NEW need help with behringer amp

[shawn40]

your are right i swear it said 3 pin but when it arrived it was identical thank you

[shawn40]

ok so the input was 5 pin identical to the original sorry for not mentioning that.the volume pot has a 6pin wire that plugs in the pcb board i checked the tracks on the board and brushed after soldering to remove solder lag. iwill try what you mentioned unsoldering and messin with it my only concern is with power on handling the board do i need to worry about static elctricity or frieing something.. the volume has like 10 leds that go in a circle around it. all knobs like that but the volume is the only 1 that does not function or light up and it comes straight off the pcb

[oc disorder]

"ok so the input was 5 pin identical to the original sorry for not mentioning that."
A photo would help here or someone that knows this amp..however I'm not sure if the jack is on a separate pc board or mounted on the main board along with the pots etc.
Initially I thought it was just a little separate PCB for the input jack but perhaps its on the main preamp board with the pots etc.
Really need some photos.


"the volume pot has a 6pin wire that plugs in the pcb board i checked the tracks on the board and brushed after soldering to remove solder lag. iwill try what you mentioned unsoldering and messin with it the volume has like 10 leds that go in a circle around it. all knobs like that but the volume is the only 1 that does not function or light up and it comes straight off the pcb"

Worry about the lights later...

Try the hum test ..not much different to putting your finger on the end of a guitar lead plugged into the input.This will help to see if its just the jack causing the problem.

"my only concern is with power on handling the board do i need to worry about static electricity or frying something?"

Well keep away from the power input end so you don't fry yourself and as long as you don't have nylon carpets... Touch the chassis before you turn it on so you are not charged.
The processor section is where damage can happen which I assume is down the other end.

I'm assuming you can have the board resting in position where it won't short out.
I slip a magazine between the board and the chassis when the board is loose to stop shorts to the chassis.Can you slip the board back into position where you can access the jack solder pads?


Again a photo will help as its all a bit abstract at the moment.

[shawn40]

thanks again for all the help i did the hum test thing i touched my fingers on the connections found 1 that would hum when touched but i still cant get sound when hooking up guitar i unsoldered and held input on board wth fingers and wiggled/moved around with guitar plugged in still nothing you cant rotate input it fits 1 way only and only reason i mentioned master vol led problem is i think its related.what do you think maybe pcb board went bad.from what i been reading its impossible to get those.

[Enzo]

If I have to "reverse" the jack pins, I don't even think about it. SO I don't remember if it is necessary on these or not.

Those jacks have one beveled corner, where the ground pin is. Then on one side of that is the tip and tip cutout contacts. And on the other side is the ring and ring cutout contacts. SOme ersatz brands of jacks look about the same, but reverse the two sides. SO the tip is on the ring side and vice versa.

Look at the board where the jack solders on. With the amp running, touch the points where the jack pins would solder. Use a meter probe or small screwderifer or even a bent piece of wire. When you touch the point that carries the input signal into the amp, it will hum. Now look into the jack and see the tip contact. Eyebal which pin is the one for that. Does THAT pin on the jack wind up being over THAT hole on the board? Or does it wind up on the other side of the jack?


Up near the front of the jack - where the threaded bushing is - ther are small square windows, holes if you prefer. Each pin of the jack is a piece of metal that slides into grooves inside the jack, then a small tab snaps into those holes to keep it in place. By pressing in on the little tab, you can pull the contact out of the jack and reinstall it on the other side of the jack if you need to. I don't recall if I had to do this on the Behringers, or if the new jacks went right in. But it is easy to check for.

[shawn40]

thank you i will try that and let you know thanks very much

[shawn40]

ok so i tested it out of the 5 pins i have 2 that hum when i touch with a screwdriver 1 is i believe the tip it hums the loudest and it touches the groove right below tip. the other contact that hums is the 1 that touches the sleeve both the ones that hum are on each side of the beveled corner.another thing i noticed on the connector that touches the tip when i touch the solder joint right below the pin on the pcb board it hummd twice as loud dont no if it matters just thought i would mention it.please let me no what you think and thank you again for all the help and advice thank you

[oc disorder]

Hi again just back from trying to get some sun....
Maybe we should back track and can you tell me the exact part number of the replacement Jack Socket you have.

I've attached a diagram of the board you would be soldering to from the front and from the info I have
and what you described neither solder pads that hum could possibly go to the tip .

I suggest you print this thread out and take it and the amp to a tech.

Without more detail (ie a photo) it's very hard to work out whats going on.

It's sorta mirror image stuff too so its hard to tell which is back and front which may also be
causing confusion.
Besides I'm in Australia so looking from here its all upside down!

EDIT:added pic of amp that I think it is..

[shawn40]

okay so i looked at it from your picture the 2 opposite from the slant edge are the ones that hum. here is pics of what im working with so looking at the switch the the 2 the touch the 1/4 cord are the 2 that hum wich are opposite from the slant edge.sorry about the confusion from your picture it would be T & R on switch .thank you again for all the help i hope i can get it going again THANK YOU VERY MUCH

[oc disorder]

Hi again
I've chopped up the pictures and reattached them in to make it easy for others to have a quick look.
I presume the two different pictures of the back of jack sockets compare the pin arrangement of both the original broken Behringer and the new Switchcraft.
To me they look identical. (see attached)
After Enzo mentioned "If I have to "reverse" the jack pins, I don't even think about it. SO I don't remember if it is necessary on these or not."
From where I'm looking the tip and ring are in the same place.
Shawn40 you mentioned "the 2 opposite from the slant edge are the ones that hum"
well the tip should hum so thats ok but I'm not so sure the ring connection should hum unless
its a balanced input which I very much doubt as they are not normally fitted to high impedance guitar
inputs.
Why it stops humming when you solder in a new jack I'm not sure.
On the board photo I have attached I am wondering if the fine track that leads from R18, that does a right angle before connecting to a miniature through hole ... is that supposed to be connected to the tip solder pad ? It looks like it might be severed.

The ring has a track (i put red dots on) going to it so serves some function.

Two things I should have pointed out earlier.
1. Behringer only distribute schematic circuit diagrams to authorised service centers so I have no way of access to that particular diagram.The service centers have to sign a non disclosure.
2.The solder pads the jack solder to are usually through plated ie the ("tunnel") hole has metallic sides
which conduct or connect one side to the other.
Without a vacuum pump "desolderer" sometimes that tube track through the hole gets damaged
and the connection does not pass through.
Usually the reflow of solder through the hole joins it again but it may pay to check.
Try carefully/lightly soldering wires to the holes and experiment soldering to the jack loose
like you tested it before to see what hums. That way you can just change them on the jack end
without possibly causing damage to the board.
Also you can try a guitar to see if it works.. but while the "rats nest" is loose make sure it doesn't short on the chassis as before.

I am a bit busy next couple of days but I will have a look later. See if you can see any tracks leading
from the jack solder pads. Some look like they are just islands and don't go anywhere and some look
like they connect the same way the sleeve does to ground.
I'm a bit tired now but I will think about it.

[shawn40]

yes they are identical thats why i was confused when it did not work.the r18 track i can try and dab solder to make a reconnection,the red line you high lighted im not sure of its function/purpose,i got new spool of solder wick will clean it up and try soldering the wires in and testing i did not no the holes were through plated(thank you) so maybe i had a bad connection or something.everytime i have tested its been hooked to a guitar.and if you need anymore pictures or info just let me know.and i apreciate you taking the time to help me.thank you very much

[Enzo]

On the LX1200, and I assume the LX1200H, the line inputs CH 2,3,4 are indeed balanced inputs ready for a TRS plug. PLug a plain old TS in there and it grounds the ring for unbalanced. SO it would be normal for BOTH tip and ring contacts to hum when touched.

[oc disorder]

Thanks for that Enzo but I just looked up the user manual and the instrument input is 1/4" T.S. unbalanced 1meg.
It has 1 aux input which is stereo (4.7k) and the power amps are 2 x 60watt or mono power 120w into 4 ohms.
The manual is dated 2004.It has 24 bit DSP and midi.
I guess its like one of their "pods" built into a power amp.

I would have thought muting would have been done via digital means but perhaps , (as Shawn40 said one terminal hummed louder than the other) it has a mute on the output of that SMD 1458 (or whatever chip mounted near the jack) which utilizes the ring circuit which is normally grounded with nothing inserted ...not very elegant phrasing hmmm
anyway ... thats one eyed deer.....

[Enzo]

Geez, I'm an idiot. (Note to wife: shut up.) I was looking at the LX models and clicked KX1200 by mistake. Sorry.


You are correct, the input jack is unbalaced. The TRS jack should have all pins grounded except the tip contact.

[shawn40]

i want to say THANK YOU FOR ALL THE HELP so i ran wires from pcb board about 6inches then connected to the input jack started messin with it couldnt get anything then i started touching the ends soldered on the pcb board instead of jack and when i put my screwdriver from the R connection to the solder joint below the F in the part# BFO376A i got feedback from the guitar strummed the strings and i have sound.so i jumped solder from the R to that joint re assembled amp and started jammin works as good as new.maybe the pcb board is damaged or im not getting a good connection there.do you think it will hurt anything cause i will use as is.i am happy so THANK YOU VERY MUCH thankyou thankyou thankyou couldnt of fixed without the help thanks shawn