For many of us it is very famous problem. Reversed DC polarity and ... There were many discussions on this topic. Here I would like to discuss two possible solutions, with simple TO-DO for everyone 1st. possibilty Replace whole converter by modern type, sold here and there on eBay. You can find various 5V to 12V converters, or even anything to 12V converters. They're small, much smaller than the original one. They're more efficient. They can deliver more power. So why not to use them easily? The answer is simple - they inerfere with internal circuits of D6C. You need to build ground shielding around it. More, their output voltage isn't "clean" enough and it requires another filtering. Impossible? No, it just requires some time spent. Does anyone have experiences? 2nd. posibility Repair the old one. Is it easy? Yes and no. The most difficult part is to remove the converter from PCB and open the original shield. It is difficult but everyone will know how to do it as soon as he tries. I will rather describe how to troubleshoot the circuit that is inside. Here is crop from service manual. It is just symbolic circuit and it has some basic mistakes. But it is very good start point. Transformer and transistor on the left side create oscillator. Diode on the top is rectifier. Transistor and diodes on the right create stabilizer. When you reverse polarity, three parts can be burned - the ones marked with red letters and transformer. However, the wire on the transformer is much thicker than on the 33uH coil, that's why it will survive. In most cases, it is necessary to replace both red parts: 1. Inductor: in blue circle (33uH, bigger version) 2. Transistor: in blue circle. Instead of hard to get 2SD1048 you can use BC817 as 1:1 replacement. Well, the older one is little stronger (700mA vs 500mA) but in this application it doesn't matter that much. It is good to have right soldering station to be able to solder SMD parts. Or ask someone who can. I hope you find this article useful. Any comments are welcome. Marian
[QUOTE=" Does anyone have experiences? Marian" /QUOTE] Well, I have a lot of experience ruining things. Anyway, thanks for your topic. For D6C i usually use batteries since i destroyed some D6c in the past , but i like the idea of convertors. Can you please send me the link ebay or Amazon to the right one?
Marian, if you have time, could please add some details on how that circuit works ? I've been staring at it for 15 minutes, but my recollections of electronics are too lost in time... How is the oscillation caused ? Is it the capacitor close to BC817 charging and discharging ? The output tension is fixed by the zener + 0.6V of the diode + the resistor which polarise the rightmost BJT ? thanks
Yes, it is serial connection of capacitor and transformer coil, connected to the BC817 transistor base, causing circuit to oscillate. I think the transistor on the right side biases BC817. The higher output voltage, the lower bias, the lower voltage, the higher bias. About converters: I currently do experiments with converters for WM-D3. I bought about 5 versions and I compare them. Not all are suitable because they interfere with audio circuit. They also need capacitor with capacity at least 2000 uF on the output. t is not problem with D6C because there is enough space.
Hi...in my case the output voltage was significantly higher than where it should have been. The first question when such a problem arises should be, “What is your load current?” Often the answer is “I haven’t applied any load current yet. I am just testing the regulator now to make sure it operates correctly before I apply a load to it. calculate percentages
I know this is old thread but I'm restoring my WM-D6C DC-DC board and can't find anywhere the value for the two blue tantalum caps, one blow up on my board in addition to the inductor and transistor, anyone know the values?
@Deb64 is the expert on the WM6 models. If you are lucky she will see this and respond. If not this Google search https://www.google.com/search?q=ste...33i10i160.12715j0j15&sourceid=chrome&ie=UTF-8 will show a lot of her WM6 posts including those in the 0ld forum archive.
Thanks for the mention @Longman. I was typing a reply as you posted. The tantalum caps are both 10uF / 16V. Check the physical size when ordering as there isn't much space inside the can. I always replace both of them. Here is a photo of an original one. You will need to replace C317 and C607 as well since they will have been zapped by the reverse polarity or overvoltage.
Thanks @Deb64 ! I could not get the values of whats left of the 2nd one, markings were burned. C317 is still 220uF, but will replace it. Also got the typical symptoms, too fast running motor and no sound, if sound feeded into Line-IN then just low volume distorted sound over Line-Out, in addition to that, no VU meter running and just one LED if on Bat. Is there any source for the CX20084 in Europe? Also have to recap WM-EX48 and EX50 as very low volume, are there any caps that need replacement on the D6C? and here how the DC-DC board looks like
@Deb64 if the C607 is still OK (47uF) do you think or advice to replace it? same for C317, looks like they got away from zapping.
C607 and C317 are both polarised electrolytic capacitors which will have been subjected to the same zapping (over voltage or reverse polarity) as the DC-DC converter and are very likely to have been damaged by it. You will probably see that both capacitors look swollen. Even if they are not visibly damaged, they will have been internally damaged. Therefore they should be changed. The line amplifier in the D6C is powered from the 11V supply from the DC-DC converter, which will explain the lack of sound out or signal on the meter. The fast running is due to the CX20084 having been blown. Unfortunately these are now becoming very difficult to get hold of. There are still some advertised on Ali Express, however I have no idea if they are any good or some of the fakes which are in circulation. If you do find a source of good ones, please let me know.
Thank you @Deb64 on detailed post. In the attempt to follow on this instruction, I ripped one of the wire in the wound coil and had to find an alternative. Luckily, the solution I found was very effective. I joined this forum just to thank you and give back to the community on my learning. My post on DC-DC converter alternative is here.
