Kevin - Are the gerber files available ? The onboard PS version that I have is 8e and looks to be about 7.5 X 9 inches. If a simple voltage divider off of the positive voltage works, that indeed would be much simpler. Thanks.

always

 

http://gilmore.chem.northwestern.edu/kgsshvpsminifinal.zip

In case anybody here is interested in sourcing parts.

 

http://www.ebay.com/itm/301165029880?ssPageName=STRK:MESELX:IT&_trksid=p3984.m1558.l2649

 

Not much of use there for us. 

 

Kevin - Are the gerber files available ? The onboard PS version that I have is 8e and looks to be about 7.5 X 9 inches. If a simple voltage divider off of the positive voltage works, that indeed would be much simpler. Thanks.

 

The voltage divider is fixed so drive it off a regulated PSU for a regulated normal bias. 

I am considering getting some kgsshv board sets made. To keep costs down, I would like to order in quantity and distribute the excess to the group at my cost. I can get the final version of the onboard mini power supply board in quantities of 25 for about $30 each. I would also like to get 50 of the latest amp board, preferably the one that allows dual transistors, made as well. Kevin, if you could provide the gerber files, I will get a quote on these as well. I anticipate the total cost for the 3 board set to be about $80 plus shipping. To keep the logistics as simple as possible on my end, I would like to limit individual shipments to the US. If someone outside of the US wants to get multiple sets and then redistribute locally, that would be great. Is there enough interest in the group to justify getting 25 board sets made? Please post here if you would be interested so I can decide whether to procede.

Carification, the amp boards would be the offboard variety.

Just so you know, there are no good offboard versions available.  The ones I use in my tiny amp require some care or the amp will blow up (i.e. everything was sacrificed for space or rather lack there of) and the new slightly larger units aren't ready.  Too busy building to work on them. 

What about something like this? With a ground plane of course. A bit larger at 7.5 X 4.5 , but with better clearances for traces. I can get 50 of these made for less tha $20 each with 2 oz. copper on FR4.

 

Here it is with a ground plane also with good trace clearances.

 

 

A newbie question for my first stat amp build.  This is a A1968 450V offboard.

I powered up the kompact PS board and I'm getting a high reading at the bias test point.  It starts around 626V and slowly rises over 630V.

The other voltages are stable at:

-15.1V  14.9V

-455V  451V

630V is way too high right?

Is there an incorrect resistor value somewhere?

 

check which zeners you have in the string. or possibly one of the zeners is dead

Thanks Kevin.  I'll desolder the ones I can't read and see what's installed.  They should be 150 150 200.

There are 4 zeners for the bias supply, 3*150V and one 130V. 

 

What about something like this? With a ground plane of course. A bit larger at 7.5 X 4.5 , but with better clearances for traces. I can get 50 of these made for less tha $20 each with 2 oz. copper on FR4.

 

That would work but I highly recommend doing a proto run on any untested pcb. 

Doh!  I see there's a 200V in there... which of course is +50V above the 580V.

That would do it. 

That was embarrasing... I'll go crawl back under my rock now.

you are supposed to bend all the parts in such a way as you can read what

they are when they are soldered in. dale resistors, and zeners mainly.

Thanks for the advice Kevin, will do for future builds.

For Dale resistors there are always the CCF60 type which have color bands on them for easy identification.  500V spec too which is nice. 

 

That was embarrasing... I'll go crawl back under my rock now.

 

Nahh, better ask away so things can be fixed.    Fucking up is just part of the process

you are supposed to bend all the parts in such a way as you can read what

they are when they are soldered in. dale resistors, and zeners mainly.

Yeah,just wish the new breed of commercial  assemblers had been taught this.

Bloody pain when I had to fix their cockups.

I have some blank 2oz copper boards, so I will etch a pair of prototypes and see if they work.

That would be a good idea.  Having 50 useless boards does sting a bit... 

Spritzer - In your experience with this offboard amp, are there areas that are particularly prone to problems ? I am guessing that the high voltage 4686 and 1968 transistors leads would be a problem shorting to the rear of the board or the heatsink where they bend under the board. I was considering slipping some teflon tubing over the leads before soldering  them to the pcb to help prevent accidental shorts. Any other areas of concern ? Thanks

On the subject of teflon tubing, can anyone recommend a practical diameter for to220 and to92 leads? Is there a lot of variability when it comes to elasticity, and is that something I need to look out for?

I've never built a 500V offboard amp so only dealt with isolated packages but zero issues here. I do bend the leads so that they enter the PCB holes at a straight 90° angle so no chance of shorts.  This is not fun with the super tiny board...

I put together a schematic for the kgss amp circuit using dual transistors in the early gain stages as per Kevins's post a few pages back. I think its correct based on the pcb post and earlier schematics for the single device circuit.