Interesting. I have tried mine with Senheiser CX-300 II, I think about 16 ohm. Also tried with Senheiser HD300, 50ohm. Worked with both. When I serviced the unit, I put external 33ohms resistors for measuring the output signal on scope (1Meg input impedance), worked well with that too. Check the soldering on the jack itself. Does the unit work ok without anything plugged in ?
Internally it has two 33ohm resistors connected on the outputs when nothing is plugged in. I would check the jack itself for cold solder joints and cracks on the plastic housing, clean it well with a cotton swab immersed in contact cleaner. I looked at the headphone you stated, the first SONY with noise cancellation seems to have an amplifier, in which case it's high impedance. I remember I tried mine with Beats Studio which also have amplification and it does not work with those. As for the others, do they have any remote control for using on a phone ? That may be a problem. Try the simplest pair of headphones, without microphone, remote control or any amplification. Of course, a crude solution can be to solder some resistors in parallel with the output, but that will decrease the output power.
I just found this forum while searching for information about replacing the drive belt in my WM-7. In removing the circuit board, I inadvertently pulled off one of the wires that I think connects to the control panel. It's the gray wire that I've highlighted in the attached image (borrowed from an earlier post in this thread). Does anyone know where it should connect? Thank you!
If you are talking about the white wire, note that the tape holding it onto the board needs to be removed when flipping the board. It connects to the buttons PCB, I took a picture for reference. When taking out that small PCB pay attention to the marked hooks that need to be pressed. Also note there is a ribbon cable connecting to the board from underneath, care must be taken not to damage it.
Thank you, @Valentin. That's very much appreciated. Yes, that's exactly the wire I was referring to. I'd examined the underside of the control panel, but couldn't see where the wire had been soldered. Unfortunately, I discovered the tape removal tip after I'd broken the wire.
Problem solved with my WM-7 and the switching between ffwd and rev. Problem was that one soldering point was not OK in the volume pot. Redid this and problem gone. Now the rest of the issues. Right channel very low in volume, new belt installed (Marian), but high wow and flutter still. Think the pinch rollers need replacement.
Glad you solved it ! Regarding the right channel low volume, there could be a number of reasons causing it. I would start from the input, going to the output. 1. Check the head itself to be very clean. It could have oxide stuck in the gap that yields a poor tape-head contact. Also check the wires from head to PCB. 2. The forward-reverse switch that swithces the head signal should be cleaned. On mine it was very dirty, casuing one of the channels to be low or crackiling, but not all the time. 3. Some gain resistors and/or capacitors in the feedback network of the amplifier can also cause this issue.. I found this problem on many walkmans, but it is usually caused by corrosion from leaked capacitors or batteries, so I would say unless there was battery acid leaked on the board put this one last. 4. Coupling capacitors (especially the output ones) can also cause this issue. I haven't seen bad capacitors on this model, but that does not mean they couldn't go bad. So you need to investigate further. I can provide the schematic if you don't have it. Regarding the wow&flutter, have you cleaned the flywheel grooves and motor pulley well ? Also the capstan bushings need lubrication. Another potential source of high wow&flutter are the table reels that are out of round, causing uneven load on the driving flywheel. Mine has this issue and I cannot get the wow&flutter lower than 0.3% WRMS in forward direction. In reverse it's a little bit better.
