Fender champ 12 messup

[Kesi from Hungary]

Did i mess up?  I was working on a modification on my Fender champ 12 to Effectrode's scheme.  First the overdrive channel and that went well and the sound is a huge improvement.  Then normal channel.  Made the changes but no sound.  What now?  I am by no means a technical expert, but on paper it looked simple.  Not.  Pilot light is on.  Tubes glow.  I hear the normal hum.  I can hear the reverb tank when tapping.  Power transformer stays cold.  Normally when starting up I also see the fuses glow for a short while, but not now.  What to do .  I hope someone can help me.

[dude]

I did this exact mod to my red knob Champ 12, no issues and big improvement in the distortion channel but the clean channel wasn't quite as sparklingly clean as before but close.
Most likely you made a wiring mistake during the mod, go over each change again making sure you followed the schematic. Also, make sure you don't have a cold solder joint, those little traces come up easily too, don't use a big tip and lowest heat possible.
The mod works. 

[j_bruce]

I would check the fuses. If one or more is blown then you clearly made a mistake, probably in the power supply when changing the caps to 100uF. If one went in backwards???

Did you change all the values shown in the schematic you posted? if so check those solder joints and check for traces loosened up as dude suggested.

None of those changes is all that big of a deal so you must have gotten something wrong.

If you don't spot anything then post some photos of your work, use nice close shots and good resolution.

good luck,
Jerry

[Kesi from Hungary]

Hi Jerry,

I used new fuses and in the first phase of the mod I did have sound with the 100uf and the 47uf replaced. They are on the right track. I'm going to check all the solder again just like Dude says.
Thanks for your comment

[Kesi from Hungary]

I did this exact mod to my red knob Champ 12, no issues and big improvement in the distortion channel but the clean channel wasn't quite as sparklingly clean as before but close.
Most likely you made a wiring mistake during the mod, go over each change again making sure you followed the schematic. Also, make sure you don't have a cold solder joint, those little traces come up easily too, don't use a big tip and lowest heat possible.
The mod works.

I also had problems with the little traces.  Then borrowed a small soldering iron and made a small bridge.  I'm going to walk back on the PCB and will check all the solder joints what you suggest. Question. When the mod in the clean is not big improvement isn't it better to keep in the original state?  And which 6l6 is do you prefer in this amplifier?  Thanks for your comment

[j_bruce]

Hi Jerry,

I used new fuses and in the first phase of the mod I did have sound with the 100uf and the 47uf replaced. They are on the right track. I'm going to check all the solder again just like Dude says.
Thanks for your comment

I was wondering if you checked the fuses after the no sound started?

If an error in your mods caused a problem that blew the fuse then you need to know that to help you start the search.

Don't just check the solder, check the values of the resistors and caps and also check that you put them in the right places! Just to be sure.

[dude]

I also had problems with the little traces.  Then borrowed a small soldering iron and made a small bridge.  I'm going to walk back on the PCB and will check all the solder joints what you suggest. Question. When the mod in the clean is not big improvement isn't it better to keep in the original state?  And which 6l6 is do you prefer in this amplifier?  Thanks for your comment

The difference in the clean was subjective, some may hear tone different than others, I can't remember if I made a change on the clean channel. As far as make of 6L6, I didn't notice much of any difference. You may try changing the 10uf, C8 (cathode on the V1b to ground, I think it says C8) back to .68 or 1uf, it's in parallel with the 1K5 to ground.

[Kesi from Hungary]

I have used new fuses again but no difference.  Everything back as original on c9.  c14.  r52.  r18.  r16 r24. r23. Also without result. Checked all the solder joints.  nothing.
But I still find it odd that the 2 fuses in the back don't glow for half a second on startup.

[dude]

Those thin delicate wires in that amp are prone to break easily, especially when turning the bd over. I had several thin wires from tubes pins to board break at the soldered joint. Check that all wires are attached securely both to tube sockets and board.

[j_bruce]

I have used new fuses again but no difference.  Everything back as original on c9.  c14.  r52.  r18.  r16 r24. r23. Also without result. Checked all the solder joints.  nothing.
But I still find it odd that the 2 fuses in the back don't glow for half a second on startup.

I am fairly new at this stuff but I am a good troubleshooter in general so I am going to tell you what I would look at and test to start narrowing things down.

1.    you say everything is back to original on some of the changed values, but in the schematic it shows a change to C1 and C4. Those look like the only changes that could effect ALL sound if the power supply is right. If you changed those two did you use the electrolytic caps as shown? are they in in the correct polarity? if either of those is backward ( or the wrong type) that would likely create some problems. Verify those are the correct polarity as installed.

2.  I would check the power supply. The schematic shows lots of test point voltages so go check them and verify the A+, B+ and C+ as shown.

3. Check for proper voltages at A+ (before R14, R23 and R35) B+ ( at output transformer) and C+ (pin 4 of V3)

If all of that checks out then it is one of your mods or your broke something accidentally like Dude suggests.

As a side note: a fuse should not normally "glow" if that was happening for a few seconds at startup then that would concern me. A fuse will only glow if it is about to blow! But, you say now it does not glow. You have changed out the 47 uF caps for 100Uf and those likely have reduced the current inrush at startup enough to solve the glowing problem that you did not know you had.

Good luck,
Jerry

[Kesi from Hungary]

Update.

I did indeed check the tube socket wires (I've had to re-solder them a few times) and the solder joints.  Special also that 2 points accidentally do not touch each other.  And in 2 places I had to make a bridge because the little traces came loose. 
On your advice Dude I put the 0.68 of c8 back and yes sound was back. But then when switching on the drive channel went away with a soft hum. And back to clean also gone.  So something goes wrong here.
The changes I made so far

c1 (electrolyte) 10 uf 450V
r15 1k5. 
r24 3k3
c101&c103 100uf 350V
and also new c102&c25 47uf 350V
And a year ago I turned the gain knob to 250 ohms and the drive volume to 500 ohms.

If I have to measure something later, Jerry, can you give me a little lesson?