No sound from MB California Tweed 40 amp head

I am brand new to this board and look forward to learning and interacting with you all.

I purchased a brand new Mesa Boogie California Tweed 40 amp head about 6 weeks ago. However, due to some health issues (my family and myself), I only just plugged it in for the first time (I know, I know, no need to castigate me about waiting this long).

I hooked it up to a 2x12 cabinet at 8ohms (the cabinet has a Celestion Gold 50W and Warehouse ET65). I have no idea why I cannot get any sound. My other amps work through this cab so I know the cabinet is in fine working order.

I tried different cables with the same result. I have emailed both MB and the shop that sold it and waiting to hear back from them.

Any advice you might have I would truly appreciate it. Thank you

UPDATE: MB tech support just called me and had me go through some tests

The amp does produce sound when I plug the guitar directly in the FX loop Return (although, the control knobs on the front have no effect on the sound - it is just one steady volume)

MB tech support thinks it might be an issue with one of the preamp tubes so, per MB tech's instructions, he wants me to try and take another preamp tube from another amp head and swap them out

However, my other amp heads are a Port City Pearl 50W head and a Marshall Silver Jubilee 2555x 100W

Port City Amps lists the following for the tubes:

TAD matched 6L6 (x2 in 50W, x4 in 100W)
JJ ECC83 – Preamp
JJ ECC81 – Effects Loop
JJ ECC83 – Phase Inverter
5AR4 Rectifier (100 Watt is rectified with silicon diodes)

Marshall lists the following for the tubes:

Preamp valves — 3 x ECC83
Power amp valves — 4 x EL34

So, I emailed MB tech support back as I do not have any 12AX7 tubes I can try


UPDATE 2: OK figured out that a JJ ECC83 = 12AX7 and swapped the first one out and voila it worked - so, I need to order a new 12AX7 tube -- can't believe I found the dead one on the first try

I just ordered 3 tubes from StewMac since all the Mesa Boogie brand 12AX7's were sold out everywhere

The ecc83 is the same34 as the 12ax7.

Thanks - I had updated my post as I figured that out as well.

Also, the retailer is sending me a set of tubes so I should be covered.

Welcome to the board! You'll find it's pretty calm around here.. folks are too busy jammin with their Boogies!

mace said:

Welcome to the board! You'll find it's pretty calm around here.. folks are too busy jammin with their Boogies!

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Thank you - this is my first MB amp and I am glad it was just a tube damaged in transit

Hope everyone has a Happy Thanksgiving

That is odd, never came across a dead preamp tube before. Noisy one's, yes, all the time. Perhaps there was something in the tube socket that prevented connection. It could have been a broken heater filament though, that will do it.

Please look at the manual (if you do not have one, you can download it from Mesa). Not all of the preamp tubes are 12AX7 (JJECC83). V4 is a 12AT7 used as the reverb driver send circuit.