![img2](images/tascam48/img2.jpg)
I sent the rollers off to
Terry Witt
for resurfacing and started cleaning the tar out of the transport mechanism.
![img4](images/tascam48/img4.jpg)
The rollers came back looking brand new.
![img5](images/tascam48/img10.jpg)
The machine recorded on half of the channels when I tested it. I decided to switch the amplifier cards around to see where the problem was.
![img6](images/tascam48/img8.jpg)
Switching the cards around fixed all but one of the dead channels. The problem was most likely oxidation so I cleaned the contacts on the card slots. Channel 5 still had no output so I removed the channel card for a closer look.
![img7](images/tascam48/img11.jpg)
The first thing I noticed was discoloration around this 100Ω resistor. It's a dropping resistor for the -15V supply and it looked like it was getting hot. The solder also looked very thin and not consistant with the other joints.
![img8](images/tascam48/img12.jpg)
The insulation on the leads looked like it had been replaced or had been discolored from the heat that it was experiencing.
![img9](images/tascam48/img13.jpg)
Its a higher wattage resistor and it tested fine so I returned it to the board with some fresh solder.
![img10](images/tascam48/img17.jpg)
I added some new insulation on the leads too. I knew that something downstream from this resistor had to be shorted out so I began checking the components that it supplies current to.
![img12](images/tascam48/img31.jpg)
I removed two amplifier IC's to test them but they tested fine. I installed sockets in the board to make removal and testing easier in the future.
![img13](images/tascam48/img35.jpg)
Next, I looked at the filter caps on the -15V line. The short I was looking for was found in a 220μF filter cap.
![img14](images/tascam48/img37.jpg)
I replaced it with a cap of the same value and a higher voltage rating.
![img15](images/tascam48/img40.jpg)
The cap in place
![img16](images/tascam48/img41.jpg)
Final testing. All channels are in business.