Mesa Electradyne-No Sound

[Perkinsman]

The 45/90 amp is super clean, powers up but no sound unless I plug into the effects send or return. Tubes all light, everything inside looks brand new. Can’t find a schematic so can’t even check voltages. Is this an off the radar amp?

[The Dude]

Have you asked Mesa for it? My experience is that they are willing to part with schematics. Have you tried swapping preamp tubes? Could just be a bad preamp tube. If you can't get a schematic, you've verified that the power amp is working, so I'd next check voltages on preamp tubes. Even without a schematic, you can still look for a missing plate voltage or low cathode voltage indicating a lack of conduction.

[Perkinsman]

Ok, Mesa sent the schematic & all of the preamp tubes are low to very low to 0. I can’t get to the power tubes without some trouble.
edyne_schem.pdf

[Helmholtz]

& all of the preamp tubes are low to very low to 0.

What does that mean?

[Perkinsman]

Sev eral are 100v below listed vdc, several are 50v below, several are reading 0 plate & cathode voltage

[Helmholtz]

Sev eral are 100v below listed vdc, several are 50v below, several are reading 0 plate & cathode voltage

Ok, as always start with verifying supply voltages. If a tube has 0V at cathode and plate, either there is no supply or the plate resistor is open.

[vintagekiki]

The 45/90 amp is super clean, powers up but no sound unless I plug into the effects send or return.

Let's start
Set the Clean level, (rear panel ) to the Bypass position.
Connect short guitar cable between effect loop jacks J1 and J2 (rear panel ).
Plug the guitar into the input jack.
Does the LED light, and the amplifier works in all three position gain trim switch (rear panel ).
1)
Mesa Electradyne uses relays and opto couplers to select the operating mode. If any of the operating modes does not work, check + 12VDC used for relay logic operation (page 4, 6)

[Perkinsman]

I’m not sure I totally understand, the amp doesn’t work in any mode but like I initially stated, I get sound when plugging into either of the two effects send or return. The led works in all 3 modes. I also did what u said & jumpered send to return & a jack in the input but still nothing.

Supply Voltages:
A+=467
B+=466
C+=442
D+=276
E+=270

[Perkinsman]

All the plate resistors are spot on except V1a, which reads low at 46k (100k) & V5a read 82k (100k)

[The Dude]

Have you tried swapping preamp tubes?

[Perkinsman]

Yes, swapped positions after u first mentioned it but didn’t change the no sound issue.

[vintagekiki]

...

continuation

During all tests, the speaker must be connected to the Mesa Electradyne.

Check Mesa Electradyne to see if it works as a preamplifier.
Connect the send effect loop jack J1 to the input any external guitar amp which serve as slave.
On Mesa Electradyne set the clean level on rear panel to the bypass position.

If Mesa Electradyne preamp no sound on the external guitar amplifier check Q3 (J175) main mute fet, and (or) change the V5 (12AX7) with a new tube (not like new). The V5 is a drive tube for all, through which pass clean, overdrive and reverb signal

If the Mesa Electradyne preamp works on external guitar amplifier, then the fault is in the communication between preamp and power amp, or the power amp of the Mesa Electradyne is faulty.
To test Mesa Electradyne power amp plug the guitar into the return effect loop jack J2.

Interesting
Mesa Electradyne uses tandem potentiometers for both modes (clean, gain) to reduce the number of controls on the front panel. Practical yes, operational no.

[Helmholtz]

Supply Voltages:
A+=467
B+=466
C+=442
D+=276
E+=270

I see low D, E preamp supply voltages. Not low enough to explain zero sound, but must have a reason.
Are +/- 15V and +12V supplies good?
Do preamp tubes get heater voltage?

[Perkinsman]

I replaced V5 & we now have sound but it doesn’t seem that loud for what I would expect a bone crushing Mesa to be....& oddly enough, V5 doesn’t light up like the others. Is the “bypass” switch on the back supposed to be “on” or any other of that se switches that need to be adjusted?

edit: I started playing with the switches & the front hi/lo/clean only works in clean mode (albeit low volume), even if I coordinate it with the hi/lo/clean rear switch. The low will work if I turn the volume all the way up, the hi pops when I switch it but won’t produce sound. The front led lights correctly.

[vintagekiki]

Is the “bypass” switch on the back supposed to be “on” or any other of that se switches that need to be adjusted?

You need to familiarize yourself with the Mesa Electradyne user manual.
https://mesa-boogie.imgix.net/media/User%20Manuals/electraDyne.pdf

Bypass is the far-right position clean level potentiometer (owner’s manual page 5)
Clean level potentiometer is active only on clean channel (schematics page 3)