3 Channel Dual Recto- no top end on Red channel Raw/Vintage

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9985

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Hello-

just picked up a 3 channel Dual Recto (2007 model I believe based on serial # in 42000's) - great Black Friday sale at local music shop, $800 with MIDI foot switch, I couldn't say no. Total impulse buy, first Mesa amp I've owned or even played - previously only used Marshall & Randall heads. Amp looks to be well-maintained & in great physical condition, a previous owner had some work or a re-tube done to it, there's a pro amp shop service tag on the back.

Question: Channel 1 (Raw & Pushed settings) & Channel 2 (Raw, Vintage & Modern settings) all sound great, but Channel 3 (Red) only sounds good on Modern- selecting Vintage or Raw totally kills the treble - it sounds like I suddenly cranked the Presence and Treble all the way to 0. As a complete NOOB to Mesa, I'm not sure where to start trouble-shooting. Maybe a bad pre-amp tube? I have a couple of spare 12AX7 tubes, wanted to throw a post up before I starting fiddling around to see if there was any known issue that causes this.

EDIT 1: After fiddling with settings a bit, determined the issue is only present at very low volume on Channel 3 (Master set below about 20% 2/10) - turning Master level up to about 25% or higher makes it sound fine on Raw & Vintage settings, no loss of high end. No issues at all on Channel 2 Raw/Vintage, even at very low Master levels. Is this just normal for Channel 3, or do I need to continue troubleshooting?

EDIT 2: Well, this is now a much more serious issue, I'm going to hijack my own thread (great start on this board...) FX loop appears to have stopped working entirely! While playing today, volume suddenly cut out - I get only very low sound levels with the loop activated via the selector knob on the rear of the head (when set to footswitch, LOOP ON, or any of the 3 individual channels) – only when set to "Loop Bypass" does amp works normally. I replaced the V4 pre-amp tube; no help. For giggles I swapped out the MIDI cable on the footswitch, no help. Issue exists whether MIDI cable is connected to the head or not, selecting “FX” on/off via the footswitch also makes no difference.

I dug through the manual & internet but can’t find anything talking about a separate fuse specifically existing for the effects loop- does one exist? Thoughts? Head is going back to store tomorrow to troubleshoot, I don't want to return it- if anyone has thoughts, please post.

Thanks
 
Try swapping a good tube into the loop and use a Chinese tube. The Russian/East Euro tubes with spiral filaments often fail in V2, V3, and V4. A Ruby, JJ, or similar will be good.

When I first bought my amp, Modern was my preferred channel, because the other two seemed too dark. The amp is meant to be dark and the bottom is prominent.

You can experiment with adjusting the Bass to the left of midway (10:00 to 11:30) and it helps bring the mids out. Adjust Mid up from zero and stop when the middle is cutting through enough.

Treble and Presence work off of each other. If one treats 10:00 to 2:00 as the "normal" range of the Treble control, the Presence could be set to about the opposite direction in the range of 8:00 to 11:00. I often set my Treble close to 2:00 and run the Presence almost off with Vintage Mode. Modern gets set more conservatively with most controls around Noon and Presence at 9:00 or lower.

Now, Raw is much different. I put Treble and Presence halfway and set the other EQ to how I need the overall tone, because the Bass has more play in this mode.

The power settings make the most difference on clarity and brightness, as Bold/Silicon gives the most defined sound. Selecting Tube diode removes definition from the top and bottom and Spongy darkens the sounds a great deal. Both have their uses, but might take time to adjust to.
 
Thanks for the suggestion- the known good spare 12AX7 I tried swapping into V4 wasn't marked, not sure if it was Chinese or eastern European/Russian origin- didn't help. I ended up returning the head to the selling store yesterday so I can't try any other tubes in V4. The tech at the store spent about 30 minutes fiddling with the settings & digging around in manual/internet, couldn't figure out what was causing either the FX loop to be dead, or the treble loss on Channel 3 Raw/Vintage settings without pulling it apart - they are going to have a more experienced amp tech look at the amp's internals/circuitry for both, they think the FX loop issue is a bad cap or resistor, not the V4 tube, I'll pass on the Chinese tube suggestion.

A tech from Mesa emailed me back (kudos to their email support for getting back to me quickly, impressive for the non-original owner of a 9 year old piece of gear) - he thought that the treble loss could be a "sticky relay on channel 3 (perhaps RY9a or RY9b)" & provided a circuit diagram that I passed to the selling store.

Hope they can get it figured out/repaired, I really liked the amp - props to Music-Go-Round in Wilkes-Barre, PA for standing behind their used gear, they gave me a full refund with apologies & no grief, offered to sell back to me for same price as I paid previously if/when they get it figured out.
 
Got a full refund from the store, as of early January they were still waiting for their backlogged tech to pick it up & try to fix it - supposedly if repaired they will contact me & offer for original Black Friday sale price. It's been almost 3 months, I've sadly resigned myself to never getting it back.
 

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