Just thinking. How many people have the bleeder ground setup in their power supply?

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Joined: Oct 9 2011
Posts: 1063

Was working on a vintage supply and was thinking if I should upgrade it to use a bleeder resistor to ground.

I usually do this modification when building Mimeo supplies but never did it on an original Apple-1 supply. Usually I just repair broken wires, cover exposed copper and make it safe to operate.

How many people here are using a 1meg Ohm resistor from the Apple-1 ground to earth ground?

Also opinion on an original supply should I just do what I normally do which is repair not improve the supply?

Thanks for your opinions,
Cheers,
Corey

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speedyG's picture
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Joined: Nov 16 2011
Posts: 2413
Re: Just thinking. How many people have the bleeder ground ...

Hello Corey986,

i believe that there are good arguments at both sides of the parties:

pro adding:
A lot of owners modified or changed parts ot the original board while using it in the 70´s
like adding interface use to connect printer or other hardware as improvements....
so if the adding of the resistor is performed same way it would have been done in
those days ( old soldering material, old resistor from that days ) it would not
disturb the entire "picture" of the system but add safty improvement like a lot of
users would have added it, if the topic would have been published in that days...

contra adding:
strict fanatics would demand to keep the system exactly in the state the board had left the
garage.... and any changes would affect value.....

I´d just focus the topic by two examples:

If a original owner used his system heavy in the mid 70´s there is a rather good chance
that he had faced some kind of need for a repair... is the system "original" after that
repair in the 70´s ? Is there a difference between the fact if the system has been repaired
by Apple itself or is the difference caused by the fact if the system has been repaired
by DIY or third party ?

Similar discussions are also ongoing in the art-market....
you surely remember my comments on the differences of interpretation between the terms:
repair or restoration ?

Or just another example ( getting up at future ):
a car that nowadays has been dragged back by factory callback due to secutity issue:
the company changes the dangerous part and the owner gets his car back again.
think 60 years ahead in the future and the car is maybe a item for collectors....
is the car only original with the dangerous security issue without the update performed
by the manufacturer or are the cars after participating the frawback action of the company
still original ? ( remember in that thoughts that such drawback issues are often not
performed by the company itself but only by third party repair stations authorized by the company....

and now just a third example back at the topic:
the original user gets trouble with the original mainboard in the beginning of the 80´s because a
socket get´s worn out ( like the socket used to connect the kayboard ) and the guy that
performs the repair uses a replacement for that socket.....
if he uses the same socket like used in the original in the mid 70´s ( original from TI from same series ) ?
if he uses a socket that has been manufactured in the 80´s ( in such case i´d value that this damages the
state of "original" )?

Just my 5 cent´s:

The use of bleeding resistors has been allready known in the mid 70´s - but it wasn´t very common.
Therefor it´s in general not common with original systems....
and therefor i´d only perform such change as "removable option":
that may be removed without change ( except adding 2 drops of old soldering material to fix 2 wires
that lead to such resistor or to a removable connector at the expansion connector without touching
the original mainboard )....

but i´d recommend to add the resisitor to the owner
to protect the system ( also because of protection
of the static sensitiv chips on the mainboard ! )....to keep the system in it´s original state.

sincerely
speedyG

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Joined: Oct 9 2011
Posts: 1063
Re: Just thinking. How many people have the bleeder ground ...

Well on closer examination. There is a way for me to hook a bleeder without modification. This system has a case where it has an extra outlet on the back, so I can screw a wire into the ground and have it go to the Apple-1 ground with a resistor inline. So no permanent mod, and I can do it using NOS parts and wire.

Still curious who is using a bleeder?

Cheers,
Corey

Sherlock's picture
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Joined: Dec 20 2014
Posts: 135
Re: Just thinking. How many people have the bleeder ground ...

I've been thinking about this modification, since I don't have it on mine, and it seems like it would be a good mod to do.

I've already built my PEM, and don't want any additional motherboard modifications. Looking at the schematics, the Apple 1 J1 block has pins 5 and 6 shorted together, and pin 5 is connected to the central output wire of the P-8667 transformer, and serves as the floating ground of the motherboard.

Therefore, like it sounds like you're talking about in your last post, Corey, I should be able to just branch off the 1 mega-ohm resistor from the central output wire from P8667, and just route that to the earth ground pin of my 3-prong power plug. This way, the motherboard is not changed, and the modification is internal to the PEM. Is that right?

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Joined: Oct 9 2011
Posts: 1063
Re: Just thinking. How many people have the bleeder ground ...

Actually all you need to do is take pin 6 on your power connector and hook up a 1 meg-ohm resistor to the ground on your AC plug. Don't bother hooking it up to the transformer directly.

Sherlock's picture
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Posts: 135
Re: Just thinking. How many people have the bleeder ground ...

Corey986 wrote:

Actually all you need to do is take pin 6 on your power connector and hook up a 1 meg-ohm resistor to the ground on your AC plug. Don't bother hooking it up to the transformer directly.

The reason I wanted the resistor to branch off closer to the transformer was that I didn't want anything visible on the Mimeo side of things. In my enclosure, my PEM is hidden behind a panel of wood, so I would prefer to tuck this back there.

Thanks!

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Posts: 1063
Re: Just thinking. How many people have the bleeder ground ...

Just run a 6th wire in your wiring bundle. I usually put the resistor inline and shrink wrap the whole thing.