Hi everyone, I have serviced my D6C and it's sounding fantastic - what a great unit! I have now been trying to record some tapes and noticed that I have some static/crackling noise in the background (on the left channel mostly). I will try to clean the PB/REC switch as suggested by Valentin - would anybody have any other idea of possible root cause(s)? I've attached a recording I've just made with record level set to 0 and nothing connected on line input, to show the problem. Thanks!
Are you getting it with the tape played in a different machine? I would look over the inputs and make sure the wiring is all nice, they take a beating over the years with constant in and out movement. I'd also narrow down if it happens all the time or with only the MIC or with other LINE IN equipment attached. The record volume and LINE IN/MIC Switch might also need cleaning. This is a good guide to electronic contact cleaning, over here we mainly use DeOxit but there's other formulations over in the EU. Usually DeOxit is good for rotating and toggle switches, FaderLube is good for moving switches like EQ's which have materials the DeOxit might attack. https://audiokarma.org/forums/index.php?threads/the-idiots-guide-to-using-deoxit-revisited.207005/ https://caig.com/
I am getting the same scratching sound playing the cassette on another unit. I will go ahead and clean contacts etc... and see if it solves the issue. Thanks a lot for the links!
So I have cleaned all switches (PB/REC, MIC ATT) and inputs/outputs jacks with contact cleaner, no luck same scratch. Then, I tried to record while playing with the Dolby NR and Tape switches, and noticed that the scratching sound only happens when tape type is set to CrO2. The attached recording was made as follows: nothing connected to Line IN Tape is Type II REC level set to 0 0-10 sec : Type set to Normal ==> OK 10-24 sec: Type set to CrO2 ==> scratching 24-38 sec: Type set to Metal ==> OK 38-53 sec: Type set back to CrO2 ==> scratching 53-65 sec: Type set back to Normal ==> OK Does this confirm a failure of the EQ switching modules (CP302 and CP303)? Thanks!
Were you able to clean the noise reduction switch? I always have problems with any sliding switches on portables and the two open view ports on the top might be dust collectors (or liquid).
Will try that first thing when I get back home in a couple days. I must admit I didn't clean them with the rest of the lot. Will see if this is the cause. In any case I will proceed with replacing the EQ switching modules.
I tried to clean the cassette type and Dolby selection switches - didn't help. I've changed both EQ switching modules with the ones sold by Deb and bingo - that was it! Unit now records perfectly and sounds amazing
I'm pleased to hear that replacing the EQ modules has solved the problem. This was an unusual fault. Normally when EQ modules fail, they cause intermittent loss of high frequency on recording. I have never come across EQ modules causing static noises on recordings before.
Who knows? They would have needed replacing anyway as the Sony potted modules often start to give problems after around 30 years.
Hi @Deb64 I recently replaced the EQ modules too and there was an printed photo in the parcel how to solder it, and CP303 in a different position than @dom69 . It's doesn't matter or I should resoldered it? I have issue in the record mode with left channel it works but is very very quiet both in line in or mic in, through headphones or line out. In playback everything ok with both channels. Tried to clean play/rec switch with contact cleaner without desolder it but nothing changed. Desoldered rec pot because it was broken and bridged at max rec level without rec pot but nothing changed. I also tried with fixed pot (glued it and restored contact with graphite varnish) nothing changed. Don't know what else I can check. Could play/rec switch be the cause of the very very low level in left channel? Should I desolder it anyway to check or may be it can be checked with multimeter without desoldering? Check with multimeter seems worked. I will be appreciated for any help)
Ouch I see - then same question from me, as mine is a D6C hence I could have soldered the module in the wrong way. I have recorded and played a Type II tape flawlessly, but didn't try with other types (don't have Type I nor IV tapes)...
Electrically, the EQ switching boards can be fitted either way round; they are symmetrical. The problem is that I cannot make them as small as the Sony originals and the edge connectors, which I use, make the boards stand higher from the PCB. The fitting methods for D6 and D6C which I have shown in the leaflet are the best way of fitting which I have found to avoid the EQ boards touching other parts of the mechanism. @dom69 yours should be fine if it doesn't touch any other parts of the mechanism when the main board is fitted in place. @-LV- It is possible that you may have a broken wire inside CP101, which is the MPX filter on the left channel. If you have an oscilloscope, you can try tracing the input signal through CP101 to see if it can be see on pin 6 of CP101 (the output). Another way to check is to try swapping CP101 and CP201 over and see if the fault remains with the left channel or moves to the right channel. If you do de-solder and re-solder them be very careful as the wires on the internal windings are very delicate. The record level pot is vulnerable to damage if the walkman has been dropped, as yours appears to have been. In the D6C, sony braced the Rec level pot to the CP101 can to try and protect the wafers from damage if the rec level pot is hit. Unfortunately in a severe impact, the shock is transmitted through the bracing wire to CP101, which can result in a broken wire in CP101.
@Deb64 thank you, can I use multimeter with true RMS instead oscilloscope? I don't have oscilloscope unfortunately
Thanks @Deb64! Since the modules are not higher than any surrounding component I believe it will be OK - if I sense any mechanical issue I will look at this point first thing. @-LV- with my limited experience I would say yes, you can use True RMS multimeter to trace the signal - although I am not an expert in electronics. I have been doing so on other units I am working on, having no oscilloscope myself neither.
I have never tried it as I normally use an oscilloscope. You can try with the meter and try checking the right hand channel to see if there are any obvious differences.
I will try tomorow check CP101 and CP201 output pin. As I understand I need measure voltage between ground and 6 pin on CP 101 and CP201? Their inputs is on pin 3?
I checked CP101 and @Deb64 I think you were right. I run 1kHz from my phone to line in and what I get: On line in contact R L 87mV 87mV On CP201 3 pin 6pin 51mV 47mV On CP101 3 pin 6pin 80mV 1mV I checked scheme and I think I can bypass CP101 for test. If I desolder one side of R112 and yellow wire and connect them directly. I'm right?
I bypassed CP101 and left channel works fine Than I decided bypass and CP201 too. As I understand MPX filter for records from FM radio and it shouldn't affect record from other sources? @Deb64 thanks a lot for your help. @dom69 sorry for writing in your topic I hope you don't mind
