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HELP: Hooking up two voltage regulators on a board

Hopefully this does not turn into a fiasco: Anyhow I have a Pyle mobile 6" color LCD monitor (I believe it is a PLVSHR6- NO labeling on it though). I removed two TA7805S regulators quite some time ago. Now that I am ready to put them back in after finding replacements I can not for the life of me remember in what combination they are mounted on the board. They are mounted parallel to one another on the board. There are six holes in the board. for illustration:

1 2 3 4 5 6

hole 1 & 4 are connected with copper traces as are 2 to 5 and 3 to 6. Obviously no matter how the regulators are mounted 2 will always be connected to 5 (grounds). So what I am asking is it 99% (or if you can tell me 100%) that 1 & 4 are both ins on each of the regulators making 3 & 6 outs OR should outs be hooked to ins? Holes 1 &4 lead to the positive side of a

470uf cap, 2 & 5 lead to +side of a 4001 diode, and 3 & 6 lead to the +side of a 100uf cap. Basically I guess I am asking should these be hooked like to like or opposite one another? I am sure I will be bombarded with "This is not enough information"; but I have to try something being nobody seems to be able to come up with a schematic diagram for ANY Pyle products. Thanks in advance for ANY positive help anyone can offer.
Reply to
Barry & Nikki
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You can be 99.9% sure that they are connected in plain simple old parallel. It's not generally considered very good practice to up the current rating by doing this, as you can't guarantee that both will have exactly the same output voltage, and will thus share the load exactly equally without fighting one another. However, it would not be the first time I have seen it done. I recently had a home cinema system in for repair, which I think was a JVC if memory serves. This, to my amazement, used exactly the scheme you are describing. One of the paralleled-up regulators was faulty. I replaced them both with a pair from the same batch, in an effort to get them as closely matched as possible, but still one ran hotter than the other, and I think that this is probably an inevitable consequence of doing this, and may be the reason for the early demise of one or other device. I notice you say that there is a 1N4001 in the ground legs - presumably when you say " positive side " you are referring to the anode, so it is the cathode that actually goes to ground ? This is a way of jacking up the ground leg(s) by approximately 0.6v which has the effect of upping the output volts to 5.6, without compromising the regulation.

There is no valid reason that I can think of to connect two regulators back to back. You would always be hooking input volts to an output on one of them, and vice versa. Perhaps you are confusing yourself with having seen a

5v reg following on from a 12v. In this scheme, the OUT of the 12v is connected to the IN of the 5v, and both ground pins are connected together. However, in this case, the IN of the 12v is not connected to the OUT of the 5v.

Just as an afterthought, is there absolutely no marking on the board at all to indicate which way round they go ? It can sometimes be quite subtle - just a slight thickening of one line on a box to indicate a tab-side, for instance.

Arfa

Reply to
Arfa Daily

On Sun, 16 Jul 2006 19:27:50 -0700, "Barry & Nikki" put finger to keyboard and composed:

Leave them out and switch the unit on. The pin with power is the input. Having said that, I can't understand how two 7805 regulators can work in parallel. At the very least, I would think that one would carry the brunt of the load.

- Franc Zabkar

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Please remove one 'i' from my address when replying by email.
Reply to
Franc Zabkar

I'd have thought the same as you - but a couple of years ago I built an Elextor circuit for our local Church (sort of a CD Jukebox for when the human organist can't make it) - and that used a pair of 5v 1A regulators and a pair of 12v 1A regulators - each pair of regulators connected in parallel.

I'd never seen it done before - but it's still working fine !

Regards Adrian Suffolk UK

Reply to
Adrian

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