Help with reissue Deluxe Memory Man

[LaceSensor]

FIXED! Thanks Scruffie

For future reference, when trying to calibrate the EC2002-rev E EHX Deluxe Memory Man
There are typically 4 BBD positions (left to right, U4, U5, U6, U7)
These are MN3008, or rarely, MN3005 (position U4 and U7)

Trimmers relating to the BBD voltage bias are thus:

Trim 1 = U4
Trim 2 = U5
Trim 3 = Gain
Trim 4 = U6
Trim 5 = U7
Trim 6 = Balance
Trim 7 = Gain

For the MN3005 setup, there are 3 JP (jumpers) points on the solder side of the PCB that omit U5 and U6 positions.
For the MN3008 setup, clearly you have 2 more trimmers. These are labelled SP, and noted on the board to populate those in the case of MN3008 setup. The PCB also says populate (jump) the JP markings in the case of MN3005 usage.

Its unlikely I will convert mine to MN3005s, but I might put two of them in U4 and U7 spots for shits and giggles.

For what its worth, I biased mine to 8v on each Trim, set the gains as appropriate for my taste with the Feedback knob set to self oscillate, and left the balance trim in the middle.

Yours, LaceFailure





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HI guys

I have purchased a non-working DMM
Its the EC2002-REV-E version with 4 x mn3008 chips installed.
The fault was described as:

"Was sounding great then one day I plugged it in and the Delay would only work right at the bottom of the scale ....Then no delay at all!!"

I have received the unit today. It passes signal, and the pre-amp works.
I checked the bias points of the BBDs and reset them to 1/2 supply as a starting point (pin 7 on all chips)

Edit - it seems I have 15v on pin 5and6 of all the BBDs....? That seems wrong, correct?

Pin 8 was reading a solid 14.18v on all, so I set them to 7.10v
The Balance pot I have set in the middle. Gain trims just past midday.

Now, true to the fault, still no delay.
I have probed the circuit with an audio probe and can get signal on pin5 and 6 of the compander, and pin 7 of U2
Cant hear any audio on any other dual op amps (all 4558s)

at a point around 1/10th the rotation of the delay time pot, its gets static-y and if dialed just right you can just hear a wash of noise, but unrelated to any of the other controls. I changed the B100k delay pot for a new one, no joy, and still behaves the same.

Can anyone help me out here?
I dont want this to be a paper weight and would like to fix it myself.
I figured when I bought it, that it could be one of three things:

1 - BBDs fucked
2 - delay pot needs replacing
3 - calibrations needs changing

Scruffie, any help?!

[Scruffie]

Meeee? 

Pin 7 of U2 is pre-compander.

Do you have signal on Pin 7 of the 570 and Pin 1 of U2?

What voltage do you get on pins 10 & 11 of the 4047.

Pin 8 of the MN3008 is Vgg by the way not Vdd, not that it matters too much, but your bias isn't quite 50% supply (the datasheet actually states bias should be nearer 8V... if that applies in the real world.

Edit: Ah, see you mentioned pin 5 being 15V, that's right, that's the Vdd, pin 8 is your 14/15th Vgg and pin 1 is ground just to clarify.

Compander voltages will be useful too.

[LaceSensor]

OK first things.
I have got out my 2 x MN3005 Dirtbag to compare
The BBDs there have 0v on pin 5, and half supply on Pin6.
So I am bit confused...

With regards your questions

Do you have signal on Pin 7 of the 570 and Pin 1 of U2?
No to both those questions.

What voltage do you get on pins 10 & 11 of the 4047.
10 - 0v
11 -  15.22

BBDs:
to reiterate, I get GND (0v) on pin 1
I get 14/15th supply on pin 8 (~14.28v) and I get 15.2v on pins 5 AND 6
IS that something to do with the Dirtbag being negative gnd, and the real DMM being positive gnd?

Thanks so far, duder

[Scruffie]

Your clock isn't working, try replacing the 4047 quickly and then check pins 10 & 11 voltages again.

[LaceSensor]

Your clock isn't working, try replacing the 4047 quickly and then check pins 10 & 11 voltages again.

ok i try that gimme 5 mins. cheers bro

[LaceSensor]

What voltage do you get on pins 10 & 11 of the 4047.
10 - 7.6v
11 -  7.6v

[Scruffie]

That's one problem sorted, try probing Pin 1 of U2 again and if there's nothing post the compander voltages.

[LaceSensor]

the delay pot now causes changes in the clock whine I can hear at the output that wasnt present before....
the chrous and vib mode and associated pot "modulate" this whine.

With regards U2. no signal on pin1

Compander voltages are as such:

1 - 13.81
2 - 13.16
3 - 13.16
4 - 15.05
5 - 12.06
6 - 11.88
7 - 0.75
8 - 13.24
9 - 13.24
10 - 7.09
11 - 8.73
12 - 13.25
13 - 0v
14 - 13.16
15 - 13.16
16 - 13.81

[LaceSensor]

Itts aliveeee

Changed the compander for a new one, im in business.
Set the bias points to the MN3008s to 8v

it works. thanks a bundle, scruff.
Do want me to post the new compander voltages?

[LaceSensor]

voltages on new compander:

1 - 13.81
2 - 13.13
3 - 13.13
4 - 15.03
5 - 13.22
6 - 13.02
7 - 5.04
8 - 13.20
9 - 13.24
10 - 6.97
11 - 8.66
12 - 13.22
13 - 0v
14 - 13.16
15 - 13.16
16 - 13.81

[Scruffie]

Your compander voltages are all fine except for the output of the compressor portion (pin 7) that leads in to U2 pin 3...

While i'm not usually one to debug by just swapping out parts you could try swapping out the compander quickly seeing as you have a spare on hand and they have been known to die and as the 4047 was dead which may well have been caused by static the compander may have met the same fate. Then checking voltage on pin 7 again and then for signal on pin 1 of U2 if it's more in the 5V range.

If that doesn't work, check the solder joints on the 68k voltage divider on pin 5 & 7 and 10uF cap to ground from it (C9).
Failing that,

[Scruffie]

Ha, while I was typing you did what I was going to say

Glad you got it sorted! 

[LaceSensor]

you the man
yours is a pint, if ever we should meet
or more than one, haha

[marmaliser]

Nice work Gents.  I nearly bid against you on that DMM

[LaceSensor]

Nice work Gents.  I nearly bid against you on that DMM