Trying to repair mains switch mode power supply - Bamboozled!!

Cheers for joining!

[@viccurtis7448]

@barevids looks like the main supply is not starting up after the initial kick start from the series dropper supply, or the maintenance supply from the auxilliary winding is not working. I would check the capacitor that probably runs from one end of the primary winding (opposite end to the driver transistor connection) back to the centre point between the two bulk capacitors. In this configuration the switching caps alternately switch their end of the winding so it is connected to the +ve and -ive high voltage referenced to the half voltage point via that cap. Common configuration in ATX power supplies and a frequent failure point.

[@darrenmurphy6251]

what you have done is make a power conditioner , a wein bridge oscillator at 50hz something like a 150w mosfet linear class ab amp without ouput bias (dont care about zero cross distortion ) then a torroidal mains transformer with primary /secondary swapped ,cant remember what ac volts the secondary was but used to make loads of them some for conditioning some for more accurate turntable sync on ac syncronous motors worked well but horrendously inefficent max load about 60w-70w !!

[@First2ner]

For the future: if you have any high voltage supply, in 100-130Vdc range.. you can use that to power scope, which will mean, that because supply is insulated, scope will be floating comparte to mains, so you will be able to use it as hand held, connect ground of probe and get clear signals... but only one potencial (which can be anything, even AC)

[@barevids]

Not a bad idea 😀

[@First2ner]

@@barevids also one more thing. If you have that kinda DC supply, apply that voltage directly on main caps, give you a lot of control and current limit if supply has it. You bypass any PFC stage,...

[@barevids]

@@First2ner I don't currently have 300+vdc supply but it's a great idea to have as I will be working on a lot more switchmode supplies in the future!

[@First2ner]

@@barevids i have old HP supply, model 6299a, that goes 130v full scale and that is enough for most if not all switching supplys/ amps to power switching stage

[@barevids]

@@First2ner interesting, most bulk rails I've seen are 300-400v for correct operation

[@POrscheTargag]

Any way I can send my JL Audio Amp to you for repair? It won't work until it heats up. Makes a bunch of popping noises and once it heats up it seems to work. What should I use to clean Switches with? How can I contact you? Thanks

[@barevids]

Are you in the UK?

[@POrscheTargag]

@@barevids I am not. Maybe I describe what Amp is doing and you can walk me through how to fix it. I can pay you for your time. Or maybe I could send it to you. Going to try to clean Switches to start. Can I use contact cleaner for this? Do you have a name of your company so I can Email you direct? If not I can give you my Email. You are a genius at what you do !!! Thanks for responding

[@dannyfreitas2120]

what is the biggest Class AB anp for car and it sounds amazzing?

[@barevids]

Lw audio 800.2