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OK, I´ve found the component who was leaking, after opening lines, measuring and so on I removed U103 (opto) I getting the voltage up.
But I think there is still a problem because I tested and again IC, Mosfets and some resistors burned.
Now without the optocoupler I get 17,6V at pin 12. I think now this is too much because datasheet says as a maximum 16,6V as Vs. May be this was the origin of all problems, power supply for PWM IC was always too near from the maximum allowed. Zener ZR101 then conducts so on pin 9 of IC (enable2) I get 5,6V when the maximum allowed is 5V.
I think your schematic looks suspect.
It is a half bridge converter.
What is L103 for?…ive never seen that used in other things.
Howcome L6598 is driving the upper fet directly?…surely L6598 cannot do that?..(too high voltage)
C201 and C202 are the wrong side of the output inductors.
You have no fast current sense in your power FET loop…this is very very bad.
Why have c241 and c240 got resistors in series with them…I am guessing this is because it’s a voltage mode power supply and the designer was trying to diminish the output double pole by lowering the esr zero frequency….this then gives him/her only a single output pole to compensate
C114 and c113 are bad……they are going to result in excess noise and dissipation
Is q401 to converter from uk to usa mains….if so then the L103 shouldnt be there.
Wheres the input MOV?
Wheres the input fuse?
Wheres the startup inrush limitation
D209 and D210 look suspect….they look like shouldnt be there.
You have no output divider connected to your “+v” node…you need an output divider so you can regulate vout
You seem to have an opto and a 2k resistor giving “amp-fault”..that looks wrong.
The schematic is messy, and its hard to see output ground….it should all be at same level ideally, so its easy to make it…your circuit takes a long time to analyse…its like a consultancy did it and deliberately made it hard to look at so you cant easily see all the faults.
This is one of a few times I can work with schematic and documentation so for me is nice to have it, even if design of SMPS is not good. I wish I always have documentation to repair units. I found the documentation at Internet.
On Monday I receive components to be replaced so I´ll keep you updated.
I realise now its a resonant converter......C240&C241 should be swapped with c202&c201....they are the wrong way round like they are now......your output filter lc resonance frequency should be more than three times the converter bandwidth otherwise it go unstable
I presume your trxformer has significant leakage inductance inside it?...I hope so , because if not then it is very bad for the psu. What is the leakage value.....the rezonent frequency of the leakage and the 18nf capacitor should be equal to the switching frequency at your nominal max loading and nominal vin.
there is no current sensing anywhere in the schem...so if you get short on +v,-v rails that psu is going to suffer......I hope L6598 has overload/sht circuit protection.
There IS NO OVERLOAD OR SHORT CCT PROTECTION MENTIONED IN THE DATASHEET OF L6598 (sorry about caps)....so that looks like a bad design to me...surely the EN pins should be used in some kind of current sense shutdown
also what is the power output?....because those output caps that you have are very very small.....I would say they are going to burn out...bass guitar amps usually are at leat 300W output...and if its a class a amp then that will be bad...if its class d bass then that's better, but still those output caps are too small...unoless they are film type?...and not electrolytic
Finally I have solved the problem, the opto was the leaking component so after replacing Q101, Q102, Q103, Q104, U101, ZR101, U103, R101, R102, R103, R104, D105, D108, C119 the power supply works correctly. Thank you for all your help to solve the problem.
CONGRATULATIONS 2pac... there's nothing quite like the satisfaction of repairing a piece of gear by finding an obscure failure on some component.
I think I've seen optos go leaky, but it's always going to be a tricky one to find.
I know what you mean about schematics and manuals too - it usually feels like a victory to find one, no matter how messy or illegible! And is fairness to Bose, that service manual is very informative by standards.
Thanks Tomizett, any help is always good, I work alone in my company repairing marine and industrial electronics almost always without schematics, so sometimes is hard.
With schematics and documentation you can learn a lot, as for example reading the theory of operation of this Bose Subwoofer, but sadly nowadays is difficult to work like that...
Would be good to open a post to know where are working all these people from the forum, I see very clever and prepared people, nice to know their experience in electronics field.
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