Tascam Porta One with No High End on Channels 1&2

[Bay DuBeau]

Hello Tascfam,

I am new to the forum and this is actually my first thread (hopefully I posted it in the right place). I have been trying to restore a Tascam Porta One to its former lofi glory. I swapped all the belts and did other general servicing on the tape mechanism. I also calibrated all of the settings to the suggested values in the service manual. It was working perfectly for a short while, but suddenly there is no high end on channels 1 & 2 (recording and playback). Even with the highs fully up on the EQs, it is still noticeably dull. After looking over the schematic, I realized that these channels share several components on the amplifier board. The first is an M5219L amp chip and the other is an AN6291 chip that I believe is part of the NR circuit. I'm trying to avoid any drastic measures like the recap that some of my tech friends recommended I try.

Let me know if anyone has an idea as to what might cause this problem. Given the nature of the NR circuit, I am suspicious of that chip. Any help or discourse is much appreciated.

Thanks a lot!
-BAY

 

[-mjk-]

Usually loss of audio fidelity is caused by a bad capacitor. ICs tend to work, or not. You are better off just replacing all the electrolytic caps. That's why your tech friends are recommending that course of action. I personally have recapped a number of large format recording consoles with amazing results.