Teac C3rx cassette deck issue

[xazrules]

Hi everyone, some time ago i've bought this cassette deck, after some contact cleaner on the switches it work really good but it has an issue that i can't get my head around.
when recording on tape there is a copy of the original sound but before it, i've already tried cleaning and demagnetize the heads but it didn't work.
have you some hints?
i've attached an example of the problem, recorded a 808 hat to make it very clear and a schematic of the tascam 122 that's the same model but without the dbx.
thank you!

 

[ruffrecords]

This sounds like print thorough where the layers of tape affect each other as it is wound on the take up spool. This is worse at high recording levels and with thin tape. Which tape are you using? Noise reduction should reduce this effect.

Another possibility is that this is a three head deck and on playback there is some leakage from the record head into the playback electronics but this would create a copy after not before the original.

Cheers

Ian

 

[xazrules]

Hi Ian thanks, this is recorded on normal tape, i've tried type 2 and type 4 formulas but the problem reamin exactly the same.
yes this is a 3 head deck. i can't understand why there is a ghost note before the original sound, at first i thought was the direct signal that in some way get through the output but now the ghost get printed on tape, like if there another record head before the real record head.
the only thing i think about is that the erase head gets some leakage, looking at the schematic maybe it is possible but don't know where to put my hands on...

 

[ruffrecords]

Is it better of worse with noise reduction on and off?

Cheers

Ian

 

[Tubetec]

Could the record electronics be leaking audio into the erase path ?
That might explain the pre echo , maybe check the continuity of the sheilding in the wiring to the heads .
Does it properly erase a pre recorded tape without any input signal ?

 

[xazrules]

with dolby is still present, with dbx the noise and the pre echo almost disappear, but i like the sound without NR.
i'll try to erase some recorded tapes and report back.

 

[gyraf]

could it be a simple erase (-head) problem?

 

[xazrules]

the erase head is functioning properly, recording without input on previosuly recorded tape there's only hiss.
so i suppose the bias electronics and the head is working correctly, right?

 

[xazrules]

or maybe make the transport run at double the speed? is like shortening the heads gap?
anyway it seems run slower than another tape deck i have.
how can i check the transport speed? is a resistor or a cap that sets it?

 

[Tubetec]

Theres usually a preset pot that sets capstan rpm ,
https://fixyouraudio.com/product/speed-calibration-tape/You'll need a frequency counter of some sort to do the alignment ,
Bear in mind a worn out drive belt might cause problems , this is an issue on the deck in question ,so worth checking in any case .
You could also record a 3khz tone on tape yourself , on a known good performing deck , then playing back on the Teac adjust so it plays back the right frequency , downside is any missalignment in the deck you use to record will lead to some error , still you probably will be able to improve matters to some degree .
Probably worth paying the 8.70 euros for the proper test tape ,

 

[xazrules]

ok i'll check it. in the schematic there is no sign of a pot for rpm control, just a square box that reads servo amp and the capstan motor connected, no schematic of the servo amplifier.

 

[Tubetec]

Figure 4.5 in the service manual give the details on capstan speed adjustment ,

 

[xazrules]

many thanks i haven't see it in the manual, let's try