JLM ACDC Power Supply

I feel I made a BIG mistake :sad:

I bought 3 JLM ACDC PCB's & thought I could easily find the parts & maybe even save a few bucks... I was wrong. For one, the parts aren't as cheap as I thought so I saved nothing & waisted way too much time especially with the large caps.

13mm is all the room available for the Large electro's = 1000uf @ 50v. I searched the Digikey & Mouser catalog & for one, couldn't find too many "Low ESR" & all the 50v caps were 16mm... way too big

When they say "low impedence, is it the same as low ESR???

1000uf seems a bit small for PS filtering so I really don't want to go lower. I could go with 35v but wouldn't that be too low???
... Phantom is 48v & my rails are +/- 24v.

I found all the parts but these caps... if anyone can help me, that would be cool. I'm using the supplies for mic pre's if that makes a difference choosing parts.

Next time I won't be such an ass & I'll buy the FULL kit. I'm holding up 2 orders because of these caps...grrrrrrrrrrrrrrrrrrrrr... me stupid.

Thanks,
Kevin

EDIT: Didn't mean to offend anyone. Sorry!

Peace,
Al.

[quote author="alk509"]
I will say, though, that if you can't figure this stuff out by yourself, you probably shouldn't be taking orders. And I mean that in the nicest way possible.

So what are you doing? racking stuff and selling it?

Peace,
Al.[/quote]

I think he meant that not finding them was holding up a digikey/mouser order, but I could be wrong.

matt

EDIT: :thumb:

Peace,
Al.

I think you understand what your looking at & the specs MUCH better than me.

LOW ESR is what was recommended by JLM -
Most of the specs sheets say LOW Impedence, NOT LOW ESR... Is this the same thing?

Seriously, I don't want you guys to order for me I just need some advise.

I really don't know how to ask a question around here...

BTW, who said I was selling this stuff... I'm making 1 or 2 for a friend :?

[quote author="khstudio"]I really don't know how to ask a question around here...[/quote]

Actually, I think I'm the one who can't answer your questions in a way that you won't be offended by... I really was trying to give you some advice, not put you down or anything. So I apologize.

Peace,
Al.

I think I may have a plan:

The problem is the caps I want to use/buy are 16mm... too big so,

What if I drop the value for the phantom to 470 or 680uf (keeping the voltage @ 50v) & drop the voltage of the 24v rail caps to 35v & keep them @ 1000uf.
There are 13mm available for those.

I didn't think about it til now
Does anyone see a problem with this idea or have any recommendations of brand/model. I don't want to spend more than I have to if it's not needed.

Kevin

One more dumb question:
I would think that PS filtering for a mic pre is important - are there any rules? Like, how low is too low or what is considered optimal?

I think most modern caps are low esr at this point

maybe email Joe and see what caps he chose - I am sure there is a source in the US

I am glad I ordered the PCB with the parts after reading this!

Are you sure about the ESR?

BTW, there are caps available but the (50v 1000uf) are 16mm.

There seems to be 3 ways around it:
#1 Order from them
#2 lower the value & keep voltage
#3 lower voltage & keep value

The more I'm thinking about it, doing a little of both seems to be the way to go.

I like the JLM boards but they don't leave you with too many options with regards to those caps (sizes) except to reduce... I'd rather go up.:green:

Kevin

FWIW : i experienced the same problem with the caps and went for 680µF/50V Nichicon PW's from Digikey.

PSU works fine with 2 channels of dual JLM99V's

:wink:
Mike

1000uf seems a bit small for PS filtering so I really don't want to go lower

Click to expand...

The AC/DC runs 2 x 1000uF caps in parallel per +/-rail so there is 2000uF. The PowerStation run 3 x 1000uF caps in parallel per +/-rail so there is 3000uF. Even dropping the value of the cap to 470uF would still be enough for the LM317 and LM337 to regulate perfectly.

I could go with 35v but wouldn't that be too low???

Click to expand...

35V caps are all that is normally needed. The 2 x 22vac to 24vac transformers will give you about 34v unreg under load which is perfect. The 48v rail has 2 caps in series doubling the cap voltage allowing for 70v unreg going to the 48v reg. The 2 pump charge caps for the 48v rail also only have 35v across them at any time. So all caps can be 1000uF 35v with most 22vac to 24vac transformers if you don't go to over kill on the VA size. To be sure measure the unloaded AC volts of the transformer secondary winding. Apply this maths VAC x 1.414 + regulation % - 1.4v = Voltages unreg. This will tell you what voltage caps you need for all caps on the AC/DC or PowerStation PCB.

Also note on the NEW AC/DC ver2 PCB's the voltage pump has to be strapped to Doubler or Tripler. For +/-24v supplies it is set to doubler by strapping the centre pad to the pad marked D. For +/-15 to 18v rails using 15vac to 18vac transformers set to Tripler by strapping the centre pad to the pad marked T. This allows 48v to be generated to suit from a wide range of power transformer voltages.

Most of the specs sheets say LOW Impedance, NOT LOW ESR... Is this the same thing?

Click to expand...

Basically you could use any type of electro caps and it will work just fine. But I just use caps that are good quality 105 degree & Low ESR & high volts & more Farads than needed so in 20 years time when the caps are not feeling so new the power supply will still be working perfectly.

Wow, that was great.
Thanks Joe :thumb:

I'm running 24v rails & I would have missed the strapping...

I must admit, I forgot all about arranging caps to double the voltage/value... Some of the guitar amps I built did the same damn thing in the power supply.

Your cap voltage calculation will come in handy.

Kevin