Hi
As mentionned in the title, I accidentally inverted the power delivery while building the B1 Nutube Preamp. Lasted for 20/30sec, time for me to figure it out.
I remplaced the capacitors of the power supply section.
With the correct polarity, i get 24V across resistor (T1, 1st measurement)
But the 9.1V diode 1N4739 at T4 doesn't give me anything and the 270ohms resistor is warming up very fast.
So, i happen to have at disposal some 1N4740 which are the same family but would give 10V if not mistaken.
Hence my question
1) Can i remplace the 1N4739 by a 1N4740
-short term just to test if power is now OK and if this diode is the only thing to change
-even long term if it works and it doesn't impact too much the circuit
2) Should i remplace others components (resistors) because they might also have gone bad / have degraded ? (wouldn't think so, but since i will be changing components...)
Newbie question for sure, but if somebody has a quick answer, that would be very helpful.
(if not, would wait for the next online order of components to have the right remplacement)
Take care and have a nice day.
As mentionned in the title, I accidentally inverted the power delivery while building the B1 Nutube Preamp. Lasted for 20/30sec, time for me to figure it out.
I remplaced the capacitors of the power supply section.
With the correct polarity, i get 24V across resistor (T1, 1st measurement)
But the 9.1V diode 1N4739 at T4 doesn't give me anything and the 270ohms resistor is warming up very fast.
So, i happen to have at disposal some 1N4740 which are the same family but would give 10V if not mistaken.
Hence my question
1) Can i remplace the 1N4739 by a 1N4740
-short term just to test if power is now OK and if this diode is the only thing to change
-even long term if it works and it doesn't impact too much the circuit
2) Should i remplace others components (resistors) because they might also have gone bad / have degraded ? (wouldn't think so, but since i will be changing components...)
Newbie question for sure, but if somebody has a quick answer, that would be very helpful.
(if not, would wait for the next online order of components to have the right remplacement)
Take care and have a nice day.
Should be ok to sub the 10V Zener to test the other components briefly.
Check all the power supply components.
However, it's probably best to replace them all, including the capacitors.
Check all the power supply components.
However, it's probably best to replace them all, including the capacitors.
The 9.1V zener sets the Nutube filament power supply voltage. Subbing a 10V zener is definitely not a long term fix.
For testing you can lift one leg of the 475R resistor at the Nutube filaments so you don't power up the filaments and overstress them. Note that this would for testing the power supply. With no filament voltage the Nutube would not be functional.
For testing you can lift one leg of the 475R resistor at the Nutube filaments so you don't power up the filaments and overstress them. Note that this would for testing the power supply. With no filament voltage the Nutube would not be functional.
Thank you very much!
Only the power supply components were installed so far, no NuTube on the board yet.
So, I will order a new 1N4739 9.1V later and change what's needed to change
Thanks and have a nice day
Only the power supply components were installed so far, no NuTube on the board yet.
So, I will order a new 1N4739 9.1V later and change what's needed to change
Thanks and have a nice day
Ok. The schematic is the one from the https://guides.diyaudio.com/Guide/B1+with+Korg+Nutube/12
On top the power supply. Zener diode i am talking about is the one @T4, where i should measure 9.1V but have nothing.
Polarity inversion happened because i really inverter + and - at the power supply connection because...it was late and i didn't checked long enough.
While measuring, i could smell the capacitors a bit, stopped everything, capacitors were warms, not blown.
Voltage @H will later go to the Nutube (not installed), hence Ben Mah's comment.
On top the power supply. Zener diode i am talking about is the one @T4, where i should measure 9.1V but have nothing.
Polarity inversion happened because i really inverter + and - at the power supply connection because...it was late and i didn't checked long enough.
While measuring, i could smell the capacitors a bit, stopped everything, capacitors were warms, not blown.
Voltage @H will later go to the Nutube (not installed), hence Ben Mah's comment.
Yes, will do.
Was just trying to see if there was a bit of leeway... not so.
Thanks all for the confirmation
Was just trying to see if there was a bit of leeway... not so.
Thanks all for the confirmation
Thanks.
You definitely need a 9.1V Zener there, since it directly feeds the delicate filament/cathode (it´s hair thin)
You might increase the 475 ohm dropping resistor value but why bother?, it´s easier to do it the right way.
Using it without Zener is suicidal . (for the Tube I mean).
Thanks for the many different suggestions.
Time to get a remplacement diode is no issue yet. I will combine it with others components i need but not available yet anyways.
Give me time to think and plan different others stuffs.
Have a nice day
Time to get a remplacement diode is no issue yet. I will combine it with others components i need but not available yet anyways.
Give me time to think and plan different others stuffs.
Have a nice day
Hi.
Just the final update. Zener diode and 270ohms resistance changed.
Input voltage from the power supply 24.4V (specs says 24V, but this is what it is)
Voltage at the diode 9.7V (build guide of B1 Nature suggests 9.5V. Guess it s ok given the 24.4V input)
This mistake was somehow a blessing in disguise (sort of...never good to invert voltage...) = i needed IRFP9240 for something also. The vendors i was used to could only get them in a few months. Went with another one that had the Zener diode and the IRFP9240 !
So, thanks for the recommendations / advices on my questions.
Have a nice day
Just the final update. Zener diode and 270ohms resistance changed.
Input voltage from the power supply 24.4V (specs says 24V, but this is what it is)
Voltage at the diode 9.7V (build guide of B1 Nature suggests 9.5V. Guess it s ok given the 24.4V input)
This mistake was somehow a blessing in disguise (sort of...never good to invert voltage...) = i needed IRFP9240 for something also. The vendors i was used to could only get them in a few months. Went with another one that had the Zener diode and the IRFP9240 !
So, thanks for the recommendations / advices on my questions.
Have a nice day