freestompboxes.org

If anyone is interested

Looks like a DM-2 variant.

Do you have this one, or are these photos from someone else? What I am curious about is if the charge pump is being used to create a split rail rather than producing 18v.

Anyway, amazing they packed so much in there. Thanks for the photos!

Hi Madbean,

I knew you would manifest yourself on this one

this is my dead Malekko, that my my mate f***ed up.

I am not sure what the Max1044 is actually doing in there. Let me know what detail you what detail you want me to investigate.

Benobo

max 1044

pins:

-1 : 9.13v
-2 : 9.13v
-3 : 9.03v
-4 : 8.70v
-5 : 8.70v
-6 : 7.37v
-7 : 7.80v
-8 : 9.13v

benobo wrote:max 1044

pins:

-1 : 9.13v
-2 : 9.13v
-3 : 9.03v
-4 : 8.70v
-5 : 8.70v
-6 : 7.37v
-7 : 7.80v
-8 : 9.13v

Yeah, I think the TL074 is probably getting +/- 9v.

BTW: I don't recall what the voltages should be exactly, but I think pins 6 and/or 7 might be off. Seems like one of those should be 1/2 the supply. I'd have to check some of my builds to confirm...or just look at the datasheet, I guess.

my mistake, the pedal was off

new max 1044 reading with pedal ON:

1 : 9.11
2: 8.77
3: 0
4: 0.66
5: 0.66
6: 7.35
7; 8.12
8; 9.11

TL 074

1: 8.20
2: 0.10
3: 0
4: 9.10
5: 0
6: 0.05
7: 0.78
8: 0.78
9: 0.05
10: 0
11: 0.66
12: 0
13; 0.07
14: 8.22

benobo wrote:Hi Madbean,
I am not sure what the Max1044 is actually doing in there. Let me know what detail you what detail you want me to investigate.
Benobo

These Max1044 chips are typically used to either double (triple, etc) a DC voltage under 10v, or create a negative voltage.
Check the datasheet for the chip as a reference, and see if you can identify what the chip was supposed to be doing according to the components connected to the MAX1044.

Or see if the op amps are seeing ground (or not) at their negative rail.

From there you can likely see what's going on and identify what components are likely fried, including the chip itself. You're voltages indicate something awry there as far as I can tell. Most common pedal issue is from people using the wrong adaptor. an AC adaptor can fry a pedal's functionality or a chip like this fairly easily.

benobo wrote:TL 074

1: 8.20
2: 0.10
3: 0
4: 9.10
5: 0
6: 0.05
7: 0.78
8: 0.78
9: 0.05
10: 0
11: 0.66
12: 0
13; 0.07
14: 8.22

Definitely something wrong here. There's no bias voltage to the IC. I'm also unsure what the charge pump is doing since it seems to not be supplying 18v or -9 to the IC.

I would replace that charge pump first and see if the voltages on the TL074 correct themselves. Also, you can check the pins on the v3205 to see if they are getting proper voltage. Pin5 should have between 5 and 8v, pin8 should be about 14/15 of whatever pin5 is, pin1 should be 0v.

Also, those MAX chips usually only tolerate a max of 12v (I think they are rated at 10v) so if a larger DC supply was plugged in it could have damaged it.

Thanks for your advice Madbean,

I am going to check all that and will post it asap

Benobo

NE570N

0.87 1.82
1.81 2.43
1.81 2.43
0 9.11
1.22 2.88
1.22 2.38
1.22 2.38
1.82 1.82

V3102


7.25
3.91
0.59
3.92
3.86
3.98
3.89
6.82

V3205 (1)

0
3.92
4.80
4.80
8.47
3.91
4.63
6.82


V3205 (2)


0
3.92
4.52
4.52
8.47
3.91
4.47
6.82

all 4 transistors : 2N5088

Trim pots ;

gain : 30 k
Regent : 5 k
Delay : 350 k
Bias 1 : 7.5 k
balance 1 : 10 k
bias 2 : 7.5 k
balance 2 : 10 k

Pots;

Delay : B500K
Mix : B50K
Repeat : B50K

benobo wrote:NE570N

0.87 1.82
1.81 2.43
1.81 2.43
0 9.11
1.22 2.88
1.22 2.38
1.22 2.38
1.82 1.82

Bias output for the NE570 is 1.8v so you are good there. From the voltages, I think the two resistors used to formulate the gain of the compression part are probably 10k. Anyway, this part at least looks right to me.

benobo wrote:V3205 (1)

0
3.92
4.80
4.80
8.47
3.91
4.63
6.82


V3205 (2)


0
3.92
4.52
4.52
8.47
3.91
4.47
6.82

8.47v is on the high end of the maximum supply for the v3205, but they might still work this way. You'd have to trace it back to how the VDD supply is done...usually an 8.2v zener, but here they might have just used a resistor or two. Other than that the voltages look okay.

Do you have an audio probe?

madbean wrote:Also, those MAX chips usually only tolerate a max of 12v (I think they are rated at 10v) so if a larger DC supply was plugged in it could have damaged it.

Can I replace the MAx1044 with a 7660scpa? I believe it's cool but just want to double check/


thanks