From what you have told me here, the first thing I would try would be to remove and clean the switch inside the mic socket, using the photos above. The problem only seems to happen when recording using a microphone, so the recording level control seems OK - otherwise it would crackle when recording through the line in. There are two microphone pre-amps, one for left and one for right. If one of these was faulty I would expect the problem to only be on one side. In post #13 you state that there is lots of "scratch" when you move the mic in the mic in jack and when you turn the rec level Control. If the rec level control was faulty, it would scratch when you record from line in as well as it is common to both inputs. Normally the switch will be in the "line" position and will only change to "Mic" if a jack is inserted into the mic socket. Therefore the common and line contacts in the switch are normally covered by the wiper and the mic contacts are exposed to the air, damp, smoke etc. The switch is anywhere between 15 and 33 years old so the contact may be dirty or oxidised, depending on how the D6C has been stored during that time. Another possibility is; are you using an electret microphone and using the "Plug in Power" facility to power the microphone from the D6C?
Hello again and thank You for Your engagement. I haven´t had time to desolder the jack because of other dutys but I´ll report as soon as I have done it. I can even tell that there is litttle less distortion after I sprayed the mic jack with contact spray but it is not perfect. I have tested with both kind of microphones: Sony F-99EX and Sony ECM-959V.
Happy New Year! He is the latest from my issue. I thougth it would be too risky to dissambly the jack so I replaced it with a new one I bougth on Ebay. The quality of recording became better but there is still lot of scratching from the recording level pot and the is much more "humming" compared with my other D6c,s. After this I dared to dissamble the old mic jack and clean it mechanically and put it on one of my other D6C,s which also had problem with scratching jack. After reassembled it thefre was still littlef scarthing but wfen fixed in a position ther was no scrathing and even no backgroud humming. The most interesting thing was yet that there was no scrathing from the rec level pot!! Could it still be a problem with same IC connected to the pot or is it only the pot that is the problem?
Well done. It sounds as if you are making some progress. What type of mic socket did you buy on Ebay? Can you please post a link to the listing or the item number? Did you manage to find a genuine Sony WM-D6C socket? If it is not exactly the same type as you have taken out, you may not have the same pin connections. If you are getting a lot of humming, there may be an earth connection which isn't connected. Did you put the metal back panel on the D6C and did you fit the metal spring which connects the back panel to the audio ground on the main PCB? If not then you may get humming. It sounds as if your second WM-D6C is now working properly with no scratching on the mic socket or record level pot and no humming. There is no IC connected to the record level pot. The mic pre-amp consists of two discrete transistors and assorted resistors and capacitors per channel and there is a single transistor amplifier after the pot. There is a Dolby IC (CX20068) on each channel, which handles record and playback signals. If this was faulty then you would be getting problems on play as well as when recording from line in. Also, if the record level pot was faulty then you would get scratching when recording from line in.
Here is the jack I took from my other WM-D6C and the partnr from the new I bougth. I´m not sure what You mean with metal back pandel and the metal spring You mentioned. Only thing I associate with ground is the litlle copper thing screwed on the mainboard.
By the metal back panel, I mean the back cover. The metal spring is this; I take it that this is the little copper thing screwed on the main board. When the back cover is fitted, the copper spring makes contact with the metal cover through the round hole in the clear plastic insulating sheet inside the metal cover. The grounded metal cover shields the main board from radio and electrical interference. You were very lucky to find a genuine Sony mic socket on Ebay, they must be quite rare now. If you are still getting scratching noises with the "new" mic socket, then it may be worth cleaning the contacts on the jack socket and switch assembly on it as the "new" socket may have been in storage for up to 33 years.
There is only scrathing from the rec lever pot when I turn it while recording. The humming is still there but disapper with medium loudness.
Here is the new mute module fitted to my WM-D6. It plays very nice now but You can hear a"phoff" when You start play and even when fwd and rew buttons are pushed down and there is a little delay before You can hear the music play. Not very disturbin if You dont think about it. I dont remember how it was with thef old module cos I didn´t use my D6 very often. I quess it should behave as i described. In stop mode it behaves like my D6C,s.
Glad to hear that the mute module is working OK. It reduces the output signal, both from line out and headphones, by about 44dB for about half a second on power up and shut down. This is the delay which you're hearing before you can hear the music play. When you press "play" on a D6 or D6C, this switches on all the audio circuitry and amplifiers as well as the motor. This is why you get a loud thump on the outputs without the mute module and why Sony included a muting circuit in the design. I had a bit of scratching on the record level pot on one of my D6s. I put some Deoxit fader cleaning into it and turned it a few times and it seems a lot better now. Ideally the best thing to do would be to replace the pot but I have not been able to find a replacement which will fit into the Walkman yet. I'm a bit puzzled about the humming which you're getting. Is it a 50Hz mains hum or do you think the noise is coming from the walkman's motor? Are you powering the walkman from a mains adaptor or using batteries? Are you listening using headphones or have you got the line out plugged into an amplifier? I'm wondering if you could have an earth loop caused by earthing your audio electronics in two separate places (through a mains adaptor powering the walkman and through an amplifier).
To be accurate about the noise i should describe it as a combo between humming and whinig and it occurs as far I can hear only when recording through a mic . You can hear it first when You increase the loudness. And all this when I listen to the ongoing recording with earphones. No matter if I use mains or batteries.
I have to admit that I'm a bit puzzled by the noise you're getting. I don't think I'll be able to diagnose the fault without actually seeing your walkman. That said, I have a D6C on my bench at the moment which I will soon be refurbishing. I will try and see if I can get a similar noise on mine but I may not know for a week or two. This D6C has been used on a beach sometime in the past so I need to strip it down and get all of the sand out of it first. Do you hear the noise on playback at all? Do you hear it if playing back the tape which you have just recorded via the mic (and heard the noise while recording). Do you get it when playing back any other tape or a blank tape?
Hey! No noise when playing tapes not recorded through mic. Noise heard in playback with tapes recorded through mic. No noise with blank tapes.
