Dynaco Stereo 120 Power Amplifier TIP mod info

Several people have asked for the info to make the TIP mod to their ST-120. Here is the info, copied directly from a Dynaco service update sheet. This mod assumes familiarity with electronic component repair techniques. I am not responsible if you toast your amp trying to update it using these changes. Good luck, and let me know how well it works.


Q1 replace 40233 (100-250 beta) with BC108A (130-180 beta)
Q2, Q8 replace 2N3053 (100-200 beta) with 2N5320 (160-260 beta)
Q3 replace 2N3053 with TIP31C
Q4 replace 2N4037 with TIP32C
Q5, Q6 replace 2N3055 (17-25 beta) with 2N3772 (60-90 beta @ 1A)

C1 replace with 5uF 10V tantalum

Add C13 68 pF from Q2C to Q2B, both channels
Add C14 0.01uF from Q3C to GND, both channels
Add C15 27 pF from Q2C to Q1E, both channels
Add C16 .01 uF across xfmr secondary at rectifier bridge on PC-15

This page created and maintained by Greg Dunn.
Copyright © 2000 Greg Dunn