Thoughts on a dead Line 6 DL4?

[Dave_B]

I have an opportunity to buy a dead Line 6 DL4 for $125.  That's about half what they go for normally, but it's not showing any signs of life with fresh batteries.  I didn't have an AC adaptor to test with.

Has anyone here had any chance to work on one of these?  Are there any known issues with the power supply that might make purchasing it worth the risk? 

After fixing the Whammy pedal last week, I'm feeling a little overconfident.   

[Dave_B]

Hmm.... They've now got three of these things that suffer from the same issue.

[BDuguay]

It makes me wonder if an attempt was made to power them up with the wrong adapter and that adapter was used on all of them. The good folks at line 6 replied to an email I sent asking if those pedals handled their own power rectifying and filtering and they said yes. If you can, check to see if the internal voltage regulator is shot. If that's the case, it's an easy fix. Beyond that, I can't think of anything else.
B.

[Johan]

does any of them work with batteries?..
I used to work as repairman for the scandinavian Line-6 distrubitures, so I think I can help...due to signed non-disclosure agreements, I cant send you copies of the schematics, but i can guide you through...
..so follow me now...
...first thing to do. Plug a monoplug into the mono input, press footswitches 1 and 4 down and apply power. dont let go of the switches for at least 5 seconds. if nothing happens, its time to open up.

from the AC-in, power goes throu a 3,6v Zener ( D16 ) then on through D11. the 3,6v zener are known to fail, but doesnt affect battery operation.
after D11, power meets up with the battery in... next comes U14, a little 8-pin ( SMD ) MAX887. this one takes things down to 3,3volts ( mesure pin7/ signalground ). if you have 3,3volt on pin7, go on to U20.
U20 is a MAX660 wich is a voltage doubler. check the DC voltage on pin1 ( or 8, they are tied together ). if you have 6,6volt here, next in line is a tiny thing called LM3480 ( U21) this one will even out things for the digital domain to 5 Volt...if you havnt found fault yet, and reset doesnt work..dont bother...

..so the most likely suspects are
1: 3,6v Zener ( D16 )
2: MAX887 ( U14 )
3: MAX660 ( U20 )
4: LM3480 ( U21 )

hope this help...

johan

[BDuguay]

Johan is my new best friend online!
I own a DL4 and that info may come in handy someday, although I hope I never need it! Thanks.
Say Bellyflop, do you plan to but more than one?
B.

[Dave_B]

Thanks Johan.   No, none of them worked with batteries.  I plugged a cable in the mono input and pushed the buttons individually.  Nothing.

Is it still possible they might come to life by with the reset procedure?  Do I need to hold down buttons 1 and 4 as I put the batteries in?  If so, I'll need to take someone with me.     

BDuguay, no I only plan to buy one.  The SMD chips are a bit of a roadblock, though.  My wife could replace them with her eyes closed, but then I have to tell her I bought it.    

[Johan]

Thanks Johan.   No, none of them worked with batteries.  I plugged a cable in the mono input and pushed the buttons individually.  Nothing.

Is it still possible they might come to life by with the reset procedure?  Do I need to hold down buttons 1 and 4 as I put the batteries in?  If so, I'll need to take someone with me.     

BDuguay, no I only plan to buy one.  The SMD chips are a bit of a roadblock, though.  My wife could replace them with her eyes closed, but then I have to tell her I bought it.    

try the reset either way..
if using batteries, power up by simply plugging in with the footswitches pushed down.. 

johan

[Dave_B]

try the reset either way..
if using batteries, power up by simply plugging in with the footswitches pushed down.. 

Oh sure, it sounds obvious now.     Will do. I'll report my findings back here.

[yettirockc]

Johan,

Any ideas on where to go if I get 5 V on  the upper right-hand side of LM3480 ( U21 )?  Just curious.   I seem to be getting the right voltages everywhere else, it just doesn't turn on.   

Help!?

-Joe

[Dave_B]

try the reset either way..
if using batteries, power up by simply plugging in with the footswitches pushed down.. 

Oh sure, it sounds obvious now.     Will do. I'll report my findings back here.

I just realized I didn't report back.  I tried all the delays a couple of days later.  I couldn't get any response with the reset procedure.  I decided to let it be someone else's opportunity.  Thanks for trying, Johan.

[icepot]

i think you did the right  thing, i just  bought  a used dl-4  for 150 at a local music  pawnshop... the thing  came with  an adaptor  and both  adaptor and unit are in excellent shape. ill keep an eye out for another one, and let you know about it  if you really want one?
i know this was the one pedal i just had  to have... and findingit for 150 was like yeah! even  on ebay they go from 180-250.

[yettirockc]

I'm really hoping to fix the one I have, though if I can't...  one for $150 with adapter is a pretty good deal!

[Tombeau]

DL4 – A fix for Dead-After-a-Year problems.

Strange device...  Lots of people complaining about a failure that seems typical and predictable to all the Line-6 products based on this circuit board, the DL4, MM4 and FM4. Lets see what's going on.

First we open up. Man those knobs are hard to get hold of to pull off the shafts. I used good-sized slip-joint pliers set wide and went for the square ends of the grip hoping to leave a less perceivable mark and it went well. The 4 little white nylon spacers hidden in the foot button springs will all fall out when you finally separate the circuit board from the case, so watch for them. These spacers can be fine tuned in length if you want to make sure that your stomp button bottoms-out before placing full pressure on the tact-switch under it. Another note about these tact-switches; they are available in three flavors, practically free, dirt-cheep and cheep! The ones used in production are practically free. The difference between the three is, how much pressure they will take during cycle tests before failing. I replace these in lots of designs from many different stomp makers. They are a common switch and fail frequently. Replace them with the good ones (at .30 cents each from Digi-Key SW412-ND) with yellow buttons marking them rated at 260grams cycle tested. These will last. Ok, back to the failed circuit board.......

We have a digital circuit based on standard D/A, A/D stuff. Don't expect problems with most of the real workings. Good Jacks and user interface hardware. This looks like a power supply implementation problem right up front and center to these types of complaints. I did the reset operation and checks outlined by Johan who had some time in working for Line-6.

Basic voltage checks at the usual front-end points and at the;
MAX887 (U14) Dc-Dc-converter pin8 (chip input) = 6+v (batteries), Pin7 (output) = 3.3v (expected) (got nothing on mine, device dead).

MAX660 (U20) voltage-Inverter/doubler Pin8 (output) = 6.6v (expected) (Ok after removing the dead MAX887 and substituting good 3.8 (3.3) volts at its pin7.

LM3480 (U21) 5v-digital IC power regulation, (so far things tell me our circuit will probably stand up to 6.5 volts anywhere on the board without frying anything). Volt test for 5V ok here with the preceding MAX 887 bypass for good 3.8 (3.3) volts.

OK... an important note here. I actually needed to push at least 3.8 volts DC onto (the now un-populated) pin7 of (U14) to get the DL4 to light up again and to get the other test points working. I don't know if there is a small load somewhere, or if things just got old and tired after a year but even if the MAX887 was working, this stomp would still be dark without a little more juice driving it. This may be why so many DL4's out there are determined dead after passing the "factory" volt tests.  Maybe things are running a little too close to tolerance. Try the following fix since yours is dead anyway. We are only going to remove a few things from the board and push it another half-volt harder, so you won't even need a run to the store to try this.

One more problem, keep reading.

If you take the circuit board out of it's case, remove the MAX887 (U14) and simply power pin7 with about 4 volts DC, the lights (hopefully) will come on, but all blinking because it thinks the batteries are low and it has not finished the boot-up to full functioning (yet). We will need to satisfy this issue during boot-up.

Now I am planning at this point to power this fix with a new (4.5v DC) wall transformer from Radio Shack, skipping the original AC to DC rectification part and keeping the battery option working too (although with only three of the batteries instead of four, (4.5V)). All I need to convert the power jack input over to use a DC adapter is to remove the Zener Diode (D14) which is trying to clamp my volts down to 3.6 volts (which I have already determined is not enough to drive this stomp any longer and is known to fail in this stomp with a 9v adapter against it anyway). I will leave the other two rectifier diodes in. They will not affect the conversion.

Poking around for volts while going through a couple of power-ups and downs will show that the Cap (C40) needs to rise above 5.6 volts before the low battery trigger will stay off and we need this to happen immediately on power-up to avoid a brain lock. If batteries are in the device, this cap remains charged all the time and is ready. Without batteries it charges instantly when the adapter is plugged in. This is a 1000uf cap and I found I could get enough volts from the MAX660 voltage doubling cap (C59) to work, but it charges (C40) too slowly to prevent a boot lock up. I don't need (C40) and remove it. This is the point where the stomp came back to life.

I hope this info will help others to find their own suitable fix for this stomp.

Recap.
1)   Remove MAX887 (U14) – (this fix is based on this device failing)
2)   Remove 1000uf Cap (C40) – (removes the boot timing delay)
3)   Remove 3.6V Zener Diode (D16) – un-necessary for 4.5vDC aux. Power and stops a weakened circuit that may need a little more juice from working
4)   Jumper +pin (C59) to +pad (Removed C40) – to establish "power good"
5)   Jumper +pad (removed D16) to pad-pin7 (Removed U14) – to route our new power in
6)   Make a "C" cell sized pass-through dummy spacer for the battery box – to make 4.5vDC
7)   Get a "Pin Positive" 4.5 vDC wall adapter for the aux. power input. – re-label this jack
   Replace the four cheep switches for better. – option for lasting stomp performance
9)   Throw away your warranty card.

[O]

"To the WiKi, batman!"

or at least the FAQ's...

[Tombeau]

Regarding the "fix" just posted.

This does not address the input-pin on/off feature, where removing the input plug grounds pin1 of the MAX887 putting it in shutdown mode.
You will either need to remove the batteries, shove a guitar pick between them, or add your own power switching scheme, or just use the aux. power transformer.
This device is always on.

[Dave_B]

Makes me wish I'd bought the thing.   

To the Wiki, indeed!

[Tombeau]

P.S. to my fix Dead-After-a-Year post
Hasty post.   Just wrapping things up today.
For the board to see the batteries with the MAX886 removed you will want to short pins 7 & 8 short together when you put the jumper on 7. You also will want to put a diode in line with the battery + to prevent any possibility of an adapter trying to charge the batteries if used.

[Tombeau]

 
Oh hell.. that's not right . STILL WORKING on getting the wall adapter/battery isolation right.
Don't short the pads (removed)MAX887 (U14) 7 & 8 together! Just move the red battery wire to the +pad where (D16) was removed and the jumper to (U14) pad 7 is connected and settle for three "C" cells for 4.5vDC for now.

[Mr.Huge]

Here ya go....
http://aronnelson.com/gallery/MrHuge/DL4_ps

[Processaurus]

Thanks for the write up, Tombeau, and the schematic, Mr Huge!  I will take out my dusty busted DL-4 and give the PS a look.  T'was once my favorite pedal...