Hello,
I'm fixing my fathers Akai CS-F21 cassette player.
Last time it has been used as cassette player was around 2008, later I was using it as headphone preamp I would say it was around 2014 to 2016.
After that it was stored at room temperatures.
I had changed the belts, cleaned heads and other moving parts.
I can't see any obvious problems, caps look good, no oxidation, ...
It can play and record well, I'm using cro2 tapes and man it sounds nice.
Problem is that after about 30 minutes of playback music gets cut out by a loud buzz. If I stop and when I hit play I can hear the music for a split second. Buzz can be seen on db meters and if I change cassete type (cro2, normal metal), buzz also changes, buzz does not change when I move dolby switch and volume can still be controlled with output level switch.
Buzz is not there if I use it as preamp (REC PAUSE), but I had not tryed to actually record while problem is there.
I don't know much about cassette players and what stages it has (got to do some reading on that) , but my diagnose is that problems is somewhere between the tape head and it's preamp, but before dolby or output preamp.
My plan is to take the pcb out and inspect for bad solder joints and if I cant find anything obvious I will try to find schematic and do some signal testing with the scope and maybee listening on some test points with headphones / small speaker.
My question is:
Can tape head go bad and cause a problem only once it warms up?
Did anyone had a problem like that and fixed it?
Here is the video of the buzz:
Video
Thank you
I'm fixing my fathers Akai CS-F21 cassette player.
Last time it has been used as cassette player was around 2008, later I was using it as headphone preamp I would say it was around 2014 to 2016.
After that it was stored at room temperatures.
I had changed the belts, cleaned heads and other moving parts.
I can't see any obvious problems, caps look good, no oxidation, ...
It can play and record well, I'm using cro2 tapes and man it sounds nice.
Problem is that after about 30 minutes of playback music gets cut out by a loud buzz. If I stop and when I hit play I can hear the music for a split second. Buzz can be seen on db meters and if I change cassete type (cro2, normal metal), buzz also changes, buzz does not change when I move dolby switch and volume can still be controlled with output level switch.
Buzz is not there if I use it as preamp (REC PAUSE), but I had not tryed to actually record while problem is there.
I don't know much about cassette players and what stages it has (got to do some reading on that) , but my diagnose is that problems is somewhere between the tape head and it's preamp, but before dolby or output preamp.
My plan is to take the pcb out and inspect for bad solder joints and if I cant find anything obvious I will try to find schematic and do some signal testing with the scope and maybee listening on some test points with headphones / small speaker.
My question is:
Can tape head go bad and cause a problem only once it warms up?
Did anyone had a problem like that and fixed it?
Here is the video of the buzz:
Video
Thank you
Anything is possible but that would be about last on the list in my experience 🙂
Wires that solder to the head can fracture due to the head plate moving but that's an easy fix. Just gently touch them to make sure they are secure.
First thought for any buzzing that shows on the meters is a dodgy record/play switch assuming it has them. They look like this and there may be two of them (if it uses them).
https://www.diyaudio.com/community/threads/pioneer-ctf9191.195121/post-2690338
Later decks moved from mechanical to electronic switching so if it hasn't got these then it's something else.
Also possible of course are power supply problems but the R/P switch is a common failure item on anything that uses them.
Thank you for your anwser.
Wires to the head are good, they actually did a great job on routing head & erase wires and are holded by plastic that moves with the mechanism.
There are no record / play mechanical switches, so this is not the problem.
I will also measure wires from power supppy when working & when buzzing starts to see if there is any drop.
I had found the schematic and there is a 2ch relay on the board near the playback level adjusting pots... and I can hear it click randomly when buzzing starts...
I think that I can almost say that problem is there... I can only hope that problem is bad solder joint or possibly some not hard to find transistor that drives it...
That is as far as I can get right now because I'm at work... looks like I will do some late night work when I get home...
It's the relay... looks like I will need to swap it for something else.
Attachments
Excellent, well done. That looks like it could be some kind of reed relay... which might be a problem getting hold of one.
Looks like it is used for record /play switching. Nothing lost in removing it and seeing what is under the wrapper... I can't tell from the picture really.
This shows the relay coil and one of the contact sets. The other set will be on the other channel with a common coil.
Looks like it is used for record /play switching. Nothing lost in removing it and seeing what is under the wrapper... I can't tell from the picture really.
This shows the relay coil and one of the contact sets. The other set will be on the other channel with a common coil.
Hy, I had actually unwinded it and there are reed switches indeed. 12m of 0.1 wire for the coil and problem was at the end of the line, where wire gets joined with 2cm of thicker wire that gets soldered to the output pin. Can't take pictures because I forgot it at work.
But this is exactly what switches inside look like:
I had used this exact schematic before diving into it.
I want to say thank you for helping me many times before waay back, I had just remembered by your username. I'm jumping back and forth between audio, cars and other mechanics stuff and some logical circuits so I wasn't here lately.
Yep, that is the reason why I decided to rewind the relay. Waiting for wire to come in the mail.
I didn't realise you were rewinding it, I thought you had repaired the wire end. That's brilliant if you can rewind it.
Sadly problem was the joint under the coil 🙁
I hope I will be able to do it, I didn't rewind anything before, I will try to improvise device that will hold and turn the relay slowly.