Texan Amplifier Repairs

Texan T20-20

Texan T20-20 Amplifier

This was a Practical Wireless article from 1972, I remember it being all over the magazine at the time. This worked but went into distortion at random intervals it was also very sensitive (the inputs). One of the PCB pads for the tone control pots was broken causing the distortion. The sensitivity was reduced with 47k resistors placed in series with the inputs. Someone had previously put 2k5ohm presets in to set the quiescent and removed the fixed resistors, which made the adjustment cramped at one end of the rotation to get the correct value. Soldering in a 390 ohm across them made the adjustment more, adjustable! Sounded okay after.

I had enough of the crude way of reducing the sensitivity of the two inputs so altered the 82k feedback resistor to 33k, which made the amp much more useable.