TU-8340VK Noisy in Right Channel

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Hi All,


I have been getting an increasingly bad noise in the right channel of my ELEKIT 8340 for a while now. Just intermittent to start, but now there all the time. I have checked all the usual starting points, so not valves or external stuff, speakers, leads etc. Sounds like maybe a bad resistor/component or solder joint.

I need to lift the hood and start looking inside for the issue. I am going to go over everything and re-flow solder and check for dry joints etc, but any useful hints or potential component issues anyone else has found previously would be appreciated.

This has been my main stereo amp for over 3 years now and with the transformer upgrade is a fantastic amp. Getting lots of extra use due to COVID isolation time, and I have the time to tinker and fix.


Any help greatly appreciated.


DjK
 
Thanks for responding.


I re-flowed all the solder, and especially around the solder bridges to the speaker jack boards.
I also checked all the test point voltages which was a good suggestion from VK.
All voltages plus or minus ok ranges.

Once reassembled, voila, no more noise. So yes, an easy fix as well, and back to just listening to music.


Cheers,


DjK
 
Hi Tom,



I am running NOS Phillips 7581 power and original Mullard ECC81/CV4024 pre valves.
I also have Triangle Esprit EZ and Comete speakers and a Doge 6 Valve preamp CD player hooked up to this.

The 7581 valves never sounded any good in guitar amps, so I tried them in the smaller TU-8200 ELEKIT amp and they tightened up the bottom end, gave more headroom/volume, and are very neutral in the mid-range. I had 4 so I put them in the 8340. With the VK mods/caps/transformer change, the 8340 can play any type of music with ease now. Even synthy super low bass stuff.

The Mullard CV4024 valves are a secret sauce. Still available at reasonable prices. I put them in the phase inverter position of any guitar amp that should have a 12AX7 there, and it improves tone and headroom every time. So I tried them in the 8340 and they are staying for good. I also have them in the Doge 6 pre amp. Just right, not too much gain or mush, and generally low noise. Lot's of microphonic ones about now though.

EL34/6CA7 valves never made me smile much in guitar amps. Barky mids and a weird low end. The best were the old Mullards, but they are unobtanium now. Probably all used up by 70's rock bands. Maybe ok for Marshall guitar amps in a band where there is a bass underpinning everything, but I found out 6V6 valves in a Marshall are killer. Lower volume for smaller gigs but with enough gain to bring road kill back to life.

I was going to try EL34 valves just for reference in the 8340, but do not have any handy and just never get around to it. Maybe I should just to see if I am missing some mojo.

But so happy with the 7581s that I just play music and enjoy the 8340. Unfortunately good 7581s are around 120 bucks each now. Ouch. I think I got my four for $150 years ago.

A few here by the looks. Not an ad for these guys, just a rough price reference for these types.



Power tubes
mullard cv4024



Cheers,


DjK
 
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