Thanks! I should have checked for a new version 1st.

//edit// Found the 1N914 above.....never mind.

Very cool board, thanks!

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What are all those little diodes on the board? Jumpers?

gt

Edited December 29, 201411 yr by GrindingThud

No, they are diodes.

Diodes are diodes?  That is inconceivable!

diodes are there to protect the inputs from voltages > +/-12

on those amplifiers with high power output

Did you have any luck locating a 47uf ceramic? I've been hunting and can't find one greater than 10V.

Old thread, sorry: Kevin, do you have a schematic for the current version of this board?

//UFN

EDIT: Oh, and some BoM-questions:

1) I assume the diodes are just standard 1N4148/1N914?

2) Is the 47uF cap supposed to be ceramic or similar since it hasn't got the same footprint as the electrolytics?

Edited December 29, 201411 yr by GrindingThud

Well, it seems the 25V part is backordered at Mouser until February. I haven't done anything yet, but maybe a 47uF bipolar electrolytic will work instead? Looks like you can get at least an 8mm part into the board (and maybe 10mm at a pinch).

 

//UFN

Yea, that's what I'll probably do for test until they come in.

Well, it seems the 25V part is backordered at Mouser until February. I haven't done anything yet, but maybe a 47uF bipolar electrolytic will work instead? Looks like you can get at least an 8mm part into the board (and maybe 10mm at a pinch).

 

//UFN

Perhaps check out "pos-cap"? I am not sure the generic non trademark name, but that's what I would use.

no matter what i order, or when, mouser is always backordered on something

1. For the 100uF cap, I measured the leads at 2.5mm, and thought to use 647-UMA1E101MDD from Mouser. Is that adequate?

 

2. There are 7 short components on the board labeled "100k" left of the terminal blocks, but they don't look like normal resistor silkscreen images (2 by the in block, 3 by the out block, 1 to the right of each row of 1uF caps). Are they just resistors I'm supposed to mount at an angle so they fit?

those are vertical mount resistors to keep the board size down

Thanks! Is there any reason to use something like this slightly pricey Ohmite part (SM101031003FE) which seems like a perfect fit, rather than just bend the leads of an ordinary axial resistor for a vertical mount?

Ready for test. 1st install will be in my SuSy Dynalo.

I was going thru the schematic and the gerbers for this to do a layout including a muting switch and Molex KK connectors, which I like better than the terminal blocks. From what I am seeing in the gerbers, I had a couple of questions:

 

• It appears that the LM339s are powered by V+/V- rather than V+/GND?
• The LM339 has 4 comparators in it. It appears that 2 are being paralleled for each input signal?
• The input protection diodes run from V+/V-?

• There are a couple of 1uf capacitors (the yellow ones on GrindingThud's board above) that I am not sure where these go?

I attached a pdf of the Eagle schematic I have worked up so far.

 

 

Gilmore_protect3_schematic.png.pdf

Edited March 12, 201511 yr by Pars

• It appears that the LM339s are powered by V+/V- rather than V+/GND?

yes

• The LM339 has 4 comparators in it. It appears that 2 are being paralleled for each input signal?

yes, one for the + limit, the other for the - limit and then repeated 4 times for each of the signals

• The input protection diodes run from V+/V-?

to the inputs of the lm339, not as shown.

 

this should make it easier

 

http://gilmore.chem.northwestern.edu/protector3.jpg

Edited March 12, 201511 yr by kevin gilmore

Thanks Kevin. Yes, that is much easier to see than what the gerber viewer was showing me

This version should incorporate all of Kevin's corrections from my previous version.

 

One further question:

 

I know on Ti Kan's protection circuit, the relay drive requirements were pulling the + rail down, though he was using a virtual ground scheme on his. A user was the one who suggested the use of the 2N7000 and a 24V rather than a 12V relay, so that both rails were involved in supplying the relay drive.

 

I notice here the you are using a 12V relay and driving it with V+ / GND. In actual use, does this present any problems?

 

 

Gilmore_protect3_schematic.png.pdf

test circuit certainly worked, and I don't believe in virtual grounds for all sorts of reasons.

 

when you are running a dynahi with 400ma of bias, 25ma to turn on the relay seems tiny

Its running happily in my SuSy Dynalo with no issues that I've noticed.

Provides a nice little startup delay and cuts out if I induce DC on the output.

Edited March 12, 201511 yr by GrindingThud

the 15 second startup delay is intentional.

 

you can change the resistor string to make it more or less sensitive

This circuit should work single ended with both negative inputs grounded, yes? I'm planning on putting it in the CFA2.

Edited April 7, 201511 yr by GrindingThud

yep

 

in fact you can delete a number of the parts.

 

2 sets of RCRC and then a jumper on the C to ground.

Pardon the ignorant question, but... does using this circuit make any sense with an electrostatic amp, like a KGSSHV or KGST?

Nope, DC isn't a problem for electrostatics.