Building a replacement MTX PSU

About original Memotech hardware.
wyerd
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Location: Upstate New York. USA.

Re: Building a replacement MTX PSU

Post by wyerd » 01 Jul 2015 23:17

Yep, that's what I thought but it's best to check. Thanks.

It doesn't matter what side of the fuse holder I use does it?

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1024MAK
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Re: Building a replacement MTX PSU

Post by 1024MAK » 01 Jul 2015 23:43

Actually, comparing the schematic and the pictures I have posted, there is an inconsistency :oops:. So can you hang fire please.

I'm at work right now. When I finish and get home I want to double check.

Mark

wyerd
Posts: 88
Joined: 13 May 2013 23:16
Location: Upstate New York. USA.

Re: Building a replacement MTX PSU

Post by wyerd » 01 Jul 2015 23:50

Sure - no problem.

You're working late. :o

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1024MAK
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Re: Building a replacement MTX PSU

Post by 1024MAK » 02 Jul 2015 00:06

The company where I work requires 24 hour cover, so I have to do nights every cycle.

Mark

wyerd
Posts: 88
Joined: 13 May 2013 23:16
Location: Upstate New York. USA.

Re: Building a replacement MTX PSU

Post by wyerd » 02 Jul 2015 14:23

1024MAK wrote:Actually, comparing the schematic and the pictures I have posted, there is an inconsistency :oops:. So can you hang fire please.

I'm at work right now. When I finish and get home I want to double check.

Mark
Mark,
Have you had a chance to check?

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1024MAK
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Re: Building a replacement MTX PSU

Post by 1024MAK » 02 Jul 2015 16:08

Hi, panic over :mrgreen:

Last night, I was going to put a link up to a picture that I posted earlier in the thread. But when I looked at it on a iPad I could only see three wires :shock: , and this does not tie in with the schematic that I posted :(

However, after physically checking the wiring of the prototype PSU, I can confirm that the schematic is correct, it is just that the photo is very misleading :oops:.
This photo:
Image
The terminal on the top of the fuse-holder (as viewed in the photo) actually has three black wires and one red wire connected to it. As you can see from the photo, at first glance, it looks like only two black wires. If you look a little closer, the red wire is hiding behind one of the black wires...

So one black wire and one red wire go to the DIN plug, one black wire is going to the resistor (for the LED). The remaining black wire goes to the strip-board.

The terminal on the bottom of the fuse-holder, is the high current wire from the transformer secondary windings.

And as I was about to say last night, for fuse-holders used in low voltage circuits, it does not matter which way round you connect the wires.

If it is easier for you, the black wire going to the resistor (for the LED) can be connected to the 0V track on the strip board instead, leaving just three wires to connect to the "output" fuse-holder terminal. Once you have stripped the ends of the insulation off, gently twist all the four(three) wires together. These are low current (thin) wires and the fuse-holder is rated at 6.3A (or 10A) so it should not be a problem getting the wires through the terminal hole and nicely connected.

Mark

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1024MAK
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Re: Building a replacement MTX PSU

Post by 1024MAK » 02 Jul 2015 16:21

Here is a image adjusted (I've slightly boosted the red in the image) close-up:
5A fuseholder2.JPG
5A fuseholder2.JPG (183.03 KiB) Viewed 2256 times
Mind, on my iPad, the red wire still looks black :?

Mark
Last edited by 1024MAK on 02 Jul 2015 19:27, edited 1 time in total.

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1024MAK
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Re: Building a replacement MTX PSU

Post by 1024MAK » 02 Jul 2015 17:08

I have updated the schematic (see this post).

Mark

wyerd
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Joined: 13 May 2013 23:16
Location: Upstate New York. USA.

Re: Building a replacement MTX PSU

Post by wyerd » 02 Jul 2015 20:48

Great - thanks for the info.

Getting there!

Image

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1024MAK
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Re: Building a replacement MTX PSU

Post by 1024MAK » 02 Jul 2015 20:52

Coming along nicely 8-) :D

Mark

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