Allen & Heath Xone:92 mixer problem - faulty phono channel outputs on one side only

[analogicalmind]

Hi all,

Wondering if anyone here can help – I have an Allen and Heath Xone:92 silver mixer with one faulty channel – channel 2 is only outputting on one side (right side) when set to a phono input. It works fine with a line input, and all the other channels work perfectly with phono and line inputs. I'm not sure when this happened as I rarely use the faulty channel – it could well have been like this for years! Any thoughts on what might be causing the fault and how it could be repaired? I can do some basic soldering, so I'm hoping I might be able to fix it myself.

Thanks!

[redwire]

Re: Allen & Heath Xone:92 mixer problem - faulty phono channel outputs on one side on

If you can put a low signal into the RCA jack and just tap and rough up the mixer to see if it's a loose connection.
Likely a bad solder joint on the jack board, they do experience a lot of wiggling and force. You'd have to take it apart to see.
Or maybe the phono pre-amp IC TL072D is blown.
https://www.manualslib.com/manual/17...h-Xone-92.html

[analogicalmind]

Re: Allen & Heath Xone:92 mixer problem - faulty phono channel outputs on one side on

Many thanks. I'll give that a go and have a look inside

[analogicalmind]

Re: Allen & Heath Xone:92 mixer problem - faulty phono channel outputs on one side on

If you can put a low signal into the RCA jack and just tap and rough up the mixer to see if it's a loose connection.
Likely a bad solder joint on the jack board, they do experience a lot of wiggling and force. You'd have to take it apart to see.
Or maybe the phono pre-amp IC TL072D is blown.
https://www.manualslib.com/manual/17...h-Xone-92.html

Thanks. I've tried this but no luck unfortunately. I've also opened it up and couldn't see any bad solder joints on the jack board. Is there a process I could use to diagnose whether if phono pre-amp is blown? I'm fairly novice with electronics, although I have a multimeter!

I was thinking of swapping the jack board with another channel to see if the problem is on the channel board.

[analogicalmind]

Re: Allen & Heath Xone:92 mixer problem - faulty phono channel outputs on one side on

Not sure if this is useful for diagnosis, but the level indicators only light up on the right side as well as only outputting sound on the right side

[petehall347]

Re: Allen & Heath Xone:92 mixer problem - faulty phono channel outputs on one side on

is it modular or all one board ?

[analogicalmind]

Re: Allen & Heath Xone:92 mixer problem - faulty phono channel outputs on one side on

is it modular or all one board ?

Modular - separate PCB boards for each of the channels. What were you thinking?

I'm going the faulty channel PCB board with one from a working channel and see if this isolates the problem

[analogicalmind]

Re: Allen & Heath Xone:92 mixer problem - faulty phono channel outputs on one side on

A bit of an update - I've tried cleaning the ribbon cable connections with no success. I've also swapped around the channel 2 (the faulty channel) PCB board with the channel 3 PCB board - channel 2 is still faulty after swapping the boards so I guess the rules out a fault with the channel PCB board.

I'm guessing (naively!) this points to a problem on the slave or master boards, or the ribbon cable. I'm assuming that the other boards wouldn't produce such a channel-specific fault.

[analogicalmind]

Re: Allen & Heath Xone:92 mixer problem - faulty phono channel outputs on one side on

Actually... I made an error earlier - when the channel 2 (the faulty channel) PCB board is swapped with the channel 3 PCB board, the problem moves to channel 3. I guess the fault is somewhere on the channel board

[budwich]

Re: Allen & Heath Xone:92 mixer problem - faulty phono channel outputs on one side on

that should make it easier. pull two boards ... one good and the bad one. get a meter and use the resistance check to compare readings against the two boards at "well chosen points". Hopefully, you will be able to quickly isolate where the "break" is and go from the result.

[analogicalmind]

Re: Allen & Heath Xone:92 mixer problem - faulty phono channel outputs on one side on

Nice, I'll give that a go. Thanks!

[budwich]

Re: Allen & Heath Xone:92 mixer problem - faulty phono channel outputs on one side on

hopefully I understood your post and "correction".... restated, you moved the bad chan 2 board to chan 3 and now that channel has the same issue (ie. one chan of phono in is dead). IF so, then the problem likely lies with the "bad" channel 2 board. Hopefully, you are labelling them to keep them identified properly. You should be able to do some relatively simple resistance checking at "strategic points" to identify the issue. Hopefully, it will be a simple fix there after.

[redwire]

Re: Allen & Heath Xone:92 mixer problem - faulty phono channel outputs on one side on

The phono/line switch SW3 pg. 14 switches in the preamp or not.
IC TL072D U12, U13 are the preamp, right at the end of the board by the RCA jacks.
There's some jumper link options JP1-JP4 cut to set it as flat pre-amp input or left in for phono RIAA curve.

I usually go for the RCA jacks or switches and broken solder joints there.
I notice this mixer doesn't have any ESD protection for the mic and phono preamps. Which can mean blown IC's.

[analogicalmind]

Re: Allen & Heath Xone:92 mixer problem - faulty phono channel outputs on one side on

hopefully I understood your post and "correction".... restated, you moved the bad chan 2 board to chan 3 and now that channel has the same issue (ie. one chan of phono in is dead). IF so, then the problem likely lies with the "bad" channel 2 board. Hopefully, you are labelling them to keep them identified properly. You should be able to do some relatively simple resistance checking at "strategic points" to identify the issue. Hopefully, it will be a simple fix there after.

Thanks for the clarification. Yep, you understood correctly - there is a bad channel board. I've now labelled the boards after the error (I put the same boards back in the same slots...).

Apologies for the naïve question - I'll test at the points that redwire has kindly suggested - are there other particular strategic points that you would recommend testing at? I've attached the schematics for the board if you have the time.

[analogicalmind]

Re: Allen & Heath Xone:92 mixer problem - faulty phono channel outputs on one side on

The phono/line switch SW3 pg. 14 switches in the preamp or not.
IC TL072D U12, U13 are the preamp, right at the end of the board by the RCA jacks.
There's some jumper link options JP1-JP4 cut to set it as flat pre-amp input or left in for phono RIAA curve.

I usually go for the RCA jacks or switches and broken solder joints there.
I notice this mixer doesn't have any ESD protection for the mic and phono preamps. Which can mean blown IC's.

Many thanks, redwire. I'll check these out.

[budwich]

Re: Allen & Heath Xone:92 mixer problem - faulty phono channel outputs on one side on

Thanks for the clarification. Yep, you understood correctly - there is a bad channel board. I've now labelled the boards after the error (I put the same boards back in the same slots...).

Apologies for the naïve question - I'll test at the points that redwire has kindly suggested - are there other particular strategic points that you would recommend testing at? I've attached the schematics for the board if you have the time.

redwire has given you very good direction. My "strategic" means I look at the physical board and pick points easy to reach with a meter... choosing component points that are readily identifiable on schematic.... start at the input in question (ie. phono jack R) and following the track to the nearest component that it leads to. I use a "continuity check" broadly to help follow tracks... much like a "blind man's cane" to help follow the track thru the board and components.... comparing between a good and bad board and even side to side (left versus right) on the same board.

I currently don't access to a printer... trying to follow a schematic on a small screen is difficult at this point. A good picture of the areas in question might help.... but again redwire has provided good direction at this point.