Strange sounds...

[pdm4606]

Coming from my new to me Wollensak 4765 cassette deck.
It works great except for the pinch idler roller. I fixed a temporary until I make a new one. However the other day we were doing our morning mac-mini browsing and my wife asked if I had any pre-recorded cassettes to listen to on the new 4765. It just so happens that I picked up a Tom Jones greatest hits cassette recently and never did give it a try. Now up to this point I have been very happy with how the 4765 sounded and performed. I of course, did a complete lube/ switch cleaning on all switches and moving mechanical items.

I inserted the Tom Jones cassette and engaged the mechanism. It played for around 10 seconds then came up with a horrible screeching sound covering the music. Nothing wrong with the deck in any way. I then tried an old cassette of mine and it sounded great as it had until the Tom Jones tape. I then did the Tom Jones tape again and it didn't take 10 seconds this time. It immediately started the screeching.
Then I took the Tom Jones tape and played it in my older players. I have an older Yamaha, Onkyo, and Sony. They all played fine. No screeching. As did other tapes of mine.
Only the Tom Jones tape screeched on the Wollensak 4765. I have other pre-recorded tapes and haven't had this issue on the 4765.

Later I came to realize that maybe the old tape playing on the old deck had some sort of "copy protection" and some how it only kicked in with the 4765.
Any thoughts on this???

I am at a quandry as to what is happening.

Paul

 

[The Ghost of]

Was this an electrical screech heard through the speakers or a mechanical screech generated from an unknown friction?

 

[pdm4606]

Screech was an electrical....

and it came through my speakers.
I tried several things but it did not stop.
Several things I tried was to re-route the cables. I am using an outboard selector switch(nothing electronic inside) as I use different tape machines from time to time. The 4765 was routed through the outboard selector as my other decks are. I took the outboard selector switch "out" cables and connected then directly to the 4765. Same. Flipping the cassette didn't improve anything.
I thought for sure the tape was damaged. It wasn't. It played fine with my other decks(Sony, Yamaha, Onkyo).

As I said other old tapes I recorded played fine on the Wollensak 4765.
I have not tried other pre-recorded tape on the 4765 as I have so few. I will have to look for them.

Paul

 

[The Ghost of]

Sounds like it might be the bias trap filter being slightly out of adjustment on the Wollensak. Perhaps it needs to be re-tuned while that tape is playing to adjust the screech out of the audible range.

Pre-recorded tapes are often manufactured at 4x or higher transfer speeds, so the bias frequency that they are printed at gets de-multiplied, (lowered) on playback. This would explain why your own tapes are fine vs the pre-recorded ones. The Wollensak may not have been set up from the factory to deal gracefully with high speed, mass produced tapes.

My 2 cents anyway.



Cheers!

 

[Gazdatronik]

Either that or the biggest Tom Jones fan played the tape so much that the lubricant is gone:lmao: And that tape is resonating like a violin string.

My father managed to do this with his Frank Zappa tape of Billy the mountain. It would screw up exactly like you are describing, screeching like a banshee by the cassettes 22nd year of operation.