Help with 5e5a startup

[mlp-mx6]

It's hard for me to tell with the pictures of the jacks, as they're not quite in focus. Still, I'm concerned that you do not have the jacks wired correctly.

First, unplug the amp.

To test, put the speaker wire in the jack and check the resistance between the tip of the other end of the speaker wire and your chassis. If you read 0 ohms, you're shorting the output to the chassis, which would explain the "no sound" thing.

[Structo]

Hopefully if the OT is ok it has survived not having a load on it.

[CapnCrunch]

I checked continuity on the OT. I have continuity between both the 8 and 4 ohm taps and the Common. I also have continuity between the taps and ground, but that makes since the common is grounded. I think.......

I was going over it for like 20th time and just spotted the fact that I have the anode and the grid reversed on the PI (pin 6 and 7) of the 12ax7. The iron is heating up. Could that cause this. I tripped to it when checking voltages and the voltages were WAAAAAAY off on V3.

[CapnCrunch]

Latest in the on-going saga:

I swapped the plate and the grid wires on the PI. I now have crackles and pops when checking voltage. Here's what I have.

B+1=438V
B+2=433V
B+3=334V

Bias Voltage at Pin 5 on both V4 and V5 is -45

Heaters on all heater pins is 3.35 to 3.38 each

V4 & V5 Plates=434V, Screens=435&436V

V3a plate=250V, Grid=0, Cathode=0

V3b plate=300V, Grid=0, Cathode=0

V2a plate=146,

v2b plate=29, Cathode=150

v1a Plate=152

v1b Plate=150

I got no measurement on the grids or cathodes for v1 or v2 (0's on my meter).

[Phil_S]

I got no measurement on the grids or cathodes for v1 or v2 (0's on my meter).

What meter are you using? Can you set it for a lower scale? I don't know this amp, but typical cathode voltage for preamp tubes is something less than 1 to about 1.something. 2 or 3 volts is certainly possible. 5V would typically be on the high side. I am thinking you've got voltage less than 1V and your meter can't "see" it to give you a reading.

With no signal, zero on the grids is about right. Sometimes you see a little something, sometimes you don't.

With noise at the speaker on probing, and what appears to be reasonable voltages, you should try plugging in an instrument and see what comes out of the speaker!

[Structo]

Yes you should be getting some reading on the cathodes.

Are you still on the limiter?

If so it's probably safe now to plug it straight in.

If the voltages are still wacky double check your preamp resistors and or dropping string.

[CapnCrunch]

Hey,

I wanted to say thanks for the help. I went back tonight and touched up some solder joints and plugged my guitar into this amp. It made music!

At least I'm over that hurdle with thanks to those that helped me out. Thank you.

There are a couple of remaining issues though (aren't there always?)

First, the amp doesn't have much volume, my 5e3 is considerably louder.
The amp stays clean, and sounds o.k., though lacking body, up to about 3/4 volume with a strat and up to about half volume with a Les Paul.

Second, when it starts to break up, it isn't in pleasant sort of way. It is really harsh with either guitar. It almost sounds like a blown speaker or a speaker with a blown voice coil. This is the same in both the bright and normal channel. I plugged the 5e3 into it just to check and both speaker and amp sound great (no speaker rubs or rattles).

Third, the presence control doesn't seem to do much. I've never played an amp with presence so I'm unfamiliar with it. I can tell a subtle change in the amount and quality of the high end between off and full on, but it is subtle, almost like adding in a very small amount of reverb. If someone stood at the amp and gradually turned the knob from off to full up while you were playing, you might not notice it. On the other hand, the bass and treble pots are like gain controls. They both have very significant effects on gain as you adjust them even slightly.

Now the real fun begins..................