Hi everyone. Recently picked up a WM-DD9 and a WM-D6C as a package deal. Both had been in storage for awhile and required replacement of all rubber parts. The WM-DD9 is now working perfectly but the WM-D6C plays way too fast. From a quick search of the internet, I've learned that the problem is most likely caused by the CX20084 speed controller chip at IC601 (this one is pre-26000, serial #192043). I ordered a replacement chip through eBay (from China), removed the old chip from the board, and soldered in the new one. Even with the new chip in it is still playing way too fast. A quick check with a DVM indicates that the motor is getting near 10V when it's supposed to only get 2.4V. My question is, is there a way to determine if the new chip is defective as well and also if there could be other cause(s) to this problem? Thanks
Hi neighbor, Welcome to S2G!! You will find tons of info for D6C at tapeheads.net, Ive seen this problem discussed at length there
Hello biomayhem and welcome to S2G. With regard to your WM-D6C, if you're getting nearly 10V across the motor then there is something badly wrong. The motor is driven from an unswitched 6V supply, via a transistor (Q601), and the 11V rail isn't connected to the Cx20084 or motor drive circuit so, even if the CX20084 was faulty, you should not get 10V across the motor. Since the motor is only rated for 2.5V don't power it up until you have found the fault as you could damage the motor. I suspect you have a short from the 11V rail to part of the motor drive. You need to check over the board with a magnifier looking for solder bridges or loose whiskers of wire causing shorts. Check that all the wires are soldered into the correct places. Check that the orange wire from the DC-DC convertor (11V) is soldered to the correct pad. Take your time over this and be meticulous. Check everything, not just the parts which you have worked on. Maybe somebody has tried to repair it before and made a mess of it. I have attached a copy of the PCB layout which may help. Be aware that even if you find and clear the fault, depending on where the 11V was shorted to, it is possible that you may have damaged the new CX20084. There have been a few stories posted on the internet stating that there are some fake CX20084s in circulation. I ordered a batch from this supplier in China and have tested a couple of the chips, which are fine. https://www.ebay.co.uk/itm/182469064571
Hi Deb64, Thank you for the suggestions. I was also able to find a copy of the service manual. Unfortunately, I will be busy this coming week with work so I won't be able to get back into it until next week. I will provide an update as soon as I get back into the WM-D6C. Hopefully I will be able to find the cause of the short. Thanks again for your help.
