From: Justin Richards <justin.richards@gmail.com>
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Date: Tue, 7 Sep 2021 01:58:08 -0700
Subject: Re: [EE]: Resistor codes - How to read Pink 2 watt, 5 band resistors
Thread-Topic: [EE]: Resistor codes - How to read Pink 2 watt, 5 band
 resistors
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Hi Peter,

Thanks for taking the time.

I was mainly curious about the resistors

see in line for answers

Some questions:
>
> 1). Are the pink resistors discoloured is any way, possibly altering the
> actual colours on the pink (ceramic maybe) ?
>
On the PSU board I was surprised to see no signs of any discolouration
anywhere.  It seems well designed and built.  I think the fault lies
outside the PSU, although initially I thought it was the suspect.

There are several pink resistored dotted around but I only measured 3. (two
were the same value)

>
> 2). Are you measuring each resistor out of circuit (this most likely
> will be important, depending on where the resistors are in circuit) ?
>
As the values were so low, I had to take them out of circuit to satisfy my
own doubts.

>
> 3). Use freeze spray in and around the small startup capacitors, and on
> the solder joints too, while powered (CAUTION HIGH VOLTAGE - DANGEROUS) ?
>
I think this is a LED strip issue that many have suggested elsewhere on the
web.  I have working hack just now.  2 ohm resistor in series with the LED
strips.  I figured it was error-ing on detecting too much current. (or two
little).  Seems to start up ok with a range of 2 - 10 ohms in series with a
measured volt drop of about 1 - 6v respectively.  I decided to go with a
hack job repair as I figured it matches the hack job manufacturing as this
TV died within warranty and was given to me to dispose of.  There seems to
be many others that have had a similar failure.

>
> 4). Look for any poor solder joints around any of these small capacitors =
?
>
Again, I am amazed at the quality of the PSU with a big guard zone around
the input side, all joints look good.  Very clean, little residue, quality
caps that measure very close to their stated values.

>
> 5). Use heat gun (hair dryer), to heat up around these small capacitors
> (CAUTION HIGH VOLTAGE - DANGEROUS) ?
>
High voltages seem to be DC between 120V and 180V.  The caps are rated at
200V.

>
> 6). Is this a 110VAC or 240VAC mains input ? and what voltage readings
> (CAUTION HIGH VOLTAGE - DANGEROUS) are on the input capacitors (possibly
> there are two, or only one, depends on design) ?
>
It states 110 - 240V.

>
> 7). Is there a life support 5VDC supply active within the SMPS primary
> or secondary ?
>
I think so, as the LEDs flash away when it is fault detect mode.

>
> 8). Is there any other discolouration on any other parts within the SMPS =
?
>
Exceptionally clean with no marks. I looked and surprised there were none.
It did fail young but I suspect was on for extended periods.

>
> 9). Is there any noise or squeal coming from the power supply, when
> turned ON ?
>
Silent.

>
> 10). Are any chopper MOSFETS / HEXFETS, shorted (CAUTION HIGH VOLTAGE -
> DANGEROUS, MAKE SURE ALL CAPS ARE DISCHARGED BEFORE TESTING) ?
>
This was an intermittent fault so I suspect they are all ok.  They have
built in discharge resistors and do so in about 20 seconds.

>
> 11). Can you look for a schematic of the SMPS online ?
>
I always assume they are un-obtainium.

>
> 12). Check any OPTOCOUPLERS in any feedback circuits for shorted, or
> open output transistors, or dead input LEDS ?
>
There are 5, but one is reversed compared with its neighbours.

>
> 13). Sometimes, there are also circuits within the SMPS, to shutdown the
> SMPS, on startup, because of some internal error; (short circuit, down
> stream on the mainboard or backlight circuits for example) ?
>
I think this is shutdown on out of spec current detected when riving the
LEDs.  I can see the voltages hover around 120v then discharge as soons at
it goes into fault mode.  I should have measured it once it was running but
I was too quick to get it in the lounge.

>
> 14). Look online for a service manual, to decode the LED flash sequence,
> which may point you in the right direction of failure ?
>
Seems to suggest an issue with the panel.


> Also SMPS can have annoying smarts these days, which can fight you when
> there is a fault.
>
Yes, there is a bit of that going on with this.

>
> If you can supply a high res picture and model number, maybe able to
> look closer.
>
If it fails again, I will do just that.

>
> Hope some of this information helps.
>
Much appreciated.

>
> Best of luck.
>
> Regards,
>
> Peter.
>
>
> On 7/09/2021 3:08 pm, Justin Richards wrote:
> > Attempting to (and failing miserably it seems) repair a Sony TV that
> > randomly powers on.  Sometimes, just a glimpse of the SONY logo then th=
e
> > LED flashes. (I think 6 times) so it looks like LED strips.  Quick chec=
k
> of
> > suspect caps would indicate they are all consistently in spec.
> >
> > The PSU has several low value resistors that I read as follows:-
> >
> > Shorted Probes -> 0.3 - 0.4 ohms
> >
> > BROWN - BLUE - SILVER - GOLD -  GREEN -> 0.4 - 0.5 OHMS
> >
> > RED - BLACK - GOLD - RED - GREEN  -> 2.0 - 2.1 ohms
> >
> > The internet has not helped answer what value I should assign the GOLD
> and
> > SILVER bands.and I have been unable to work back from what I have
> measured
> > and the bands.
> >
> > Anyone had experience with these.  I eliminated the possibility they we=
re
> > inductors as they had R-designators
> >
> > Cheers Justin
> --
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