02-10-2017, 09:07 PM
Just a quick word on how I am currently providing my 50V supply for the rod tubes.
Having been interested in lower voltage operation of valves for some time I have several power supplies about but none of these is very small. Just prior to starting work with rod tubes I put together a small invertor powered via a couple of AA cells which gave around 60V out but only upto 1mA so Ok for one tube but rather limited!
Currently I am using the MT3608 board (as shown in the photograph). These are available online for around £1 each. I use two of them in series, each set to around 25V to give 50V post filtering. I use a capacitance multiplier for electronic filtering. This appears to reduce noise on the output by a factor of 10 (roughly seen on the oscilloscope, but obviously not an exact method).
This is the quoted spec:
Input voltage: 2V ¨C 24V
Output voltage: 5V ¨C 28V
Max output current: 2A
Efficiency: >93%
Dimension: 36mm x 17mm x 14mm
Looking online, I have seen that people have had problems with these modules, but I find them Ok. The voltage setting is a little harsh. The pot seems incorrect as multiple turns give little change, then change comes rapidly. Many people seem to have pumped 12V in without setting first, the output voltage at that point being below the input, which has maybe caused their units to burnout. I set with 6V in which went Ok. My method, when using in series, is to set the output voltages separately first.
Shown is the module, my test supply which also includes a regulator for 1.24V, and a unit just holding the HT supply and smoothing (this one probably for the pantry Tx). Also my block diagram.
Thus far I have had no issues, but time will tell. The units are small enough to fit almost anywhere. It will be just if any switch mode interference caulses problems, but when testing my modulator no problems were apparent. I very roughly measured efficiency and found it to be around 70%. I will perhaps have a closer look but it's still probably better than I could easily achieve. I have tested to tens of mA but do not forsee use anywhere near it's limit at the moment.
Having been interested in lower voltage operation of valves for some time I have several power supplies about but none of these is very small. Just prior to starting work with rod tubes I put together a small invertor powered via a couple of AA cells which gave around 60V out but only upto 1mA so Ok for one tube but rather limited!
Currently I am using the MT3608 board (as shown in the photograph). These are available online for around £1 each. I use two of them in series, each set to around 25V to give 50V post filtering. I use a capacitance multiplier for electronic filtering. This appears to reduce noise on the output by a factor of 10 (roughly seen on the oscilloscope, but obviously not an exact method).
This is the quoted spec:
Input voltage: 2V ¨C 24V
Output voltage: 5V ¨C 28V
Max output current: 2A
Efficiency: >93%
Dimension: 36mm x 17mm x 14mm
Looking online, I have seen that people have had problems with these modules, but I find them Ok. The voltage setting is a little harsh. The pot seems incorrect as multiple turns give little change, then change comes rapidly. Many people seem to have pumped 12V in without setting first, the output voltage at that point being below the input, which has maybe caused their units to burnout. I set with 6V in which went Ok. My method, when using in series, is to set the output voltages separately first.
Shown is the module, my test supply which also includes a regulator for 1.24V, and a unit just holding the HT supply and smoothing (this one probably for the pantry Tx). Also my block diagram.
Thus far I have had no issues, but time will tell. The units are small enough to fit almost anywhere. It will be just if any switch mode interference caulses problems, but when testing my modulator no problems were apparent. I very roughly measured efficiency and found it to be around 70%. I will perhaps have a closer look but it's still probably better than I could easily achieve. I have tested to tens of mA but do not forsee use anywhere near it's limit at the moment.
