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Tech Help - Projects Page / Re: Total Recall no modulation

« on: February 06, 2021, 09:26:37 AM »

OK, so I traced down the siren to the delay pot:

edited with new info:
Replaced that and it’s quiet. Now my 4047 pin 1 reads 0V and pins 2 and 10 read -15.2. Voltages seem fine on the 4047 socket if the IC is removed. So does the delay pot (-15.2V). I get delay on pin 3 of the bbd but it is very weak. Have to find the next issue

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Tech Help - Projects Page / Re: Total Recall no modulation

« on: January 24, 2021, 08:21:32 PM »

I wonder if I have a wrong Cap value in there that is bringing the clock down into audible noise. Will check in the morning

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Tech Help - Projects Page / Re: Total Recall no modulation

« on: January 24, 2021, 02:15:05 PM »

The problem evolves. I replaced all of the caps around the delay pot, and now I can tell that the mod circuit is working, but there is very loud constant audio from that area. If I try to bias pin three on IC six, it is an incredibly loud solid audio tone. The pitch is controlled by the mod pot. If I even get the audio probe near those caps, I can pick up the audio. I’ve since replace those caps with another round of new ones, and replaced ICs 8 and 9 but the problem remains. Any thoughts?

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Tech Help - Projects Page / Re: Total Recall no modulation

« on: January 20, 2021, 06:26:34 AM »

Thanks Dan,

I switched out the mod pot and still no luck. I can hear the tiniest hint of mod if I let things ring for a while. I get no mod at the delay time pot. Shouldn't this be where it has its effect on the sound? maybe that cap network there is my problem.

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Tech Help - Projects Page / Re: Total Recall no modulation

« on: January 18, 2021, 06:34:21 PM »

Hi Thomas,

Pin 1 isn't grounded, but does read 0V. It does this on my Total Recall taht works as well. Pin 7 fluctuates between -6.9 to -8.1V.

I keep getting a weird reading on pin 3 of the mod pot. Mainly its 0 but if I press harder I get -7ish

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Tech Help - Projects Page / Re: Total Recall no modulation

« on: January 17, 2021, 07:54:32 PM »

pic

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Tech Help - Projects Page / Re: Total Recall no modulation

« on: January 17, 2021, 07:53:43 PM »

pic

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Tech Help - Projects Page / Total Recall no modulation

« on: January 17, 2021, 07:52:39 PM »

Hi all,

My Total recall doesn't modulate. I get echoes and it biases properly. I get varying voltages in the modulation clock section, but no mod. The only voltage that seems odd is pin 1 IC9, whcih reads 0 when it should be varying.

Things I've checked/tried:
Verified resistor color codes in the mod section
swapped out the 4558 (IC9), 4047, and both BBDs for known working ones
Replaced the mod pot
checked the mod switch (works electrically but has no effect on circuit)
no continuity across caps in that section
compared resistor voltage drops with a working Total recall
Removed IC9 socket
diode seems to be electrically sound
reflowed all joints in that section
Cleaned back of board with flux remover

Looking for more ideas.

Thanks,

Marty

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Open Discussion / Re: So that's where all our valve pedals went...

« on: March 30, 2020, 08:26:34 AM »

"They add a 3 dimensional aspect to the tone that has to be heard to be believed"

Congratulations on the great review! Wish it had come earlier for you guys.

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