Two days ago, the right channel blew. While playing at a soft volume at night, I heard a "pop" and then total silence. Good thing the RTR SSR and SMPS shut things down.
Upon repairing, I found the output mosfets shorted, but no sign of any punctured or burn marks on them.
I replaced those outputs and readjusted the bias. Nothing else was found to be faulty.
The amp is singing now!
My pcb is the REV1, may I know if I should do the R39 and R40 mods?
a) How important are they? And what do they do?
b) Any reason why mosfets fail while playing at soft volume? I am on +/- 53Vdc rails.
Thanks
Upon repairing, I found the output mosfets shorted, but no sign of any punctured or burn marks on them.
I replaced those outputs and readjusted the bias. Nothing else was found to be faulty.
The amp is singing now!
My pcb is the REV1, may I know if I should do the R39 and R40 mods?
a) How important are they? And what do they do?
b) Any reason why mosfets fail while playing at soft volume? I am on +/- 53Vdc rails.
Thanks
Attachments
Did you consider oscillation and the critical coupling through the thermal-pads - as outlined and discussed previously?
Hi Meanie, sorry to hear about your damaged V4H.
I had an oscillation issue when my V4H
was a newborn. I performed this mod (ver1 pcb’s) outlined by Shaan and haven’t had a problem in over 3.5years of almost daily service. For peace of mind I did install speaker DC Protection boards.
I hope you have a speedy and successful repair! 😉
From Shaan’s post# 625:
The Solution:
R27,R29 and R28,R30 i.e. the gate resistors (initially 330R and 220R), all increased to 560R (and gate-source capacitors removed).
I had an oscillation issue when my V4H
was a newborn. I performed this mod (ver1 pcb’s) outlined by Shaan and haven’t had a problem in over 3.5years of almost daily service. For peace of mind I did install speaker DC Protection boards.
I hope you have a speedy and successful repair! 😉
From Shaan’s post# 625:
The Solution:
R27,R29 and R28,R30 i.e. the gate resistors (initially 330R and 220R), all increased to 560R (and gate-source capacitors removed).
Thanks Vunce and Norgaard!
I will hook up a scope and check if any oscillations occur or not.
Will definitely replace those gate resistors to be safe.
I will hook up a scope and check if any oscillations occur or not.
Will definitely replace those gate resistors to be safe.
I am using SMPS which provided me exactly +/-55Vdc.
As for linear PS, your transformer should be 40Vac (multiply 1.4142) which will give about +/- 56Vdc.
Please check your line input AC voltage, most transformers will output much higher secondary than rated.
So final voltage may be a lot higher than +/- 56Vdc...
As for linear PS, your transformer should be 40Vac (multiply 1.4142) which will give about +/- 56Vdc.
Please check your line input AC voltage, most transformers will output much higher secondary than rated.
So final voltage may be a lot higher than +/- 56Vdc...
I am using Cresnet's smps AKA Micro-audio 600w model.
https://www.diyaudio.com/community/threads/audio-smps-units-for-sale.281413/
https://www.diyaudio.com/community/threads/audio-smps-units-for-sale.281413/
Hi, isn't clear to me if I must use Shaan's post# 625 or post 644 solution "Get 6 nos. 47pF/500V capacitors, ceramic or silver mica (12 nos. for two channels). These can be the same caps used for C5 and C6. Also get four 100ohm / 0.25W resistor for each channel."
I did it and the amp is singing that it's a pleasure to listen to it. And I must say that it's really silent when not playing music.
Thank you Shaan
Hi shaan,
Any recommendations on buying J1 and J2 the female jumper shunts. Many choices makes it confusing 🤔
Thanks for the help,
MM
Any recommendations on buying J1 and J2 the female jumper shunts. Many choices makes it confusing 🤔
Thanks for the help,
MM
doesn't really matter, as long as they are 2.54mm spacing. Pick whichever you like, type/color/height or most important - price. You could create a solder bridge and the amp would work the same.