122 mk3 cassette deck xlr output problem

[Øystein Frantzvåg]

I have a problem with the right side xlr output on my 122 mk3 cassette deck. It’s several db’s quieter than the left side. Both on input and auto mode. I’ve tested the unbalanced inputs and outputs, and they seem to work as they should. Anyone have an idea what the problem can be?

Thanks

 

[SkywaveTDR]

The balanced output was an after thought on these and they did not even make adjustment pots to allow them to be where they need to be at +4dBu. Often times they are +2dBu. In any case your problem may be due to the unbalanced -balanced switch. They get dirty and sometimes broken. It is a real hard switch to find size wise. In my case I would put in a -10dBV 1KHz signal and then make repairs so that the levels coming out are correct by adjusting the gain on the op amps that develop the plus and minus output signals. You might also have a dirty pin in the XLR connector- this can be sprayed with Deoxit or the output where the pins are visible can be worked with a small Rifle brush- the kind to clean rifle barrels with- that is about the only thing to fit in there. I have used a .223 stainless now and then. Use of a scope to find out what is happening would be of help as well. If the signal going into the converter is correct and the Op Amp out correct then that just leaves dirty XLR pins. Loosing one polarity of a XLR then results in a 6dB drop in level.

 

[Prahlada Rangaraj]

I recently had similar problem on my TASCAM 122 MK III. The right channel XLR output was sounding muffled. It was the faulty NJM 5332L Op-Amp. NJM5532L is an 8-pin high performance dual low noise operational amplifier.

There are two of them for each channel in SIP configuration on the BAL AMP PCB. Please check for voltages on this IC. The right channel operating voltage on my 122 MK III was less than 1 V. NJM5532L has an operating voltage of ±3V to ±20V. You can order IC on Mouser. I have attached below the link

https://www.mouser.in/ProductDetail/NJR/NJM5532L?qs=Q/2SSTfRgqHKnaKw39C8cA==

 

[SkywaveTDR]

This is certainly a possibility and you wonder how do these amps get blown out- the answer is a thing called Phantom power. Do not apply 48Vdc phantom power to these connectors as it will just be a matter of time before a voltage spike takes out the amp.

 

[Øystein Frantzvåg]

Thanks guys. I’ll try your suggestions.

 

[SkywaveTDR]

I check there inputs and outputs on ever deck I work on and so far all but one worked and the one that did not was messed around with by a hack.