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Subject: Re: [PolySix] Re: Dead voice and too fast EG

From: Bob Grieb <bobgrieb@yahoo.com>
Date: 2014-06-06

74C175 should also be OK.

Maybe try flexing the board near where you were probing to
see if that's what made it work.   Maybe you have a flaky connection
somewhere?

Buzzing out means using an ohmmeter to check continuity between
the different chips that should connect together.  You can't monitor
the digital signals without an oscilloscope.

   Bob

From: "dtonthept@yahoo.com [PolySix]" <PolySix@yahoogroups.com>
To: PolySix@yahoogroups.com
Sent: Thursday, June 5, 2014 11:00 PM
Subject: [PolySix] Re: Dead voice and too fast EG

 
Hi Bob,

Okay so we've had a bit of a poke around... Thanks a million for the pointers, VERY useful.

The dead voice does indeed stem from a lack of voltage from the appropriate pin on a 4175 so we'll need to replace that. I had a look on Syntaur and they don't have 4175s, indeed an ebay search turned up nothing as well, however they do have a 4174 flip flop - are these interchangeable?

IC, MC14174B Flip-Flop

Otherwise would you have any suggestions for a replacement?

Secondly, we were trying to get voltages for IC10 and IC11. These voltages didn't change when I adjusted the controls, but they did move as the envelope cycled.

What's interesting is that when we were probing pin1 of IC11, suddenly the envelopes (which were set to maximum ADR) began playing exactly as you'd expect! It was a sudden miracle, which, unfortunately, only lasted for maybe 20 or so seconds before the behaviour reverted back to its normal problematic self.

We spent a bit of time prodding the board to see if we could recreate the normal behaviour but didn't have any luck.

We ran out of time just as we were trying to figure out the last bit of your instructions, by "buzz out" do you mean monitor the voltage the whole way along the signal path between those points?

Let me know if the sudden "correct" behaviour triggers any other suggestions, and otherwise please accept my sincere thanks for your help so far.

Best wishes,

D :-)