slipperyflax
Well-known member
Hi,
first of all I must say I'm very new the the world of cassette decks and the repairs. I've done quite a few builds of professional audio gear such as compressors and equalizers so I can carry myself with a soldering iron. However my schematic reading skills isn't what they should be, even if I'm getting better as I'm going along. Now to the issue at hand..
My father likes Tandberg and he recently bought a very rough TCD 310 deck (Mark I). It had been standing in a barn for quite some time and the owner didn't know if it worked. When plugging it in the first time it was obviuos a lamp had to be changed and the drive belt re-attached. Simple enough. Did that along with a lot of cleaning and then tried to pop in a cassette and this super loud, horrible buzzing came out of my headphones in playback mode (dead quiet when stop button is down). I think I measured the signal to above 3V from the outputs. After a lot of fault searching I have finally come to the point I need help. Here's a video of what's happening:
https://www.youtube.com/watch?v=ppl0xjrMI8E
As you can see I have the deck in playback mode and the buzzing get's crazy. If I then put a cable between C311 (left channel) and signal ground the buzzing disappears and I can hear music pretty fine. However the signal is quite low at this point (I know that's adjustable later on if needed when the main problem is fixed) and if I put the deck in pause I can still hear a, what I believe, ground hum.
https://drive.google.com/open?id=1mIOn2aNxBkhyzRenYI1xtBpgzP8Se4aB Here you'll find the schematic where I've squared the point where I could ground to get it more quiet. I've done a bunch of probing and measuring, even voltages on the mother board and they seem fine. On the other hand I've done a bit of continuity tests also for ground points.
I did notice that I got 23 DCV with reference to ground between Q108 and Q109 (says 21.3 V on schem) at the circuit for power to amplifier boards but.. Don't know if that matters. My only conclusion is that the problem should lie between the tape head and outputs and perhaps be ground related or if I maybe have some faulty components along the way but.. This is exactly where it would be handy to be able to read the schems a bit better :-[
As you can tell I'm a bit lost and could certainly use some pointers.
Thanks!
first of all I must say I'm very new the the world of cassette decks and the repairs. I've done quite a few builds of professional audio gear such as compressors and equalizers so I can carry myself with a soldering iron. However my schematic reading skills isn't what they should be, even if I'm getting better as I'm going along. Now to the issue at hand..
My father likes Tandberg and he recently bought a very rough TCD 310 deck (Mark I). It had been standing in a barn for quite some time and the owner didn't know if it worked. When plugging it in the first time it was obviuos a lamp had to be changed and the drive belt re-attached. Simple enough. Did that along with a lot of cleaning and then tried to pop in a cassette and this super loud, horrible buzzing came out of my headphones in playback mode (dead quiet when stop button is down). I think I measured the signal to above 3V from the outputs. After a lot of fault searching I have finally come to the point I need help. Here's a video of what's happening:
https://www.youtube.com/watch?v=ppl0xjrMI8E
As you can see I have the deck in playback mode and the buzzing get's crazy. If I then put a cable between C311 (left channel) and signal ground the buzzing disappears and I can hear music pretty fine. However the signal is quite low at this point (I know that's adjustable later on if needed when the main problem is fixed) and if I put the deck in pause I can still hear a, what I believe, ground hum.
https://drive.google.com/open?id=1mIOn2aNxBkhyzRenYI1xtBpgzP8Se4aB Here you'll find the schematic where I've squared the point where I could ground to get it more quiet. I've done a bunch of probing and measuring, even voltages on the mother board and they seem fine. On the other hand I've done a bit of continuity tests also for ground points.
I did notice that I got 23 DCV with reference to ground between Q108 and Q109 (says 21.3 V on schem) at the circuit for power to amplifier boards but.. Don't know if that matters. My only conclusion is that the problem should lie between the tape head and outputs and perhaps be ground related or if I maybe have some faulty components along the way but.. This is exactly where it would be handy to be able to read the schems a bit better :-[
As you can tell I'm a bit lost and could certainly use some pointers.
Thanks!
