Thanks for the prompt though, unusually for me, I had noticed this. i was initially confused by the asterisks but it slowly dawned on me.
For the negative regulator are the suggested devices basically the same or is there a reason to select one over the other for a particular application?
Take care.
For the negative regulator are the suggested devices basically the same or is there a reason to select one over the other for a particular application?
Take care.
There are several suggested MOSFETs only because of recent supply shortages. They perform basically the same but pick SQP120N10-09_GE3, as it was used in enough successful builds by forum members.
New version with everything on one PCB is here:
https://www.diyaudio.com/community/...ctifier-rf-filter-and-super-regulator.420933/
https://www.diyaudio.com/community/...ctifier-rf-filter-and-super-regulator.420933/
@tombo56 Really excited about your dedicated single rail PSU. I haven’t had a chance to study the differences between the original R21 circuit and this new PSU, but is it possible to change any parts and/or values on the R21 to adopt the soft/start, ‘always regulated’ feature of the dedicated PSU?
It is possible, of course, but I’m not convinced that it is worth at all. That first 3 seconds of raw unregulated output are hardly any problem for amplifiers. Change would require one track cutting, one jumper, removal of seven components and change of one resistor value. PSRR would fall a little at low frequencies.
Fun fact is that development versions of R21 supply module were with soft start and always on regulation up to revision 1.3. To avoid any possibility of regulator failure, in whatever extreme conditions could it be used, I made final R21 version as is.
Fun fact is that development versions of R21 supply module were with soft start and always on regulation up to revision 1.3. To avoid any possibility of regulator failure, in whatever extreme conditions could it be used, I made final R21 version as is.
Yes, it’s probably worth it to keep as-is. I’ve just been thinking about the extra bit of reassurance the soft start offers when using depletion device like SIT in output. That said, it should never be a problem for me so long as I have a decent amount of capacitance before the reg, which gives my bias circuit time to come up first (it’s on a separate secondary/PSU).
Quick troubleshoot question, @tombo56 . I was making some adjustments to a voltage reg on my amp board and inadvertently lifted a copper trace. When I hard wired the connection I accidentally went to a ground node as opposed to the neg rail. On startup the reg started up, but the red light was flashing intermittently and I noticed a hot smell (nothing appears visually discolored.) In simulation, the bias voltage was reduced and the SIT begins passing considerable current. I fixed the erroneous connection and everything starts up fine, but the reg is now simply passing the raw rail voltage. Amp plays fine, just the presence of the 120hz hum. Green light displays as you would expect, but no action from reg and no red light.
Any obvious suspects that may be fried on the reg board?
Any obvious suspects that may be fried on the reg board?
Thanks for the quick reply! And, bingo, you're right – the mosfet is burned. I'll place an order for the mosfet right now. Any other obvious parts that could've potentially suffered from an over-current event?
Hard to guess as I don’t know what exactly was done wrong. MOSFET can take an extreme punishment (I’ve deliberately burned PCB with high current and all was fine after repairing PCB) but not prolonged very high power dissipation, as we can’t take away heat fast enough.
Nothing was done wrong with the reg board. The error happened on the amp board. The bias current runs through a buffer that takes its POS from the regulated supply and the negative from a separate, supply that uses an onboard 7912 (same configuration as Singing Bush). When I hooked the 7912 up incorrectly, it essentially dumped the negative voltage for the buffer. The -4v or so that I use for biasing the SIT went to near 0v. So, the 6-7 seconds that I had the amp turned on, the right channel was drawing a LOT of current.
If you burned 10 of them and give away your design for free then maybe the builders could sponsor you with a few new MOSFETs. Just an idea. Seems fair.
Ah, no need to even consider, although I've burned a lot more components. 😆
This is DIY where you can enjoy what other members share, and I did. I’m just returning the favor.
Or perhaps I just like inhaling the magic smoke, not ready to admit a problem. 🤣
