Bonfigl
14-04-2022, 09:04
Good morning everyone,
After building a clone of the kondo M77, which is electrically finished but I haven't built the case yet (don't worry I'll post everything in the dedicated post https://theartofsound.net/forum/showthread.php?63885-This-guide-is-to -help-you-build-the-DOUK-KSL-M77-Preamp-clone-kit), I decided to build a tube power amp based on the Radford STA-35.
It all started when I read this article https://blog.ampliekit.it/index.php/i-nostri-kit/14-kh-021-radford-sta-35-dual-mono, I decided to design the schematics on fusion360 then I generated the gerber files and finally I made the PCBs by JLCPCB.
Attached you can find the wiring diagrams and some photos of the finished board.
Everyone ready!!! I connect the power transformer, the output transformers, I connect an 8 Ω resistor as a load on the secondary of the T.U. and make tension without valves (the T.U. is produced by Toroidy.pl and I am attaching the photos)
It didn't explode !! :) All voltages are fine.
I decide to insert the valves, I energize and immediately the high voltage fuse blows (Vaa in the diagram), I discharge the capacitors, I change the fuse and try to burn again.
I check all the circuit and the components and they are all ok, I give voltage without the final tubes and the fuse does not burn, I have tried to change the final tubes, and with all the fuse burns (2 + 2 EL34 Tung-sol and 2 JJ) .
If I measure the voltages on the sockets of the amps without the tubes mounted and with the bias at zero I read the following values:
PIN 3 465V
PIN 4 465V
PIN 5 -59V
Do you have any suggestions why I am going crazy to solve this problem and I cannot find a solution.
You can find the wiring diagrams and photos at the following link https://drive.google.com/drive/folders/17wr34KiBkkMsO7Md7qEI8U4RoYIbVnn6
Thank you so much everyone in advance
PS in a moment of desperation I mounted a 1 A fast fuse and that too blew.
Luca
After building a clone of the kondo M77, which is electrically finished but I haven't built the case yet (don't worry I'll post everything in the dedicated post https://theartofsound.net/forum/showthread.php?63885-This-guide-is-to -help-you-build-the-DOUK-KSL-M77-Preamp-clone-kit), I decided to build a tube power amp based on the Radford STA-35.
It all started when I read this article https://blog.ampliekit.it/index.php/i-nostri-kit/14-kh-021-radford-sta-35-dual-mono, I decided to design the schematics on fusion360 then I generated the gerber files and finally I made the PCBs by JLCPCB.
Attached you can find the wiring diagrams and some photos of the finished board.
Everyone ready!!! I connect the power transformer, the output transformers, I connect an 8 Ω resistor as a load on the secondary of the T.U. and make tension without valves (the T.U. is produced by Toroidy.pl and I am attaching the photos)
It didn't explode !! :) All voltages are fine.
I decide to insert the valves, I energize and immediately the high voltage fuse blows (Vaa in the diagram), I discharge the capacitors, I change the fuse and try to burn again.
I check all the circuit and the components and they are all ok, I give voltage without the final tubes and the fuse does not burn, I have tried to change the final tubes, and with all the fuse burns (2 + 2 EL34 Tung-sol and 2 JJ) .
If I measure the voltages on the sockets of the amps without the tubes mounted and with the bias at zero I read the following values:
PIN 3 465V
PIN 4 465V
PIN 5 -59V
Do you have any suggestions why I am going crazy to solve this problem and I cannot find a solution.
You can find the wiring diagrams and photos at the following link https://drive.google.com/drive/folders/17wr34KiBkkMsO7Md7qEI8U4RoYIbVnn6
Thank you so much everyone in advance
PS in a moment of desperation I mounted a 1 A fast fuse and that too blew.
Luca