Hello. The Walkman has a problem with playback, the A side of the cassette plays perfectly, while the B side plays both sides at once. The tape path is in perfect condition, the 3-position switch moved by the FWD / REW arm has been cleaned, nothing has changed, do you have any ideas?
Did you also try with a different tape, or reversing the same tape? There might be a longer than 12 second blank space (or almost inaudible recording) that the device detects as something to skip near the end. Because of it and the tape reaching the end as result, subsequently reversing the playback direction?
Hi there Dariusz, I have worked on a few 808s, they are really fiddly, maybe I can help. I have to ask a few questions to narrow this down. 1. When you say it plays both sides at once, are you referring to both pinch rollers engaging at once, or you hearing two audio channels at once? 2. Did you buy used? If so, was there an old gum stick battery that leaked inside? Any battery corrosion? 3. How did you clean the tape position switch? Was it dirty or damaged? 4. When you press the reverse button, does the mechanism physically change to move the tape in the opposite direction?
Hi. ad1. I can hear two audio channels now on both sides of the cassette. ad2. I bought it used inside like new no corrosion. ad3. I changed the switch but I managed to measure it with a meter. ad4. So it changes direction. I resoldered the individual elements, nothing being the source.
Wow, what a peculiar fault. So no matter what, you hear both sides? That's really interesting. You should use it to trick your friends lolol So if it changes direction without a hitch and you didn't bridge anything when soldering, I'd say you have an electrical problem of some kind and I highly doubt its mechanical. Let's K.I.S.S. for just another moment before we take a deep dive: This is the whole motherboard/cassette assembly, with just the top cover removed. Take a look at point number one. That ribbon connector is what goes to the tape head, and it folds over on the motherboard before curving around back into the connector. This puts stress on the cable where it folds, and also stress on the connector on the board. Check this out to make sure the ribbon cable isn't damaged, has any breaks, or has missing/folded back pins. This connector is really fragile, and I had a cracked connector on an EX that made it to where I had to fold some cellophane tape and jam it in the connector to add thickness to the edge connector so it would insert tightly. You could also try poking and pushing around on this cable with a plastic spudger or pencil eraser while operating to see if it changes anything. Do this all gently. If all of this looks good, and nothing changes, you can move on to the motherboard. Now for the deep dive... Let's circle back to that switch really quick. There is another switch you may not be familiar with, called the A/B switch. Let's see the schematic: As you can see, the red square indicates S702, and S703. You can also see the Blue block is where S702 fits into the system control circuit (IC701), and also where S703 connects up (orange block). S702 bridges either pin X. rew, or X. fwd to ground... But A/B switch bridges the A/B pin on IC701 directly to B+. I'm really curious as to what this A/B switch does now, being how it fits into the circuit. Let's now jump over to section 5 of the service manual, and we can look up a glossary of all pins on IC701 and what the switches controlling the flow to the pins do. Let's start with the obvious... S702 (the switch you cleaned)'s pins: MD condition check. Sounds like it's a check of the mechanism and what position it's engaged in currently. Accurate. Now, let's look at that A/B switch: This looks like NOT what I suspected this switch to be. This switch tells the mechanism if the inserted tape was inserted on A side up, or A side down. I was kind of hoping this was what we needed. BUT, That's when I found this: Pin 9 is the control pin coming out of IC701 that tells IC301 what section of the tape head to use. High logic state for one side of the head, Low logic state for the other. Here's the block diagram: Pin 9 of the control IC goes DIRECTLY into PIN 27 of the amp chip IC301. no components in-between. Here's what you need to do. First, check continuity between them. then, Check to see when it's High, 'H', or Low, 'L'. If it is switching from high to low as S702 changes position, the chip is working properly, and IC301 is most likely failed. If it is NOT switching from H to L properly, IC 701 or a supporting component for IC701 has failed. “Acceptable” output signal voltages range from 0 volts to 0.5 volts for a “low” logic state, and 2.7 volts to 5 volts for a “high” logic state: Here's the complete path for reference:
Welcome back. Recaptcha thanks a lot for the exhaustive topic, I was supposed to take care of it after Christmas, IC701/IC703 was left to check, I'll check and let you know, thanks again for taking up the topic.
excellent explanation @Recaptcha I could not have done better But if it is not the switch S703 that causes the logic level to change on pin 9 of the ic701 control cip ... what makes it change there must be a mechanical lever that crushes s703 when it changes reading side ... supplying a positive voltage to pin 44 or vice versa ... there is nothing of ic701 on the network
Thank you all for your suggestions, the operation was successful, the patient survived, IC701 was replaced, best regards.
This is excellent news. I'm so glad you got it fixed! I have never seen a bad IC before in an EX, so this was a first for me.
