Proel DS 10 troubleshooting

[JebemMajke]

Hello

A friend of mine asked me to check out his Proel DS 10 pedal

There is a farting sound coming out, so I've decided to measure all the voltages and they are bad

starting with zener first

+ - 1.67V
- - 6.18V

IC - 4558

1 - 1.86v
2 - 1.43v
3 - 1.12v
4 - 1.70v
5 - 0.87v
6 - 1.17v
7 - 5.22v
8 - 6.23v

Here is the schematic, i nicked it from the "other" forum





I was thinking of replacing zener. But is it really necessary here?

[JebemMajke]

[thermionix]

Those voltages are low, and strange.  Pin 4 should be 0VDC regardless of battery or zener.  If that schematic is correct, I don't know why they didn't put a filter cap at +VS.

[JebemMajke]

Well ...

Their switching system is crazy as well.

[ElectricDruid]

Where did you have your ground probe when you were taking the voltage readings? Is it possible it was somewhere that is maybe supposed to be connected to ground but isn't?

As Thermionix said, that pin 4 reading is just weird. You need to be able to get 0V there or something fishy is going on.

HTH,
Tom

[JebemMajke]

DC jack's ground.

I ll measure voltages again.

[JebemMajke]

I finally found some spare time.

After rechecking wiring i found out that it was kind of wrong.

So new voltages are

1 1.9
2 2.08
3 3.199
4 0
5 0.77
6 2.37
7 2.76
8 5.69

Zener
- 6.11
+ 0

Any advice?

[ElectricDruid]

The pin 8 voltage is pretty low - not even 6 volts. That's borderline and probably why it doesn't sound good. If you were running from a battery I'd say "dead battery", but if you're running from a power supply, then mostly likely is that there's a short somewhere that's dragging the voltage down. So perhaps there's still one more mistake to find in the wiring, or perhaps there's a tiny bridge of solder or a end of a lead touching something.

HTH,
Tom

[Kipper4]

Your Zener and pin8 the same?
Pin5 almost at gnd?

8 should be nearer 8v5
5   ".      ".      ".    4v3 ( value of the Zener. )

Or as Tom suggest flat battery. The op amp might struggle to function at such low voltages.

I'm not too familiar. Is it a DS 1 alike ?

[JebemMajke]

There is a schem above.

Some sorts of TS stuff

I don't really know.

It doesn;t produce any kind of sound now, after I rechecked the wiring.

I am not really sure what it should sound like.

[ElectricDruid]

Yeah, it's broadly speaking a Tube-screamer type circuit, in as much as that's what we call stuff with the diodes in the feedback path of the op-amp, since it's the most famous example. DS-1 is an op-amp followed by hard clipping diodes to ground, like the RAT. That's another style.
But either way - the tone stack has been tweaked. This one is roughly a Big Muff Pi style thing, rather than the original screamer tone circuit. In that regard, it *is* more like the DS-1. So maybe it's a mixture of the two, front end of one, followed by back-end of the other, more or less.

Tom

[JebemMajke]

Um

Changed 100 uf cap and that 1n4001.

0 v after 1n4001

Before diode it is 9 ( power supply )

It is shorting somewhere in power supply chain ....

[ElectricDruid]

Yeah, that's what it sounds like. Something is dragging the power down.

Post some photos of the board, both sides, and we'll all have a look. More eyes on the job makes life a lot easier!

T.