Line 6 XPS-AB Schematic

[Billguitarvin]

Hi there! I’m looking for a schematic or service manual for a Line 6 XPS-AB. This is the unit that powers the 300, 500, 600 and 700 Variax guitars so you don’t have to use batteries and also acts as a foot switch to toggle between a 1/4 inch and XLR output. I have no voltage coming out of the TRS input so my Variax is not powering up. Thank you!

[gaztech]

Hi. PM me.

I have the Variax Service manual which I can send you. It's too big to put here! I'm pretty sure that what you need is in there.

Cheers

[Billguitarvin]

Wow, thanks gaztech! Can you tell me how to pm you? I am logged in but when I tried clicking on your name it says I don’t have permission.

[gaztech]

Hi, I guess it could be that your profile is not set up to send or receive messaging. I think it's turned off by default. Go to your profile and edit it, Select General and you can edit your permissions there. I can't send to you if you don't have permission to receive messages from members. It's likely if this is turned off you won't be able to send either.

Once you set it, go to Notifications on the top of the screen select Inbox - which will take you to messaging and then try to send me a message.

[Billguitarvin]

Thanks for the quick reply! I will see about editing my profile.

[Billguitarvin]

I seem to be in a catch 22. I click on my name and click on profile but I get the same message - I don’t have permission. Not sure why I can’t get in to edit my own profile unless I haven’t been approved by the administrator?

[Billguitarvin]

Okay, went to try and edit my profile again and all of the sudden I now have a “Private Message” icon, so sent you a pm.

[gaztech]

HI Bill,

Sent to your email. Hope all is well.

[Billguitarvin]

Thanks gaztech! I really appreciate your taking the time to read my post and send the pdf. Take care!

[DrGonz78]

Line 6 Variax Service Manual

[Billguitarvin]

BIG Thanks DrGonz78!

[Billguitarvin]

Big thanks again to gaztech and DrGonz78 for sending me a file of the Variax Service Manual. Unfortunately I must have a later version of the XPS-AB box that supplies power to the Variax. On the circuit board of the XPS-AB it says “MG1 MGB REV B”. Then underneath that is the same part number as the REV A model (35-00-0138) and beneath that is the date 6/9/03. The REV A version is dated 8/20/02. Any idea where I can get a schematic for this REV B XPS-AB? Looks like the REV B model has 2 relays instead of one and various other changes. Thanks so much!

[gaztech]

Hi Bill,
Has the unit ever worked?
The footswitch unit should be powered by a separate mains adapter. You haven't changed the adapter have you? I seem to remember an incident a long time ago regarding one of these where the customer had changed the adapter and it was the wrong one. The original adapter I think was an AC adapter not a DC one - 9v AC @ 2000mA. I just had a quick look at the schematics I sent you and there's not a lot in the box that would go wrong. I would have thought, any fault, if it's just the box, should be obvious.

If you look at the MGB schematic, you will see that it does indeed suggest that the adapter is AC - not DC. A DC one won't work because of the arrangement of the diodes in the front end of the power supply section.

I'm wondering now if it's not actually the box at fault. Are you sure it's not the mains adapter? It's difficult without physically looking at it to make a reasonable diagnosis of this. Can you give me some more info? Maybe we can work through this for you.

[Billguitarvin]

Thanks so much, gaztech, for the reply! I feel I must preface my reply with the fact I am pretty much a noob when it comes to repairing electronics. I’m a musician of 50 plus years and have been soldering guitar cords for many years and over the last 3 years have watched many electronics YouTubes as well as read parts of the NEETS modules on line, but my knowledge is very limited, so any help I can get is greatly appreciated.

Yes, the unit was working. I bought it used about 6 weeks ago. I haven’t changed the ac adaptor and it is the one made by Line 6 for this unit. You are correct, the adaptor puts out an ac voltage. I measured the voltage coming out of the adaptor and it is putting out around 11 VAC. Is that enough to rule it out or are there some other tests I can do on the ac adaptor?

I am wondering if the electronics in the box or the ac adaptor could have failed due to a heating problem. I am ashamed to say I left the box plugged into the ac adaptor and guitar for 5 days never unplugging the power, so the box was on 24 hours a day for 5 days. It stopped working on the 5th when I was playing the guitar. I noticed in the owners manual it said to disconnect the box from the power if you aren’t going to be using it for a while. Is it possible something could have overheated?

When I opened up the box then plugged in the ac adaptor, U6 (the quad comparator model LM339 located on the right side of the board between the TRS IN and ac adaptor input) and the area around it felt very hot.

The next thing I did in order to confirm what part was getting hot, (and might not have been the smartest thing to do) was put some flux in that area and proceeded to watch pin 3 (VCC in) on the LM339 burn up, then the light emitting diode D16 stopped glowing. I have since replaced the LM339. I also replaced U2 (C082C op amp) and D8 which are located above and to the left of the ac input) as they looked like they had some heat damage too after I put flux around the LM339 area.

In the process of removing the op amp by using some Chip Quick low temperature melt solder I must have gotten some solder on 2 resistors (R 28 & 33) that are very close to the op amp, because to my surprise there were both missing after I removed the op amp. So I am waiting to get the 2 resistors in the mail before I try plugging in the box to ac. They are supposed to arrive Saturday, so hopefully by Sunday at the latest I will have soldered them in and report back.

In the mean time any help or advice is greatly appreciated. I just posted a couple of pics in my albums of the circuit board in case that may help. Thanks!

[gaztech]

HI Bill,
You really must be careful with soldering on something like this! It's very easy to break the copper tracks...

Ok, so when you have the resistors soldered back in, you are only concerned with the voltage across 3 capacitors. These measurements will tell you what is going on:
Across C12, should be -5V (with negative probe on the -ve of the capacitor)
Across C11, should be +5V (with negative probe on the -ve of the capacitor)
Across C2, should be +7V

It's probably worth taking a measurement across C9 too - that should read about 9V.

All of the above are DC readings of course!

Report back on your findings. If any of these are missing then it's a relatively simple job to fix (probably). If these are all up and working then the problem is more serious and I doubt you will be able to fix it yourself.

Let me know how you get on.

Cheers.