Case 645432 . 02.04.2023. Marantz 2275 receiver repair. No sound. Poor front panel illumination.
Problem solved by cleaning push switch “Tape monitor” on front panel. Deoxit spray used (needle injection inside switch ) . Illumination lamps changed to LED lamps by customer request.
Some technical experience and view to share about front panel illumination lamps. LED or original incandescent lamps ? Which one is better ? Are there any advantages ?
Some customers like LED , some original incandescent lamps. We provide pictures for comparison LED and old school lamps illumination. In this case we compare 8 volt lamps for Marantz 2275 front panel illumination.
On picture right meter illuminated by LED lamp, left meter by original incandescent old school lamp and small function lamps illumination to compare.
How LED design lamp works – electrical current goes to special microchip inside with semi-conducting material layers and produce visible light.
How old school incandescent lamp design works – electrical current goes to the tungsten filament inside lamp and start burning tungsten metal process, producing visible light. Basically you see light from burning metal named tungsten in no oxygen glass tube or sphere.
LED lamps pluses –
1. More brightness 20 -70 %.
2. Longer work life time 70-300% .
3. Ability to choose from many colors and light tones ( white, warm white , cold white, blue, light blue, icy blue ,dark blue …………….)
4. Lower electric current to produce same brightness 30-200 % (your electric consumption lower means your electric bill is lower ,not significant amount but still good news ).
5. Lower heat generation 20-80% .
6. No need to keep inert gas and no oxygen condition inside glass lamp like inside old incandescent lamp .
7. Big variety of shapes and designs.
Minuses for LED lamps .
1. AC or DC application (polarity) importance for some lamps.
2. Lower and limited light producing angle on some LED lamps, instead 270-360 degree wide angle on old school lamps you getting 60-180 degree direct light angle only. In some application it is extremely important.
Both type of lamps don,t like over voltage . They will stop working in short period of time if you apply bigger voltage then they designed for.
All old school incandescent lamps are universal AC or DC voltage and wide light angle by design.
eakers, speaker wires and input audio signal . All modules inside and power transformer not shielded. Zero attention to AC line interference . 
