Building a replacement MTX PSU

[1024MAK]

More photos...







I'll put more up on Sunday

Mark

[Dave]

Interesting !

It looks like you're putting DC out?

regards
Dave

[1024MAK]

Outputs:
Two 7.5V AC feeds (for feeding to the diodes that in turn go to the +5V regulator and the -5V zener diode supply circuitry)
One +16V DC feed, for feeding to one of the diodes that in turn supplies the +12V regulator.

The +16V DC supply is generated by a LM2577 based step up DC to DC converter, which in turn is supplied by two diodes and a 2200uF 16V smoothing capacitor, which gets it's supply from the two 7.5V AC feeds.

Because I am using a 50VA transformer with a 230V primary, the two 7.5V AC outputs actually produce a bit more than the specification suggests when used at my house (where the "230V" mains supply is at, or close to 240V).

Schematic will be made available, along with a parts list when I get around to it

Also when I demonstrated it at Memofest 2014, Claus asked me about the performance when operating at 230V. So as I have a mains isolating transformer with various tappings, I will see if I can set it up to give 220V and 230V outputs, I can then test my MTX PSU using these voltages.

Code: Select all

My replacement MTX power supply unit
Test and set-up of LM2577 based step up DC to DC converter:-
LM2577 based step up DC to DC converter
Test input 8.01V at 19.7mA. Output (no load) 16.015V

Unit constructed, test load data:-
DIN  Wire      Output        No load
Pin. Colour    Name          Voltage
 1.  Yellow.   +16V DC       16.025V DC, 6mV ripple (meter)
 2.  Green.    7.5VH AC       8.93V AC
 3.  Red.      0V
 4.  Black.    0V
 5.  White.    7.5VL AC       8.92V AC

Internal DC supply (feeds LM2577 module):- 11.45V DC, 33mV ripple (no load).

Unit constructed, test load data:-
DIN  Wire      Output      Lamp          Current  Voltage  
Pin. Colour    Name                   
 1.  Yellow.   +16V DC     Two 24V 5W    360mA    15.785V DC, 28.2mV ripple (meter)
 2.  Green.    7.5VH AC    One 12V 21W   1.37A     8.15V AC
 3.  Red.      0V
 4.  Black.    0V
 5.  White.    7.5VL AC    One 12V 21W   1.38A     8.18V AC

Mark

[Crazyboss]

Mark

I think more people could be interested, cause people always miss the power unit.

As mentioned at the Memofest 2014, I am interested to buy one.

I am sure more people will be interested, so you can start a production line

Around what price can you produce one of those?

[1024MAK]

All in good time

Timing and cost is directly proportional to how much use I get of a TARDIS, should one be made available

The prototype has a mains switch which glows red when on and a green "output on" LED. For the "production version", I am open to suggestions as to the colour of this LED.

How many people are interested in buying one?
If you are a "maybe", but are going to remain undecided until the cost is known, please say so.

Also, for those people who would prefer to build their own, I will post up the details once I have drawn the schematic in a eye friendly form

Mark

[Dave]

mmm, what colour should the LED be . . .

Difficult question, maybe 1 led is too restrictive, maybe we should have 1 LED per output voltage?
Even better, 2 LEDs per output, that flash at a frequency proportional to the voltage

It could replace my Christmas tree lights then

OK - interested in buying, depending on price

(If you want me to draw the schematic for you, send me your "drawings" and I'll KiCad them)

regards
Dave

[1024MAK]

Construction Details

First, the DC board:

DC board 1.jpg (216.42 KiB) Viewed 17666 times

DC board 2.jpg (149.08 KiB) Viewed 17666 times

DC board underside.jpg (582.78 KiB) Viewed 17666 times

Diodes:
Two 1N4001 or 1N4002 or a higher voltage rating.
Capacitors:
The small blue capacitor is a 100nF ceramic multilayer type, 5mm spacing.
The large capacitor is a 2200uF 16V electrolytic.
Fuse:
PCB fuse clips, 5mm pins, suitable for a 20mm type fuse.
1A anti-surge (A/S) / time delay (T) 20mm x 5mm glass fuse

More tomorrow (sorry it's slow, I'm a bit time poor...)

Mark

[1024MAK]

DC board 3.jpg (157.87 KiB) Viewed 17661 times

Step up DC to DC converter:

Step up DC to DC converter.jpg (237.97 KiB) Viewed 17661 times

Inside:

Inside #01.jpg (227.42 KiB) Viewed 17661 times

[1024MAK]

Inside #02.jpg (202.07 KiB) Viewed 17661 times

Inside #03.jpg (155.21 KiB) Viewed 17661 times

Inside #04.jpg (198.62 KiB) Viewed 17661 times

[wyerd]

Looking good Mark! Will you be posting circuit diagrams and a parts list as I'd like to make a 110v version?