The power supply that is normally used (board available from the store.) Along with build guide.
Uses 8 off 10,000 - 15,000 uf caps.
50v is fine, but 1000uf is probably not enough for this amp's power supply.
https://diyaudiostore.com/collections/circuit-boards/products/universal-psu
Resolution to single dead channel question #4,822
To Gary and Zen Mod - I solved the issues. I had overstimulated the JFETs with my signal generator. My biggest concern was why there was no output signal and the repeated burn out of the R4 resistor. More pointedly, was there a greater systemic issue I needed to address?
The amp is now an exceptional asset to my sonic arsenal.
For fellow members of the "I'm still trying to figure this out" Club, here is what I deduced:
1. The original problem of no sound was most likely due to a poor connection to the input RCA jack. The Kimber hookup wire has a transparent sleeve under the external insulation that I suspect I did not fully remove and compromised my solder joint.
2. In my efforts to trace an input signal into the amp circuit, I most likely overwhelmed the JFETs with excessive voltage. I was using an 1 kHz Oscillator from Akitika. The maximum output is 1.5V and I cranked it up quite a bit, far past the 200 - 300mV suggested by Zen Mod. I have since measured the output and marked the levels to make sure I don't do this again.
3. The excessive input voltage fatally damaged the JFETs. I removed them and confirmed their demise. They are now added to my damaged goods wall of shame.
4. Since the JFETs were non-functional, far too much power was delivered to the R4 resistor that continued to burn out after repeated replacement with increasingly higher watt rating. They did their job.
5. I had the lower Idss Linear Systems JFETs purchase from the diyAudio Store in my boards. Currently the only Toshiba products are available at the suggested higher Idss. I contacted the diyAudio store to inquire if there were any concerns with having the different active devices (I assumed not, but I wanted to make sure I was not going to have odd output differences - none that I can tell so far). Elena put me in contact with "np" who seemed to know quite a bit and offered up some replacements.
6. After some back and forth emails, np had me measure a few things and made a few suggestions that confirmed that, yes I had cooked the JFETs and that the rest of the circuit was in good shape. Putting the Toshiba devices in fixed the problem. Yeah!
Thanks all
To Gary and Zen Mod - I solved the issues. I had overstimulated the JFETs with my signal generator. My biggest concern was why there was no output signal and the repeated burn out of the R4 resistor. More pointedly, was there a greater systemic issue I needed to address?
The amp is now an exceptional asset to my sonic arsenal.
For fellow members of the "I'm still trying to figure this out" Club, here is what I deduced:
1. The original problem of no sound was most likely due to a poor connection to the input RCA jack. The Kimber hookup wire has a transparent sleeve under the external insulation that I suspect I did not fully remove and compromised my solder joint.
2. In my efforts to trace an input signal into the amp circuit, I most likely overwhelmed the JFETs with excessive voltage. I was using an 1 kHz Oscillator from Akitika. The maximum output is 1.5V and I cranked it up quite a bit, far past the 200 - 300mV suggested by Zen Mod. I have since measured the output and marked the levels to make sure I don't do this again.
3. The excessive input voltage fatally damaged the JFETs. I removed them and confirmed their demise. They are now added to my damaged goods wall of shame.
4. Since the JFETs were non-functional, far too much power was delivered to the R4 resistor that continued to burn out after repeated replacement with increasingly higher watt rating. They did their job.
5. I had the lower Idss Linear Systems JFETs purchase from the diyAudio Store in my boards. Currently the only Toshiba products are available at the suggested higher Idss. I contacted the diyAudio store to inquire if there were any concerns with having the different active devices (I assumed not, but I wanted to make sure I was not going to have odd output differences - none that I can tell so far). Elena put me in contact with "np" who seemed to know quite a bit and offered up some replacements.
6. After some back and forth emails, np had me measure a few things and made a few suggestions that confirmed that, yes I had cooked the JFETs and that the rest of the circuit was in good shape. Putting the Toshiba devices in fixed the problem. Yeah!
Thanks all
First, congratulations on getting it working!
If I'm incorrect, then I welcome some pointers toward a better understanding, particularly if that diagnosis came from "np" or his mightiness.
I don't think that's very likely and/or I'm misunderstanding. I'm not saying this to correct you, but so that others don't think that feeding a 1V5rms signal at the inputs to their properly functioning F6 should cause it any harm / overwhelm their JFETs ... and I'd like to understand this a little better myself in case I'm completely off.
If I'm incorrect, then I welcome some pointers toward a better understanding, particularly if that diagnosis came from "np" or his mightiness.
IAIMH, Good points, and I'm not sure IF the F6 board was properly functioning. Hence my concern as to other underlying issues. As far as I can tell the 1.5V jolt from the oscillator induced the damage. I cannot say that it was the only reason. As I increased from what estimate to be about 200mA (I had leads across one of the input resistors) to much closer to 1.5V, that's when things popped. Could I have shorted something? Perhaps. My advice would be to go slow, not be over caffeinated, and if R4 burns out repeatedly, get some new JFETs.
JCB
JCB
^ First... I love the methodical approach. Second, I'm not the brightest bulb in even a DBT, so...
I didn't read everything about your previous issues.
But... Maybe what happened was...
JFETs are "normally closed". So, if one of your JFETs was bad for any reason upon installation (or some other reason)... then when power was applied to the circuit, if you consider one of the JFETs as a short from drain to source ... what's the most immediate path to GND through R4 for the positive (or negative) rail?
Edited to correct terminology - I don't know why I can't consistently get that open means no flow...
See... not the brightest bulb.
I didn't read everything about your previous issues.
But... Maybe what happened was...
JFETs are "normally closed". So, if one of your JFETs was bad for any reason upon installation (or some other reason)... then when power was applied to the circuit, if you consider one of the JFETs as a short from drain to source ... what's the most immediate path to GND through R4 for the positive (or negative) rail?
Edited to correct terminology - I don't know why I can't consistently get that open means no flow...
See... not the brightest bulb.
Last edited:
FQH44N10-F133 is in stock.
Can I use FQH44N10-F133 as output transistor instead of FQH44N10?
https://www.rocelec.com/part/01t4w00000PP5grAAD-FQH44N10F133
Can I use FQH44N10-F133 as output transistor instead of FQH44N10?
https://www.rocelec.com/part/01t4w00000PP5grAAD-FQH44N10F133