the nephew of PS porn

I finally got around to reworking the single-voltage supply to better fit the case. It also has provisions for the board-mounted Talema, but could also be used with the bare toroid. It is more or less the positive half of a modified PS1, with a couple other adjustments, reworked into a "U" shape. It was fun messing around with the layout... I have no experience with Eagle or Express, so the board is basically chop and move photochopping.


The cord is tabbed on below for now, but will go in the blocks after a DPDT switch is wired into the adjacent pads. 6"x3"


Apologies for the worn-out thread title .

edited to change image hosting

Thanks David. It's funny... while I'm doing something like this I keep wanting to finsih so I can try it out. Then as soon as it's done, I wish I was still working on it.
The FR4 is from Mouser... very translucent. I'm used to the greenish stuff I get from Digikey.

The box is a film capacitor before the bridge.
As for it's suitability for a PPA- that's what my plans are. It is capable of 300mA, which is fine. The tranny in there now is a 15/15 that I had on hand with the same footprint, just to check things out. I am getting the 22/22v model which will allow 30.5 to 33.5 before the reg. The secondaries are in parallel. Right now I am maxed out at 23v, so I trimmed the output down to 20V. I was surprised to see that the regulator handled this with that small amount of overhead. I had to turn the variac down to about 102 volts before it dropped out.

I plan to run the PSU at 23-24 volts when the proper transformer is in. It could allow up to about 26-27 volts, but the caps on my amp won't like it much.

Heh... they don't go on sale. It's a one-off. I do have some plans to post a few pics of my etching tank.

This is the first board out... I usually make them in a 5x7 darkroom tray. What a difference. The tray method works, but is excrutiatingly boring during the etching phase, and it's a bit difficult to agitate enough without sloshing. Maybe use a small plastic pail instead of a tray!

Anyway, the tank- I was having a hard time finding a narrow plastic juice pitcher to use, seems most are boxier in cross-section around here. Yesterday I saw a vase at Target for $8. It is sort of oval in cross-section, but quite flat/thin. About 9" tall, it takes 1 quart to make the solution 4" deep, and will easily take another pint if needed for a larger board Most of the jugs I looked at were much bigger. I stuck the airstone in, added the small aquarium heater (jacked up to about 120F), and after drilling a small hole in the edge of the copper for a lifting wire (steel, not copper ), I dunked the board and turned on the air. Six minutes to finish, and I did not even inspect it until four minutes. Very nice not to be there for 20-25 minutes rocking a tray, and the etch seems to leave a cleaner line at the resist, probably due to the quicker immersion time. But then again the temp is higher, so I really don't know if that's it. Slick. I dumped the etch into a tight container for later use, and ran some clean water through the vase/aerator.

All Electronics has a fairly decent setup for about $40, but that seems a bit high for very occcasional use, and I already had the heater and air pump. So I bought the airstone bar for $3, and the vase for $8. Done.

The 70035 is the one that fits. The next one up is a larger footprint. You stil can do 300+ mA, so it's fine for this amp. It draws under 200mA in just about any config, often far less.

If you just wanted more headroom, or have other devious plans in mind, you can use the bolt-mounted toroids, which allows the equivalent of the 70045 or even 70055 to be used, and There is a pad for each lead, to keep things neat. There is also enough room to just copy the tranny pad and make it larger to fit the bigger potted tranny.

I can send you the jpeg (300dpi) after I make a tweak to the output block mounts, and one cap mount that is a bit off-size. Oh, and I'll get together the parts numbers.

Yes ppl, that's it. I do have several of the linear tech regulators on hand as well. I don't see a very large benefit in this application though, typically. The differences are so minor that I tend to use the LT1085(if I recall correctly) on request.

On a PS with much simpler design, such as the Stokes-type design, I do see some tangible (or more tangible, at least) benefit from using the Linear Tech regulator. Interestingly, Sheldon used the 317, though.

I think I have some of your posted tweaks somewhere on my hard drive... so far, the values in this PS are the same as Welborne, with exception of the R on the output leg being 499 ohm, and the R on the adjustment pin is now a 10k trimmer. I typically use 909 ohm and 20k respectively, but altered this to better suit what I had on hand.

Another possibly interesting point to note is that in the LM datasheet, the resistor on the output pin is stated to typically be 220 ohm, regardless of desired output. The LT design notes spec a much higher R value here. Sometime I'd like to fit a small PS with trimmers for both locations and do some extensive measuring to see what effects this places on the output. So far the improvement supposededly offered by the LT reg seem negligible in this layout. I believe that it is Borbely's, actually, but not sure. I also have a 1uf X2 snubber across the toroid before the bridge. Which is the Illinois capacitor that Arzela was asking about.

I have not tested this against one half of a straightforward PS1 yet, but the listening tests are very nice thus far. The electrolytics in the PSU are all Muse KZ series. On the PPA I have Cerafines.

One thing I want to say about this PSU is that I am not stating it is the end-all powersupply by any stretch. It is basically a somewhat hopped-up conventional schematic, as many of them are. What it is, to me, is a very nicely suitable PS that is fairly simple to build, and offers very good performance. I also have Didden-Jung super regulator four-output PS under way... stifled by parts availability. Almost there now, though.

edit: I also plan on doing the cap multiplier at some point. Not only am I curious, I like to build things. Worries me a bit.

D3 I do not recall at the moment, R5 does help keep the reg warm, but also helps to bleed the caps down when you power off.

It's fun to do (okay I guess I might be a dweeb), and if you plan to make more than just one board for one project, the heated and aerated tank is the way to go. Even if you bought the heater and airpump, it's about another 20-25 dollars, so still very competitive to the kit.