TECH : "Remote" +5V adjustment

[arcadeoriginals]

[ukvac] TECH : "Remote" +5V adjustment
Good evening everybody,

I have a question :
The power supply from my jamma testrig has a little potentiometer to adjust
the +5V. I would like to place a new potentiometer on a more comfortable
place for easy adjustment of the voltages.

I removed the original potentiometer today and took it with me to the shop
to get a new one : one that doesn't need to be soldered on a board but can
be fixed with a bolt or something. The guy at the shop examined the original
but there was not much info on it. He sold me a new pot.

I have just installed it and I can only adjust the voltage from +5.0 to
+5.1. That is not enough, I need at least a voltage-range from 4.5 to 5.5 I
think.

I took a different power-supply (working 100%) and replaced the pot with my
new pot. On this one the voltage drops down to +3.5V ???

I guess it is not the correct potentiometer or I am doing something wrong ?
Can someone tell me what I need to ask for tomorrow when I go back to the
shop ?

Many thanks )

Regards,
Marco.

 

[John Bennett]

Re: [ukvac] TECH : "Remote" +5V adjustment
You may not be able to go higher than 5.1v as this may be the most this
power supply outputs

kind regards
Mark



DATA Imported from archives: originally posted by markgwilliams (markgwilliams@ntlworld.com)

 

[guddler]

RE: [ukvac] TECH : "Remote" +5V adjustment
Marco,

Why not take the original pot off the PSU and mount it on a small piece
of veroboard. Then use some wires to connect it back to the original
pins on the PSU.

Then using PCB spacers or whatever connect it whereever you like, and if
that happens to be in your test setup just drill a small hole, mount the
veroboard inside and you now have a setup very similar to the orinignal
in the PSU, but this time it's somewhere convenient on the front of the
test box...

Just a thought.

Guddler.

-------------------------------------
Martin White

http://www.guddler.com
Arcade search site with PCB info too...

>

 

[d-type]

RE: [ukvac] TECH : "Remote" +5V adjustment
You need to measure the resistance between the two ends of the pot (this
will be the highest resistance between any two of the three pins). This is
the resistance rating of the pot e.g 10kOhm.

The wiper (the middle bit that taps into the resistance) will ramp from one
end of the scale to the other as it's turned. Some pot's wipers will give
more of a range than others. Test the resistance that the wiper will give at
various points on your old one, and compare with the new one.

Small pcb mounted carbon pots will often go right to the ends of the scale.
You might also be losing voltage in the cable if they are thin and long.

Usually if a power supply is bang on 5.1 V then you should be OK for all
boards and never need to adjust, as TTL likes 5.1V. This is the standard
output of a DC voltage regulator usually to power TTL PCBs.

If you find you're always having to fiddle with the voltage at the PSU,
you're probably adjusting your way around a different problem, where the
volts are being lost to the PCB. This could be dodgy edge connector or
simply not powerful enough PSU and it's 'degrading gracefully' under load to
save itself.

I have NEVER needed to adjust a PSU from 5.1V on any of my PCBs.

Phil.

>

 

[arcadeoriginals]

Re: [ukvac] TECH : "Remote" +5V adjustment
Thanks for the explanation, I will check the resistance now, I did not know
that

> I have NEVER needed to adjust a PSU from 5.1V on any of my PCBs.

This pot is for my small testrig. Some of my early 80's games need a little
bit adjustment. Not much, but just a little bit to avoid some 'noise' on the
picture on the monitor. But I must admit that I usually don't measure the
voltage so maybe you are correct and 5.1V should work on all pcb's. So I
will set it to 5.1V and leave it that way for a while and see if everything
works fine.

Martin's idea about using the original pot on a piece of veroboard is also a
good idea and an easy way to solve my pot-problem. I will first check the
resistance now and then I will see what I will do.

Thanks everybody for the fast help )
Marco.

----- Oorspronkelijk bericht -----
Van: "Phillip Eaton" <inbox@phillipeaton.com>
Aan: <ukvac@yahoogroups.com>
Verzonden: vrijdag 28 december 2001 21:48
Onderwerp: RE: [ukvac] TECH : "Remote" +5V adjustment

> You need to measure the resistance between the two ends of the pot (this
> will be the highest resistance between any two of the three pins). This is
> the resistance rating of the pot e.g 10kOhm.
>
> The wiper (the middle bit that taps into the resistance) will ramp from
one
> end of the scale to the other as it's turned. Some pot's wipers will give
> more of a range than others. Test the resistance that the wiper will give
at
> various points on your old one, and compare with the new one.
>
> Small pcb mounted carbon pots will often go right to the ends of the
scale.
> You might also be losing voltage in the cable if they are thin and long.
>
> Usually if a power supply is bang on 5.1 V then you should be OK for all
> boards and never need to adjust, as TTL likes 5.1V. This is the standard
> output of a DC voltage regulator usually to power TTL PCBs.
>
> If you find you're always having to fiddle with the voltage at the PSU,
> you're probably adjusting your way around a different problem, where the
> volts are being lost to the PCB. This could be dodgy edge connector or
> simply not powerful enough PSU and it's 'degrading gracefully' under load
to
> save itself.
>
> I have NEVER needed to adjust a PSU from 5.1V on any of my PCBs.
>
> Phil.
>
> >