JVC THS9 Home Cinema System SMPS No outputs or standby power

[Percyveer]

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

Start up DCV, UV/OV DCV
VCC It has to reach 16VDC for IC to start up.

Yes thank you budm see Capleaker post 7, but how do we achieve that?

In reply to your post 15.
I have measured all output pins to secondary ground point (assuming you meant FM901 and FM902) and all FM902 pins are in the megohm region, FM901 pins 1=45.6K, 2=47.7K, 3=780, 6=4.41K, 7=22K, excluding all the Grd ones which were grounded.

Percy

[budm]

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

How about the Resistance of GND pin of the SMPS IC against all other pins of the SMPS IC?

[Percyveer]

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

budm: pin 1=open, 2=0.6, 3=short, 4=meghoms and rises as probes measure,(I assume this is the DDM charging C914) 5=short

[budm]

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

Wait a minute, pin 3 is the Gnd pin that is used to measure against other pins, so what did you use for the meter black probe? You report pin 3 = short.

[Percyveer]

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

Wait a minute, pin 3 is the Gnd pin that is used to measure against other pins, so what did you use for the meter black probe? You report pin 3 = short.

The primary grounding point as indicated on the diagram.

[budm]

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

Something is not quite right in the schematic, that R905 (68K, start up resistor) connected to pin 4 VCC pin has another end connected to incoming AC instead of to the + leg of the main filter cap as shown in the spec sheet.
Can you verify that connection?

[Percyveer]

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

budm: Yes I confirm it is built as schematic and also verified from the pcb underside picture.

[Percyveer]

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

For clarification........ the pcb is currently with these resistors disconnected from circuit until Capleaker confirms that I can resolder them.

Thank you all for your help so far....

Capleaker: Measurements as follows R910= 465k, R911= 466k, R905= 67.5k.
Shall I resoldered them back in as within spec?
The IC901 has 13.18vdc to pin 1, data sheet states on state voltage between 14.4-17.6vdc.
So appears that voltage is too low, but why?
STR-G6651 data sheet uploaded.

budm:
Pictures of PCB top/bottom uploaded.
Owned from new, not used much, but just started using more now that 5.1 surround is being broadcast here on some programmes, we power it off/on as we use it, never use standby mode in the interest of energy saving.

Redwire: Thanks for the headsup..

Percy

[CapLeaker]

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

Those 3 resistors are within spec. So that isn't it. You can solder them back into place.
The short you measure on IC901 between pin 2 and 3 is due to R907 being so low in value. So by rights, if you lift a leg from R907, the short on IC901 should be gone.

Check / replace C914. Check D904 and R903 and that section.

So there are no shorts on any of the secondary output rails to their corresponding GNDs, correct? Also there is absolutely nothing coming out on any of these secondary power rails?

[budm]

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

BTW, the R910, R911 are for the over Voltage protection if the incoming AC gets too high.
I thought he already checked/replaced the startup cap C914.

[CapLeaker]

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

BTW, the R910, R911 are for the over Voltage protection if the incoming AC gets too high.
I thought he already checked/replaced the startup cap C914.

Not that I know of that he checked or changed C914. If that is bad, the IC901 won't turn on either. First I thought the R905 (68k startup resistor) is bad, but it can't be bad if he's got a constant 13.2V on IC901 Vcc and it measured good out of circuit.

[budm]

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

Something is holding that startup Voltage down from reaching 16V startup pointy, but I wonder if there was any output Voltage for seconds not when first power is apply. he may have to leave the Volt meter on the output to see if it jumps up, or on the startup cap to see if it jumps up to more than 16V or not.
At this point I would just replace the IC if all other parts tested OK.

[CapLeaker]

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

Something is holding that startup Voltage down from reaching 16V startup pointy, but I wonder if there was any output Voltage for seconds not when first power is apply. he may have to leave the Volt meter on the output to see if it jumps up, or on the startup cap to see if it jumps up to more than 16V or not.
At this point I would just replace the IC if all other parts tested OK.

I was wondering about the same thing, that's why I had to ask earlier if there isn't anything at all coming and not measuring any shorts on the output rails. On the other hand, maybe you could explain something to me:
Why would you change IC901 if lets say all other parts test o.k? You know that it can't turn on with 13.2V at Vcc pin 4? That round thing doesn't go in my square head. What am I missing? I mean I would understand it if Vcc would be 16V and the IC doesn't turn on. I say Percyveer has a few things to chew on now.

[Percyveer]

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

Yes guys thanks, working on your feedback now......

[budm]

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.

[Percyveer]

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

Those 3 resistors are within spec. So that isn't it. You can solder them back into place.
The short you measure on IC901 between pin 2 and 3 is due to R907 being so low in value. So by rights, if you lift a leg from R907, the short on IC901 should be gone.

Check / replace C914. Check D904 and R903 and that section.

So there are no shorts on any of the secondary output rails to their corresponding GNDs, correct? Also there is absolutely nothing coming out on any of these secondary power rails?

Have now resoldered those resistors.
I can confirm short across IC901 pins 2 and 3 goes when R907 is removed (have resoldered).
C914 reads megohms when tested across its leads, and rises as it charges so would appear OK?
D904 0.4 forward voltage, open when leads reversed.
R903 as spec.
I have again checked, and the only voltage coming out of the secondary side of T901 is 0.2vdc on pins 7 & 8 to secondary Grd point indicated on diagram.
Secondary output terminal pin measurment results in post 21.

[Percyveer]

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

Something is holding that startup Voltage down from reaching 16V startup pointy, but I wonder if there was any output Voltage for seconds not when first power is apply. he may have to leave the Volt meter on the output to see if it jumps up, or on the startup cap to see if it jumps up to more than 16V or not.
At this point I would just replace the IC if all other parts tested OK.

Have just done this check and it initially starts at around 21vdc, but that is for milliseconds, and I think it is just power surge, as within the next second it is 13.18vdc.

[Percyveer]

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.

I could series up a couple of 9v batteries, would this do it?

[vinceroger69]

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

[budm]

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

You must be real careful because you are working in the primary side.
You can run the VCC test by running the board by itself, DO NOT CONNECT THE BOARD TO AC, hook up the 18V batteries, negative to GND, the positive lead to 100 Ohms 1/4 W resistor, the other end of the resistor to pin 4, then check the DCV on pin 4 and GND to see what you get.