mwl168

Thanks Kevin. I experimented with the opto server tonight (this time with the OP27 in place) and here are my observations: Without the servo jumpers in, I first adjusted the offset of both boards to be about +18 VDC at cold start, measured between the + output and ground (this applies to all subsequent measurement). I then inserted the jumpers and powered on the Carbon with opto servo now engaged. The offset on one board measured -2.5 VDC right from the start, it dropped to about -1 VDC after 5 - 6 minutes, from there it hovers around -0.9 VDC, drifting about 0.5 VDC or so up and down. I measured again at 20 minutes and then at one hour marks with same results. At the one hour mark, I adjusted the balance from around 2 VDC to within 0.5 VDC (absolute value). This brought the offset to hover around -0.1 VDC. The other board exhibited similar behaviors but started with and ended at lower offset voltage. (Without servo, this board has always had lower offset and balance compares to the other one.) It appears to me that the opto servo is working and it's effective from the very start although it does take about 5 minutes or longer to reach the lowest possible offset voltage. As I have mentioned in the past, the Carbon, without the servo, is very stable to start with. It seems to me the main advantage of the opto servo is to keep the offset at a low voltage from the start and settle it down faster. Without the servo, my Carbon typically takes between 15 - 20 minutes for the offset to settle.

Thanks Kevin. For clarification, my Carbon's output voltage as measured from the O+ to ground is about -14 VDC at start up. Do I need to adjust it to + 20 VDC at start up for the opto servo to work?

Thanks Congo5. I was wondering the same thing (if OP27 is needed for the opto servo to work) after reading the schematic. I will install OP27 and give it a try. One question, does the output need to be as high as 20V for the servo to work? Shouldn't 5V or so be enough for the OP27 to sense the differential? From the get go with the offset and balance pots centered, my Carbon has not seen higher than 15VDC offset.

EDIT: Got it all wrong. Post deleted.

Thanks all for your kind consideration and offer. We are all fine. Also, as of today, all boards have been shipped including the international-bound ones. Happy building!

Ah-Oh! I goofed. One of the SRX amp boards from PCBNet has an obvious cosmetic defect at the left lower conner where the version number, etc. is silk screened. I have intended to keep it for my own use but in the process of taking a photo of the defect to inform PCBNet and packing the boards for shipping, I must have shipped it to one of the GB participants by mistake. I apologize. Can the unfortunate recipient of this defect board post or PM me so we can discuss what to do about it? PCBNet has informed me they did find a spare that they can send me for replacement but unfortunately we'll have to cover the shipping cost. Given the circumstance I had agreed to simply let PCBNet include this replacement board next time I order boards from them.

All US bound boards were posted via USPS Priority Mail today. I have the quotes from USPS for international First Class Air Mail shipping based on weight today. I will PM each individual GB participant with your shipping charge. Be prepared for a bit of unpleasant surprise - USPS raised the price of its services on January 17.

JoaMat is correct - MPSW06 pinout is different than the 2SC1815.

Better quality photos of the boards as promised.

A bit more information will help others to offer their assistance. What version of boards are you building? What voltage PSU are you running? What's the offset and balance at cold start and are they responding to adjustment? A few good resolution photos of your boards will be very helpful.

Got home very late tonight to find the PCBNet package sitting in the foyer. Delayed one day by the snow storm that hit upper Midwest Tuesday. Quick visual inspection of boards shows typical quality fabrication as can be expected from PCBNet. These 2mm, 4oz boards have a hefty feel to it. Will post better quality picture this weekend under daylight. Shipping will start next week.

FWIW, I use a 200VA transformer and run my HV at 15mA output current. I use NTC thermistor on the prmiary of the transformer and use 3.15A fuse. It has been working fine for a few months. I have not gotten around to try smaller fuse yet so it provides proper protection in the event of faulty operation.

I did an experiment earlier today - changed the bias resistors on my off-board KGSSHV to run at 15mA per output devices. It has been running continuously for 5+ hours and it appears to be working fine. I am running 415VDC rails PS. As far as I can tell by using an infrared thermo gun, my puny heatsinks are measuring around 50 C or so. It's a bit difficult to get good measurement of the case temperature of the 2SC4686A because how they are mounted to the heatsinks but my best guess is around 60 C, again, based on the infrared thermo gun reading. That's pretty close to the 7W dissipation limit at 60 C as stated on the 2SC4686A datasheet. For long term peace of mind, I will be looking for a chassis with ample heatsink for my HV.

I really like the idea of including the 330R + .022uf snubber on the board.

A variac will be your friend in this case. I bought one and have found it to be a valuable tool to have especially for building and testing these high voltage circuits.

This may not explain the zener problem, but what shoulder washers are you using for the 10M90S? There are some discussions over at the KGSSHV thread on using washers that prevent shorts between the screw and the tab of 10M90S for high voltage applications. Basically, the "tube" of the washer needs to be long enough to extend into the insulation pad below to prevent accidental shorts.

Thanks all for your help. I decided to pull the trigger on the JBC. I know I cannot go wrong with either the Metcal or the JBC. Both, and many others, will be a major step up from my entry level Weller station which has served me well for a decade or so. At the end, it comes down to my personal preference for the ergonomics of the JBC and the fact I found a store offering a nice discount for it (it's being replaced by a new model).

Yes, that's it.

Sorry Pars, I don't have the part number handy. I just grabbed them from my parts bin. I'll need to look up my past Mouser orders and see if I can find it. There is also the possibility they came wih kits I bought in the past. I do remember the heatsinks were for TO220 package but happen to work in this case. ( I was not able to save edit to my last response so have to submit a separate response.)

I've been thinking about upgrading to a better soldering station. I am just a hobbyst so the tool is mostly for DIY work. I started out wanting to limit my budget to $200 US. As always the case, once I started reading stuff on the web, I am more and more tempted by those that are way over my budget. Right now, I am looking seriously at: 1. A JBC CD-1BD for around $400 2. A Hakko FX951-66 for around $260 I would love to hear your experience, experience and recommendations. Thanks!

Received confirmation for our order from PCBNet today. Boards will be shipped from factory on or before Feb. 5.

Payment sent. Thanks for the GB!

Thanks for offering to help! I just confirmed with two GB participants of their orders and, 3 minutes ago, submitted our order to PCBNET

The board is set up for TO220 package DN2540 only. The TO92 package has different pinout.

I would love to hear your impression on how it compares to the Dynalo MK2. By Dynalo MK2, do you mean the SuSy Dynalo aka multiamp, or is it something else?