its getting pretty tight...

 

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

 

laying the rest of them horizontal is going to be a bit of trouble.

 

For those who still have c2240 and c2705, are the newer pzta part subs better?

 

Also, if one used the 1486 would it need to be heatsinked given your comments on the stn9360?

no difference between the 2sc parts and the pzta or mpsw or mpsa parts

 

1486 does not need heatsinking.  About 188mw

If anyone wants to do a board run of the carbon I would be interested.

 

I don't know who many working carbons are around at the time, but is there anyone who can comment on their strength and weakness compared to our other amps?

you can get your own one-off done, won't break the bank

 

I think JoaMat is the only one with a working unit at this point, maybe Kevin? Beta tests are open, register at http://gilmore.chem.northwestern.edu/boards/

 

I have a set of the boards prior to these upgrades if you're interested. I think it's equivalent to the version that Birgir posted earlier in this thread

Mine are ready for testing but other stuff has taken over for a while.  Might even be pushed back further for the new Megatron PCB. 

 

As for SMD, if you want resistors that are equal to the RN60D's then they are 1$ each or even more.  SMD was never designed for HV in mind... 

no difference between the 2sc parts and the pzta or mpsw or mpsa parts

 

1486 does not need heatsinking.  About 188mw

Great, thanks. Just need to check the pin-outs on the parts - hopefully not much twisting will be needed.

/

Edited November 11, 201510 yr by JoaMat

I have Carbon boards as well, but unlikely to have time to do anything with them for at least a couple of months. Even if they are not the newest version I assume they are OK to use?

 

//UFN

Birgir has said they're untested, so same boat as the newest version

Yup, untested. 

latest version with correct resistor values for Kerry's servo

 

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

 

parts set for 16ma at 450v

Edited April 23, 201511 yr by kevin gilmore

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Edited November 12, 201510 yr by JoaMat

no, just 2 transistors for the servo output drive.

identical to Kerry's schematic.

the final output is the Motorola part because

its about 350mw

and if you turn the current up, its more like .5 watt

Thanks, it's great to have Kerry's Servo on board.

Edited November 12, 201510 yr by JoaMat

This is very nice. Is hard to keep up with all your ideas!

Just checking the board/schematic around the servo.  Looks good.

 

You can change the label for PZTA28 to PZTA06 (same pin out) or some other NPN.  Keeping the MJF15030 part is a good idea.

 

Also, the 5K pot should probably go down to a 1K (or 2K) POT and also change the 20K to a 24K (TBD) resistor.  Varying by 400 ohms moves the output about 6 - 8 volts.  It's just a matter of making it have enough range, but not being too sensitive.

 

The last thing is that I currently have 2pF caps across both legs of the 2 x 1M resistors on the KGST build.  I'm not sure if this helps or hurts.  I'll try pulling them out this weekend.  I'm hoping the 220pF cap can manage any possible oscillation.

 

I'll confirm the rest of the board then built the LTSpice model next.

Edited April 24, 201511 yr by Kerry

I was also justing looking at the new board and wondered if the lm4040-10 sot package couldn't be replaced by a to92 to make it easier.

 

Furthermore could someone elaborate on the advantages of the new servo? I am really interested in that.

The net benefit is that it will have a larger operating range. 

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Edited November 11, 201510 yr by JoaMat

I just built the spice model for the Carbon and noticed the same thing.  It should use a 2.5V or max 5V reference.

certainly can replace the reference with a to92, current datasheet does not list the pinouts.

 

I did trim the emitter resistors to 25 ohms, so there is still about 9v on the servo.

 

But will change values to the final parts when we all decide what those are.

 

also added a pot in series with the 20k resistor to adjust the dc to exactly zero.

 

the 25 ohms decreases the thd a significant amount at 20khz because of the

added gain.

 

let me know which parts and values to change.

Edited April 24, 201511 yr by kevin gilmore

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Edited November 12, 201510 yr by JoaMat

Capacitance between the ground planes?

just tried it, very little actual ground plane due to all the wires.

 

eventually when we go to all surface mount everything, the board will

be at least 3 layers.

/

Edited November 12, 201510 yr by JoaMat