congo5

File names are CFP2 which stands for Current Feedback Amp so sometimes referred to as CFA CFP2 is SE CFP3 is balanced and Large I have built dmt ver1.05, emt ver1.06, and had boards made and built fmt ver 1.07 which are 3.7" x 4" they all work gmt Ver1.09 is the newest from memory there were small changes only between them what part of schematic does not match? its been a while but will try to help

Here is what I drew up, no fancy ground plane like yours.......yet and why did I double the caps? dumbo turbo?

Absolutely agree with everything above! I often look up and admire my Dynahi, Dynalo and Kerry's mini as I plug into the CFA2

Thank You MLA It seems way better than expected, different but very very good.

No rush, as you said no parts available, all I have are the ksa1156 a combined board would simplify the wiring a bit Its been 10 months and I would like to hear other opinions about this amp. possibly its a great low budget amp, ( or spend 37k and you know its the Best Ever)

Amazing how many parts are out of stock for this? So in order to use this on a tight shelf I bought some 4x10" heat sinks and modified the case to use them Only 60 holes to drill and tap. now moar better.

Still interested in the direction you would take the board design. and any changes or updates you might make. I'm fine with through hole parts as the footprint is already small, but an ultra tiny amp would be Neat! I used mine yesterday to power some DIY stats for testing, and although a simple plates are enough sink for testing its too hot for long term when jammed in a case. So ordered some .7 C/W heat sinks for each channel.

Variac's are nice for many reasons, and can prevent catastrophic failure, many components at once I slowly turn the voltage from 0 to 120v (USA) while looking for heat/smoke and watching voltage meters on power rails, bias test points invaluable for bringing up these high voltage boards, much cheaper than having blown transistors and burnt traces. although it is exciting to watch 800v flash and smoke a bunch of parts mine was $50 and its 500va, You can place smaller fuses in the front panel holder so it blows early, think I put 2amp fuses in they make bigger and better ones, get what you like.

much better photo's that 20k should never see hardly any wattage, something is bridged/blown, tracks,pins, transistors possible Q5 & Q8 direct short through all pins

that 20k is connected to ground, or in this case negative rail how much voltage is on input? what value are resistor dividers, voltage? 390k+390k=400v picture kinda small, can't see too much are the 390k resistors 390R? if those 390k where 0 ohms that would give you 8W across your R7 20K resistor

I saw an OP07 in one of Kevin's pictures and have been using them Mouser lists it for +-18v rails, data sheet says max is +-22v they are under a dollar OP07CP

not really when I played with it the values needed did not line up with a Led online calculator or what I expected, So not a normal Led? The point is to check it and adjust if needed don't remember what I used. Yes think it was much lower resistance.

the GRHV "sw" boards are the original size with the optocoupler switch (CPC1117) and the sws boards which are the shrunk size with the optocoupler switch. the opto will both turn on soft, and turn off soft. the opto is normally on, which keeps the power supply off, applying 5 volts thru a 10k resistor turns the opto off which allows the power supply to start So power your choice of timer board and send output to the switch with a resistor to limit current through the opto check data sheet, think its 3-5ma

Kevin's boards show a resistor marked "open" this connects Q2 base, the input of the servo to ground which if grounded, wouldn't it turn Q3 off disabling the servo? Or what is its purpose?

Yes to 10k pot in front for unbal stereo amp Yes to boards Dynalo works, and will provide gain reg drive is what the GRLV connects to

EL609 Green Insulating Varnish - Aerosol - Sprayon it moves out of the way when soldering, or reworking. don't need to mask or remove its available locally and works but real mask is better alcohol removes it I like it for prototype usually I spray when done, after flux is removed

Thanks, there is no ground plane at all, not at these voltages. the groves are where I cut the 2oz copper, all that's left are traces Just the cut (.020") would be enough for 80v but not 800v don't think Kevin's board files have any planes, like the grounded grid. From looking at the schematic I thought that servo cap would normally not have more than 10-20v but on start it could see hundreds, so used a 450v Panasonic, thanks for confirming this! I chose this one thinking it will be more different sound wise then a tube input carbon should have missing parts this week

looks good to me, What is voltage of .1uf cap on servo?

Yes still like it, its different, darker but fun last week > Megatron, BH and it there may be some tweaks to the circuit that could be found but not if no one builds it Please try it before building it a home in a multi thousand dollar enclosure

I added some parts to mouser project you still need to pick resistors, terminal blocks, transistor mounting hardware and maybe change the big caps Mouser has some new 600v ones for the prereg side they are higher voltage than necessary for 400v supply's also you can look over the KGSSHV BOM for ideas as many parts are similar http://tee8tee4388.blogspot.com/2013/07/kgsshv-amplifier.html

no on the CFA but its simple / not a lot of parts, used xicon 1/2W resistors, or RN60D but have this on BHultramini its years old and think the trim pot is wrong, should be a pv36Y I think. see if the three pins are staggered or in a row on yours http://www.mouser.com/ProjectManager/ProjectDetail.aspx?AccessID=108619691e check it against the, board some of it will help

minor differences: board looks good, don't see any problems board uses resistor + zener string instead of U10 D3 has a 350K resistor to ground connection of R15 changed and values of that and R16 adjusted Q7 Q8 Q9 Q10 are KSA1156 instead of STN9360 on schematic trimpot added to R12 for offset Q13 collector has an added 100k 2W resistor

http://www.heisener.com/Products/Finder?pn=273-240-RC+ http://es.heisener.com/Products/Finder?pn=273-487K-RC+ http://es.heisener.com/ProductDetail/Xicon/273-402K-RC http://es.heisener.com/Products/Finder?pn=273-499K-RC+ http://es.heisener.com/Products/Finder?pn=273-40.2-RC+ http://es.heisener.com/Products/Finder?pn=273-287K-RC+ http://es.heisener.com/Products/Finder?pn=+273-82-RC+++ in stock, min Qty 1 etc etc

Yes I use kapton or aluminum tape to protect what's nearby good point

yes that is what I found also just a light coating or its a problem so you might tin it and wick some off the outside can and should be redone with a small tip iron. the kester flux I have dries up too early and gets sticky so that doesn't help haven't found any really good flux for this yet paste might work better here but don't have any recommend checking for shorts before power, I lost one that wasn't checked with practice and the right tools this can be done many times with out damage to the board preheating is a good Idea, even to 150F helps toaster oven-candle warmer-heating pad-light-something