Vox VT50 - digital board power cycling

[jondoe]

So this morning I have disconnected the transformer from the bridge rectifier and directly connected 6.4v to it's +/- legs, thanks for confirming I could do that g1, I must admit I've never tried it before. It's a bit of a Heath Robinson affair, with a 12v lead acid into boost/buck convertor, but it's working.

The digital board is working as of right now, I've left it all powered up with an audio source playing at moderate volume to see if this changes over time, which has been the case before. Total power draw is still at 0.6A, which is within the 1.5A max of the bridge rectifier.

If this continues to work I'll order up a replacement bridge rectifier, along with changing the filter caps while I'm there, getting the power board out is a pain in the ass so the less times I have to do with the better

[Jon Snell]

Sounds like you are on the right track. I always try to keep it simple by removing a section at a time and work backwards from the output to the input.
It is probably the capacitor and/or the diodes making up the bridge or bridge block as it seems the regulator and Digi Board is OK.

[jondoe]

I do feel like progress is being made, thank you for the support. I left it running all day, occasionally cycling the power, or leaving it off for a minute and firing it back up again, it never missed a beat and kept chugging away fine. I did test how low the voltage needs to drop for the digital board to malfunction, lowering it to about 5.2v causes the board to cycle just like the original fault.

A new rectifier is coming in the post and I have the cap I need already, fingers and toes crossed this resolves the problem. I'll let you know how I get on

[jondoe]

New rectifier and capacitor fitted, three days of on/off testing and the fault hasn't returned.