Mark V90 clicking sound only in 45W mode

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Dre Oliveros
Bottle Rocket
Posts: 2
Joined: Tue Mar 20, 2018 9:41 pm

Mark V90 clicking sound only in 45W mode

Post by Dre Oliveros » Tue Mar 20, 2018 9:47 pm

Heeeey its me again, i have been experiencing some clicking sound ( a lot like the sound when footswitch cable is bad, or when you change channels, that small "click") I've notice it only happens when you play lets say palm muted notes and only in 45W, I've already check the obvious, cables, footswitch, tubes, all modes all settings, but as i said its only in 45W mode does anyone here knows what could be , i have idea that i read somewhere that at some point the FETs has to be replaced any ideas ? thanks again guys.

bandit2013
Triple Recto
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Joined: Fri Feb 22, 2013 7:31 am
Location: North Carolina

Re: Mark V90 clicking sound only in 45W mode

Post by bandit2013 » Sun Mar 25, 2018 11:07 am

I doubt the issue is with any FETS as when they fail they get stuck on. Are you using Full power or Variac power? If Variac power is used, I can see that being an issue since the control circuitry to switch the relays and such for each channel and or voices may become erratic do to drop in voltage. The channel logic is not based on a digital signal (meaning on and off) but more so an analog voltage signal that is used to determine what channel the amp is in. If the reference voltage drifts due to change in input power using Variac power mode this could be the cause for the erratic channel switching or relay chatter. I would give Mesa Technical service a call as it may be probable that you have a diode issue with the low voltage power supply that feeds a 12V regulator used for the relay switching and a few preamp tube heaters, also this feeds the 5V regulator circuit and this is used as a signal level reference for the channel decoder chip (LM3914).

Preamp tubes that use the 12V dc heater voltage are V1, V2 and V5. Doubt this could be related to anything.

Then again, if you are hearing a pop noise at random, it could also be the Rectifier tube as that can contribute to similar sounds if and when the plates decide to discharge onto the cathode.

Dre Oliveros
Bottle Rocket
Posts: 2
Joined: Tue Mar 20, 2018 9:41 pm

Re: Mark V90 clicking sound only in 45W mode

Post by Dre Oliveros » Fri Sep 28, 2018 1:41 pm

Well sorry for answering like now, but it its not a pop sound its a click, like when you select with footswitch a channel, its like if your were pressing to change channels, but without doing it or changing it , so it occurs more noticeably when doing palm mute so I'm aware it might be related to vibration, it does not happen neither in 90W or 10W mode, (i do hear it with tube or diode selected) and its intermittent so doesn't occur all the time or affect the playability, you just kinda hear that relay related sound whenever the amp wants.

the other thing sometimes do is lets say you play in ch3 and go to ch1 via footswitch its making a delay (which may vary to half second to whenever you hit hard the strings to restore sound) again not always, i dunno if its related, and also happens more often in certain modes, like from markVI to Clean, I've been using tweed - mark 1 - markC2+ as my main sound for 6 years now and never had an issue, recently i changed to mark VI and clean or fat, and yeah i realise it has that,

thanks again if anyone has any input.

ifailedshapes
Single Recto
Posts: 1034
Joined: Fri Jun 20, 2008 3:31 am
Location: California

Re: Mark V90 clicking sound only in 45W mode

Post by ifailedshapes » Fri Oct 12, 2018 2:57 pm

Engage channel 1, then look at the back of the amplifier. Under the reverb knob is a switch that lets you select which rectifier to use. Does the clicking sound go away when you use the silicon rectifier? I had a tube rectifier that made a very similar sound to what you are describing.

My brain goes here because the 90w setting defaults to the silicon rectifier.
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