Build done. No sound. What next?

[a_e_a]

Ok so I've just finished building a plexi style circuit.powers up. Light works. Tubes light up nicely. Getting no sound at all. What is the next step to troubleshoot? It's there a logic progression to work through the circuit? Any ideas? Tried a few things but I'm feeling a bit lost at the moment. It's not my first build but the first that hasn't worked straight away.
Thanks in advance!

[sluckey]

Print out your schematic. Use a highlighter to trace out the circuit as you verify that your actual build agrees with the schematic. Also verify all component values are correct. Most new build problems are due to wiring errors and/or incorrect component values. Many times we hear "I've verified the wiring multiple times and it's right", only to learn later that it ain't right.

It's a good idea to use a light bulb limiter (LBL) to turn the amp on initially. If no bright light, sparks, smoke, or crazy sounds, then plug amp into wall.

The very first thing to do ***BEFORE*** you plug in power tubes is verify that you have sufficient negative voltage on the output tube socket grid pins (usually pin 5 for big tubes). Adjust that negative voltage to the max negative voltage. At this point you can plug in the output tubes.

Then measure B+ rail voltages at each filter cap.

Then measure plate, cathode, and grid voltages on all little tubes.

Now you have some clues about which way to proceed.

[10thTx]

Check some of the obvious:

Is the cord from the speaker to speaker jack having continuity? Have you tried a different guitar cord? Have you tried a different guitar? Have you tried known good tubes?

Are all the voltages correct on the cathodes, plates, etc......

Check values of components.

IF the amp has an FX loop (whether passive or active) plug into the return jack from the effects. Does the speaker make noise now? If so, the issue may be in the preamp?

IF this amp has an FX loop AND you have another one with an FX loop ............. Can you run the preamp into the power amp of the other amp and get sound? IF so, the issue may be the power amp section of the amp you just built.

Jumper across sections bypassing areas. Does one of those bypass jumpers allow the amp to work? IF so, the bypassed areas may be the problem?

These are some of the things I try in trouble shooting.

With respect, 10thtx

[pdf64]

Miswiring of the input / speaker jacks is a common issue which results in this symptom, and seems to be easy to overlook when checking.

[ViperDoc]

Also look for proper and improper grounding. I built a Princeton last year and forgot to wire in the preamp ground and had no sound until I fixed it.

[Stevem]

The quickest and easiest is still the good old pop test.
Set you meter for dc volts and touch the input grid ( pin 5) of each output tube.
If the output stage is working you will hear a very light pop sound out of the speaker.
If that checks out then move to the input of the PI.
If that’s working then the pop will be louder.

Keep moving back up stream from grid to grid and wherever the pop stops is your dead stage.

[Phil_S]

Print out your schematic. Use a highlighter to trace out the circuit as you verify that your actual build agrees with the schematic. Also verify all component values are correct. Most new build problems are due to wiring errors and/or incorrect component values.

Sage advice. I'd add, if you find nothing, then do it again, however, instead of working from the input jack to the output jack, do the verification in the reverse order. Also, check all solder points for a missed or dry solder. If it's absolutely quiet, I'd suspect a missing ground.