Tascam 122 mkII stability problem

[thefig]

Hi!
I just acquired a fine looking tascam 122 mkII cassette player. It had been previously used in studios of YLE (the broadcasting service here in Finland). It seems to be a well built and impressive workhorse, but it has a serious flaw.

When a cassette tape is recorded or played back an annoying fluctuation in the sound level can be heard. It's not about wow or flutter, it is the volume level that is rapidly jumping. This is most apparent when monitoring the built-in bias oscillator, making the otherwise pure 10khz tone sound like scratching your fingernails against a blackboard. The weird thing is that the right channel sounds somewhat OK, but left channel just jumps like crazy. This can be seen by just watching the VU meters. When the bias oscillator is on, right channel seems to be quite stable and nice. The needle on the left channel, however, bounces and dances in a sort of a random way. So it's not about a fluctuation in pitch, it's more a fluctuation in amplitude.

I've tried my best to clean the tape path with isopropyl alcohol, but it didn't help at all. Maybe the heads are just too worn after the years of heavy usage.

 

[Tim Gillett]

Certainly sounds like a tape to head contact problem. This is a 3 head machine and so more potential for things to go wrong.

These machines arent easy to set up or even just inspect the heads as the metal cassette door frame blocks your view severely.

Are you are using a good tape? The same effect (weak left channel) can be due to tape edge damage.

Cheers Tim

 

[thefig]

The tape deck is making that garbled sound on every tape i use. On some, the effect is stronger. Weirdly, used and cheap normal bias cassettes work better than my brand new Sony Esprit IV metal bias tapes.

My theory is that since the deck has been used so heavily, a groove has formed in the heads, causing the tape to skip. But it's hard to check thanks to that fancy hi-tech cassette door.