NO CHANNEL 2 on MUCH BELOVED FENDER SUPER CHAMP XD.

[XDaddict]

A sad day!!! my beloved XD amp cut out at a blues gig and after the help of this forum, I replaced a blown R79 with 5 watt upgrade and power amp and tone controls worked once more BUT now it won`t switch to channel 2. Nothing wrong with DSP board itself as switched it for a mates board and same problem, both DSP boards work fine in his XD. My line out just gives Channel 1 sound no 2. Checked R4,R25,R87,R88 (none open) and replaced burned out R79 as stated. D23 & 24 both ok, U10 12v and 6 v Any help and advice would be appreciated from anyone who knows this c. board after a R79 blow.

[DrGonz78]

...after the help of this forum, I replaced a blown R79 with 5 watt upgrade and power amp and tone controls worked once more BUT now it won`t switch to channel 2...

As I study this schematic and read your questions about the amp problem... I have to just ask what help were you given on this site? I think it would help us out if you included the link to the thread that helped you. Just some background as we move forward from here, thanks.

Good thought that it is probably something on the preamp now, but why did it suddenly stop working?

[Jazz P Bass]

I would suggest that you verify TP10 & TP11.
I doubt that this has anything to do with R79 failing.

[DrGonz78]

Yeah I have seen two threads to other websites but can't figure which thread on the MEF website is the one you were referencing.

How reliable is Fender Super Champ XD? Any known problems?

Fender® Forums ? View topic - Fender Super Champ XD - Dead

I looked all over the site here with keywords like Fender Champ XD R79...
Nothing found on this site.

Apparently, R79 ("Choke" Screen Resistor) blows commonly as a result of bad output power tubes. Also, to note that a short can happen in the P18 Lead on the transformer... That is all in the links I have provided... What resistance readings are you getting between P13 and P18?

Edit: I was looking at TP10 and TP11 on the schematic and that is exactly where I ended up too!

[XDaddict]

Hi, thank you for your help Dr Gonz78 and Jazz P Bass. I must have read a thread elsewhere, so my apologies, I read as many threads on the Super Champ xd problems as I could find over two nights, so obviously got mixed up. But from you all I certainly got clued in about this great sounding little Fender. As for your questions :-
TP10 reads 1.98 vdc with amp set on Channel 1, set to channel 2 it reads 2.52 vdc
TP11 reads 2.93 vdc with amp set on Channel 1, set to channel 2 it reads 3.50 vdc
Resistance between P13 and P18 reads (on 200 scale) 27.1 ohms?

I hope this is useful info, I am an amateur at this job, so please dumb it down for me. I AM enjoying wearing Latex gloves!!

Thank you again , XD addict.

[Jazz P Bass]

Just to make sure the switching circuit is functioning properly, what are the TP (10 & 11) voltages with the channels 'off'?
You have stated that Channel Two will not come out the 'Line Out'.
But does it come out of the main speaker or not?

[XDaddict]

Line out just gives channel 1 sound i.e channel one vol, bass, treble but no FX at all.
Line out with channel 2 switch chosen gives the same. TP10 voltages do alter when channel selection switch is IN and OUT.
The sound heard from amp speaker remains channel one on all channel switch settings. no Led comes on for chan 2 as it should. It may help to note that after fitting new R79, when switched on for the first time the amp was in Channel two setting. The red channel indicator came on, BLINKED SLOWLY and faded away. Cannot switch to channel 2 since then, amp is stuck on channel 1 with no effects. TP10 readings indicate changes when channel 2 is chosen but the amp sound remains unchanged.

[Jazz P Bass]

Please post TP 10 & 11 voltages (NOT 'THEY CHANGED) when Ch 1 is off & also when Ch 2 is off..

[XDaddict]

Hi Jazz P Bass, Please look at #5 posting on this thread. I gave voltage readings there for TP 10 and 11 when channel 1 selected and when Channel two is selected for both test points. To repeat :

TP10 on the working channel 1, 1.98 vdc but when channel 2 selected reads 2.52 volts dc
TP11 .............................. 1, 2.93 vdc but when channel 2 .......... .......3.50 volts dc
Resistance between P13 and P18 27.1 ohms (on 200 scale).

Readings taken from 1st and 3rd chip pins . Sorry if I am not following what you are after. That is all the readings at those two Tp`s . Thanks.

[g1]

Sorry if I am not following what you are after. That is all the readings at those two Tp`s . Thanks.

I think Jazz is looking for readings with EFFECTS on and off for each channel, for each test point.
On the schematic, there are boxes near the test points that show the proper voltage values. We want to compare your readings with the ones shown in the boxes.
So for example, TP10, ch.1 FX on = ?, TP10, ch.1 FX off = ?, and so on, for both TP's and both channels.

[Jazz P Bass]

Thanks G One.
It is not noted on the schematic but I am assuming that P15 gets mated to P17.
I will post a clear copy of the schematic later. (the one I got from Fender is a bit blurry)
Both channels go through the DSP section.

[XDaddict]

Thanks G1, for explaining. That can only be done with dedicated foot pedal on XD, no FX `off` option from front panel. I have the footswitch so I`ll get at it. Thanks

[XDaddict]

Using footswitch to switch out FX on TP10 and TP11 readings are :

TP10 Chan 1 FX ON = 1.81 vdc FX OFF = .12 vdc
TP11 Chan 1 FX ON= 3.39 vdc FX OFF = 1.58 vdc

Thanks again all.

[Jazz P Bass]

Fender Super Champ XD Service Manual

Here is the schematic.
Test voltages on Ch 2 on & Off please.

[g1]

It is not noted on the schematic but I am assuming that P15 gets mated to P17.

Yes, I was thinking the same, also, 10_6 from U1-A ends up at pin2 of U6-A.
As most of the voltages at TP10 & 11 so far are good, I'm going to guess/hope U6 is bad, otherwise unit may not be repairable.