I love the old DCC stuff. I repaid a lot of DCC 130 and DCC 170. I have two DCC 130 on my working bench that I am not able to fix. It is about the 5 volt switching transistor Q2. So it is not related to DCC - I think it is a "common" problem. As I am a tax consultant this is just my weekend work. Philips_DCC_130_5_Volt_rail by Franzbauer posted Apr 22, 2024 at 5:57 PM The 5,5 volts are coming from the battery/power supply an going directly in a choke coil (L4). I can measure the 5,5 volt on the three sides (but not on the fourth side - which goes to C11). I have the 5V on the collector of Q2 but on the base - there I have just 0,30 volts. There it should be 5,3 volts. I checked the caps C3 and C5 - they are ok. I checked the Q2 and it should be ok. My questions: 1) Should there be an 5 volt rail on the fourth side of the choke coil? 2) Is there a problem with the C11 oder C12 caps oder maybe the R5 and R19? The 5,3 voltage rail goes directly in the DC-DC-converter. It tried a direct cable from the C5 to the input of the DC-DC-converter and it worked perfectly. Thank you very much Stefan
I assume the problem is the unit does not turn on. L4 is a transformer by the looks of it, being part of the DC-DC convertor. From my understanding, this DC-DC convertor is used to maintain a constant voltage of 5.3V regardless of input. On both coils of the transformer you should have some pulse square signals. 1) What I can tell you is there should be continuity between the sides of each coil of the transformer. If one of the coils is open circuit, the DC-DC won't work. 2) C11 and C12 are very small value capacitors, so they are likely ceramic. Unlikely these are a problem, but not impossible. You can check in resistance/diode mode (to check if there is a short), but be sure to not bias the BC junction of the transistor, so put positive lead on collector side and negative on base. R5 and R19 again you can measure them with multimeter, but it's unlikely these are the fault. Pin 16 of IC1 seems to be the output of the DC-DC converter. When you connect the battery directly there you essentially bypass the DC-DC converter and feed the main voltage rail directly, hence why it works. Attached you have the schematic of the DC-DC circuit together with example circuit from AN8086 datasheet, the block diagram and the datasheet of the IC itself. The electrolytic SMD capacitors have all been replaced ?
