kevin gilmore

12 volt filament version with pin 6 grounded. for existing boards modification is easy. solder short wire from pin 6 to the ground pin on the .1uf 630v cap nearest to that tube. megatron12vcs - CADCAM.ZIP

will look into the megatron boards and see if the mods are easy. likely they are.

since pin 6 of the tube is a no connect, you can modify the amplifier and tie the 4 pin 6's to chassis ground. then in the adapter, pin 6 to the heatsink.

great idea. but there had better be a tail to ground the heatsink. otherwise not safe.

someone asked for this, so here is the amp board. working on power supply board now need to find a suitable chassis. power supply board in progress. cfaelectrostatschem2-4 - CADCAM.ZIP cfaelectrostatschem2-3.PDF cfaelectrostatschem2-3ps - CADCAM.ZIP

well there are apex chips that do sound good. but they are stupid pricy. and require large heat sinks.

it could have originally been 2 different transistors for the darlington in which case the original diagram might have been correct. since this is 30 years old, any original ideas are long gone.

you are not looking carefully enough. there is much more wrong with this thing. hint: power supply

makes sense.

same push pull stacked circuit with higher voltage all smd parts. also this https://buyee.jp/item/yahoo/auction/d1165787088 ac powered version of stax d10 with the lower voltage apex parts.

this is why i have 4 sets of tires for 2 cars. seriously under 40 degrees F is death for summer only performance tires. besides which the tires will crack and then you have to throw them out.

koss pro4a ? definitely koss

with the sanyo transistors 5v results in about 500ma bias. which was the original design spec for this board.

you need to measure the voltage across q36 should be about 5 volts. if not adjust rv2 and if that is not enough change r36

minimum power supplies +/-24 might have to change a couple of resistors in the bias generator for this output transistor.

what is the name of the gerber file for the output board

super thin traces are never a good idea. just ask cavalli.

yes the distance matters. always put caps as close to the chips as possible. probably need a scope to see whats happening to the power rails. possibly one of the diodes on the input lines is in the wrong direction.

solder on some .1uf caps on the power supply lines on each chip close to the pins. also no diodes that i see across the relay coils.

much better. max sensitivity of the qa403. 60 hz and multiples are very hard to remove, moving wires around in the box and things will change. completely inaudible. the synchronous rectifiers may take out even more noise. mumetal shielding around the transformer is also a good idea. glad that more and more people are buying the qa403. higher quality diy coming soon

might want to try again with a good quality mylar cap say 1uf in series with the power supply outout. you should be able to get better resolution.

need to see the whole board. definitely missing the power supply caps at the lm339

pretty close to production now.

first picture is baseline with 6db antenna 0 to 100mhz 10db/major division 10mhz per horizontal major division top line -30dbm 1 inch from power supply. second picture is with the 600v power supply turned on and into a 1meg ohm load. 3rd picture is hall probe on the input power supply line. so 200khz flyback switching frequency.

i did some quick tests and they are pretty quiet. but i plan on doing more exact tests. cap.inductor,cap should be more than enough. spec sheet seems to imply 20mhz which cant be right. will get out the spectrum analyzer to make sure.