is not perfect, but much better than aluminum ones.
 

Zetr0

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@Amigafanboi

hello there, where did you get this adapter?

If you have replaced the SMD with the correctly rated through-hole component then being the only problem it should work.

I am however assuming you have the polarity correctly orientated and that the capacitor used is a new unit.

At this point I would suggest two things

1. Remove the battery - its old and if it hasn't leaked already it will VERY soon.
2. Clean the contacts of the board - including the Oscilator socket.
3. Remember the correct orientation of the 80mhz crystal.
4. reseat the socketed Mach Chip - be VERY carefull

5. reassemble and post here the results.

good luck =)


@stan

I believe rkauer ment his caution in using Tantalum components in circuits not originally designed for them.

As Tantalum caps have such tight opperating tollerances they do no lend themselfs well in circits based on aluminium capacitor - truth be said that we must know the hardware intimately before replacing non-like componenets on all things - but this is more so when substituting aluminium caps with tantalum caps
 
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