deluxe memory man no blend

[LaceSensor]

Hey all

Recently got an EHX EC2000 early 90s MN3005 memory man
it was DOA, expected (acquired as for parts / to fix).
addressed all the obvious issues, replaced all the op amps.
I have fully operating delay controls, but no clean sound mixed in.

Anyone familiar with this know what I should check next?
I havent changed out the compander, or delay chips as that all sounds "legit", and the schematic makes me think its just something simply like a cold joint or a dead cap on the PCB. Nothing obvious to the eye though.

this is the closest schematic I could get
http://bee.mif.pg.gda.pl/ciasteczkowypotwor/SM_scena/Electro-Harmonix/Electro-Harmonix-Deluxe-Memory-Man-Delay-Reissue-(Rev.A)-Schematic.pdf


I have changed out the blend pot, no difference. So I am reckoning its something to do with
R1 / R2 / R3
C1 / C2
R28

Otherwise I dont really see where I am losing the clean sound.
I can of course audio probe in due course.

Scruffy?!

[Scruffie]

Hmm... well I missed the end of that auction (I'm guessing it's the same one) by 3 minutes so...

Bypass works? If not then yes probably a bad C3.

Do you actually have delay signal? If you do it can't be the input stage its self.

[LaceSensor]

Bypass works yes mate
Will change c3 and report back

Cheers buddy yes it was eBay and scored a deal it seems 🤭

[LaceSensor]

Hmm... well I missed the end of that auction (I'm guessing it's the same one) by 3 minutes so...

Bypass works? If not then yes probably a bad C3.

Do you actually have delay signal? If you do it can't be the input stage its self.

Ok read this wrong

Yes when engaged the pedal creates delay and all functions work
Blend makes the delay signal louder
Level raises the volume up til distortion


Only issue is there isn't a dry signal on the mix
And at lowest blend, there is nothing, where there should be only the dry signal

As before I changed the blend pot, same issue

[Scruffie]

Actually the bypass question only makes sense if it's wired like the schematic but I'm guessing it's true bypass.

So I'm still going with C3.

[LaceSensor]

Actually the bypass question only makes sense if it's wired like the schematic but I'm guessing it's true bypass.

So I'm still going with C3.

yeah its wired TPB, I should have qualified that mate.
Getting the soldering iron heated up now...it will be fixed today (!) *



*I hope

[LaceSensor]

ok so its not C3. Gonna try some other stuff.

on close inspection, with the blend turned all the way to dry, and cranking totally the Level, you get a faint but evident dry (and, as expected disorted) signal.

so its like a lot of the dry signal is being lost somewhere but its not 100% gone

[Scruffie]

Well you know the input stage works as the level control and delay works so there is a dry signal there, it's just not reaching the blend pot. So the only things between the input and the blend pot are some PCB traces, C3 and R28.

If R28 was a short, the blend control would act like a delay level control so do some continuity testing between blend and ground and blend and C3.

[LaceSensor]

Ive got beeping on my continuity tester from the wiper of Blend, to ground.

Or I thought I did. seems to be intermittent. really wierd

[LaceSensor]

fixed

was a short R28.

Thanks for the sanity checks dude.

My main issue now is that I think someone has replaced the MN3005s with 3008s cos the delay time available is quite poor, at least compared to my 4x3008 one.

[Scruffie]

Check the clock frequency at the longest delay time, it should be about 7.5KhZ for 550mS.

[LaceSensor]

Check the clock frequency at the longest delay time, it should be about 7.5KhZ for 550mS.

Hey Im getting approx 11khz at max delay time, from approx 130khz at minimum.

you reckon this is a tuning issue or a "wrong chips" issue?

Bear in mind I havent taken out / measured / replaced the clock caps and/or delay time potentiometer...

[Scruffie]

Chips don't affect the clock, 11kHz gives you... 372mS max delay time.

It's a tuning issue, it wasn't uncommon on the earlier reissues as they didn't use 5% 240pF caps, you just need to tack an extra small value cap in parallel to the clock cap (C43) until your max clock time is 7.5kHz-ish.

[LaceSensor]

Chips don't affect the clock, 11kHz gives you... 372mS max delay time.

It's a tuning issue, it wasn't uncommon on the earlier reissues as they didn't use 5% 240pF caps, you just need to tack an extra small value cap in parallel to the clock cap (C43) until your max clock time is 7.5kHz-ish.

Hey man thanks for the help again.

For point of reference I took the following readings from my other "memory men"

MBP Total Recall = 80khz/8.2khz
EC2002revE (4x3008 big box reissue) = 110khz/8.8khz

[Scruffie]

You're missing out on some delay time then! Your 3008 unit only has 465mS and your Total Recall 500mS.