tube power supplies, switchmode

[ruffrecords]

this thing is actually pretty powerful for 305VDC...
kind i curious... is it safe to use it in an audio equipment...
incase something goes wrong, while touching multiple conductive surfaces, etc!

edit : typos

300V is definitely enough to kill you or at least give you  a very nasty shock. That is why good tube gear is is fully enclosed in an earthed metal enclosure. Even when power has been removed, decoupling caps can hold a high voltage charge for a considerable time. In my tube designs, each removable PCB has its own HT discharge  resistor built in and there is also one in the power supply.

Take great care whilst conducting these experiments.

Cheers

Ian

 

[kambo]

re measured with new resistors reading 1k2
DC measures 305 - 220

 

[ruffrecords]

re measured with new resistors reading 1k2
DC measures 305 - 220

That is more like it. 300V into 1K2 is 250mA. That is a decent HT current.

Cheers

Ian

 

[kambo]

Mmm, 240V / 1.25K is only 192mA but the datasheet claims it can do 500mA with the current adj. full CW. So something is a little off.

figured out  :
i thought i was paralleling 2 x 5k resistors to my other 2x5k set, but apparently resistors were 1k  ???
so actual load resistor was around 350ohm...  (i must have measured after i burnt them...)
680mA. 


edit:
oh other set was 2500r... they all damaged from extreme heat  ;D

500r paralel to 2500r = 416ohm
240/416=576mA

edit-2: typo

 

[ruffrecords]

figured out  :
500r paralel to 2500r = 416ohm
240/416=576mA

edit-2: typo

So it looks like it does what it says on the tin which is 305V up until 500mA, then as the current draw increases the voltage starts dropping. So it should be good for at least 400mA at full volts. Interesting. The MK III tube mixer I am planning has 14 modules each drawing about 25mA which is a total of 350mA. I already use Mean Well for the heater supplies. If I found a small 48V one for phantom power it could be SMPS all round.

Cheers

Ian