Just converting this Stripboard that was posted a few days ago… My mind is melting. Does it look correct? I think it looks odd in my minds … But I think my tired brain is just not functioing.
I think If I flip the bottom section so the two grounds for the 7x12’s are on one line it will look better an make more sense
Here for comparison is the MFOS wall wart supply
On the stripboard the diodes seem connected differently than your schematic. D3 is from pin 1 to pin 3 on the L7812 for instance.
Once the diodes are corrected, at a glance I think it’s basically the same as the MFOS circuit. The latter has load resistors added:
The load resistors were added as a convenience for testing without a load and are not necessary. The negative regulator needs a slight load to begin regulating which is normally provided by the circuit being powered. These resistors provide a small load so the output voltage can be observed prior to connecting the supply to your circuit.
The diodes are very wrong. You want one backwards protection diode across the regulator, and one from output to ground.
Interesting. I kind of wish I had given this a stab instead of the FC design - but I already ordered so I am kind of committed. Still, I’ll be watching to see if this works!
Yeah, i can see that now, my brain was not working when I started and now it’s waving a little white flag for the evening. LOL.
I had assumed the resistors provided a little load but did not know why.
They are all essentially the same I guess, with just a different bit of spin.
Cheers
Rob
Yeah, I have 3 FC’s but I want to have my own. Sick of wall warts so there will be an encapsulated transformer on the PCB.
I looked at it like 50 times, I think Dyslexia sometimes just means you miss the blindingly obvious.
Thanks.
What do the two diodes actually do for it? Never used them in any standard DC 780x Circuit.
Cheers
Rob
I guess adding an LED+Protection resistor is the ideal way to add a test load 
If you’re getting a transformer, a 2x12 (or 2x15) costs no more than a 1x for the same VA and that let’s you use a full bridge rectifier and avoid the half wave wall wart stuff.
10,000uf of bulk filtering capacitors will reduce the “conduction angle” of the diodes CR1 and CR2 causing a very high short current through them and it may cause the diodes to fail. For a wall wart, that’s probably OK because there is a lot of wire between the transformer output and the diodes. The wall wart may put out a lower AC voltage too and the added capacitance may help. For a mains transformer, it may be too much capacitance even at light loads. One 3300uf cap is enough for up to 1.5A of output current through a regulator. Also, add some 100nf caps close the input and output of U1 and U2.
The FC Power uses 3x4700µF. Like the MFOS supply it has no 100nF caps. For whatever that’s worth.
The MFOS transformer supply does have 100nF caps on the regulators. It has 20000µF on each side.
Oh, that is super stressful on the diodes. Unless the transformer is crappy, then it will not matter so much. Here is why it can be bad to have too much capacitance in the bulk filter.
The 100nf caps have a much higher self resonant frequency than the 1uf parts and they are better at filtering out higher frequency noise. Sometimes even small caps are added in parallel to remove RF which is more of a problem now that we all have cell phones, routers, and BT.
Yep based on that, ordered a 2x12 and will be redesigning from scratch… the Transformer is available as both 240 and 115V so the PCB would work for most situations.
I see on eBay that FC are selling built PSUs ( without a wart) for £60 , I think this design even with the Transformer will tally about ~£10-£12
Not going to bother with a +5V as I think the general agreement is taht for a few pence/cents/etc it may as well be done on the module.
Working nicely, needs some form of case.
Although a footprint I revised seems to have got overwritten when doing a schematic update… The mounting holes should have been bigger, but the tips just fitted enough to get a good joint.
Will share the files later
Probably works out about £16-£17 all done ( excluding hardware )… Which compared to a FC and an elusive Wall Wart works out far cheaper.
I had this power block kicking around, no idea what it was from but it was a decent 12v AC output… I originaly thought it could be used with a Frequencey Central PSU…
But it did not work and it’s fuse was blow.
After replacing the fuse it went bang! Not sure what this was but it’s not how happy.
So the innards were stripped to provide a home for my power supply buld.
I omitted mounting holes unfortunately, so Mr hot glue has to do.
I have a mains rocker switch on order.
Not 100% sure what I am going to do with the output. Aviation style gx connector seems OK but I need panel mounted female…
Should have enough power for now 
Rob
The blown part looks to me like a capacitor which I’ve seen combined with a resistor in a casing like this. They form a filter, probably used to prevent signals from the circuit to go into the power net. Though they have a purpose they are not essential for the functioning of the power supply. Chances are, that the rest of the circuit is still usable.
Yeah, the cap looks like an old X2 filter cap (iirc PME is RIFA and known to blow up after 30-50 years). But isn’t there a suspicious amount of diodes and regulators (?) in there for an AC supply?
EDIT: Googled a bit, and 1) Durst describes this enlarger supply as a “stabilised mains supply system” so I guess DC (in contrast to the cheaper “simple transformer”), 2) PME is indeed RIFA, and 3) plenty of hits from other EST305N owners who’ve had that cap blow up. As Jos say, you can replace it with a modern X2, or drop the PCB and just reuse the transformer.
