DIY JE-990 DOA

[mnats]

Hi Mnats, I saw your pdfs and gerbers files and there an error on this.
There are no CR11 placed.

I think CR7 is the place for CR11, then CR8 is the place for CR7+CR8.

Yes, there are some minor errors on the component overlay, but each diode used in the circuit is exactly the same component (1N4148) so the designation mistakes won't matter to the function of the circuit.

The additional CR9 next to CR8 on my Version 1 .pdf file is actually the location of CR7. The placement for CR8 is correct - there is no need to put two diodes in for CR8 since there is already a series-connected diode footprint there.

Thanks for finding this error and I will fix my files as soon as I have some time to do so...

 

[DAN_000]

[quote author="mnats"]

Hi Mnats, I saw your pdfs and gerbers files and there an error on this.
There are no CR11 placed.

I think CR7 is the place for CR11, then CR8 is the place for CR7+CR8.

Yes, there are some minor errors on the component overlay, but each diode used in the circuit is exactly the same component (1N4148) so the designation mistakes won't matter to the function of the circuit.

The additional CR9 next to CR8 on my Version 1 .pdf file is actually the location of CR7. The placement for CR8 is correct - there is no need to put two diodes in for CR8 since there is already a series-connected diode footprint there.

Thanks for finding this error and I will fix my files as soon as I have some time to do so...[/quote]

Then CR7 is CR11, and CR9(overlay) is CR7.
No need to modify anything on the board, only a simple overlay error.
:thumb:

 

[John Hardy]

but each diode used in the circuit is exactly the same component (1N4148)

All of the small-signal diodes of the 990 are either a 1N4448 or a 1N914B. These have tighter specs than the 1N4148 or 1N914.

I believe that the 1N4448 is identical to the 1N914B, but the 1N4448 is an official JEDEC number that properly specifies the DO-35 package instead of the DO-41 package. I've forgotten most of the actual story, and probably missed a major point or two, but it is something like that.

John Hardy
The John Hardy Co.
www.johnhardyco.com

 

[AnalogPackrat]

Thanks for the additional info, John. When you say tighter specs, do you mean Vbe or something else? If it is Vbe, could one not simply match 1N4148 or 1N914s for Vbe (under some nominal condition) and achieve the designer's intended result?

Thanks,
A P

 

[John Hardy]

When you say tighter specs, do you mean Vbe or something else?

Check the specs sheets and see. (I would put a smiley here, but I hate those things)

John Hardy

 

[AnalogPackrat]

John,

OK, I took a look at several different datasheets. Some were confusing, but it appears to me that the 1N914B and 1N4448 have either a steeper V-I curve (than 1N914 or 1N4148) or it is shifted so that the Vf is lower for a given current. None of the datasheets I found had V-I curves for both types (is it me or are datasheets getting awfully terse these days).

1N914 or 1N4148 Vf 1.0V @ 10mA
1N914B or 1N4448 Vf 0.72V @ 5mA, 1.0V @ 100mA

The Fairchild datasheet also seemed to indicate tighter Vf tolerance (100mV min-max spread) whereas the 1N914 and 1N4148 just had max Vf specs. So the net effect appears to be lower and better matched Vf for the parts Jensen spec'ed. So did he want lower Vf, better matching, or both?

In any case, it was an interesting little diversion into diode land. Reminds me a bit of the neat comparative V-I graph in Pease's book...hmmm. Need to go dig that up. Thanks for the prod <bzzzzt--ouch!>

A P

p.s. I just realized that my previous message contained a reference to Vbe for diodes . See what happens when you post from work (doing nasty things like SW, no less) at the end of a long day?

 

[John Hardy]

So did he want lower Vf, better matching, or both?

All of the above, I'm sure.

John

 

[clintrubber]

I've been gathering the non-Ptownkid-990-kit parts and stumbled on two pesky capvalues:
62pF (C2) & 91pF (C3). Can't find these (NPO).
(Ahh, too late, it'd have been nice to have had them in the 990-kit...)

So what are people doing, messing around with other values in parallel ?
Or just measuring a few neareast values and try to find one with a pretty close value ?

I haven't built or simulated the circuit yet, so I don't know how critical these exact values are. I guess there be some room.
Ah, as PRR might say, if it'd be that critical then it'd be a poor design. I'm not willing to assume that right now :wink:

Regards,

Peter

 

[mnats]

62pF (C2) & 91pF (C3). Can't find these (NPO).

Fairly easy to find in SMD form. Should also be easy to solder on the copper side.

 

[clintrubber]

[quote author="mnats"]

62pF (C2) & 91pF (C3). Can't find these (NPO).

Fairly easy to find in SMD form. Should also be easy to solder on the copper side.[/quote]
Thanks for the hint. :wink: Hadn't considered SMD, silly oversight.

Regards,

Peter

 

[sonicwarrior]

Hi there,

I'm new to this list and started doing DIY soldering only a few months ago (that's a good excuse for asking dumb questions :wink:

Has anybody already tried the SSM2210 instead of LM394 in this 990 circuit?

I'm just asking because I have a pool of them lying around
and the LM394 is harder to get in Germany.

 

[mikeyB]

[quote author="Swedish Chef"][quote author="mnats"]Go Chef!

I'm pretty sure he means PCBs - no one would consider getting into the 990 business now except maybe Behringer :wink: Seriously though, there are at least two, maybe three businesses doing finished modules already who have earned their place in the audio world and deserve to be promoted and supported. To me, this is just an interesting distraction and a fun way to share some DIY.
[/quote]

Yeah I do not have Beh-spit icon here-ringer allusions. :green: Pcbs was what I was thinking, but was unclear. sorry for any confusion casued by my fatigued brain!

I'll talk to my fabrication folks on Monday and let you all know what happens asap :grin:
At some point I will find the headspace to go through all the cool stuff in this thread and try and see if I can't get some to stick :sad:

Cheers

chef[/quote]

I like the look of this DOA - any news on PCB fab?

 

[sonicwarrior]

[quote author="mikeyB"]
I like the look of this DOA - any news on PCB fab?[/quote]

Well, six days later the following thread was opened with PCBs from brasil:
http://www.groupdiy.com/index.php?topic=14712

So: PCBs are already available. :razz:

 

[evm1024]

So having boards in hand and inductor cores from ptownkid what are the recommended wire size and turns for the inductors?

Looks like 3 turns (6 passes thrugh the core) and whatever guage that fits the core.

thanks

 

[keefaz]

Hi, look at this thread and scroll down a little:
http://www.groupdiy.com/index.php?topic=1401&postdays=0&postorder=asc&highlight=je990&start=45

I see an isolator at the opamp output from the John Hardy's shemos,
is it possible to DIY it ?

 

[evm1024]

Missed that in my read through....

6 passes through the inductor core with 30 guage magnet wire.

Thanks, Ethan

 

[dissonantstring]

just beginning to build the JE-990 with mnats designed boards and ran into something i thought people should consider when building these.
i found that the Q1 & 2 (LM394) transistor should be soldered onto the board before soldering in Q5 (PN4250A) transistor. The tab on the can of the LM394 get's in the way of properly mounting the transistor if you've already placed Q5. Also the tab sits dangerously close between the legs of Q5 so i put a shrink tubing on each leg of Q5 to prevent shorting. just something to consider. i'm sure others will find better alternatives to this.
regards,
grant

 

[Ptownkid]

thanks for the info grant, that's quite helpful.

 

[hejsan]

Hi, I have 3 stupid questions.

mnats: In your 990 pdf you list C4 and C5 as 1uF, but I'm guessing that's supposed to be 0.1uF, right?

The 62pF cap, how important is it to have it excactly 62? Would 56pF or 68pF do?
I can see from the photo of your 990 that it has a through hole cap where the 62pF should be, could you possibly source it? I have pretty shaky hands and am afraid of smd..

Has anyone else found 62pF in non-SMD form?

One more question, what are monolythics?

[quote author="mnats"]

mnats..what caps are you using?

NP0 Ceramics for the small values and monolythics for the 0.1uFs.[/quote]

thanks,
hejsan

 

[ChrioN]

monolithics I think is the same as multilayered ceramic caps, but I'm not 100% sure.. Anyways, the radial ones often looks like this: