From: Peter <great_pic_n@westnet.com.au>
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Date: Tue, 7 Sep 2021 01:26:32 -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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Hello Justin,

I have not repaired SMPS in such equipment now for many years, any=20
chance of a picture and model number ?

Some questions:

1). Are the pink resistors discoloured is any way, possibly altering the=20
actual colours on the pink (ceramic maybe) ?

2). Are you measuring each resistor out of circuit (this most likely=20
will be important, depending on where the resistors are in circuit) ?

3). Use freeze spray in and around the small startup capacitors, and on=20
the solder joints too, while powered (CAUTION HIGH VOLTAGE - DANGEROUS) ?

4). Look for any poor solder joints around any of these small capacitors ?

5). Use heat gun (hair dryer), to heat up around these small capacitors=20
(CAUTION HIGH VOLTAGE - DANGEROUS) ?

6). Is this a 110VAC or 240VAC mains input ? and what voltage readings=20
(CAUTION HIGH VOLTAGE - DANGEROUS) are on the input capacitors (possibly=20
there are two, or only one, depends on design) ?

7). Is there a life support 5VDC supply active within the SMPS primary=20
or secondary ?

8). Is there any other discolouration on any other parts within the SMPS ?

9). Is there any noise or squeal coming from the power supply, when=20
turned ON ?

10). Are any chopper MOSFETS / HEXFETS, shorted (CAUTION HIGH VOLTAGE -=20
DANGEROUS, MAKE SURE ALL CAPS ARE DISCHARGED BEFORE TESTING) ?

11). Can you look for a schematic of the SMPS online ?

12). Check any OPTOCOUPLERS in any feedback circuits for shorted, or=20
open output transistors, or dead input LEDS ?

13). Sometimes, there are also circuits within the SMPS, to shutdown the=20
SMPS, on startup, because of some internal error; (short circuit, down=20
stream on the mainboard or backlight circuits for example) ?

14). Look online for a service manual, to decode the LED flash sequence,=20
which may point you in the right direction of failure ?

Also SMPS can have annoying smarts these days, which can fight you when=20
there is a fault.

If you can supply a high res picture and model number, maybe able to=20
look closer.

Hope some of this information helps.

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 the
> LED flashes. (I think 6 times) so it looks like LED strips.  Quick check =
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 an=
d
> SILVER bands.and I have been unable to work back from what I have measure=
d
> and the bands.
>
> Anyone had experience with these.  I eliminated the possibility they were
> inductors as they had R-designators
>
> Cheers Justin
--=20
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