hello ZM,
i am measuring a bare pcb without the SIT or M1 device connected yet.
on IRF source it is 6,3v reading on my dmm
on SIT pcb, with P2 set to max (3K3 on R10), i only can get -4,5v at the gate pad.
i try to uninstall R10, still the same -4.5v at the gate pad.
is this safe to connect the SIT and M1 device with this number??
i plan to use 2sk180
thanks.
i am measuring a bare pcb without the SIT or M1 device connected yet.
on IRF source it is 6,3v reading on my dmm
on SIT pcb, with P2 set to max (3K3 on R10), i only can get -4,5v at the gate pad.
i try to uninstall R10, still the same -4.5v at the gate pad.
is this safe to connect the SIT and M1 device with this number??
i plan to use 2sk180
thanks.
Last edited:
I revisited the humming Singing Bush this week. After gathering parts over ~1 year I finally got to this project in the queue. There have been a LOT of projects in the past year....
I swapped the donut for a custom Toroidy. Changed to PCB based PSU. Swapped 2SK182ES for THF51S. Reset pots and went through startup procedures. It seems with THF's the fire-up is much easier than I remember. Anyway, I'm still getting some hum. I can't recall if it was worse than before. I took a long look at this thread and followed Rick's epic saga with much interest. Voila, I'll check all solder joints (one wire is particularly twitchy) and then dress up the wires. Hours later I have rebuilt one channel. Found a solder joint I wasn't happy with. All new wires. Twists. Dressed. Time to fire up.
BA-DA-BOOM + Smoke!!!!!! Rookie mistake - all wiring on boards was good. PSU GND & + were reversed!!! I was in a hurry, and I paid the price.
I took voltage measurements of the good channel and bad channel. Topic for a future post.
Fast forward a few hours - I swapped in a fresh THF51S and spare boards that I was planning to use on a buddy's build.
Side note: My buddy has my 2nd SissySIT. The only way I will get the SissySIT back is when I deliver a Singing Bush...
First priority - get amp working. Max Iq is can get is 2.03A. I have run out of P1 on the mu/mosfet board. Should I swap in a different R1? Maybe a 5k? 7k? I see good Vds voltage on SIT.
2nd priority - figure out what blew up on the old boards and replace the components. That will be a future post.
Good news is that twisting and wire dressing has hum down significantly in the rebuilt channel. When I get the bias figured out I'll re-wire and check all solder on the other channel. And be careful in power-up. And finally I'll get to distortion analysis.
I swapped the donut for a custom Toroidy. Changed to PCB based PSU. Swapped 2SK182ES for THF51S. Reset pots and went through startup procedures. It seems with THF's the fire-up is much easier than I remember. Anyway, I'm still getting some hum. I can't recall if it was worse than before. I took a long look at this thread and followed Rick's epic saga with much interest. Voila, I'll check all solder joints (one wire is particularly twitchy) and then dress up the wires. Hours later I have rebuilt one channel. Found a solder joint I wasn't happy with. All new wires. Twists. Dressed. Time to fire up.
BA-DA-BOOM + Smoke!!!!!! Rookie mistake - all wiring on boards was good. PSU GND & + were reversed!!! I was in a hurry, and I paid the price.
I took voltage measurements of the good channel and bad channel. Topic for a future post.
Fast forward a few hours - I swapped in a fresh THF51S and spare boards that I was planning to use on a buddy's build.
Side note: My buddy has my 2nd SissySIT. The only way I will get the SissySIT back is when I deliver a Singing Bush...
First priority - get amp working. Max Iq is can get is 2.03A. I have run out of P1 on the mu/mosfet board. Should I swap in a different R1? Maybe a 5k? 7k? I see good Vds voltage on SIT.
2nd priority - figure out what blew up on the old boards and replace the components. That will be a future post.
Good news is that twisting and wire dressing has hum down significantly in the rebuilt channel. When I get the bias figured out I'll re-wire and check all solder on the other channel. And be careful in power-up. And finally I'll get to distortion analysis.
Thanks for the quick response ZM! Do you sleep?
I went to my stash of resistors and swapped in a 4k7 and it easily biased up to 2A3. Next steps: dress wires on the other channel. Then cook and test & tune distortion.
Today has proven that my Hakko desoldering gun is perhaps the best tool purchase in the past 12 months.
ZM - I took some voltage measurements of the good and bad channels. These are not exact, but probably close enough for this exercise.
To repeat - I attached PSU + and GND in reverse. I saw a current surge on the ammeter, and some smoke from ???? before I killed the power. I do not know what is blown up.
Any ideas of what I will be replacing on the bad boards? I have 510's in my spare parts. Maybe zeners. No 4N37's. No tiny JFET critters...
To repeat - I attached PSU + and GND in reverse. I saw a current surge on the ammeter, and some smoke from ???? before I killed the power. I do not know what is blown up.
Any ideas of what I will be replacing on the bad boards? I have 510's in my spare parts. Maybe zeners. No 4N37's. No tiny JFET critters...
hard to think in early morning, while just starting first coffee
first check all parts for interelectrode shorts, using buzzer DMM test**
at first, I see that neg bias circuit is OK, same as mosfet above JFets and JFets....... which is good
**if in doubt about part, remove it from pcb and retest
connect relay contacts in parallel to speaker - to keep output shorted while output cap is filled up
see https://www.diyaudio.com/community/...-pt-2-n-channel-assembly-by-mighty-zm.385977/
though, you're first one to have that sort of problems
btw. do you have any resistor across output pads ( before speaker delay)
try putting 100R 1/w and see what's happening after 5sec delay
if there is no resistor , there is no path for cap to fill, and it is simply waiting for speaker connection to start topping it
see https://www.diyaudio.com/community/...-pt-2-n-channel-assembly-by-mighty-zm.385977/
though, you're first one to have that sort of problems
btw. do you have any resistor across output pads ( before speaker delay)
try putting 100R 1/w and see what's happening after 5sec delay
if there is no resistor , there is no path for cap to fill, and it is simply waiting for speaker connection to start topping it
