I am troubleshooting an AIWA alpha-2 walkman mechanism that doesn't want to autoreverse. The mechanism works perfectly fine in forward. Upon hitting reverse, however, the capstans/pinch-rollers will correctly reverse directions, but the other take-up reel will not turn, thus producing slack tape and stopping the mechanism after some seconds. I have discovered that the reason for this is that, upon reverse, the gear assembly (1) is not swiveling to the right as indicated by the arrow towards making contact with the gear (2). Gear (2) supplies the optical rotation data, but also drives the other take-up reel. Even if it does appear to, but the assembly (1) is not making contact with (2) here: However, when it does make contact (which it does about 1 out of 10 times), it looks like this. Notice the brass guiding pin of lever (1) moving entirely outside the cam gear (2) (as supposed to): You can watch what it does in a short video here, showing, first, the problem, and then, second, how it looks when it works: http://drops.bijankafi.de/v/jWk1Sx I am "making it work" here because I am activating the solenoid shown by hand and then letting it go gently after half a turn of the cam gear. I know that this is very hard to say without having the thing in front of you, but would anyone hazard a guess what's the issue here? I know there is a second cam under the cam gear with guiding pins and I suspect something's being "misguided" here. Are there any photographs or even a documentation what has to go where under here? I'd love to know before I ruin the timing on this.
Remove this gear you called 1. It has a spring tensioned clutch, a plastic washer holds everything together, but the clip that holds the washer tends to break. It's not difficult to fix, but gluing it doesn't work, as incredible as it may seem, I managed to fix some of these by sewing the spring tight with a very thin copper wire. Pass it through the openings in gear 1, turn it around and pass it through the smallest curve of the spring.
Many thanks for the hint! I think I got what you did. Not sure if this will resolve my issue, but I'll give it a shot as soon as I find the time.
Thanks, @Romulo Lubachesky, you seem to have been right. This is what I found: Is the idea here that you have: 1) lower, felted part of clutch, 2) spring (narrower part towards felt), 3) second half of clutch on top? And the washer would keep the parts together? So the job of the spring is to keep the two halves of the clutch apart? And if I get you right, you suggest sewing the spring to the lower part of the clutch (with the felt) in the two marked spots?
The spring maintains pressure on the clutch, so this is the order of the parts: The stitching will go through these 3 openings in the large gear and the thinner spring loop, making it tight like this: It is important that, when looking at it assembled from the side, the spring is completely retracted, so the use of that small washer is unnecessary.
Many thanks, @Romulo Lubachesky, that was extremely helpful. I've now had time to repair the clutch. Sadly, while things seem to have improved, this does not solve my autoreverse problem. After the repair, reversing still does not work with the aforementioned symptoms. However, the player is now no longer eating tape. That is: the failed reverse action isn't carrying on endlessly as before, but stops correctly as soon as the player realizes something is amiss. Before that, the player was entering an endless back-and-forth loop leading to chewed tape. Now, I have a sneaking suspicion that the double cam gear (the one on the far left in the top picture) is the source of the problem. But since the clutch is now repaired, at least the player correctly seems to sense when the procedure isn't working and stops much quicker. I suppose I will have to take that cam apart sooner or later. Pictures or educated guesses would are always appreciated.
I'm happy to have helped. I recommend that you check the logic buttons. In all the devices I worked on, these buttons closed some contact, even when they were not pressed. Perhaps residue from the capacitors has penetrated them. This caused the functions of the other buttons to not work correctly, not switching sides, for example, or always going into fast forward mode. My solution was to dip the plate containing the buttons in IPA, wait for it to dry well and reassemble it, but I'm afraid that in some cases it will be necessary to change the button.
Thanks, @Romulo Lubachesky. I am 99% sure that the buttons are fine. As far as I can say, they do what they are supposed to do. I have turned my attention for the moment to the issue of bleedthrough that I am getting when playing a tape and that has been bugging me for a while. When listening to a tape, I can hear the other side backwards in the right channel. Not super bad, but much too loud to be normal. I also noticed two other, possibly related issues: Firstly, I can hear sound when fast forwarding/reversing. I don't think it's supposed to be this way. And, secondly, when switching to "Normal" bias *and* switching on Dolby B, the volume is cut by about two thirds. Everything is fine with Dolby turned off and also with and without Dolby in "Chrome" mode. I am beginning to suspect a faulty amplifier and may need to replace some ICs...
The fact you hear sound when FF/REW means the amplifiers are not muted. You shouldn't hear anything during FF/REW, not even the noise floor of the amplifiers. Which walkman are we talking about ? Then the problem you hear the other side in reverse means the signal from the other side does still get coupled into the preamplifier. The TA8115F pre/power amp has those switches integrated into the amp itself and the switch itself is controlled from pin 14: FWD 0.6V, REV 0V. Do you get these voltages at pin 14 ? The 120/70us EQ is done in the preamp section. Control is done via pin 6 of the IC: normal 0.7V, metal 0V. Do you get these voltages ? Dolby function is controlled at the Dolby ICs and its unlikely both the preamp/power amp and Dolby ICs have gone bad. Most likely the problem is elsewhere (a floating ground due to open via for example).
As usual, many thanks @Valentin. Let's tackle the first problem first; it will take a while before I can check the voltages on the relevant ICs. We're talking a PL55 here. The mute switch is realized using 3 transistors and is linked to Pin 14 on the microcontroller in one direction and goes directly to the volume wheel in the other. I guess I should check parts, traces and vias between these two points first.
Especially the vias, then the traces and the least I would suspect are parts. What I would do is check all vias near capacitors (especially where bad leakeage has occured) and check the continuity. The unfortunate part is some of these vias may be under capacitors, so if you have re-installed electrolytics you will need to use the PCB diagram to see where the vias are. There are also quite a bit of vias underneath the volume potentiomter, which should also be removed, cleaned underneath and all the vias checked/repaired if needed.
