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Group Build: Dynafet


luvdunhill

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http://b.j4cbo.com/temp/gbf2.brd

http://b.j4cbo.com/temp/gbf2.sch

Here's the current layout; consider this Release Candidate 2. If nobody finds any show-stoppers, I'll work with Icarium to get prototype boards ordered this week.

Changes since the previous layout:

- Added 5mm spacing for the film caps on the rails

- Fixed orientation of LED3

I'd like to get a recommended BOM together before we order the boards. Just so we can verify that all the spacings are appropriately sized for components we actually want to use.

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Here is a stab at a BOM. Got parts from Mouser and Parts Connexion.

Don't have complete info, but feel free to make suggestions.

Hmm.... Don't know how to upload an .xls

If somebody wants it or wishes to figure out a way to post, I'll email it to them.

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Just noticed that all 2 ohms were connected to the source pins on both of Kevin's pcb's, and it would match all schematics if you look at the symbol for the J76 and turn it upside down.

I'm now working witha build using LED3 reversed as it is on all of Kevin's pcb's and I have the output of the 2nd stage down to +/- 15V which looks high. I will connect the servo tomorrow and see what happens.

Enjoy the rest.

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I'm assuming Jacob is still validating the boards and going to place the order for the prototype boards. I'm also assuming Icarium has placed an order for the toroid prototype. I'm planning on ordering the rest of the passives for the prototypes as well, just need to sit down with the board files and the BOM and see if the BOM makes sense or not. I thought Jacob was posting a BOM, hence the reason I haven't done this, as I was going to compare his to Digipete's as well...... so, I'm in a holding pattern as well.

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I haven't ordered anything yet I was going to wait til when we ordered the prototype boards. Jacob's laptop blew up and he only recovered it I think Thursday with everything on it gone. I imagine barring anything random happening we'll order things next week and I'm sure his BOM will available as well.

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I've made some component name tweaks and fixed the 2SJ76 pinouts:

EAGLE brd, EAGLE sch, Gerber files.

And here is my BOM. It's based heavily on DigiPete's; I went through and checked all the footprints, tweaked the capacitor choices, and fixed up component names for my changes. This assumes we're using an OPA445 and jumpering over the regulators, which is probably the best choice for the first prototype run.

To the best of my knowledge, those Gerbers are ready to be ordered.

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ok, so I'm in the middle of working on this and figured I'd post the issues I have so far with the BOM:

It seems to me that the speced resistor will not fit in R35-R38. This location is 0.3" pitch and the 281 series have 10mm bodies. It would be nice to fit 9.0mm body at a very minimum. Is it possible to add a bit more room in here?

For R47-R54 it would be nice to space them out a bit more, as I think there are some of us that would like a larger power rating there. I'd prefer a 15mm-16mm body resistor, with 0.80mm lead diameter. Seems very doable to me.

For the LEDs, 2.0 Vf seems too much. I'd recommend 630-HLMP-D150.

I see that C13 is the input filter cap, but where the heck is C31 connected and where does it go? I cannot seem to find it on the .sch.

Is there any reason to add a jumper so that the R19, R20 node can be connected to FB? I didn't look at the traces, but would this be difficult? (I realize Kevin said to choose one or the other, but it seems that it would be a nice option to keep on the board especially during prototyping).

I've converted some of the the values in the circuit to a more narrow E-series. In this way, all of the values will be available in PRP. I'll be sure to test, as it deviates from the schematic. This way there won't be mixing at matching and we have to only test one set of values.

Ok, I'm going to finish looking at the other parts and hopefully will have this done tonite!

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ok, so I'm in the middle of working on this and figured I'd post the issues I have so far with the BOM:

It seems to me that the speced resistor will not fit in R35-R38. This location is 0.3" pitch and the 281 series have 10mm bodies. It would be nice to fit 9.0mm body at a very minimum. Is it possible to add a bit more room in here?

For R47-R54 it would be nice to space them out a bit more, as I think there are some of us that would like a larger power rating there. I'd prefer a 15mm-16mm body resistor, with 0.80mm lead diameter. Seems very doable to me.

For the LEDs, 2.0 Vf seems too much. I'd recommend 630-HLMP-D150.

THose look good. The original Dynalo LEDs were the FLV110s, but these have gone thru several suppliers (used to be at Digikey but now at Mouser) and the Vf range is higher (1.6V-2.0V vs. the 1.6V-1.8V on the ones you came up with).

I see that C13 is the input filter cap, but where the heck is C31 connected and where does it go? I cannot seem to find it on the .sch.

C31a is right of R57 and goes from the input to ground.

Is there any reason to add a jumper so that the R19, R20 node can be connected to FB? I didn't look at the traces, but would this be difficult? (I realize Kevin said to choose one or the other, but it seems that it would be a nice option to keep on the board especially during prototyping).

As it is (on the schematic), the servo is driving the input; one thing I always lked about the dynalo, etc. was the fact that the servo did not directly drive the input. I would agree with Marc's comment on R19/R20 if doable.

I've converted some of the the values in the circuit to a more narrow E-series. In this way, all of the values will be available in PRP. I'll be sure to test, as it deviates from the schematic. This way there won't be mixing at matching and we have to only test one set of values.

Ok, I'm going to finish looking at the other parts and hopefully will have this done tonite!

Percy carries a wider E range than PartsConnexion or Soniccraft do. For example, the 30K is available in either Roederstein or Holco. I personally like the Roederstein MK3s, and these should fit (if the board will fit the 1/2W PRPs).

EDIT: Looks like the board layout will fit 0.3" resistor spacing; the 1/2W PRPs are 0.4" body length, so guess that isn't gong to work (at least without creative lead bending). Ditto for the Roedersteins )0.325" body, closer). Holco are 0.375" for H4 (and he doesn't seem to have H8 anymore ??) Caddock TF020 are 0.6", so no go there; I'm sure the Vishay bulk foil are similar :lol:

Edited by Pars
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Back in the day of playing with the Xono, I found the perfect low noise LEDs. They are a very strange package, they are leaded, but the leads aren't under the bulb.. think axial LED. They are super expensive (for LEDs), I think about $1.50+ each. I sent a bunch to Scott Wurcer and John Curl a while back, and one of them did some tests on a Audio Precision 1 and said they were about as good as you can get. I can see if I can find them again, but I'm not sure they'll fit very easily. I also have a bunch of transparent orange LEDs that are dead on 1.7V that I used in Kevin's other designs, but sadly they are no longer being made.

Ok, I see C31A now. I think 220pF will work here, that's what I'll prototype at least.

I'd like to revise my suggestion for R19/R20... at minimum a pad here for prototyping. Ideally, a way to connect to FB or to ground with minimal trace length.

I think the MK3 are rather nice in fact, but you'll really have to change things around a lot due to availability. Just calculate things as ratios and you'll be fine.

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Back in the day of playing with the Xono, I found the perfect low noise LEDs. They are a very strange package, they are leaded, but the leads aren't under the bulb.. think axial LED. They are super expensive (for LEDs), I think about $1.50+ each. I sent a bunch to Scott Wurcer and John Curl a while back, and one of them did some tests on a Audio Precision 1 and said they were about as good as you can get. I can see if I can find them again, but I'm not sure they'll fit very easily. I also have a bunch of transparent orange LEDs that are dead on 1.7V that I used in Kevin's other designs, but sadly they are no longer being made.

Ok, I see C31A now. I think 220pF will work here, that's what I'll prototype at least.

I'd like to revise my suggestion for R19/R20... at minimum a pad here for prototyping. Ideally, a way to connect to FB or to ground with minimal trace length.

I think the MK3 are rather nice in fact, but you'll really have to change things around a lot due to availability. Just calculate things as ratios and you'll be fine.

I just mix PRPs and MK3s... that is what I did on both my Dynalo (a couple of them) and the Dynahi. No value substitution that way.

Ideally, FB to either a pad between R19/R20 and pad at the input where it is currently; make the user choose?

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