1st build, need a little help

[martin manning]

Everything looks pretty reasonable there voltage-wise. So if the power supply and DC operating points are good, then the problem is with the signal flow- something grounding out, a poor joint or a bad part. Do you get a pop when you probe pins 2 and 7 of the 6H2N, and pin 5 of the 6SNC? This might be a clue as to where the problem is. Do you have any test equipment besides a DMM?

[DFMoore]

Yes,

There is a faint hum that disappears when I prob pins 1 and 2 of the 6H2NEB. I also get a buzz when I prob pin 3 of the 6N6C.

I do not own anything other than a multi-meter, which I just fried...fuse still in-tacked. I maybe be able to borrow a fluke.

I have attached the actual layout I used.

[rogb]

OK when you get hold of another DMM, have you measured the heater volts, should measure around 3.15v AC each side of the pins 4 and 5 and 2 and 7 respectively.

[DFMoore]

Luckily I have already measured them and they are a little over 3 volts ac.

[Structo]

I don't think your input jack is wired correctly.

The 1Meg resistor should go from the two outside lugs, then the wire to the 68K grid stopper from the right side lug.

The middle lug gets jumpered to the left lug.

[martin manning]

Looks OK to me... if the center is jumped to the left, it doesn't matter if the 1M is connected center or left.

[Structo]

True.

[DFMoore]

Just rewired the input as suggested. I went from very low distorted volume to none.

[DFMoore]

Let me make sure I understand. The tip of the guitar cable should go to the resister and then to pin 2, the other is ground.Is this correct?

[Structo]

Yes, the right hand lug is the tip, the middle lug is the switch leaf and the left hand lug is the sleeve or ground.

I think you are narrowing down the problem if this changed what it was doing.

[DFMoore]

OK, picked up a new multi-tester. The heaters are now showing 6.8 volts AC up from 3.1 volts AC. The 100 ohm resisters are now showing 49.6 ohms. What would cause this?

[Phil_S]

The 100 ohm resistors are wired parallel. They should read 50 ohms. That isn't a problem.

Your heaters should not be measured to ground for ACV. They should be measures from one pin to the other on the same socket. 6.8v is a little high, but within 10%. I don't think that's a problem either.

[tubeswell]

Need a clearer (higher resolution) picture of your actual wiring. You probably have a signal wire not connected properly.

For troubleshooting of this kind, you need to start at the beginning of the circuit and carefully work your way through all the connections. It helps if you have a pencil and the schematic handy so you can mark and 'x' on all the right connections when you have checked them.

For example, if the 6V6/6P6S/6n6C is wired properly, the plate (pin 3) should be going to the OT primary, the screen (Pin 4) to the screen supply node (junction of C7 and R10 and R11), the cathode (Pin 8 ) should be going to the (ungrounded) junction of R8 and C5, and the grid (Pin 5) should be going to the junction of R7 and C4, and so on for the pre-amp tube - similarly check your plate, grid and cathode connections. Then check the input jack to the grid of V1A and the junction of C2 and the vol pot input, and the wiper of the vol pot to the v1b grid. the volt pot ground needs to be grounded.

[surfsup]

As structo said, if you rewired only the input jack and the symptoms changed, ie low vol to no output, you have an issue at the input jack. Fix that first. On those jacks, the tip is the long prong sticking out. Follow it to the base and look to see what ring it is on. Then follow the ring around till you locate the proper lug that is for the tip. This is the signal wire that should go to pin 7 on the tube socket. The 1m should also be connected to this lug on one end, and the 1m should be connected to the other lugs on the other end.

In the input jack photo, the jack seems to be hanging out of the hole. The photo is poor. Is there some sort of metal ring keeping the jack floating? The base of the jack is usually flush to the chassis. Just curious.

[playonit]

Are you testing with a guitar plugged in?? if so, have you made sure it's not the guitar? Just a thought...