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+5VDC drops to +1.7VDC with c64 when connecting core8 module


tob

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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?

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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.

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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 by tob
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