Journal Entry 6 Oooh That Squeal

Your solid state Echoplex is a prized possession. The tone is impeccable. Heads are clean. Degaussed. Recapped. Ready to make sweet sweet music. But there's one problem.

During your super psychedelic mind altering solo, you cranked the REPEATS knob all the way up to signal the mother ship to beam you up. But the coolness was shattered by a yowling Squeal. Not the good kind. Side bands and harmonics from the high frequency oscillator are killing the groove.

Thank you to Jim for asking about this problem. I am going to try to suggest things that have worked for me in the past. Results may vary, as this is not always the same root cause. I am going to list these areas to check in order of most common to least common.

REPEATS 500k pot wiper is shot

2N3053 transistors have a problem

Bad wiring around the REPEATS pot

Bad trace on a board

The DPDT toggle is worn out

These are just some of the places I have cleared the Squeal from, definitely not all of them. The Squeal comes from a feedback loop, somewhere. If you have not cleared it with changing the areas above, be prepared for the long haul of replacing resistors one at a time, power up to test, change another resistor, etc. Sometimes, it can be a bad disc or orange drop capacitor.

You WILL find the bad part. This is one of the hard parts of repairing Echoplexes. Be prepared, be methodical, be careful, and most of all, stay in a good mood while working. If you get frustrated, take a break. Frustration causes bad things to happen usually because we get careless with our hands. Working too fast also can mess you up. If you are not enjoying the hunt, pack it up. Consider professional help. For the machine that is, before you too need professional help!

Have a great day!

Bart

Mr Echo