Luxman LV-103 going into protection mode.

[keller212]

Hi,

I got given a Luxman LV-103 recently. Everything works perfectly, except after a couple of hours of use (sometimes shorter or longer) it goes into "Protection Mode"... If i then turn it off & unplug power for a few minutes it works again, until it cuts out again & so on.....

Could this be an overheating issue ? Or a fault on the Protect PCB ???
Any advice to head me in the right direction would be greatly appreciated !

 

[sgrossklass]

Could be any of these, really. Maybe it just turns out to be a bunch of bad solder joints. A keen eye, a loupe (or an inverted SLR wideangle lens), freeze spray and a hairdryer may prove handy when proceeding.

 

[ICG]

The LV-103 got 3 protections, heat, DC offset and over voltage. Heat could ofcourse be an issue, the amp does not have very much power (50W) and does not like low impedances at all. Did you turn it up high or got low impedance speakers connected?

A heat fault of a part is possible. Before you start with cold spray, check for heat and heat problems first. The amp gets quite hot and cold spray is flamable! If it's not heat, I would then measure the DC offset and BIAS, only after that I'd start with cold spray.

 

[mjstriker5]

I'm going to reiterate what was already said. Get a temp probe and a multimeter to check offset. Monitor both to narrow down the problem.

 

[Welcome]

It's cracked solder joints. You need to resolder the entire amplifier. This applies to every amp in this series.

 

[keller212]

I think i found out the culprit...
There is a "Thermistor" on the MOSFET heatsink that is shorting out even when the FET's are not overheating, tripping the protection relay...