strophlex Posted April 3, 2012 Report Share Posted April 3, 2012 If these readings are correct it seems there is a short between the switch and J73 somewhere. As SmashTV said, it might be that the capacitor is acting like a short to the multimeter. Next thing to try would be to connect the PSU and measure DC at the power connector pins (2 and 3) with the power switch turned off to make there is no short before the power switch in the ciquit. Do you get my resoning? Quote Link to comment Share on other sites More sharing options...
graantjes Posted April 3, 2012 Author Report Share Posted April 3, 2012 With the PSU connected and the powerswitch off, I measure no DC current between the power connector pins. I follow your reasoning but I really don` t want to break anything. Thanks. best regards, Joeri Quote Link to comment Share on other sites More sharing options...
strophlex Posted April 3, 2012 Report Share Posted April 3, 2012 You should not measure current. Do it again and messure DC voltage. Also, be very careful when dealing with the probes when power is on. It is easy to break the fuse in the C64 PSU. Quote Link to comment Share on other sites More sharing options...
graantjes Posted April 3, 2012 Author Report Share Posted April 3, 2012 I am sorry, I meant voltage. So I only measure with the switch off? or both? best regards, Joeri Quote Link to comment Share on other sites More sharing options...
strophlex Posted April 3, 2012 Report Share Posted April 3, 2012 Messure the 5V of your PSU again. I suspect the fuse in the PSU to be blown but the reason for that is probobly a short on the board somewhere. If the PSU is still OK, it is wrong that you have no voltage at the connector. Try to verify that the pinout of the PSU is right... Concentrate on mesuring dc voltage with the power switch off to verify the first few parts of the power supply section of the board. Quote Link to comment Share on other sites More sharing options...
graantjes Posted April 3, 2012 Author Report Share Posted April 3, 2012 I think you may be right, I only concentrated on the fuse of the psu on the outside, which is fine but there is one in the inside as well? I used to have 9vac at both pins on the connector at the backside, now I only have 9vac at the round connection and not at the square one. 5vdc is absent. thanks again for the patience, best regards, Joeri Quote Link to comment Share on other sites More sharing options...
strophlex Posted April 3, 2012 Report Share Posted April 3, 2012 I don't understand what you mean with the fuse outside, but yes, there is a fuse inside. It is easy to replace it and fuses are cheap but leave the brick disconnected from the wall for some hours before opening it and be careful when replacing the fuse. Also, I don't understand what you mean by square connector. Quote Link to comment Share on other sites More sharing options...
graantjes Posted April 3, 2012 Author Report Share Posted April 3, 2012 With the outside fuse I mean the one you can see a little in the bottom-left corner of the psu in the picture. It is a cylindrical hole with a fuse inside next to the power chord. With the square connector I mean the square pad on the bottom of the psu connection which should measure 9vac according to the base pcb diagram. I will replace the inside fuse tomorrow and let you know. thanks! best regards, Joeri Quote Link to comment Share on other sites More sharing options...
strophlex Posted April 3, 2012 Report Share Posted April 3, 2012 Your PSU brick is not the same design as mine, and mine doesn't have an external fuse, so I am not sure your has an internal one but anyway it may be that the external fuse is blown. Check it with your multimeter. It might be broken although it looks OK to the eye. Quote Link to comment Share on other sites More sharing options...
graantjes Posted April 5, 2012 Author Report Share Posted April 5, 2012 Hi Strophlex, The fuse is still ok, I replaced it with a new one and it gave me the same results. The power connections on the back don` t give me the needed voltages though. I guess I will be searching for another power supply. Thanks, best regards, Joeri Quote Link to comment Share on other sites More sharing options...
technobreath Posted April 5, 2012 Report Share Posted April 5, 2012 Here's the golden rule to put to use when searching for errors. Start in one end and check if things are ok. If ok, go to far end of the circuit and check if it's ok. If ok, divide the circuit in your head in the middle, and check one half at a time and so on. This is the fastest way to locate unknown errors in a circuit. One example so that you for sure understand what this method means in practice: Look at this circuit: 230v wall plug -> 20meter cable -> box where cable is spliced with another -> 20meter cable -> lightbulb. The most logical way to fix this is to first start at one end. Is the wall plug plugged in? if yes, go to the lightbulb, is that ok? If in doubt, replace it. Is the circuit working now? No? Then divide in 2 halfs, wich means, go check the box where the two wires are connected together and so on. I realize you have failed to search the right way here. And don't worry, most people do so - error searching is one of the most complicated things to wrap your head around, human nature always seems to get in the way somehow, and in bigger systems and circuits, it takes a great deal of self disipline to be able to start the right way and follow that through :). But you see what I mean, yeah? instead of starting to check for shorts / broken traces "in the middle of nowhere" you should've started with measuring the PSU at first to make sure that was allright. Especially since they have a bad reputation :) hehe. Personally I wouldn't use a c64 brick for supplying anything that is as sensitive and valuable hehe, but that's my personal crusade - there are many people using the brick with their sid synths and are happy with it :). After all, it's all retro :). Quote Link to comment Share on other sites More sharing options...
strophlex Posted April 5, 2012 Report Share Posted April 5, 2012 I also measured the psu pins and I have a correct 5VDC pin and a 9VAC pin Quote Link to comment Share on other sites More sharing options...
graantjes Posted April 5, 2012 Author Report Share Posted April 5, 2012 I also measured the psu pins and I have a correct 5VDC pin and a 9VAC pin I know,that was before, who knows how I broke the psu? I have a new c64 psu on the way. I also took it apart and it seems it doesn` t have an internal fuse, so something must be broken. I will get there eventually :) technobreath: the psu was fine before, it seems to be broken now... the beginning and end checks I understand, it` s when it comes to understanding the circuit itself and looking for errors there when I need some help. Thanks everybody, I will post next resulst when my new psu is in. best regards, Joeri Quote Link to comment Share on other sites More sharing options...
strophlex Posted April 6, 2012 Report Share Posted April 6, 2012 Good luck and keep the faith. Your synth will be operational soon. Quote Link to comment Share on other sites More sharing options...
graantjes Posted April 17, 2012 Author Report Share Posted April 17, 2012 ok, So I got a ``new`` power supply in the mail today and the 7 pins measure out fine, what` s the next thing to do considering the 2 almost broken pads and the bridge that is gone. I don` t want to brake something so I am taking it slow this time. best regards, Joeri Quote Link to comment Share on other sites More sharing options...
strophlex Posted April 18, 2012 Report Share Posted April 18, 2012 You should locate if and where there is an unintended bridge between ground and +5V. First mesure with continuety mode and if no short is found, connect psu and make sure you mesure 5V between gnd and +5V. Now that the bridge is removed, you can apply some divide and conquer methodology. If the first part of the PSU looks OK, resolder the power switch. Think twice before doing. It will help you if you make notes as you go along and make messurements. Good luck! Quote Link to comment Share on other sites More sharing options...
graantjes Posted April 19, 2012 Author Report Share Posted April 19, 2012 (edited) Today I measured the psu again and found that according to http://www.allpinouts.org/index.php/Commodore_C64_Power_Supply (looking at the picture as a MALE connector) I get 5vdc between pins 2 and 5 and only there but the 9vac confuses me, I get 9vac between pins 2 and 7, and 5vac (sometimes 12 or 2) between pins 1 and 6 or 3 and 7 Is this correct? thanks Edited April 19, 2012 by graantjes Quote Link to comment Share on other sites More sharing options...
strophlex Posted April 19, 2012 Report Share Posted April 19, 2012 Don't confuse the DC and AC pins. Pin 5-2 should measure 5V DC Pin 6-7 should measure 9V AC Don't mix and match. Measuing between dc and ac pins will give you strange readings. Quote Link to comment Share on other sites More sharing options...
graantjes Posted April 19, 2012 Author Report Share Posted April 19, 2012 Don't confuse the DC and AC pins. Pin 5-2 should measure 5V DC Pin 6-7 should measure 9V AC Don't mix and match. Measuing between dc and ac pins will give you strange readings. 5 and 2 are ok, But when I measure ground (1 or 3) against 6 or 7 I get strange readings (and I do know how to set the multimeter to AC) thanks Quote Link to comment Share on other sites More sharing options...
strophlex Posted April 19, 2012 Report Share Posted April 19, 2012 Think of your wall outlet. It doesn't have a + and a gnd connector but two ac connectors plus possibly a ground connector. There are two AC connectors that alternatively push and pull electrons. When you measure one of the AC pins against ground you are measuring a voltage that is fluctuating between 0 and 9 volts. That is not really what you measure if you measure the two ac pins. As I said, don't confuse ac and dc. Quote Link to comment Share on other sites More sharing options...
graantjes Posted April 19, 2012 Author Report Share Posted April 19, 2012 (edited) ok, that explains a lot. Now the power supply measures ok. So doing this one step at a time, I looked at the base pcb pdf and turned the board around with the psu connected and the switch off. the outer lugs measure 9vac but when I measure the inner lugs (red probe on 5v, black probe on gnd) it measure nothing. thanks for the patience :) It` s really appreciated. best regards, Joeri Edited April 19, 2012 by graantjes Quote Link to comment Share on other sites More sharing options...
strophlex Posted April 19, 2012 Report Share Posted April 19, 2012 Did you measure the switch or the female power connector on the board? Quote Link to comment Share on other sites More sharing options...
graantjes Posted April 19, 2012 Author Report Share Posted April 19, 2012 Did you measure the switch or the female power connector on the board? female power connector on the board best regards, Joeri Quote Link to comment Share on other sites More sharing options...
strophlex Posted April 20, 2012 Report Share Posted April 20, 2012 It sounds like you might have found a problem then. - Disconnect the powersupply and make a continuety check between the inner pads on the board (5V and gnd) - Double check that the 5V on the PSU did not brake (blown fuse) - try to continuety check from 5V in of female connector (pin 5) on the board to the pad it is soldered to to make sure the din connector is not broken. - Do the same with the gnd (pin 2). Quote Link to comment Share on other sites More sharing options...
graantjes Posted April 20, 2012 Author Report Share Posted April 20, 2012 -PSU is still ok -no continuity between inner pads -continuity between pin 2 and gnd -no continuity between pin 5 and 5v (continuity between pin 4 and 5v) Quote Link to comment Share on other sites More sharing options...
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