[HELP] Dead Line 6 DL4

[HeaD]

Hi all! How are you?

I've bought a dead Line 6 DL4 on eBay, it not showing signs of life. I think there is a problem in the power section. I found an interesting old post by Johan, but I don't understand what kind of problem is. Please, can someone help me to find out what's wrong with it? Click here to download the power section schematics.

First of all I've rebooted the device, nothing happened. Voltages are:

- U14 (MAX887) PIN 8: 6.4 V   [OK]
- U14 (MAX887) PIN 7: 0 V      [so, here is the problem...]

I've ordered some MAX887 from maxim-ic.com, arrived yesterday. Today I've replaced U14 with a new MAX887 but nothing happened again. Another thing, C14 (a small 2.2uF capacitor) seemed to be broken, so I replaced it with a new elec. 2.2uF capacitor.

Please help me!

[HeaD]

No one can help me? Is there a way to understand where is the faulty component? I forgot to say that before me a person has tried to repair it without results.

Here is a picture of the power section before my replacements:



Another info: The PCB seems dirty because of the exploded batteries liquid.

Any ideas?

[Austin73]

can't  really see whats going on in the pic and the chip thing means nothing to me.

But I did manage to fry my FM4 Filter modeler which blew the second diode along which I replaced with a 1n4001 standard silicone diode. Looking at tyhe circuit I also damaged the  torodial coil which i think the pic shows a bit melted?

From what I found checking out forums (line 6 forum is not bad for help unlike the company) these things get fried by people putting the batteries in wrong way round 

I'm not sure of your experience fixing things but I just looked at the back of the board and found the burn't bit (diode) replaced and hey presto but when I was researching how to fix mine people had some horror stories.

I'm sure this is of no help  but best I can do at mo. If I get chance later will try and find more info for you.

Aus

[Dave_B]

I can't help either, sorry.  I wrote about some dead DL4's I ran across last year, but I never bought them. 

[Austin73]

trying posting here http://line6.com/support/forum.jspa?forumID=15&start=0

I did have a quick look but couldn't find anything.


Good luck

Aus

[HeaD]

trying posting here http://line6.com/support/forum.jspa?forumID=15&start=0

Thank you so much Austin.... I try

[HeaD]

I can't help either, sorry.  I wrote about some dead DL4's I ran across last year, but I never bought them. 

Thank you anyway Dave

Any other ideas? Please help me!

[HeaD]

Line 6 forum is not so populated. I wrote a thread, but I don't think that will help me for this kind of problem.

I don't understand... I was sure on that MAX887 IC...

Please take a look at the schematics... why I got 6.4V on the pin #8 and 0V on the #7?

[Processaurus]

something is likely shorting the output of the regulator chip.  One thing to check is for shorted smt big tantalum caps in that section of the power supply. C45, c58, and the zener diode d15.  keep in mind whatever was wrong may possibly have killed the new chip.  I would probably just replace all three of the parts  (just stick electrolytic caps on in the place of the tantalums) and if that doesn't work, the chip again.

Personally I wouldn't touch a dead DL4 with a 10ft pole, though luckily the power section isn't so complicated compared to the rest of the pedal.

[PerroGrande]

I agree -- something is pulling down the output from the 887 (or the 887 is cooked).  Tantalum/Electrolytic caps are great candidates for this, as are diodes.

Another possibility upon further review...

What shows up on Pin1 of the 887?  This pin should show a voltage greater than about 2.4 volts for the chip to turn on.  If it is below about 0.8v or is at ground, the 887 will be off and the output of pin 7 will be 0...

[Processaurus]

Another possibility upon further review...

What shows up on Pin1 of the 887?  This pin should show a voltage greater than about 2.4 volts for the chip to turn on.  If it is below about 0.8v or is at ground, the 887 will be off and the output of pin 7 will be 0...

good call, the modeler pedals use the stereo input jack trick to turn the pedal on, but it does it remotely (ie all the current doesn't flow through the input jack ring to sleeve).  I bet either the shutdown pin is connected right to the input jack ring connection, or to a simple transistor circuit that turns that pin on (or off) when the ring is connected to sleeve.

[HeaD]

Thank you for the answers Ben and John.

One thing to check is for shorted smt big tantalum caps in that section of the power supply. C45, c58, and the zener diode d15.

I would exclude C45 because I have replaced it together with the MAX887. I've replaced that 2.2uf tantalum with a 2.2uf electrolytic one. It's ok?

D15 is a schottky power rectifier. Here is the datasheet. With what component could I replace it? Is there a way to test it in order to understand if it is broken?

What shows up on Pin1 of the 887?  This pin should show a voltage greater than about 2.4 volts for the chip to turn on.  If it is below about 0.8v or is at ground, the 887 will be off and the output of pin 7 will be 0...

Ok, at Pin1 the voltage is 0 volts when the input jack is disconnected. Only 0.03V when I plug the input jack.

Any other suggestions? Thanks so much guys!

[PerroGrande]

Well, only 0.03 volts on pin 1 is not sufficient to turn on the MAX887.  The power section schematic did not indicate where that pin goes.

We need to figure out what controls the input to pin 1 and why you're not getting a good solid ON voltage to the 887.

[Processaurus]

D15 is a schottky power rectifier. Here is the datasheet. With what component could I replace it? Is there a way to test it in order to understand if it is broken?

Oh, well, you can test it like a normal diode, by taking one end out of the circuit and beeping it both ways, and it should beep the forward biased way.  But John is right, that's not the immediate problem.  To trace down the trouble with the insufficient voltage on pin 1 to turn the Maxim chip on, you could either reverse engineer from that pin, or from the ring connection on the Left channel input jack, either way, you'll end up in the same place.  It must be a simple (I'm guessing 1 transistor and a couple support components) circuit in between the input jack, because the ring being grounded has to turn on a voltage seen by the shutdown pin (1) on the maxim chip.

Maybe check with a meter that the plug inserted does in fact connect the ring to the sleeve, on the jack lugs contacts on the PCB, and that those joints aren't cracked, by resoldering the jack.

[HeaD]

We need to figure out what controls the input to pin 1 and why you're not getting a good solid ON voltage to the 887.

To trace down the trouble with the insufficient voltage on pin 1 to turn the Maxim chip on, you could either reverse engineer from that pin, or from the ring connection on the Left channel input jack, either way, you'll end up in the same place.

Hey guys, pin1 seems to be connected to the input jack through a miniature signal relay (-->NEC EA2<--). But it's very difficult to figure out what other components are involved without a complete schematic. Where can I find that?

[PerroGrande]

This unit was damaged by battery chemicals?   It is possible that this little relay, although it appears to be sealed, might have been damaged.  Try tapping on the relay with your finger - perhaps it is mechanically stuck.

Also -- make sure that there is power to the coil of the relay.

[HeaD]

This unit was damaged by battery chemicals?

Yes, the guy that sold it to me said so...

It is possible that this little relay, although it appears to be sealed, might have been damaged.  Try tapping on the relay with your finger - perhaps it is mechanically stuck.

Also -- make sure that there is power to the coil of the relay.

I've tried to tap but nothing happened... there are two little relays, and there is no power to the coils!

Here is a picture of this section:



As you can see, there are a lot of components involved in that relay circuit. I'm scared that without a schematics I cannot figure out what the problem is... What could I check now?

[PerroGrande]

I haven't had any luck locating a schematic for this unit yet -- sorry. 

I don't blame you for being a little bit reluctant without a schematic.  It doesn't look like a trivial circuit...

Without knowing for certain what is connected to SHDN (Pin 1), I'm a little reluctant to recommend anything.  If the pedal uses SHDN for power-on, then you might be okay to try briefly (and I mean BRIEFLY!) connecting that pin to the V+ supply through a 100K resistor and see if the 887 chip starts.  On the other hand, if the pedal circuit is somehow using SHDN as a protection mechanism, defeating it would be a very bad idea.

I would also check and clean all mechanical connections -- everything.  1/4in jacks, jumper blocks, etc, etc.  Inspect all traces and solder connections for damage from the battery splooge. 

[HeaD]

If the pedal uses SHDN for power-on, then you might be okay to try briefly (and I mean BRIEFLY!) connecting that pin to the V+ supply through a 100K resistor and see if the 887 chip starts.

Ok John, I did it. I've connected Pin1 to the V+ through a 100K resistor and the MAX887 actually starts! There are 3.1 V on pin7. By the way, three leds (2, 3 and 4 button) starts to blink, and I don't think this is normal... 

[PerroGrande]

I have no idea what is normal, as I don't own a DL4.

However, what we have learned is that the Max887 chip is good, and the voltages supplied by it seem to be correct.  So the diode, the caps, and all look to be okay.

The pedal may still be freaked out because there MAY be other voltages that are produced elsewhere that didn't come on as a result of your testing. 

Perhaps the relay that activates SHDN does more, and there are other voltages that need to come on.