1979 EH Memory Man Delay Calibration instructions -or how to use an oscilloscope

[newperson]

Are there instructions on how to set up and calibrate older Electro Harmonix Memory Man delays somewhere?

or

I am just learning how to use an oscilloscope.  Could someone share with me the steps or "how to" calibrate one of these pedals with an oscilloscope?

Thanks for any links or drawn out teach me like I am 14 instructions.

[StephenGiles]

Aren't we all still 14!!

[newperson]

Anyone ever set one of these up?

[Dave W]

from fsb. howard davis posted this iirc. read the whole thing first. hope this helps.

Since i have read many posts about squealing EH MemoryMan's and Electric Mistress', i decicded to give some info (even for beginners) on how the trimpots have to be set up in BBD-based circuits. I know, not all circuits offer the possibilities to adjust EVERY aspect of the BBD, but this should only be a guide to get the best out of them and what to look for
To tell you the things to be done, check out the Deluxe ElectricMistress schematic at http://smoke.csoft.net/~stompbox/pedals ... deluxe.jpg. Luckily, this circuit has 5 trimpots for all adjustments as seen on the Memory Man as well.
Be sure you have a scope and a sine-wave low-frequency generator since this will give the best results...
Here we go:

Step 1: BBD balance
settings: Feedback, Rate, Range & Levels to CCW
This is a scope job if you want best results...
Connect the scope tip to the taper of the 1K 'BAL. ADJ.' pot that is connected between pin 6 & pin 12 (outputs) of the SAD1024 and adjust for minimum bleed-through of the clock signal. You can't adjust this to 'ideal zero', so the best is a setting which shows both clock-wave components at equal minimum level. The ideal balance setting varies with delay time, so maybe re-adjust for best results over the entire delay time range.

Step 2: BBD offset/bias
settings: Feedback, Rate, Range & Levels to CCW
This is a scope job if you want best results, but could be done by ear, too. This is an important setting since it determines the maximum undistorted output level of the BBD.
Connect scope tip to taper of the 1K 'BAL ADJ.' pot. Feed 400Hz sinewave into input. Increase output level of generator until the signal shows clipping. Adjust the 10K 'BIAS ADJ.' pot for symetrical clipping / proper sine wave. IMPORTANT:
Most BBD- based circuits have a pre-emphasis network in front and a de-emphasis network behind the BBD. This means, treble is boosted in front of the BBD and cut down the same amound behind the BBD to keep BBD-noise level low. This maybe affect the ideal offset setting. For best offset setting, check the adjustment of the 10K 'BIAS ADJ.' pot with different input frequencies! The ideal offset setting varies with delay time, so maybe re-adjust for best results over the entire delay time range. BBD offset and BBD balance interact a little with each other, so check back!

Step 3: BBD gain
setting: Feedback, Rates, Range & CCW, Delay Level to MAX
This could be done by scope or by ear. This setting sets the level of the delayed signal in relation to the dry signal. This could be adjusted to taste, but the most common setting is to have equal volumes on delayed and dry signal. On short delay times (as on flangers) there's a scope trick to achieve equal volumes: Connect scope tip to pin 7 of the 4558 (right of the SAD1024). (REMEMBER: Don't connect to the taper of the 1K 'BAL. ADJ.' pot this time, because we need to cancel out the effects of the pre/de-emphasis network this time!) Feed 400Hz sinewave into input. If you now change the delay time knob, you can see the sinewave going up an down in volume as long as you turn the knob. Because you vary the delay time, there are boosts and cuts at certain frequencies due to phase cancelations. Adjust the delay time knob to a position where a maximum cut/cancelation occurs. Now adjust the 10K 'GAIN ADJ.' pot for zero output. Now, delayed and dry signal are in equal volume, because the sine wave is fully canceled. This adjustment interacts with the 'BBD balance' setting, so maybe you have to re-adjust it after setting BBD gain. Due to the tolerances of the resistors and caps in the pre/de-emphasis networks, the ideal gain setting should be re-adjusted with differnt input frequencies. Delay time setting affects this adjustment too, so check back with different settings or just adjust to taste

Step 4: BBD clock
setting: Feedback, Rates, Range & CCW
This is mostly an uncritical setting, since it just determines the minimum/maximum delay time covered by the delay time knob. This pot affects the clock circuit that drives the BBD. On the schematic, it's the unnamed 100K trimpot connected to Ub and the 3k9 resistor left of the CD4013. Only on long delays, this setting might be critical. If the clock frequency is adjusted too low (high clock frequency = short delay time, low clock frequency=long delay time), the clock signal might come down to audio range and will be heard as 'faint' signal. So adjust this trimpot until no clock is heard or adjust to taste and get some weird sounds

Step 5: FEEDBACK
setting: Feedback to MAX, Rate to CCW, Range to MAX
This is no direct BBD-related adjustment, but is found on most delays, flangers and phasers.
This trimpot (the 100K 'F.B. TRIM') limits the range of the Feedback knob. While feedback knob in MAX position, adjust for maximum possible feedback with no self-oscillation. Re-adjust with different delay times, some circuits intend to get into self-oscillation at shorter delay times....or adjust to taste for driving the circuit into self-oscillation for wild feedback orgy ;-)