Good known at the above mentioned models are the burned low wattage zener D112 (HZ20 or HZ22) after blown bulb.
The developers assumed that the lamp never burned out (which is why this bad design came about) and therefore the zener diode never has to process the additional current for the lamp.
Check out this URLs:
Second opinions needed on a Luxman L-215 mod.
LUXMAN L-210
Luxman L 190 L 210 L 215 L 235 L 225 L 230 L 400 PCB Extra Holes Against Heat Problem Of Zener Diode | against, d112, diode, extra, heat, holes, l190, l210, l215, l225, l230, l235, l400, luxman, of, pcb, problem, resistor, zener | hifi-forum.de Bildergalerie
My previous approach was to replace the resistor R153 (330R) by 820R-1K2 (dependend of the new lamp - mostly 1K) in 17W version - go to
Security Check
and the electrolytic capacitor C133 with a 470uF/63V version, so as to remove the zener diode without replacing it.
Now I will try an other variation with various LEDs. Therefore I will connect the LED (to avoid flicker) between the positive and neg. rail of the power amp across an appropriate resistor. Now one get the benefit to have no error currents on the ground path.
There is sometimes an other unwanted effect, for some guys obviously very hard to find (for me actually not):
different (sometimes distorted) level between left and right channel through conducted mute transistors Q114a/b, controlled by the node of R149/150.
The reason are not defective 2SK117 (Q114a/b).
The reason is the too low neg. (somtimes even pos.) voltage on this node. Reason are the small signal diode D153 (1S1553, similar to 1N4148) which then has an internal interruption.
I replace this diode by a BA159. For C131/C130 I use 63V or 100V version (should always replace).
The developers assumed that the lamp never burned out (which is why this bad design came about) and therefore the zener diode never has to process the additional current for the lamp.
Check out this URLs:
Second opinions needed on a Luxman L-215 mod.
LUXMAN L-210
Luxman L 190 L 210 L 215 L 235 L 225 L 230 L 400 PCB Extra Holes Against Heat Problem Of Zener Diode | against, d112, diode, extra, heat, holes, l190, l210, l215, l225, l230, l235, l400, luxman, of, pcb, problem, resistor, zener | hifi-forum.de Bildergalerie
My previous approach was to replace the resistor R153 (330R) by 820R-1K2 (dependend of the new lamp - mostly 1K) in 17W version - go to
Security Check
and the electrolytic capacitor C133 with a 470uF/63V version, so as to remove the zener diode without replacing it.
Now I will try an other variation with various LEDs. Therefore I will connect the LED (to avoid flicker) between the positive and neg. rail of the power amp across an appropriate resistor. Now one get the benefit to have no error currents on the ground path.
There is sometimes an other unwanted effect, for some guys obviously very hard to find (for me actually not):
different (sometimes distorted) level between left and right channel through conducted mute transistors Q114a/b, controlled by the node of R149/150.
The reason are not defective 2SK117 (Q114a/b).
The reason is the too low neg. (somtimes even pos.) voltage on this node. Reason are the small signal diode D153 (1S1553, similar to 1N4148) which then has an internal interruption.
I replace this diode by a BA159. For C131/C130 I use 63V or 100V version (should always replace).
Last edited:
Same problem / same fix (?)
I recently purchased a refurbished L400, with a 90-day warranty. My phono bulb stopped working after the warranty ended. I checked the Zener diode, and sure enough, it had been recently replaced. I will go ahead and order some replacement bulbs to see if that corrects the problem. The D112 diode on the board looks intact and OK. If a new bulb does not light, I will replace the diode. In hindsight, I was leaving the amp powered on 24x7, with the phono setting selected. Could be the bulb was nearing end of life and this just exasperated the problem.
I recently purchased a refurbished L400, with a 90-day warranty. My phono bulb stopped working after the warranty ended. I checked the Zener diode, and sure enough, it had been recently replaced. I will go ahead and order some replacement bulbs to see if that corrects the problem. The D112 diode on the board looks intact and OK. If a new bulb does not light, I will replace the diode. In hindsight, I was leaving the amp powered on 24x7, with the phono setting selected. Could be the bulb was nearing end of life and this just exasperated the problem.