Line 6 DL-4 troubleshooting

[tiococo]

Guys!
I'm trying to troubleshoot a DL-4 I have.
The previous owner conected a 110v walwart into a 220v socket, and he had to rebobinate the primary. So he used it with batteries.
When he got the repaired transformer the the DL-4 wont turn on plugged.


I opened and the 1000uf capacitor C40 was blown, and the power section was making a faint buzz when plugged (???)
I replaced it and the buzz went out. But the pedal never started again, neither with AC or batteries.

I measured everything and it seems ok, only the out of the doubler is a bit "weak" measuring 6.06v instead of 6.6v
Also the dps is running a bit warm, (not hot)

The rest of the voltages are ok.
I also tried to reset the unit to no avail

I'm using this schem.


What can I do???

[tiococo]

Guys

I supose that I have good news (???)
I left the AC power section off by disconecting the 3,6 v zener and used the bateries.

Let it rest for one day and when I plug the input the pedal light up light a christmas tree :icon_smile:
The only problem is that if I want to repeat the procedure the pedal wont lit again until I let it rest for a while

Anyone can point what do I check for that intermitance?

I havent tried with a regulated 6v in place of the 4 batteries. Maybe those are the problem

[nickb]

"Lighting up like a Christmas" tree sounds bad to me. It may well be an indication that one or more of the voltages are wrong and that is bad if it's too high. When dealing with faulty power supplies it's nice to be able to disconnect the power supply from the rest of the system if all possible. Partly to help isolate the problem(s) and partly to protect the rest of the system. I'd certainly be hesitant to power up via the AC in case I caused more damage without some kind of current limiting. Personally, I'd isolate U14 first get that going, then U20 and then finally U21.

Do have any test equipment at all? It's going to be tough to approach this logically without a meter.
Did it work with the batteries in?
Does it still work with the batteries? If so that is good.

Suspecting that something gets hot and that is the reason for the behavior, you could feel around (carefully) for anything hot.
I would not be all surprised if the MAX887 switcher is bad as it's rating would have been exceeded. How well set up are to replace surface mount chips? Also, I see there are a couple of 47uF 16V tantalum (both seem to say C58?) that would be questionable.

[tiococo]

Nick.
By lightning up like a christmas tree I mean that the pedal works. It changes patches when you press the buttons and the tap tempo also works.
I have a multimeter. I checked all voltages along the chain of the power supply and they seem correct.
Every chip of the power supply is supposed to do its work.

Now its working with batteries. Partially working cause when you let it rest and turn on everything goes well
When you try to repeat the same operation the pedal doesn't work unless you let it rest for a while
I haven't tried to power from the battery clips with a regulated dc supply. Maybe the batteries are dying and the voltage needed (or the amperage, because of the doublers)
is meet when you let them rest
I'll try with that to start ruling things off

It's an intermitent fault

[nickb]

Batteries running down could be cause by a bad electrolytic somewhere, certainly an indication of high current draw.
Check for hot parts for clues.
When it's stops working what are the voltages?

[g1]

Have you tried it with fresh batteries at all? Or hook up a meter across C40 and see if the 6V is dropping out when it doesn't work.

[tiococo]

Guys, I have tried it with batteries measuring 5.5 v in tandem, and with a regulated celular power supply delivering 6.4v across the battery clips.

I could never measure the voltages with the pedal on, always in "lock up" mode.
The MAX 660 doesnt delivery 6.6 volts. Sometimes is 6.06v an sometimes is 6.43, it never reaches nominal level.

I think the processor reads that voltage and thinks that the batteries are dead and locks up.

[g1]

The problem with using the battery clips is that there are still components and the jack switch between the - batt. clip and ground.
Try connecting the regulated supply directly across C40.