Tube Amp Archive

Did you change the resistors on the board? Yes both 68K R's have been replaced with new. Double-check the new resistors to make sure they are not 68R instead of 68K. At jack 2 you read 134.9 ohms to ground (roughly 2 x 68R) when it should be 136K (2 x 68K). Good eye Firestorm, I've got 68ohm resist...

Those Switchcraft jacks are like the ones I've been complaining about. You took some great macro photos there. See the switch contact? Make sure that is indeed making contact with the other side. That is where the trouble lies with these jacks. I've checked these with an ohm meter and they are work...

Sounds to me like either the 68K resistor on the #2 jack is bad, way too high a value or isn't making good contact on the solder connections, or the contact on jack #2 is not breaking contact from with the switch when a plug is inserted. I've checked these, the good jack will work fine through eith...

So where at in the circuit does jack #2 get it's signal reduced?

Tillydog wrote:My 0.02p:

Check that the solder on the tip contact hasn't shorted the tip & switch contacts on the RH jack.

What is soldered to the sleeve contact on the LH jack?

Andy

Just replaced both jack and have the same issue. Nothing is soldered to the sleeve jack at this time.

in the above highlighted picture - I see that the lead of the 1M resistor is not poking through the 2 holes of the input jacks. Make sure you do that to hold the whole assembly together then hook the 68k through there and solder it all together at once I usually put it through the front holes of th...

Firestorm wrote:Did you change the resistors on the board?

Yes both 68K R's have been replaced with new.

LeftyStrat wrote:With a plug inserted into jack 2, measure the resistance between the tip and ground.

Jack 2 is 134.9 ohms. jack 1 reads 1meg

ChrisM wrote:Looks like maybe the lead of the 1M resistor may touch your cable when its plugged in.

Just checked and there's plenty of room, looks close in the pic but I have about 3/16"

I just replaced both input jacks on the champ, along with the 1MegR attached to jack 1. input 1 works fine but input 2 has very week volume, so I removed the 1MR and both inputs worked as they should with the expected noise. Then I reinstalled the 1MR with another new one and the problem returned. ...

Are you using brand-name Switchcraft or less expensive knock-offs? The reason I ask is that you can't always go by the pictures with the knock-off. Sometimes the tabs are in a different order and you will need to establish for sure what is tip and what is sleeve. These are the real Switchcraft jack...

Take a look it's wired identicle to the pick with the exception of the two wires which run directly to the 68k resistors attached to the board. Either jack works seperately or both will work without the resistor. I've even tried grounding jack 2 with no change. Neither jack is isolated, both ground ...

I just replaced both input jacks on the champ, along with the 1MegR attached to jack 1. input 1 works fine but input 2 has very week volume, so I removed the 1MR and both inputs worked as they should with the expected noise. Then I reinstalled the 1MR with another new one and the problem returned. E...

Ok, makes sense. Thanks

So now I have a new problem, originally when I tested the amp I had good volume on input 2 but low on input 1, so I replaced input 1 and the attached resistor. Now input 1 works grat, plenty of volume but input 2 has low volume. I replaced #2 with the original from #1 with no change. I dont have any...