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

Gil W. gil_we at yahoo.com
Fri Mar 14 00:19:32 CET 2014


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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