tob Posted September 18, 2011 Report Share Posted September 18, 2011 I have build this PSU from the c64 brick http://www.ucapps.de/mbhp/mbhp_8xsid_c64_psu_optimized.pdf I get +14VDC and +5V. I have removed the 7805 regulator from core8 module and I have bridged leg 1 and 3. But when I connect the +5VDC to the core module J2 (no others module connected and no display and no IC i sockets) it drops to about 1.7VDC on all measurement points. IC1:MCLR(1) - IC1:Vss(12) = 1.7V IC1:Vdd(11) - IC1:Vss(12) = 1.7V IC1:Vdd(32) - IC1:Vss(31) = 1.7V IC2(8) - IC2:(5) = 1.7V What can be wrong? Quote Link to comment Share on other sites More sharing options...
Altitude Posted September 18, 2011 Report Share Posted September 18, 2011 Sounds like something is shorting the 5V rail, check for continuity between +5 and GND Quote Link to comment Share on other sites More sharing options...
tob Posted September 19, 2011 Author Report Share Posted September 19, 2011 Sounds like something is shorting the 5V rail, check for continuity between +5 and GND It's the pcb and componets from smashtv. I can't see anything with my eyes, is it possible to measure shortingin some way? I have a multimeter with ohm,A F,V (DC & AC) and HZ plus a beeper. My bridge reflector (BR1) get's very hot is this normal? I get a beep when I put the probes on J2 but not on J1. Quote Link to comment Share on other sites More sharing options...
tob Posted September 19, 2011 Author Report Share Posted September 19, 2011 I desolder the bridge reflector and now I got +5 on every pins ( I didn't see any instruction to desolder BR1?) When I put in the two IC and turn it on I now I get around 1.6V on the points, is this wrong? Quote Link to comment Share on other sites More sharing options...
Altitude Posted September 20, 2011 Report Share Posted September 20, 2011 set your meter to beep, put one lead on +5 and the other on GND, it should NOT beep. The rectifier should not get hot, make sure it is in the correct way. Sounds like problem is there Quote Link to comment Share on other sites More sharing options...
tob Posted September 20, 2011 Author Report Share Posted September 20, 2011 (edited) Thanks for your help, now I know what was wrong. I had wrong polarity to J2 I putted the pic and opto in the sockets with wrong polarity! :cry: I was fooled by the left + on the picture http://mbhp.avishowtech.com/images/core/coreR4DETAILJ2.gif and I missed +/- on my multimeter, when I checked on the points. Very stupid!! Now when I connect the power with right polarity the background light of the display is lighten up. But the display is displayling some squares and then it disepears. Do you think the core8 is bricked when I switched the polarity? Edited September 20, 2011 by tob Quote Link to comment Share on other sites More sharing options...
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