SONY MDS JB980 noise / hiss when recording

[ClaudioG]

Hello everyone. I have a recording noise / hiss problem on my MDS JB980: as soon as I press the rec button from the line / headphone outputs there is a strong white noise / hiss and, low in the background, the input audio. The problem is present on any input (analog, optical, coaxial) and also in the passband (ie simply pressing the rec button, with no disc in the drawer, as is always done to adjust the recording levels). Unfortunately, since I don't have other minidisc machines or pre-recorded discs, I don't know if the problem is present even in read-only mode. If, in rec, I lower the recording volume to zero the noise disappears completely. Last detail: with any audio input the volumes on the vu-meter appear regularly; in the absence of an input signal, the vu meters show nothing (but in both cases the output noise is heard). From these observations I think that the origin of the problem is electronic and not of the pick-up but I don't know how to solve it. Please, can anyone help me? Thank you all.

[NGY]

37 minutes ago, ClaudioG said:

Hello everyone. I have a recording noise / hiss problem on my MDS JB980: as soon as I press the rec button from the line / headphone outputs there is a strong white noise / hiss and, low in the background, the input audio. The problem is present on any input (analog, optical, coaxial) and also in the passband (ie simply pressing the rec button, with no disc in the drawer, as is always done to adjust the recording levels). Unfortunately, since I don't have other minidisc machines or pre-recorded discs, I don't know if the problem is present even in read-only mode. If, in rec, I lower the recording volume to zero the noise disappears completely. Last detail: with any audio input the volumes on the vu-meter appear regularly; in the absence of an input signal, the vu meters show nothing (but in both cases the output noise is heard). From these observations I think that the origin of the problem is electronic and not of the pick-up but I don't know how to solve it. Please, can anyone help me? Thank you all.

Welcome to the forum.

So the hiss appears on both the RCA line out and the headphone too, does it? Is this noise at equal level in both (L/R) channels? What is the case in normal playback, any noise?

Try this: set the input to analogue, connect an RCA audio cable to the deck's analogue input jacks, at the other end of the cable shortwire the mid pins to the shield contacts per channel, then press rec pause and set the input level to 0 dB (default) - is the noise still there?

This is not related to the pick-up, it most probably has to do with the analogue circuitry (or the D/A converter) part of the deck.

 

Edit: can you possibly take and post here a short video with this noise audible, so we can hear it?

[ClaudioG]

Thanks for welcoming me to the forum. It's incredible! I had already disassembled the main board convinced of having to change at least some electrolytic capacitors, then, to try what NGY suggested, I reassembled the main board ... and now the problem has disappeared: now the deck records regularly from any input. I don't know what to think ... maybe it was the fault of an electrostatic charge induced by the dust, maybe some strange metallic contact of the supports on which the main board rests, maybe some demonic possession ... but now it works. I'm not too happy though ... I wouldn't want the deck to hear me and start making noise again. Thanks NGY.

[NGY]

Great to see that the noise is gone.

My bet would be either on those little grounding strips that connect different parts to the chassis, or, some of the internal cable connectors. Oxidization of the contacts can show such problems.

[freddyjollo]

1 hour ago, ClaudioG said:

Thanks for welcoming me to the forum. It's incredible! I had already disassembled the main board convinced of having to change at least some electrolytic capacitors, then, to try what NGY suggested, I reassembled the main board ... and now the problem has disappeared: now the deck records regularly from any input. I don't know what to think ... maybe it was the fault of an electrostatic charge induced by the dust, maybe some strange metallic contact of the supports on which the main board rests, maybe some demonic possession ... but now it works. I'm not too happy though ... I wouldn't want the deck to hear me and start making noise again. Thanks NGY.

presumably you had to disconnect cables? maybe it was a bad contact some where producing some resistance or capacitance? I find this can be a problem with my old ( c2006) desk top computers esp in hot weather due to expansion and contraction. esp the hard drives which can play up

[ClaudioG]

I too thought, among other things, of some oxidized mass among those that dot the device but I discarded the idea almost immediately because just last week I disassembled the mechanics to change the disc loading belt (Sony spare 4 -227-025-01) for the usual disc not coming out problem. To do this, I unplugged and reattached all the earth cables and the device, immediately after, worked perfectly for six consecutive days. Yesterday, after recording a program from the tuner, the noise in play came out. Mah ... I hope I have resolved definitively.

[freddyjollo]

23 hours ago, ClaudioG said:

I too thought, among other things, of some oxidized mass among those that dot the device but I discarded the idea almost immediately because just last week I disassembled the mechanics to change the disc loading belt (Sony spare 4 -227-025-01) for the usual disc not coming out problem. To do this, I unplugged and reattached all the earth cables and the device, immediately after, worked perfectly for six consecutive days. Yesterday, after recording a program from the tuner, the noise in play came out. Mah ... I hope I have resolved definitively.

presumably not any cables other than connecting the mechanism? I would reseat them all.

[NGY]

I think there is more than that. I.e., the cables to and from  the  front panel, especially the headphone's mini pcb. Or the PSU wires.The drive is talking to the main pcb on digital lines anyway, and if that could cause any audible noise, it would be that "typical" digital noise.

I remember I worked on an S38 then a 500 too, with similar problems. And weird enough, it was the tiny audio cable that brings the audio signal from the main pcb to the headphone board. It could play in as well, that the flat copper grounding sheet of the panel was not properly put under the screw that seems holding the front bezel but it does the earthing in fact.