Roter_Flieger

As I already said, there is NO voltage regulator on my CORE module, so I can easily feed 5 V into it. ;) (BTW: since I have read the 78xx datasheet, I know about this particular fact :)) The problem was totally different. I still do not know why I fried my rectifier, but apparently the C64 PSU was broken. The C64 I got it with was not functional and I now guess the PSU was the cause. Without any load, it delivered 12V at its 5V output which dropped below 1V with a load applied. Strange... I now connected an old standard PC PSU with regulated 5V and 12V lines and finally, the CORE had all the required voltages. The bootstrap loader kindly asked for its OS and everything seems to work fine now. I would still like to know why the fscking rectifier heated up that much, but that will probably remain a mystery.

Well, the PIC was not put into the IC-Socket yet, same is true for the optocoupler. I will never put expensive ICs into a circuit without verifying the voltages first. I have not even unpacked the PIC from its shipping box yet, so it definitely cannot be blamed for this. I am still not sure about the voltage regulator and the rectifier though. Since I am using the optimized C64 PSU, I already have stabilized 5V right out of it, so I do not need the 7805 and left it out. I shortened the leftmost and the rightmost pin of the mounting holes for the 7805, leaving the middle pin (i.e. ground) untouched. Is that correct? May I still use the same capacitor values as if the 7805 was in there? And why does a rectifier get hot? I connected my 5V DC to the AC input of the rectifier (I double checked that it was soldered in properly and that its terminals are in the right place) but I thought this would be ok and also gives me 5V DC with the right polarity at the output. Does a rectifier get damaged when it is fed with DC current? Also, the problem still persists when the rectifier is soldered out and the CORE modules is supplied by J2. I checked the schematics and the circuit almost all night and I still have no clue. Maybe I should get some sleep before I proceed...

Hi there, I completed my CORE module today and powered it by an optimized C64 PSU. The voltages of the PSU are just 5V and around 14V as they are expected to be. But the core gives me a headache. The core is not stuffed with the 7805, instead, I shorted its input and output lines. I accidentally connected the PSU to J1 instead of J2 as suggested in the optimized PSU guidelines but I though that does not matter at all? Anyways, the moment I wanted to start measuring my voltages, I realized that familiar smell of burning electronics. I quickly disconnected everything and found the rectifier burning hot. Everything else seemed to be cool. So I reconnected everything, this time with the PSU at J2. The rectifier stays cool, but the voltage is only around 0,5V at all points within the circuit. Even at the PSu output, the voltage is not correct anymore, as soon as I connect the core (it is 5V as long as the core stays unconnected). I checked my soldering for any shorts but was not able to find any. Everything seems to be ok. When I measure the resistance between +5V and GND on the board, I get a steadily increasing value (natural because of all the capacitors in there) so there is no obvious short between the power lines. Now, I do not know what else to check. Can you give me some piece of advice?

I know, but that was also the case with the original circuit in the C64. In the SID specs I read something like: "Any signal applied directly to the pin should ride at a DC level of 6 volts and should not exceed 3 volts p-p." So I guess an open SID input line rides at 6 volts. Connecting an external input without a coupling capacitor would be very bad in this case. I heard those stories directly from two people I know and whom I told about the capabilities of the MBSID. They both (independently) tried to connect a guitar amp to the audio input of the C64 and sent their SIDs to death. So no links for them. :) However, Google Groups found this for example: http://groups.google.de/group/comp.sys.cbm/msg/4d0f7ad691379dc6?hl=de& He states that the coupling capacitor will discharge into the SID if it is grounded with the C64 turned on and that a solution would be an additional resistor that connects the input line to ground in order to let the capacitor charge and discharge in a defined manner. Actually, later C64 boards had exactly this resistor he is talking about while early versions were lacking it. Well I do not know how the capacitor can discharge into the SID. What I could imagine is, that if the SID's input line is really at 6 volts and the capacitor is grounded directly, that it momentarily will drain a high current from the SID's input pin which may destroy it. Agreed! ;D

Hi there, I am on to start a MBSID for my own. I already finished soldering the core module and now I want to proceed to the SID module. What I came across is the SID input... I heard from a number of people who fried their SID chip when fiddling around with the audio input of the C64. As far as I was able to find out using Google, the SID is very fragile at this pin and will die immediately if it is connected to ground. For the optimized PSU, it is recommended to ground the input lines in order to reduce unwanted noise. I will not doubt that a number of people are using happily working MBSIDs with grounded input lines, but how does this comply to the stories of C64 users frying their SIDs? MBSIDs input wiring does not seem to differ a lot from the original wiring of the C64. I am just concerned about the SID chips. I got two 8580 (which had three perfectly working voices last time I tried them) and for me those are precious ICs which I do not want to expose to any kind of risk. Is there anything else that needs to be paid attention to when it comes to the external audio input section of the MBSID? Regards.