[SOLVED] Dumble ODS Oscillation

Hi All,

I've just completed the 3rd gen dumble build. Ive got a low end oscillation when turning on the standby switch which lasts for a second or two. Have others experienced this and if so how did you fix it? to my untrained ears it may be flyback voltage from the choke?

5 answers0 replies

5 Comments

henrikoning

Mar 25

Hi CaleySkinner, Nice build , looks good, I have a couple questions. Which Trafo s from TT did you use ? the TT transformers for 50w build or 100w build ?

most important for me , cause i am a happy good builder but no electronical engineer :) regarding the B+4 / B+5 , do i have to hardwire

B+4 > B+4 and B+5 > B+5 on the board ?

If you have some more inside out tips please let me know, i am on the begiining with the 3rd Gen amp.

Much apreciated.

Best regards, Henri

caleyskinner

Jul 02, 2023

This issue has also been resolved. Check my post about Ghost notes. I had two caps in the wrong location.

Andrea Antonello

Jul 02, 2023

Replying to

Great to know! Could you change the title to "[Solved] Dumble ODS Oscillation"? Thanks :)

Andrea Antonello

Apr 23, 2023

Hello Caley!

Can you expand on the type of oscillation you are experiencing? Would it be possible to post an audio sample?

Your build looks very neat and clean so i would exclude the obvious beginner mistakes.

Some quick checks:

- make sure all the jumpers indicated have been installed, there are some fiddly ones by the power caps

- double check your grounding scheme

This “motorboating” effect is normally caused by oscillation around the filter caps, so make sure you have the values of the resistor and caps right, the correct wiring+jumpers and report back. If it is still not solved, we can try increasing the resistance in the decoupling stage

Andrea

AA Electronics

caleyskinner

Apr 25, 2023

Replying to

Hi Andrea, I've checked over the board and components several times but cant find anything wrong. my grounding scheme differs slightly from the layout however i was recommended to do it this way by a local tech. The HT center tap goes to the - end of C19 and then one wire to ground, this was to help reduce noise, thats the only difference. As for the jumpers i can only see the one on the - end of C16.

Ill attach a video and sound clip of the noise, its a loud thud, followed by an low end oscillation, you can see the tubes illuminate and change simultaneously with the noise, like its reproducing the current inrush or something?

Thanks!