[sdiy] << FIXED >> TX802 Power Supply failure

[rburnett at richieburnett.co.uk]

Well done!  If the outputs are the correct voltages and relatively 
ripple-free, and nothing is getting excessively hot (touched after 
completely removing power!) then it sounds like it's good to go.

Q2 may have been fine when you checked it the first time, then got 
damaged when you unsuccessfully tried to power up the partially repaired 
supply.  This sort of thing is quite common with SMPS's.

-Richie,


On 2014-03-13 23:19, Gil W. wrote:
> I somehow missed Q2 it appears. Was shorted as well, for some reason I
> was sure it tested fine. Also found that
> the PCB trace going out from one of it leads was not leading and
> needed a jumper :/
> 
> Overall I replaced:
> 
> The optocoupler
> Q1 with 2SC3752
> Q2 with same as original
> D5 (1SS84) with UF4007
> All electrolytes with fresh ones
> 
> Boots just fine now, could get nice +5, +15 and -15 calibrating the 
> trimpot.
> 
> Thanks everybody for the help, very much appreciated !
> 
> 
> 
> 
> --------------------------------------------
> On Thu, 3/13/14, Gil W. <gil_we at yahoo.com> wrote:
> 
>  Subject: Re: [sdiy] TX802 Power Supply failure (replacing 3W with 5W 
> resistor)‏
>  To: synth-diy at dropmix.xs4all.nl
>  Date: Thursday, March 13, 2014, 11:14 AM
> 
>  Hi.
> 
>  So I replaced D5 with UF4007, Q1 with 2SC3572 (equivalent to
>  original 2SC3559), the 7915 and 7815 with fresh ones, and
>  the PC817 optocoupler. Also put a new 22ohm/5W instead of
>  the dead R1. I powered up and nothing... can't get the final
>  +15/-15/+5 volts.
> 
>  The two other fast 1SS84 diodes has some marks of greenish
>  acid on the leads. Could this have taken D5 out in the first
>  place ? The do not short, however. These are D2 and D6..
>  Could Q1 take out the T1 transformer while shorting ? I also
>  think about recapping it. Do you think there's a point
>  insisting to fix this ? couldn't find other bad components
>  so far (well, checked only diodes and transistors).
> 
>  I think I have a Polysix powersupply board laying around.
>  Will it do the job ? IIRC it should make +15/-15/+5/-5
>  volts...
> 
>  Thanks again !
> 
> 
> 
>  --------------------------------------------
>  On Tue, 3/11/14, Colin f <colin at colinfraser.com>
>  wrote:
> 
>   Subject: Re: [sdiy] TX802 Power Supply failure (replacing
>  3W with 5W resistor)‏
>   To: synth-diy at dropmix.xs4all.nl
>   Date: Tuesday, March 11, 2014, 4:14 PM
> 
>   
>   > Good luck!  If it was me I think i'd consider
>   retro-fitting a
>   > whole new SMPSU if you can find one that will fit.
> 
>   There is a metric shedload of room.
>   My TX802 supply died.
>   I replaced it with a 5V SMPS line lump and a simple linear
>   supply for the 15
>   volt rails.
>   Much simpler than messing with that nasty looking
>  switcher.
>   By the time it had died a fair area of the PSU PCB had
>   blackened, so even if
>   I had identified the component(s) at fault, it might need
>  a
>   new PCB.
> 
>   Cheers,
>   Colin f
> 
> 
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