So my D6C is presenting a new problem now. The sound cuts out if you tap or knock the machine, but not the power. The motor keeps running but the sounds goes off, as does the VU meter. But here's the weird bit, If you leave the unit running for a few minutes the problem goes away. Its only when the unit is started up from cold, as it were. I've searched all over but not found this particular problem.
There are a few possibilities; a dying mute module, a dying capacitor or a dry solder joint. Another possibility could be the DC-DC converter, although these generally either work or they don't work. I haven't come across an intermittent one before. There is one quick way to test if the DC -DC converter is working on a D6C. While the sound is off and the fault is present, put the walkman into FF without a cassette in it. The take up spool should stop spinning after a couple of seconds if the DC -DC converter is working. If the take up spool keeps spinning then you have no 11V rail. If the 11V is OK then I would need to look at the walkman on the bench and trace the signal through with an oscilloscope to find where the signal is getting lost.
+1 to what @Deb64 said, and maybe not D6C specific but the general problem is so common that there is a cheap solution: Once D6C is warmed-up and plays Dead, spray cold fumes over 'Evident Suspects' and see what happens... Not very 'hi-end' gizmo but it did help me to narrow down the problem in my fav National/Panasonic boombox (((I am clinically lazy and just hate to trace the glitch with oscilloscope!!!)))
Maybe a clue to your D6C fault is the fact that the LEDs stop working when the fault is present. A bit like critical battery I notice from time to time. No LEDs usually means the D6C has stopped recording too even if the motor seems to keep going at regular speed. Mute modules are known to fail too and mean no output but the LEDs may indicate interruption to the power supply somewhere on the PCB at component level or a simple dry join. Jorge's "hot and cold" may be a quick way to locate the component or trail with a dry join problem. Interested to know how you get on with this because I have found pretty much every problem with these wonderful recorders can be fixed. Many thanks again to @Deb64 for advice on the dismantling of CP602? for that repair of the IC to solve the speed problem of my D6. Still searching for a plate lock though to keep the head engaged when Play is pressed. Always something on the to do list!
Thank you everyone for all your help and advice! Its certainly sounds like a job for a professional. I'm moving house at the moment but when I get settled in and all unpacked I will take it to "my man" and see if he can diagnose whats wrong. By the way, I'm not trusting the removal guys with any of my precious decks and walkmans. They are coming with me in the car! I will keep you all updated on the outcome of the repair.
Update! We now know it ISNT the muting module or anything to do with the power supply. Still cant get to the bottom of the problem though. Its looking tricky. Will keep you posted!
I now have my D6C back from my repair man. Its not great news, but not terrible either. The fault is definitely one of the surface mounted components failing, but as the problem only lasts for a few seconds at a time it is impossible to trace where the signal is getting lost. The component has to fail completely before we can find out which one it is. I've been told to keep using the machine until the sound fails completely and then take it back for repair. Knowing my luck the dying part will linger on for years before it finally gives up the ghost!
