My Mesa d180...

[Wasnex]

I replaced the standby switch and the 0.1uf capacitor on the switch, and the amp still makes an awful clack when I put it in standby. When I ordered the switch I spoke to Mike Bendinelli at Mesa and he said the clack is normal for this amp. It's hard to understate just how obnoxiously loud the clack is if the Master is wide open and the EQ is engaged. Does everyone's D180 make a loud clack when it is put in standby with the EQ on and the Master on 10?

If I disengage the EQ the clack is hardly noticeable. So I didn't really find it all that surprising that the switch and capacitor were okay.

If I pull V2 so there is nothing feeding the EQ, the clack remains the same. So It seem the clack is coming from the EQ circuit. Weird since the EQ has it's own negative power supply rail which is not interrupted by the standby switch.

I do have one other possible theory, but I don't plan to explore it unless I have another reason to work on the power supply card. I noticed that ground and negative supply for the EQ run across the center of the amp. The wires are bundled with the screen supply and the two power supply nodes that go to the preamp. Also the top of the capacitor bank for the plate voltage is right next to this wire bundle. All of these positive nodes are interrupted when the amp is switched into standby, so my theory is a high frequency transient is being induced from the positive supply to the negative supply, when amp is put in standby.

In support of this idea, I have a gut shot of a D180 where the EQ power and ground lines have been relocated, so they do not run down the center of the amp. I.E. perhaps relocating the power lines would help reduce the clack.

 

[Zeroic]

Mine doesn't..... Though its the one without eq, if it's any help.

 

[Frankie Fender]

Mine doesn't either, but I don't use the EQ. I will test it out next week at the rehearsal space with the EQ engaged and report back.

Side note maybe worth mentioning - It makes a God awful clack when I switch the fan settings while it is not in standby. Better to make those changes with standby engaged. BTW my master is always on 10.

 

[Frankie Fender]

I checked it out last week at the studio. Yes, it makes a loud clack when it is put in standby with the EQ on and the Master on 10.

Side note, I kinda liked the EQ settings with the lows boosted and may use that setting from time to time.

 

[Wasnex]

I checked it out last week at the studio. Yes, it makes a loud clack when it is put in standby with the EQ on and the Master on 10.

Side note, I kinda liked the EQ settings with the lows boosted and may use that setting from time to time.

Thanks. I checked and flipping the fan switch can be a bit noisy on my amp as well. One setting is definitely louder than the other. Not as bad as putting the amp in standby with the EQ engaged though. I normally run my fan on low.

I really like the sound with the EQ. It allows me to dial in a nice punchy, woody sound that is not possible with the EQ bypassed. Wit the EQ bypasssed the D180 actually sounds pretty similar to some of my other Fender style amps. When I engage my EQ with the controls flat, it seem to cut the lows slightly, so a bit of boost is necessary to get back to flat.

I buttoned up the amp and am not going to worry about it. I figure if Mesa never figured out a work around, I probably won't either. If I ever do need to work on the power supply I will try rerouting the ground and negative voltage supply lines feeding the EQ away from the switched positive voltage supplies and see if that helps.

 

[Frankie Fender]

Yes I was surprised how the EQ switched on, even when set flat, changed the sound for the better.

 

[jymyben]

from the archives....

 

[Zeroic]

Great!

 

[donahue]

Wow $1K with the Graphic in '82 is no joke!

 

[tombowlus]

from the archives....


View attachment 4269331 View attachment 4269328 View attachment 4269327

I hadn't read that review before, and it's actually a very well-written, detailed, excellent review! Other than the fact that the D-180 was not the first bass amp made by Mesa. That would be the Snakeskin Mesa 450, which was Mesa/Boogie's first product. In fact, the first five Mesa Engineering products were all bass amps.

 

[map34157]

Still loving this amp. Taking her out for a spin this weekend.

 

[Fin]

Got this beast last week. Came with 2 road ready 15 inch cabs
Serial D563
Seems wierd that the 12AT7 is in V4 - doesn’t seem right?? I thought that if you had these they were in V2+V3 or only V3
It’s had a master volume mod so it’s like a bass400
It’s defo in need of a good overhaul with a tech.
Volume2 tempremental I get lots of crackle and only get sound through at certain zones or the dial rotation. 5-7 or at 10.
Mid control affects overall volume significantly
Bass doesn’t do much and treble just makes it sound harsh.
Eq very noisy.
Channel 1 is not really useable horrible distortion.
It came with a mix of Mesa Sovtek and EHX 6L6 power valves in it.. and also a few 5881WXT valves in a bag??

 

[Wasnex]

Got this beast last week. Came with 2 road ready 15 inch cabs
Serial D563
Seems wierd that the 12AT7 is in V4 - doesn’t seem right?? I thought that if you had these they were in V2+V3 or only V3
It’s had a master volume mod so it’s like a bass400
It’s defo in need of a good overhaul with a tech.
Volume2 tempremental I get lots of crackle and only get sound through at certain zones or the dial rotation. 5-7 or at 10.
Mid control affects overall volume significantly
Bass doesn’t do much and treble just makes it sound harsh.
Eq very noisy.
Channel 1 is not really useable horrible distortion.
It came with a mix of Mesa Sovtek and EHX 6L6 power valves in it.. and also a few 5881WXT valves in a bag??

Sound like it needs a lot of TLC . Hope you have a good tech. AFAIK it would be pretty difficult to fully convert a D180 to a 400, without cutting up the circuit board. The circuits are similar, but the order they come in is not exactly the same. For example, to convert the inputs to 400 specs, the tech would need to relocate channel 2's volume control and add a bunch of components to build a resistive mixer that sums channel 1 and 2.

12AT7 in V4. No this is not stock, but there is no telling what the tech did when the master volume was converted. He/she may have set up the driver sections to run 12AT7. 12AT7 is not really an extreme sub if the circuit is setup for 12AX7. 12AT7 has lower gain and it may thin out the lows a bit. This could make sense if the amp was used for guitar.

AFAIK the common mod for the MV only relocates the pot and then subs an appropriate size cathode resistor in place of the TCR. The TCR is a constant current diode. I don't think it's really even necessary to take the TCR out...just relocate the pot and bridge the gap in the circuit.

Here's a relevant post: Mesa/Boogie D-180

I would not be surprised if the TCR is still in the phase inverter stage. No need to go through the hassle of modding this part of the circuit, as it works just fine IMHO.

Sounds like channel 2 has a bad pot.

Channel 1 was originally cascaded into channel 2. Channel 1 is really just a single tube stage that was dumped into the input of channel 2 to increase gain. Channel 1 is really intended for guitar and has less lows.

Hopefully all of the mods only involved swapping components and wires, or you may have a bit of a basket case.

 

[Frankie Fender]

Got this beast last week. Came with 2 road ready 15 inch cabs
Serial D563
Seems wierd that the 12AT7 is in V4 - doesn’t seem right?? I thought that if you had these they were in V2+V3 or only V3
It’s had a master volume mod so it’s like a bass400
It’s defo in need of a good overhaul with a tech.
Volume2 tempremental I get lots of crackle and only get sound through at certain zones or the dial rotation. 5-7 or at 10.
Mid control affects overall volume significantly
Bass doesn’t do much and treble just makes it sound harsh.
Eq very noisy.
Channel 1 is not really useable horrible distortion.
It came with a mix of Mesa Sovtek and EHX 6L6 power valves in it.. and also a few 5881WXT valves in a bag??

You need to plug into Input 2, set the Master at maximum and adjust the volume with Volume 2 ( maybe start at 5) and then get back to us. That is the way the amplifier is designed for bass.

 

[Fin]

I am having difficulty finding a tech who will take my D180 on..
After some more experimenting I am finding the tone controls and volume2 all interact very strangely, if the volume is at around 7 the bass pot does very little, the mids control makes amp very quiet when turned right down..
If I turn V2 to around 9 the volume cuts right out if the mid is at 10 but then comes back loud at around 4… the bass control adds a lot of bass when like this..
The treb just adds hiss on any combination
I really can’t get my head around this amp it behaves so weirdly…

what would cause this behaviour??

 

[agedhorse]

There is something wrong with your amp. Generally this is the result of a botched repair or a botched modification, which is why I discourage non-qualified techs from messing with products they do not understand. Almost always, this results in very expensive follow-up repairs.

Where are you located? This will determine your service options.

 

[Fin]

I am in Wales, UK

 

[agedhorse]

You might see if Westside Distribution is willing to work on it, they have a couple of good service engineers that may be able to get it sorted out.

Sending if back to the factory is also an option, but I would expect the cost of doing so would be greater than it's worth.

The challenge is going to be cost, no matter what you do it's likely to be expensive. Undoing modifications and service mistakes is time consuming and tedious. Generally the cost of the parts is minimal, but the labor to really sort things out correctly is the issue. Experience is a huge time saver, but everything has to be scrutinized and this takes time.

 

[Zeroic]

You need to plug into Input 2, set the Master at maximum and adjust the volume with Volume 2 ( maybe start at 5) and then get back to us. That is the way the amplifier is designed for bass.

Yes thats the way I use mine, works perfect!

 

[Tybo77]

Anyone know what this switch does???