JVC THS9 Home Cinema System SMPS No outputs or standby power

[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.

[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

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

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

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?

[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

[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.

[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

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

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

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

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

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

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

[Percyveer]

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

Andrew: Maybe I should expand on the detail to my original post, the voltages I have mentioned in that post are the only voltages present on the primary and secondary sides.
It does appear that IC901 is not functioning, but it may be because the voltage present at Vin is only 13.18vdc not enough to start see post 7 by Capleaker.

[Andrew F. Ali]

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

Terminal 12 is on the Secondary side of SMPS Transformer. So it would appear to me the Start-up voltage is there and because SMPS IC is not oscillating you may have voltage on Primary winding. Therefore, Run voltage is not being produced to sustain the SMPS. Hence I offered IC 901 as the culprit for your failure. Apart from that I would test PC901/2, Q991 and ZD991, as well.

[Percyveer]

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

I would directly replace IC 901 if all the surrounding cap, diodes and resistors are checked OK. Look at Q991, Opto-Isolators PC-901 and 2. And yes Zener diode ZD 991, too.

Why would I look at those components when there is no voltage presented at T901 terminal 12?

Just curious and trying to understand.

[Percyveer]

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

jiroy: Yes correct, voltage readings taken in circuit.

[budm]

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

BTW, you are sure that there is not bad diodes in the secondary side, or low resistance on any of the output pins?
I suspect bad SMPS IC if other component tested OK.
BTW, what are the resistance between GND pin against all other pins?

[jiroy]

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

Jiroy: Yes taken as Capleaker suggested with one leg removed from board, it certainly does not make sense to me!

Capleaker wanted to remove one leg to check continuity and/or resistance value , not voltage .