Line 6 4x4 Schematic/Help? (DL-4, DM-4, FM-4, MM-4)

kingsteven · #1 09-01-2007, 05:42 PM

Hi,

I have a dead DL-4 here which seems to work fine when connected with a 6VDC 1A PSU across the battery terminals but not at all with the Line 6 external 9VAC PSU...

The guy who owns it has been running the DL-4 with a DC PSU (not sure how it works, but it seems to bypass the internal transformer). After a bit of poking around I discovered one of the diodes in the transformer stage has been blown to bits (D16)... I'm no mathmatics whizz so I was wondering if anyone could tell me the value/type of this diode or have a schematic of the pedal I could look at?

kingsteven · #2 09-01-2007, 05:54 PM

Also, I should mention that from what I can see the internal AC-DC transformer seems to be quite a simple half-rectifying design built around a ferite inductor, a few capacitors and three diodes.

Two of the diodes (the remaining two) are rectifier diodes (IN4002) but from what's left of the blown diode - it's in a different casing from the other two - from looking at some transformer schematics on the web very possibly a Zener diode.

I'm guessing the transformer converts the 9vac input to 4.5vdc (which would be about right for most of the dsp stuff) As the Line 6 boards are printed on both sides, it's very hard to figure out the flow, so I'm hoping there's a schematic around somewhere...

niftydog · #3 09-02-2007, 05:39 PM

I think you'll really struggle to find a schematic for any of these babies. But, we can help. First step; tell the guy not to ever use a DC power supply where an AC one is required - unless he likes sending stuff out for repair!

The "transformer" might not be a transformer, it could just be a coil used as a filter, that would explain why DC passes through to the rectifiers. How many connections are there to the "transformer"?

Can you find no markings on the blown diode at all? Pictures? Half wave rectification normally only requires one diode. Full wave centre tapped requires two, and full wave bridge requires four.

I reckon some pictures would help.

kingsteven · #4 09-03-2007, 07:10 AM

Quote:

I think you'll really struggle to find a schematic for any of these babies. But, we can help. First step; tell the guy not to ever use a DC power supply where an AC one is required - unless he likes sending stuff out for repair!

The "transformer" might not be a transformer, it could just be a coil used as a filter, that would explain why DC passes through to the rectifiers. How many connections are there to the "transformer"?

Can you find no markings on the blown diode at all? Pictures? Half wave rectification normally only requires one diode. Full wave centre tapped requires two, and full wave bridge requires four.

I reckon some pictures would help.

Hmmn, Unfortunatley the diode was scorched and blown to pieces, have a look... I don't have my camera right now so I had to scan the board, I'll get a couple of photos tonight... It's pretty confussing :-s

kingsteven · #5 09-03-2007, 09:34 AM

It turns out that inductor is a "Tip and Ring Common Mode Filter" Here's the datasheet:
http://www.coilcraft.com/pdfs/non_rohs/trf_nonrohs.pdf

I should probabbly explain I've done some DSP coding before, and built a few pedals (using other people's board layouts) I'm thinking of building a delay similar to the DL-4 (although with midi sync/ triggers) so I want to put a bit of effort into fixing this to learn a bit more about how it's put together...

niftydog · #6 09-03-2007, 05:09 PM

Hmm, no clues there, we need somebody with a working one to post pics now!

kingsteven · #7 09-08-2007, 07:16 PM

Problem solved via http://music-electronics-forum.com/ via http://www.diystompboxes.com/

Quote:

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

It was a 3.6v Zener! I also had to do a hard reset by holding footswitch A & D while powering up.

BigBeatNut · #8 11-11-2010, 04:46 PM

Hmm ... I seem to have the same problem with my MM4. That same diode seems (from looking at the underside of the board) to have fried.

I can't pull off the board to check though ... I've undone the screws on the board, and the nuts holding the jacks and stomp switches, but the board seems firmly anchored still.

I guess it must the the control knobs holding the board inside the case ... what's the secret to releasing those, do they just pull off ?

Andy

Natsaba · #9 08-23-2011, 06:04 AM

With a small screwdriver pry up slowly on knob on side opposite the line.... Comes out ez

Happynoj · #10 08-23-2011, 07:02 AM

Quote:

Originally Posted by BigBeatNut

Hmm ... I seem to have the same problem with my MM4. That same diode seems (from looking at the underside of the board) to have fried.

I can't pull off the board to check though ... I've undone the screws on the board, and the nuts holding the jacks and stomp switches, but the board seems firmly anchored still.

I guess it must the the control knobs holding the board inside the case ... what's the secret to releasing those, do they just pull off ?

Andy

They just pull off, but they are a very tight fit. I used pliers to get the knobs off my FM-4. It marked the plastic slightly, so if you're super fussy then be careful.

BigBeatNut · #11 08-23-2011, 09:08 AM

Quote:

Originally Posted by Natsaba

With a small screwdriver pry up slowly on knob on side opposite the line.... Comes out ez

Quote:

Originally Posted by Happynoj

They just pull off, but they are a very tight fit. I used pliers to get the knobs off my FM-4. It marked the plastic slightly, so if you're super fussy then be careful.

Many thanks guys, but my problem was long since solved by sending the unit to Line6 for repair

Andy

Happynoj · #12 08-23-2011, 02:33 PM

Ah. Didn't spot the zombie thread.

Natsaba · #13 08-23-2011, 10:10 PM

I bought an fm4 off ebay powers up with 6v hooked up to battery terminals.. Good awful squel with some modulation got all the way up to u21 with 3.3 vdc.. i think im good up to there..(power supply)....found d15 with full 3.3vdc both directions and a couple of low reading caps...what kind of diode is d15? Saw in dl4 no Part#.. any ideas....please help ps led flash every couple of seconds.. Lets hear some ideas...