MV60 Service/Help

[jslstyo]

Hey everyone,

I’ve been a happy owner of the Conrad Johnson MV-60 and the ET-3, am rocking them withPSB imagine T2 speakers. Have been in love ever since! I’m rocking both of them with upgraded NOS tubes (Mullard EL34, Sylvania 6SN7 black plate, Siemens ECC83 for the MV-60) (Telefunken E88CC) and have been playing all well for the past year.

Long story short, last week my MV-60 suddenly stopped working for me. It was working fine, when suddenly the bias adjust light went on there was a loud hissing/white noise that followed through. Just when i was about to shut it off, all of a sudden there was a loud popping sound and the adjust bias light went off completely. I completely turned it off, and unplugged it straight away.

Has anyone experienced similar? I am complete clueless to what caused it and have no clue what to do or where to go. I tried both calling and emailing Conrad Johnson, but no reply at all from them. Please advise!

I’m located in Southern California, Los Angeles! If anyone knows any information/shop/repair/CJ specialist please do share!

Thank you and stay safe ya’ll!

[roberto]

Hola and welcome jsistyo,

To me, you have a bad KT-120 tube. Just replace that particular tube and try again. Do this: Turn the unit off. Remember to bring counterclockwise the bias screw, once you have replaced the tube, turn the unit on and wait about one minute, then and slowly adjust the bias to a point where the led lite. Then go back to the point where the led goes off and a little bit further. Play your favourite music and have a listen...after 5 minutes of listening to the music, check if the bias led is on, if it is off, don't do nothing. If it is on, turn the bias adjusting screw again to bring it off. This is a normal behaviour. Once you have 30 minutes of listening the amp, if the led is off, you don't need to adjust the bias again.

Happy listening!

[Joe Appierto]

Roberto's method, using a KT-120 output tube as an example, is the most straightforward way for you to approach the problem. If substituting an EL-34 tube that you know is good doesn't fix the issue then further steps will need to be pursued but it does sound like one of the output tubes died on you.

[AnotherJohnson]

I agree on the bad tube diagnosis, but if someone didn’t mention it, the tube failure probably also blew a fuse in your MV60.

Fuses may continue to blow on “power on” until you’ve identified and removed the bad tube.

[jslstyo]

Hola and welcome jsistyo,

To me, you have a bad KT-120 tube. Just replace that particular tube and try again. Do this: Turn the unit off. Remember to bring counterclockwise the bias screw, once you have replaced the tube, turn the unit on and wait about one minute, then and slowly adjust the bias to a point where the led lite. Then go back to the point where the led goes off and a little bit further. Play your favourite music and have a listen...after 5 minutes of listening to the music, check if the bias led is on, if it is off, don't do nothing. If it is on, turn the bias adjusting screw again to bring it off. This is a normal behaviour. Once you have 30 minutes of listening the amp, if the led is off, you don't need to adjust the bias again.

Happy listening!

Thank you so much for your help roberto! Much appreciated! I’ve tried replacing the EL34 but no sound is coming, just a hissing white noise, ive noticed my driver tubes 6sn7 were burnt and smelled burnt which made me immediately turning the amp off and unplugging the power connector. Help! I tried calling CJ but no answer.

[jslstyo]

Roberto's method, using a KT-120 output tube as an example, is the most straightforward way for you to approach the problem. If substituting an EL-34 tube that you know is good doesn't fix the issue then further steps will need to be pursued but it does sound like one of the output tubes died on you.

Thank you Joe! Like mentioned above, i am completely lost in what to do now, could it be from the board and not the tubes? Anyone you can refer me to in terms of service/diagnose (preferably in california) CJ didnt reply any of my emails nor answer any calls. Help

[jslstyo]

I agree on the bad tube diagnosis, but if someone didn’t mention it, the tube failure probably also blew a fuse in your MV60.

Fuses may continue to blow on “power on” until you’ve identified and removed the bad tube.

Noted! Thank you i will definitely keep that in mind! Like mentioned above Im not sure about anything now and would prefer to bring it to someone experienced to check it out! Would love referrals or any information regarding how to contact CJ. I tried both emailing and calling but no response.

[AnotherJohnson]

Most folks are a bit put off by the difficulties in trying to contact companies.

I bought a 65” Vizio TV last year and it died before the warranty expired. I googled, called, emailed … to no avail.

I finally just returned it to Sam’s Club and they gave me a store credit.

My point is that it is hard to contact any manufacturers these days.

Patience is often rewarded with small companies like CJ. Call them. If you don’t get through, call again the next business day. And the next.

Most of us have eventually gotten through.

FWIW, you really don’t need professional help with this project yet. Tubes are user replaceable. The owners manual will tell you the correct fuse and tube sizes. Get some. You may have to sacrifice a fuse or two, but fuses are a lot cheaper than shipping.

There used to be instructions on the CJ web site for sending products in for bench evaluation. There is a form to fill out and include in the box.

[AnotherJohnson]

The service request form is still on their site.

https://conradjohnson.com/wp-content/up ... equest.pdf

[roberto]

jsityo,

The bias resistors are rated 8 watts, 20 ohms. Usually these resistors fail when there is a tube in short. Yes, I think you might need a qualified technician to service your beloved MV-60. When I suggest the KT-120 tube, is because my mind thought that your amp model was a MV-60SE. My bad assumption.

AJ is right too, when he said that there must be an open fuse. Don't worry, the problem is not too difficult to resolve. Your MV-60 is using the latest CJ simple circuit design, this is, the shortest path of the signal and top match quality parts.

Try an email to service@conradjohnson.com.

[rmac587]

Hi Jslstyo,
What was the outcome with your MV60? I have one as well and this is good information to know!
Thanks, rmac587