Hey folks!
Riding the diptrace/smd wave and having done it on vero before, I'd like to do a Fairfield Barbershop in smd. It's this thing here:
(http://2.bp.blogspot.com/-XcQxu0SQ_a4/T_YMCWIW7BI/AAAAAAAABqw/2q3KFrUyFa4/s1600/Fair2.png)
My question is basically can I just replace the entire voltage protection mosfet bit (Q4, D1, R10, R11) with a SS12 Schottky (20V, supposedly a 1N5817 smd replacement)?
Also built this on vero—really nice sounding circuit.
From the man himself in the FSB thread:
Series diode would replace R11, Q4 and D1. Anode at E17, cathode at C17 [referring to vero layout].
Schottky because of the low forward voltage drop but you could even use almost any small signal type such as 1N4148 or 1N914.
Definitely worked out fine.
I would love to see a "board mounted pots" version of this. I have made a few version of this from the Vero that Mark did at Tagboard and also the PCB that was floating around with standing resistors (which I hate). I will contribute any way I can since I am new to Diptrace also.
I started this thread
http://www.madbeanpedals.com/forum/index.php?topic=12501.0 (http://www.madbeanpedals.com/forum/index.php?topic=12501.0)
If anyone would like to do a joint effort to make this thing. I'm still learning how to use Diptrace.
I don't know if you missed the fact that I'm gonna be doing this in SMD. It sure does away with standing resistors (which I dislike with a passion) but it may not be your cup of tea. I was also considering doing a TH layout as well but now that you've started it I probably won't get into it and just stick with SMD. And it will definitely include board mounted pots and two trimmers.
About lvlark's layout, for some reason (eventhough I've built from his layout previously) I completely forgot to check out how he did the polarity protection and just assumed (yeah, asses and all that) that it was the same as Revolutiondeux layout, with all the mosfet bits and pieces. Whaddyaknow, he only has one 1N5817 in there, removing the R10 47R as well. Not being well versed in this kind of thing, what does that 47R does for voltage protection and is it recommended/necessary? Is it some sort of current limiter? How about that voltage drop, how much is too much? Any point in perhaps going overboard and including this?
http://www.geofex.com/Article_Folders/cheapgoodprot.htm
This looks cool, looking forward to the final board. It appears that the 47R resistor does drop the voltage down a bit before it gets to the SAG control.
It's gonna take a bit longer but I'll get it done. Nothing about DT holding me back, I'm just so swamped at work and at home lately that the best I can do is chip away at it. The schematic is done, I need to make some parts fit my needs better (trimmer and elcaps) and route it.
I'm also still hoping for input from the folks here about that 47R, whether to include it with SS12 or not?
Muddyfox, is the schem in the OP for this thread correct to the part numbers/values for your board?
Quote from: alanp on February 01, 2014, 11:21:38 PM
Muddyfox, is the schem in the OP for this thread correct to the part numbers/values for your board?
I need to check because I'm not 100% sure off the top of my head but my board follows my builddoc to the letter (there's a pcb picture as well as a table of values). I did send you the link to the builddoc, didn't I?
Er, no, sorry :(
Quote from: alanp on February 01, 2014, 11:41:16 PM
Er, no, sorry :(
My apologies. I'll PM you right away. If I managed to forget anyone else please give me a holla.
It was kinda funny when I got the envelope, I'd completely forgotten about it.
"... Eastern European mail? Did I order some more Russian transistors or something? Where the heck did this come from?" :)
(http://i163.photobucket.com/albums/t282/Gutstwohand/smdworks_zps268c5ad3.jpg) (http://s163.photobucket.com/user/Gutstwohand/media/smdworks_zps268c5ad3.jpg.html)
Soldered the board up (blu-tacked it to a 1590A enclosure, to give it some more weight and not skip around). Had to call my little brother in to read the transistors with a magnifying glass (and even then he had to guess at some letters), googled SMD electro cap orientation... wired in pots and leads... (I had to lie the board on the bench vertically, and sit the camera on the bench in front of it, being very careful to ONLY press the focus/photo button, otherwise the photo was a complete blur.)
Holy smoke, it works!
Well. I never expected SMD to ever work for me. My technique is 'orrible (solder up one pad, stick the component on with tweezers and solder one end down with the soldered-up pad, then once that's cooled, solder the other end), and liberal use of the braid was needed.
Good on ya Muddyfox, this is a good 'un :) I'll do a build report once I've boxed it up.
Nice job alanp! Just got my kit today :)
Sent from my iPhone using Tapatalk
thread necro
can this run on 18v?
Im worried about the 16v rated 220uF cap.
Quote from: LaceSensor on September 05, 2019, 05:45:30 PM
thread necro
can this run on 18v?
Im worried about the 16v rated 220uF cap.
Well, I think you answered your question right there.
From a professional point of view, I can only say that if you apply 18V you should do it slowly the first time so not to blow the cap. Usually there is a safety margin, so it should be ok without a problem, while the lifespan will be a bit reduced. However, we usually do not overly stress electrolytics in filtering caps with strong ripple (amplitude nor frequency).
The way it works when you apply more than the rated voltage is that the dielectric anodically grows in the electrolyte (with hydrogen evolving, which can blow the vent) so that the voltage rating actually increases. However due to the increase in thickness, the capacity will decrease according to C=eps*A/d (capacity=permittivity*Surface area/dielectric thickness).
So overall, increase voltage slowly, if you can, to not have too much hydrogen at once and expect voltage to be slightly lower.
hope that helps
Quote from: m-Kresol on September 05, 2019, 07:37:47 PM
Quote from: LaceSensor on September 05, 2019, 05:45:30 PM
thread necro
can this run on 18v?
Im worried about the 16v rated 220uF cap.
Well, I think you answered your question right there.
From a professional point of view, I can only say that if you apply 18V you should do it slowly the first time so not to blow the cap. Usually there is a safety margin, so it should be ok without a problem, while the lifespan will be a bit reduced. However, we usually do not overly stress electrolytics in filtering caps with strong ripple (amplitude nor frequency).
The way it works when you apply more than the rated voltage is that the dielectric anodically grows in the electrolyte (with hydrogen evolving, which can blow the vent) so that the voltage rating actually increases. However due to the increase in thickness, the capacity will decrease according to C=eps*A/d (capacity=permittivity*Surface area/dielectric thickness).
So overall, increase voltage slowly, if you can, to not have too much hydrogen at once and expect voltage to be slightly lower.
hope that helps
thanks for the reply
Yeah figures, I know its a risk. I built one years ago and having a clearout. I never bothered to run it at anything but 9v and yet the chap purchased it and is now wanting to try. Ive said it might pop the cap, at his risk basically. its an easy thing to fix mind you.
cheers
Ian