MV60 Problem

[spurn]

I have an MV-60 (later upgraded to an MV-60 SE) with no output. When I power up the power LED does not light, but the bias LED's do. I've replaced all the fuses, but in doing so noticed that there's a fuse slot marked F1 on my circuit board that is empty -- no fuse is installed there. The only two fuses listed in the owners manual are F2 and the fuse in the IEC socket (which I replaced).

Any suggestions on what might be a fix for this to avoid taking the amp in for repair? Could a bad tube be to blame?

[roberto]

Hola spurn,
If both channels are not working, the problem is at the power supply. There is a main working voltage missing somewhere. It could be an open resistor or an open secondary wound of the power transformer. This is my guessing and I could be wrong. Another open fuse could be. Test for conductivity all fuses. It might be looking to the eye ok.

[roberto]

Address your question to the CJ service dept with a call or send them an email. service@conradjohnson.com

[AnotherJohnson]

I have an MV-60 (later upgraded to an MV-60 SE) with no output. When I power up the power LED does not light, but the bias LED's do. I've replaced all the fuses, but in doing so noticed that there's a fuse slot marked F1 on my circuit board that is empty -- no fuse is installed there. The only two fuses listed in the owners manual are F2 and the fuse in the IEC socket (which I replaced).

From the manual:
**************
Internal Fuses
The MV60 power transformer is protected by a fuse on the ac power line (F1, located in a compartment in the ac line-cord receptacle mounted on the back of the amplifier), and by a separate fuse (F2, located on the pc board) for the secondary windings for the filament supply. A failure of either of these fuses is a symptom of a more serious problem, and a competent service technician should be consulted. In no event should fuses be replaced with a value or type different than that originally supplied. The correct fuse values and types are:
F1: 5x20mm 5 amp T-type if configured for 100 or 120V: 5x20mm 3 amp T-type if configured for 220 or 240V.
********

Seems like, if the AC line fuse is missing, but there is power to run the bias LEDs, that something has been “modified” … like the AC line fuse has been bypassed. Is there a jumper?

I agree with Roberto that it would be good to call CJ service.

[spurn]

Thanks, everybody -- I called CJ this morning, but got their answering machine -- hopefully they'll call back soon.

Thanks for all your help!

[admin]

Contacting CJ would be the best. Any chance that that there is a relay in there that delays the output to let the tubes warm up? If there is, that may explain why the bias LEDs are on but it never gets output. Just a long shot as I'm not that familiar with the MV60.

[roberto]

The power on led is not lit. This tells to me that the problem is in this part of the circuit. The +12V regulator might be.