Hi everyone, continuing to work on my collection of Sony WM-5's and have an interesting issue. Just want to know if this is a common problem with a known resolution, or whether I need to completely disassemble and start from scratch on clean/lube. The issue I'm having is when I press play and the center gear ridge on top engages with the Lever assembly, 8 out of 10 times it doesn't have enough oomph to actually keep spinning and pull the head and capstan into position. I can "help it" and it always engages and things start working perfectly. When it's running, the speed and sound, including W+F all seem to be working properly. New proper belt from Marian, and the belt is not slipping on the flywheel. Motor seems to spin freely. Also, things seem to work 70% of the time (improved) when I don't have a cassette inserted. Still not perfect. the whole mechanism seems free and loose, so wondering if this is a common issue. I did have the classic belt goo situation but thought I got all of the residue out of everywhere. I know I have a lot of grease in there but that was experimental to see if I was having stiction between the two pieces of plastic engaging but didn't make much difference. A little, but not a lot... Pics don't really help a ton, but figured can't hurt. Any advice greatly appreciated. Thanks!
Took things apart to this point. Everything seems extremely clean with no dried grease. All mechanical parts move freely. I even got out my old Kimwipes from when I rebuilt my Porsche 911 engine and slid them under and in between the metal parts, after soaking with IPA. Will keep investigating…. Mark
Well I put everything back together easy enough and now the lever assembly does engage better but not 100%. Unfortunately now I have a new problem that didn’t exist before. When I put together and played a tape, there was only noise in right channel but music in left channel. Removed the circuit board screws and I tried a wire wiggle but no luck. After a couple of minutes, only noise in left channel too. Amp is working as it gets louder with volume pot. Just no audio signal. I’ll check voltages tomorrow but this unit is wearing me down.
Seen this problem before on DDs with center gear mechanism and there are 2 potential causes: - mechanism is turning hard and motor simply doesn't have enough torque, case in which something is installed incorrectly (can't remember what though); - motor spindle is slipping on the rubber disc (in this case belt would slip, which you say it's not the case); My suggestion is to try engaging the mechanism by hand (with belt off) and see how much force it takes to do so. There should be quite a bit of resistance during head bridge engagement, but you shouldn't struggle (like needing 2 fingers) to engage it. Does the motor stop when this happens ? As for the electronic problem, would inspect the head cable in particular given there is noise from the amps.
Thanks Valentin, I did a lot of “manual” engagement without the belt and everything turns easy until the point of grabbing the lever. The motor does NOT stop but honestly I didn’t let it go for more than 3 seconds or so. Full voltage at stall torque can’t be good. As the night went on it seemed to get better and I have not installed any grease on any of the plastic gears yet after cleaning so will go back and do that. For the sound I wasn’t sure what else I could check. I have continuity between the head and the PCB on both channels and the neutral/ground. With a VOM when I had L channel working I couldn’t detect any voltage. I think just too small prior to amplification. I think silly question but this can’t be related to me getting a slightly magnetized screwdriver too close to the head, correct? I may have used it when fiddling to insert the lever. One odd thing. I was able to find an actual Sony Service manual for WM-5 but it seems to me like the circuit board traces don’t match what I have. The head leads on mine go to a different location than what’s in the manual. I’ll look at it again. Another question: Do people signal trace on Walkmans? It’s what I’m used to on vintage HiFi. Put a sine wave on the antenna or line in of a receiver and trace until things stop working. I assume you can’t do that when there’s no common ground throughout. I can’t touch a signal generator output to a head wire, correct? Is there any way I can confirm I’m getting signal from the head? I still have fundamental check of voltage. Thanks. Mark
It's normal to be more resistance when the center gear starts grabbing the lever, but it still shouldn't be that much that you struggle. Like you should be able to engage with one finger without putting a lot of pressure on the flywheel. You can let the motor to stall at full torque for more than 3 seconds, as long as you don't leave it for long it's ok. One thing that's still unclear is: if the motor doesn't stall and nothing slips, where does the torque gets lost ? Something doesn't add up. A magnetized screwdriver around the head shouldn't cause no sound at all, unless the head is so magnetized that it actually erases the tape as it passes over the head. In regard to the manual, I think there have been more generations, so that may explain why your board does not match the manual. You can put a sinewave at the head and test the signal path, but this would take the head itself out of the equation. That's why on tape machines, even better test is to record a tape with sinewave and play it. Circuits have a common ground, but even if they didn't only consideration would be to use signal generator/oscilloscope that don't have a common ground (which is the mains earth if mains powered). Meaning in circuits without a common ground you need a scope that operates on battery or a way to isolate the grounds.
