Cerebral Infect Posted May 24, 2009 Report Share Posted May 24, 2009 Hi,I'm building a MB-6582 from a kit of Smash TV. So this week I assembled all the sockets, headers, resistance (except R40 to R55), diodes, some capacitors, and the PSU section. Did my ground check and 5V check for continuity on the sockets.Then I put my Power supply. It's a Commodore 64 PSU. Checked the Pin on the PSU to validate if I had 5V DC and 9V AC, which I have. I assembled PSU Option A since I have 6582 chips.So I plugged in the PSU on the board and flicked the switch to on. Check the DC voltage : 5V ! good. Then check the 9-11V header and I had 13.2 Volt, witch is higher than anticipated. Checked the voltage at the SID Header and read a 9.00V at each of them. I was happy.Until I notice a little burn smell and look at the bridge rectified. A teenager during puberty could not have done better. The rectifier developped a little bulge and gets really hot. I checked my soldering underneath and it`s good.Has anything like thing happened to you ? Or my PSU is too "hot" ? See at the picbridge.JPGbridge.JPG Quote Link to comment Share on other sites More sharing options...
latigid on Posted May 25, 2009 Report Share Posted May 25, 2009 Was the rectifier correctly oriented? If not, that's a fair bit of current to sink (backwards across a diode). Quote Link to comment Share on other sites More sharing options...
fussylizard Posted May 25, 2009 Report Share Posted May 25, 2009 Looks like you had it oriented correctly, flat side toward the back of the board (facing the power switch)... Quote Link to comment Share on other sites More sharing options...
smashtv Posted May 25, 2009 Report Share Posted May 25, 2009 Hi Cerebral, Sorry this thing is giving you troubles. This looks like a faulty bridge rec but I want to approach it with caution, having seen many bridge recs play the role of canary in the mine during my years as a tech.This is also the first and only reported failure out of a large lot of bridge recs, with many (hundreds) out there known working. Currently I pull four per hundred as samples to test, obviously that ratio will change......I spend way too much time testing PICs and optos before they ship to let something as simple as a bridge cause a build problem. :)Please check your private messages and we'll move forward from there.Best regardsSmashTV Quote Link to comment Share on other sites More sharing options...
Smithy Posted May 26, 2009 Report Share Posted May 26, 2009 Awww, the bridge rec looks so sad.... :(Sitting there with its little melty face and stuff.....(I think im going insane ???) Quote Link to comment Share on other sites More sharing options...
nILS Posted May 26, 2009 Report Share Posted May 26, 2009 I think you've passed that point a while back ;) Probably caused by your approaching the guru curse. Quote Link to comment Share on other sites More sharing options...
Cerebral Infect Posted May 26, 2009 Author Report Share Posted May 26, 2009 I think it's really the power supply failing. I found this interesting link for testing PSU. Mine shows 5.2V DC. Therfore I think I have a failing regulator. The hunt for a use C64 begins now.http://personalpages.tds.net/~rcarlsen/cbm/pstester.txtI'll keep you updated. Quote Link to comment Share on other sites More sharing options...
nILS Posted May 27, 2009 Report Share Posted May 27, 2009 5.2VDC on a 5VDC rail isn't necessarily a problem. It might well be a combination of a PSU that's a tiny bit off and a voltmeter that's a bit off. Quote Link to comment Share on other sites More sharing options...
Wilba Posted May 27, 2009 Report Share Posted May 27, 2009 I concur... 5.2V DC is fine, and it's separate to the 9V AC coming out of the PSU. This melting bridge rectifier problem does not really make much sense - you would need a lot of current to make one melt like that. I say replace the bridge rectifier and see what happens before blaming the PSU. Quote Link to comment Share on other sites More sharing options...
Cerebral Infect Posted June 10, 2009 Author Report Share Posted June 10, 2009 Received the new replacement bridge rectifier by SmashTV. Desoldered the previous one. The desoldering pump was a life saver. Soldered a new one in.Turned on : no smell. Touched the bridge : no heat. Let time pass by : No pop corn effect.People on the forums were rigth, it was the bridge rectifier, not the PSU. I can resume construction of the unit. I can`t wait to test the SID I've receive from Wilba !!!Thanks everyone. Quote Link to comment Share on other sites More sharing options...
dioioib Posted June 10, 2009 Report Share Posted June 10, 2009 I would recommend following the advice Wilba recommends for testing the SID by starting with one and adding more as you go. The last thing you would want to see is another bridge rectifier problem fry all your nice Sids. Probably just common sense, but good advice. Quote Link to comment Share on other sites More sharing options...
tongenerator Posted June 15, 2009 Report Share Posted June 15, 2009 Until I notice a little burn smell and look at the bridge rectified.i actually like that picture :D Quote Link to comment Share on other sites More sharing options...
Twin-X Posted September 13, 2009 Report Share Posted September 13, 2009 So sorry to dig up this old thread but i just burned out 2 rectifier'sThe funny thing is before the fisrt one "popped" i have played on the mb whole day.So as i had no rectifiers on stock i ordered a bunch.Even the third one i put in get's extremly hot. I have posistioned it ok.Is there anything else i can check waht can cause this? Quote Link to comment Share on other sites More sharing options...
SLP Posted September 13, 2009 Report Share Posted September 13, 2009 A bridge rectifier is basically made of 4 diodes.you should check them with a multimeter for continuity and stuff like that. Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.