2266C Indicator Lamp out again!

[kbhag63]

Hi everyone,

Have read everything I could about the "purple" indicator bulb issue, the one on my amp was out so I ordered a replacement M-BULB-0007, made sure it had the diode across the LED and installed that about a month ago...now it's out again.

Is there a permanent fix for this? I can't believe Marshall would not be able to make a correction to the indicator lamp that would solve this issue for good.

Please help!

Ken, CT

[Marker]

If you like diy than you can open it removing the purple plastic cover and replace the LED yourself or even remove it and install a normal 6,3v bulb as the older Marshall amps use.

[Nickg21285]

I bought a packet of blue LED's from china, pulled the lens off the bulb, clipped the old LED and soldered a new one in its place. It has worked fine ever since.

[sikter]

I placed rectifier between my purple led and its power supply.
Never died again. I used wires with the lugs so no soldering needed on amplifier.
I used long wires so led could be pulled out easily. I don't have to take my amp appart in case the led dies some day.
There is a thread about it (with pictures)

[Tonehouse]

I have two VM's and both amps had power LED failures as reported by many owners over the years. I fixed my power LED issue during chassis inspection & bias checks. By the way I found bias was too high on both amps so check it periodically like SteveD says! To share my experience of an inexpensive power indicator fix, I purchased two replacement LEDs and a 4 pack of replacement current limit resistors at local electronics store for $5.

Inspect chassis and follow power lamp yellow & black wires to circuit board pin connectors to see power LED current limit resistor R72 = 68 ohms located beside yellow wire Pin23. Simply for point of interest shine a bright light through the circuit board to see R72 is actually bottom side trace connected to LED black wire Pin22, not that it matters in this case but good tip for general troubleshooting. Disassembled power lamp and I chose to replace failed LED with new High Brightness 5mm Blue LED rated 4.5V operating and brightness 1000Mcd @ 20mA max. Just out of curiosity does anyone know Marshall factory LED specs for stock current calculations? Factory R72 current limit resistor value 68 ohms is too low for my replacement LED max current rating so I replaced R72 with a calculated higher value. The replacement LED will initially operate with factory R72 value but the series current calculation check indicates 6.3V AC Heater Power - 4.5V LED = 1.8V across R72 therefore LED operating current 1.8V / 68 ohms = 27mA. Driving my replacement LED with more than 20mA current will needlessly stress the LED creating increased potential of recurring failures. Perhaps a bit high in some opinion but I chose to replace R72 = 270 ohm value to achieve no real loss of LED brightness yet ensure LED operating current is less than half of max rated spec, meaning my replacement LED & R72 value combination should hopefully work for the life of amp. Other than the different color stripes due to R72 resistor value change, there is zero visual indication of any modification to the amp. Have fun & YMMV