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Old 1st May 2015
  #28
Gear Head
 
piscine's Avatar
 

Hi Slack. This is the correct PCB. No wonder your display is not working: given that R22 has toasted, it must certainly be open and thus cannot deliver the +4.8 V supply to IC11!!! ;-)

So, you have to replace it with a 3R3, 0.5W (at least) resistor. Also, as skybluerental very wisely suggested, you should replace both the yellow Frako and the blue Philips axial decoupling capacitors on this board: for C13 use a Vishay 2200uF/10V (at least) with a 105° temperature grade; same temp characteristics for C14, but this time use a (Vishay again) 220 uF/25V cap. And I would also recommend that you replace the only tantalum cap on this board, C7, with a high-grade radial electrolytic from Nichicon: this one is a 47 uF/10V. The tantalums Studer used from this era have a clear tendency to go short after 25 or more years... BTW, do not bother about the pink capacitors: they rarely have issues ;-)

I would bet your display would come to life again after this little surgery ;-)


Cheers,