JVC THS9 Home Cinema System SMPS No outputs or standby power

[budm]

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

i would change c914 unless you have a capacitance/esr tester too test it correctly

I agree, that will be an easy thing to do.

[Percyveer]

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

i would change c914 unless you have a capacitance/esr tester too test it correctly

Will do.
I have to hand a 22uf/25v or 47/16v will either of those do for testing purposes?

[CapLeaker]

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

It has to be at least a 25V cap. I'd try the 22 or better a 47uF. 25V, 35v 50V doesn't matter. 50V 47uF are very common.

[CapLeaker]

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

It may be the circuit inside the IC on VCC pin 4 is loading down the Voltage, when check the resistance with the Ohm meter on pin 4 and GND it may not be valid due to the meter does not put out high enough Voltage to cause the circuits inside the IC to conduct.
One way to find out is to use isolated external power supply to feed the IC pin 4 VCC.

O.k. so in this circuit, if we take out IC901, there should be then the 21V startup juice on cap c914 then, if the IC901 is at fault.

[Percyveer]

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

It has to be at least a 25V cap. I'd try the 22 or better a 47uF. 25V, 35v 50V doesn't matter. 50V 47uF are very common.

I found a 47uf/25v and it is now soldered in.
The voltage now across the cap is difficult to measure, as it is oscillating, but is somewhere between 12.5 and 13.8vdc.
No change in any other voltages.

[Percyveer]

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

O.k. so in this circuit, if we take out IC901, there should be then the 21V startup juice on cap c914 then, if the IC901 is at fault.

Do I take this road now?

[Percyveer]

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

Thank you all for assisting me thus far, it is greatly appreciated.

Well I carried on and removed the STR G6651, and the voltage across the start up cap charged up to 76vdc, thought that a bit high so replaced the existing cap that appeared to be OK and the cap is now charging up to 37vdc.
With the IC removed I have tested across all the pins to each other and there are no shorts. Is it defective?

[vinceroger69]

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

what voltage is the capacitor you replaced? at that voltage running through it supprised it did not explode.

[CapLeaker]

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

O.k. so the voltage did rise when you took it out. Right now I'd be changing that IC901.
I can't see having 76V DC there. Vinceroger is right... something should went poof. What was c914 originally? The schematic doesn't show correctly.

[Percyveer]

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

what voltage is the capacitor you replaced? at that voltage running through it supprised it did not explode.

Vince: The cap used for testing purposes was 47uf 50v.
The spec of the original which is now back in is 39uf 25v.

[Percyveer]

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

O.k. so the voltage did rise when you took it out. Right now I'd be changing that IC901.
I can't see having 76V DC there. Vinceroger is right... something should went poof. What was c914 originally? The schematic doesn't show correctly.

Hi Capleaker, it was 39uf 25v.

[Percyveer]

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

To clarify the 76vdc was there with the 47uf 50v cap in there.
But the original 39uf 25v is still producing 37vdc, too much for its spec isn't it?
Or will it drop when the IC is replaced?

[CapLeaker]

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.

[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.

[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.

[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

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

[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?

[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,

[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.