JVC THS9 Home Cinema System SMPS No outputs or standby power

[CapLeaker]

Re: JVC THS9 Home Cinema System SMPS No outputs or standby power

Maybe.

But surely it is only because the IC is out of circuit that the voltage gets to 37vdc, so with a new IC, the currently rated 25v one should be OK.

Or am I missing something?

Nope.

[rievax_60]

Re: JVC THS9 Home Cinema System SMPS No outputs or standby power

I have done a similar thing with the part still in circuit by connecting a bench supply directly to the HVDC rail. NO MAINS CONNECTION MUST BE MADE, just the bench supply.
An alternate start resistor has to be temporarily added.
It is best to have an oscilloscope.

[Percyveer]

Re: JVC THS9 Home Cinema System SMPS No outputs or standby power

In the interest of educating myself, and maybe others here, with the IC now removed, and if I put a 16vdc power supply across pins 3 & 4, Grd & VCC, on a functional IC what should happen?
I guess pins 1 and 2 source/drain switch should start oscillating on/off, or is the feedback circuit needed on start up?
In other words how do you test it, and is it possible without an oscilloscope.

Percy

[Percyveer]

Re: JVC THS9 Home Cinema System SMPS No outputs or standby power

Does any voltage briefly appear at any output rail when power is first applied after it has had a long rest?

No, I also tried cycling the power on/off to unlatch as mentioned in data sheet, but it had no effect.

[rievax_60]

Re: JVC THS9 Home Cinema System SMPS No outputs or standby power

Does any voltage briefly appear at any output rail when power is first applied after it has had a long rest?

[Percyveer]

Re: JVC THS9 Home Cinema System SMPS No outputs or standby power

Many SMPS ICs have Over Voltage Protection. If the VCC pin even briefly exceeds usually 25V, the IC will totally latch off and wont attempt a restart until totally powered down.

Thanks Rievax.
Yes the STR-G6651 has that feature.
Data sheet has been uploaded.

[Percyveer]

Re: JVC THS9 Home Cinema System SMPS No outputs or standby power

If I were replacing that 39uf cap I would go to 100 volts if you can get one

Maybe.

But surely it is only because the IC is out of circuit that the voltage gets to 37vdc, so with a new IC, the currently rated 25v one should be OK.

Or am I missing something?

[rievax_60]

Re: JVC THS9 Home Cinema System SMPS No outputs or standby power

Many SMPS ICs have Over Voltage Protection. If the VCC pin even briefly exceeds usually 25V, the IC will totally latch off and wont attempt a restart until totally powered down.

[sam_sam_sam]

Re: JVC THS9 Home Cinema System SMPS No outputs or standby power

If I were replacing that 39uf cap I would go to 100 volts if you can get one

[Percyveer]

Re: JVC THS9 Home Cinema System SMPS No outputs or standby power

Good to know, on that basis I will place an order, and wait for them to arrive.

[CapLeaker]

Re: JVC THS9 Home Cinema System SMPS No outputs or standby power

I have to say I have about a 85% success rate with ali.

[vinceroger69]

Re: JVC THS9 Home Cinema System SMPS No outputs or standby power

too be honest everything i have brought has worked so far.

[Percyveer]

Re: JVC THS9 Home Cinema System SMPS No outputs or standby power

aliexpress are a good company been having a fair few parts etc from them but delivery time varies im on my 6th week for one part too arrive but saying that other stuffs been just over 3 weeks so cant complain i guess,

So have you bought IC clones, if so, is your experience a good one?

[Percyveer]

Re: JVC THS9 Home Cinema System SMPS No outputs or standby power

yeah, but the difference going from a 39uF to 47uF shouldn't be 37V vs 76V. It will ramp up and down all the time. Sure, the line isn't loaded now, I expected a rise in voltage, but not to 76V because you increased the startup cap by 8uF.

Did this thing go just out one day, or was there a power surge of some kind?

It did not ramp up and down, just climbed to the max and stayed there.
I can only report what happened, it would not help my cause to say any different.
Just went out one day.

[vinceroger69]

Re: JVC THS9 Home Cinema System SMPS No outputs or standby power

aliexpress are a good company been having a fair few parts etc from them but delivery time varies im on my 6th week for one part too arrive but saying that other stuffs been just over 3 weeks so cant complain i guess,

[CapLeaker]

Re: JVC THS9 Home Cinema System SMPS No outputs or standby power

You may have skipped over what I wrote.
The original is back in and the voltage is now 37vdc.
When taking these voltage measurements the probes were kept on the cap pins until it had maxed out, probably took 5 secs to get there.

yeah, but the difference going from a 39uF to 47uF shouldn't be 37V vs 76V. It will ramp up and down all the time. Sure, the line isn't loaded now, I expected a rise in voltage, but not to 76V because you increased the startup cap by 8uF.

Did this thing go just out one day, or was there a power surge of some kind?

[Percyveer]

Re: JVC THS9 Home Cinema System SMPS No outputs or standby power

Vince: Thank you for the link.
Yes it is that package.
They do not state that it is made by Sanken, I am awaiting a reply from them, it should be at that price, but I think it will turn out be an expensive clone, which if it is the case, I may as well take a gamble on aliexpress at 65p each.

Percy

[vinceroger69]

Re: JVC THS9 Home Cinema System SMPS No outputs or standby power

theres one on ebay
http://www.ebay.co.uk/itm/STRG6651-I...MAAOSw34FVCvqh
but not sure what package type yours comes in

[Percyveer]

Re: JVC THS9 Home Cinema System SMPS No outputs or standby power

Unable to obtain these Allegro STR G6651 in UK.
Can get from china, probably clones, can anyone confirm these are reliable.

[Percyveer]

Re: JVC THS9 Home Cinema System SMPS No outputs or standby power

39uF is a very odd value, but that is what the schematic shows too... I thought that was a misprint. Put the original cap back in its place for now and change that IC. Because we need to know that the IC is working to hopefully fix the situation or troubleshoot it further.
Having too much voltage on the cap isn't good, but I am wondering "what" you actually measured. I expected the voltage to rise on the cap, when the IC is gone, but surely not a value of 76V.
Lets see if budm sees this.

You may have skipped over what I wrote.
The original is back in and the voltage is now 37vdc.
When taking these voltage measurements the probes were kept on the cap pins until it had maxed out, probably took 5 secs to get there.