@manniraj
Those input caps look very familiar 😉.
Consider trying something equally budget friendly like the Cornell Dubilier 940C series available at Mouser. I remember member @pinnocchio liking them quite a bit!
Best,
Anand.
Those input caps look very familiar 😉.
Consider trying something equally budget friendly like the Cornell Dubilier 940C series available at Mouser. I remember member @pinnocchio liking them quite a bit!
Best,
Anand.
Yes Anand, I think I got these caps from you if I am not mistaken 😉
I just wanted to clean up my parts bin for this amp build that too many parts are getting piled up. Will check the CDE 940C too and keep in my cart for future usage.
Thanks
I just wanted to clean up my parts bin for this amp build that too many parts are getting piled up. Will check the CDE 940C too and keep in my cart for future usage.
Thanks
Progress metal work done using makerbeam. Is the biasing similar to original aleph J when using IRFP150 and using this layout from @RainfallSky
Thanks
Thanks
Ok reading this thread I see people have set to 1.6A bias using 0.22R but with top fet being Semisouth R100. I will aim for the same but with top and bottom fet being IRFP150
First power up with dim bulb tester passes glows and immediately goes all the way dim. Offset is full rail voltage of 25.5vdc and bias across both the 0.22 resistors is 0mV. Using 100k for offset and 2k for bias rotating nothing happens. Checked for transistor shortages and all BC and IRFP150 seems to be fine.
Manniraj,
2K pot should be for offset. 100K pot should be for bias. Please double check and verify. Did you preset the pots prior to soldering?
Verify all transistors are appropriately placed and are the proper type. 2SJ74’s for Q1A/Q1B, Q2 is BC560 or equivalent, Q3 is BC550 or equivalent.
Verify proper voltage rails are connected appropriately. It’s easy to accidentally switch V+ for V- and vice versa.
Verify IRFP150 Fets are properly isolated.
I do recommend using the HBR resistor…a value of 10-15 ohms is good if using unbalanced input.
Best,
Anand.
2K pot should be for offset. 100K pot should be for bias. Please double check and verify. Did you preset the pots prior to soldering?
Verify all transistors are appropriately placed and are the proper type. 2SJ74’s for Q1A/Q1B, Q2 is BC560 or equivalent, Q3 is BC550 or equivalent.
Verify proper voltage rails are connected appropriately. It’s easy to accidentally switch V+ for V- and vice versa.
Verify IRFP150 Fets are properly isolated.
I do recommend using the HBR resistor…a value of 10-15 ohms is good if using unbalanced input.
Best,
Anand.
Both LEDs were lit so that is a sign that V+ and V- were connected correctly. Offset at 25V and no voltage across the source resistor indicate no current was flowing.
The 100k pot should be at R27. Connect a volt meter to the gate and source pins of Q5 and another meter to the gate and source pins of Q7. What are the voltage readings at Q5 and Q7? If you have another meter connect it across R18 to monitor current.
If you adjust the pot at R27 does the voltage (Vgs) at Q5 change? Can you adjust it to about 4V?
If you adjust the pot at R7 does the voltage (Vgs) at Q7 change? Can you adjust it to about 4V?
If the pot adjustments can get Vgs of both mosfets to about 4V, then it is working as it should. Change positions of the meters to measure offset and bias and adjust for proper offset and bias.
The 100k pot should be at R27. Connect a volt meter to the gate and source pins of Q5 and another meter to the gate and source pins of Q7. What are the voltage readings at Q5 and Q7? If you have another meter connect it across R18 to monitor current.
If you adjust the pot at R27 does the voltage (Vgs) at Q5 change? Can you adjust it to about 4V?
If you adjust the pot at R7 does the voltage (Vgs) at Q7 change? Can you adjust it to about 4V?
If the pot adjustments can get Vgs of both mosfets to about 4V, then it is working as it should. Change positions of the meters to measure offset and bias and adjust for proper offset and bias.
You need to connect HBR either with a wire or 10 Ohm resistor.
This is the only place where power GND connects input GND.
Make sure R0 jumper not touching board Greek pattern, its conductive.
You need some spacing for this juper from the board.
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Those are small heatsinks. Even with the makerbeam spreading out the heat a little, they will probably get pretty hot with 1.6A bias current. Try 1.2A to start, then dial up the current once the amp is functional.
@TungstenAudio these are Conrad sinks 350/150/50mm I thought should be good for testing the amp boards
Ok success put a jumper on the HBR and now everything is perfect 👍
Removed bulb tester and set the bias to 350mv and offset is stable at 2mv
Removed bulb tester and set the bias to 350mv and offset is stable at 2mv
Did you check thath R0 jumper wire is not touching the board?
I sim for mishaps and it seems worst thing happen is Q1B will start to dissipate 250mW which is a lot.
I sim for mishaps and it seems worst thing happen is Q1B will start to dissipate 250mW which is a lot.
Doesn’t look like it is touching, zooming on his picture (from post 423):
Best,
Anand.
Best,
Anand.
Yes @RainfallSky ususlly when I put a jumper I raise a bit to make sure when desoldering it’s easy task. It helped here and both the boards I have it raised so I am good rock stable bias of 352mv and 0.02mv offset after 30 mins 👍
Listening to my AJ SS now. Modded AJ Zen boards. Pretty smooth sounding now, first listen after last mods. Iq maxed to 1A8+ (not able to get it higher now matter what changes I made so MZM said «stop!». Relevant changes: SS-gate to JFET drain resistor 100R R26, shorted SS source resistor so no degen, offset resistance circuit of 500R total (reduced from 1k25 total), pin sockets for R24-experimentation - 1k5 at the moment, 1k2 was both forward and a bit harsh. Much nicer now with a tad more AJ CCS modulation). Also, C1 shorted.
Probably positive phase 2nd now, very nice. Other relevant improvements: tighter bass, more hf extension, even more liquid, and no chance of falling asleep. Speakers not there.
Just sharing if anyone is looking for the info.
Hugz,
A
Probably positive phase 2nd now, very nice. Other relevant improvements: tighter bass, more hf extension, even more liquid, and no chance of falling asleep. Speakers not there.
Just sharing if anyone is looking for the info.
Hugz,
A
Second channel is acting a bit weird need to investigate further. With bulb tester they are glowing not so bright and the bias I could dial to 300mv and offset to 50mV. But the negative rail led is not switching on. Also observation is that both the rails after powering up dropping to +/-9.9vdc
