Squealing LT1054 - FIXED

[strat68]

I'm in the process of checking out a Flabulanche and finding that the batch of LT1054's all cause a squealing noise in the output.  I had tried one of these 1054's in another pedal with the same result but did not get around to trying the other 2 part before I found a different 1054 that was OK.

Is this more likely a bad batch of parts or is there something I can do to alleviate the squeal?
Thanks

[rullywowr]

It's possible that they may be  counterfeit and actually a 1044 type instead and just labeled lt1054.  If this is the case, bridging pins 1 and 8 should make the squealing disappear as the click will be put in turbo mode.  Did you buy these from a reputable supplier?

[strat68]

It's possible that they may be  counterfeit and actually a 1044 type instead and just labeled lt1054.  If this is the case, bridging pins 1 and 8 should make the squealing disappear as the click will be put in turbo mode.  Did you buy these from a reputable supplier?

I'll try the bridging.  Bought 'em on ebay, so probably not reputable.  My next batch is coming from Jameco.
Thanks Ben!  Anything new coming up?

[strat68]

Bridging fixed the squeal but no output past Q2.  I tried 2 different lots of 5457s and the second lot will not bias )but they do pass a little sound)at all.   Shows 17 volts and never changes regardless of what I do to the trimmers.  I'm going to have to study the schematic and see what's up.   I should have stuck out the EE degree in college.

[madbean]

You could try bumping up your T2 trimmer to 50k or 100k to see if you can dial in the bias voltage.

[midwayfair]

You could try bumping up your T2 trimmer to 50k or 100k to see if you can dial in the bias voltage.

No change at all in the bias voltage? That says to me that either the trim itself is faulty or the source resistor is wrong. Very wrong. Like orders of magnitude wrong. A really big trim there like 50k would also be a pretty hefty source impedance to drive the 100k gate resistor that follows.

[strat68]

You could try bumping up your T2 trimmer to 50k or 100k to see if you can dial in the bias voltage.

No change at all in the bias voltage? That says to me that either the trim itself is faulty or the source resistor is wrong. Very wrong. Like orders of magnitude wrong. A really big trim there like 50k would also be a pretty hefty source impedance to drive the 100k gate resistor that follows.

Correct, with different 5457's the bias voltage does not change regardless of where the trims are set.  For all 3.  I'll check the resistors but more than 1 mistake seems unlikely unless I dropped a whole bunch of the wrong value resistors into that bin.  A definite possibility.

[midwayfair]

Almost guarantee you used 470k instead of 470r for all three source resistors.

[strat68]

Almost guarantee you used 470k instead of 470r for all three source resistors.

That's what I'll check first.

[strat68]

The resistors are correct.  I'll have to continue tracing the circuit with a probe.  I can't get any sound past Q1.  I've re-flowed solder for the various Q1 parts.  Nothing makes it to the Gain pot.  I'll re-check the voltages since the doc. has a list for each transistor. 

build doc: http://www.madbeanpedals.com/projects/Flabulanche/Flabulanche_2015.pdf

[strat68]

It was the 2n5457s.  I took a close look and 3565's must have gotten into the wrong bin.  The pedal works fine now.