Microsynth Power!

[woolley]

hello all
does anybody know the mA draw of the microsynth? would a 150mA transformer be ok? i'm building bill bergman's ms, but i have no power as yet.  SWT out there?

must... have... power....  :twisted:  (sorry)

thanks

[ian87]

sorry, don't have the answer, but Andreas (stinkfoot) should be able to help... http://members01.chello.se/pastorn/fx/mods/power/draw.htm

good luck,
ian

[Peter Snowberg]

Wow! What a great site! Thanks for posting it.

-Peter

[ian87]

Wow! What a great site! Thanks for posting it.

-Peter

my pleasure, peter. andreas is a great guy as well.

-ian

[Peter Snowberg]

The power draw page is only the start there.... He has a home link at the bottom, but for anybody that missed it (like me) here is a link to his home page:

http://members01.chello.se/pastorn/

[woolley]

i checked that page before i posted, and i didn't see the microsynth anywhere. now i've checked it again, and still don't see it. did i miss it?

for anyone in the know, it needs a 24vac transformer. might 150ma be enough? or should i just ask EH?

[Peter Snowberg]

I didn't see it either, I just like what I did see, sorry.... back to your question....

I'm going to guess that 24V @ 150mA would be just fine. I wouldn't go too much lower than that without knowing. The only way to tell for sure is to hook up a meter and see. You could always test with that 150mA unit, but set your test up and THEN power up. If you see more than 150mA being drawn, power down and get a larger transformer. If it pulls less than 150, start playing some open chords with everything maxed out to try to find the maximum it will pull.

It's still not an answer, but I hope that helps.

Take care,
-Peter

[woolley]

it does help. i'll give it a shot. thanks.

[Mike Burgundy]

Wow. Did anyone do an actual PCB for that one?
I'd love to have a Bass Micro, but d*mn that's a big build...
Links anyone? I couldn't find anything ;(

[ian87]

hey woolley -- the new (reissue) Micro Synths take a wall wart, and the wall warts are 24v 100mA. not positive that you can infer that a vintage one would be the same, but odds are it is.

-ian

[swt]

Hey! Sorry for the delay. Don't know what happened to my previous reply yesterday. :? . I have a different power supply for the micro, and also use a power supply for all my pedals, with the different voltages i need. So i don't know right now, but i can get the info if you want, it's just a simple measure ( is that the word?). Let me know, if if you're still interested.

[woolley]

thanks to peter, ian87 and swt.
from what peter and ian have told me, i'd say the 150ma should be the go, and thanks swt for offering. if it doesn't work, i'll be in contact.

mike: i did a pcb for the microsynth, aswell as bill (&FP), but before i had a chance to test mine, i found bill's, and since his was proven, i ditched mine (not real confident in my own abilities). and incase you were wondering, the only diff between guitar and bass microsynth is the cutoff in the initial lowpass stage. so i guess you could build it on bill's board.
shoot bill an email, and he may be able to help you out. + search this forum for microsynth.

thanks everyone.

[woolley]

hmm, actually while i'm here, i guess it'd be good to find out how to wire up the transformer. i'm in Australia so it's a 240-24 job.

i have the 3 pronged cable, with blue, brown and earth.
i have the xformer with blue, brown on the 240v side and yellow (12v), white (0v), yellow (12v) on the 24v side.

my questions:
1) where do i connect the earth of the cable? to the enclosure?
2) do i join the yellow wires at the +24v input of the board?
3) what do i do with the white wire? the other power input on the board?
4) does the proximity of the xformer matter with regards to bypass switches, pots, jacks etc?

and i have a grommet to protect from cutting the cable.

i'm so close to having this done, so just a little more help please?

[Peter Snowberg]

i have the 3 pronged cable, with blue, brown and earth.
i have the xformer with blue, brown on the 240v side and yellow (12v), white (0v), yellow (12v) on the 24v side.

my questions:
1) where do i connect the earth of the cable? to the enclosure?
2) do i join the yellow wires at the +24v input of the board?
3) what do i do with the white wire? the other power input on the board?
4) does the proximity of the xformer matter with regards to bypass switches, pots, jacks etc?

1) Yes

2) NO! Each of those yellows is a power lead so connect one to each power input.

3) Either cut the white off, or solder it to a place where it will never touch anything. I like to double them over and put some heat-shrink tubing around them to insulate them; that way I can reuse the transformer later on if needed.

4) Yes it does unfortunately. You want to place it as far away as you can from the lowest level signals in your project. Usually that means away from everything since pedals work on such tiny signals. Keep it furthest from the input signals and any signal wiring. It's best to hook everything up and then try different placements to see where you get the least hum. Also try turning the transformer on it's side. The hum comes out in a flux pattern dictated by the transformer construction. In really critical and tight situations you can only get by using a torriodal transformer because they have a tiny fraction of the magnetic leakage of the regular IE or EI design.

Take care,
-Peter

[woolley]

so, 12v into each side of the bridge rectifier = 24v for the supply?

and there is no way to shield the xformer or anything? the box is the size of those black russian RI EH pedals (~12cmx17cm (mmm, metric)) so there isn't a great deal of free space with 2 jacks, 12 pots, 4 pcbs and a bypass switch! if i'm lucky could i get it working hum free (asuming humming is what will happen) with a bit of rotation, or can i only minimise the noise?

thanks

[Peter Snowberg]

Think of the transformer more as a 24 volt transformer with the option to take 1/2 voltage from it. Another way to say the 12-0-12 is 0-12-24. The bridge rectifier gets a full 24 across it and there is no reference to the center tap.

You might be able to use some thick sheet-metal for a magnetic shield, but if you have hum, think about mounting the transformer in a different box, away from your effects. Sorry, that's AC for you.

Take care,
-Peter

[woolley]

thanks for you help. all i have to do now, is link the boards, pots and power. fun with fiendish filtered fuzzy octaves awaits  :twisted:
cheers

[woolley]

OK, all hooked up. but, when i engage the effect, there is no effect, just dry signal with a healthy coat of buzz (from the xformer?). it doesn't buzz when bypassed. after being engaged for about 15 seconds, the LED starts flickering or fades out. so i switch it off for fear of mass explosions  :twisted: .

initially i had the bridge round the wrong way  :oops: , so i fixed that and the above is where i'm at. could something be damaged?

you might have guessed, i'm looking for some more help  :cry:

[Peter Snowberg]

I think every person who has built something has done that very same thing.

Can you point me towards he schematic you followed?

I would guess that at least one semiconductor gave it's life in that incident.  :cry:

When I'm prototyping anything I like to install a reverse schottky diode and a fuse so that sort of thing only kills the diode and/or fuse. Hopefully the damage was limited. Often you can tell what died by feeling the chips until one gives you a burn, or after it's been powered up for a while, if a chip is dead cold while the others have warmed a little.

Don't despair too badly.... it happens to all of us.

-Peter

[swt]

For all of you guys trying to build a micro remember to ask bill or me about the corrections to the schem that is around.