PIONEER EQUALIZER SG-540 : Both Slider LED Lights Became Very Dimmed / Low :

Thread Starter

smarthawk

Joined Apr 24, 2020
30
Hi,

The EQ slider leds / lights became very dimmed for no reason. the EQ still works great , he slider functions to modify sound still works fine for both channels.
Please find the attached pictures and service manual as well. Do you think some of the components might got weaker? like any capacitors etc? Need some help please. it's a vintage EQ which produces amazing sound and i have to fix it regardless.

Looking forward.
Mobin
 

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Dodgydave

Joined Jun 22, 2012
9,168
On pdf1. Locate transistors Q23, Q24, these are the drive transistors for the 7 Series wired leds on a 22V supply, per channel,, and short out the Collector and Emitter temporary to see if they go brighter the series resistor is in the Emitter leg so its a Constant Current source.
 

Thread Starter

smarthawk

Joined Apr 24, 2020
30
On pdf1. Locate transistors Q23, Q24, these are the drive transistors for the 7 Series wired leds on a 22V supply, per channel,, and short out the Collector and Emitter temporary to see if they go brighter the series resistor is in the Emitter leg so its a Constant Current source.
Hey DD, so you want me to try shorting both legs (collector & Emitter together) for both transistors ? i hope this would be safe and wont blow up any resistors or the transistors it self ... what do you think ?

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Dodgydave

Joined Jun 22, 2012
9,168
They may not be faulty, you need to do some voltage measuring with a Dvm, but first just short out the transistor C / E terminals to put the leds on maximum brightness, they won't blow up!!
 

Thread Starter

smarthawk

Joined Apr 24, 2020
30
hey DD, so i did short the legs but there's not change in brightness...
what i change the resistors ? if yes, what would be the wattage and tolerance for the resistors as per the diagram?
i'm planing to change 3.9k ohms, 47 ohms, 33 ohms and 560 ohms.
 
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Dodgydave

Joined Jun 22, 2012
9,168
The 7 leds are All in Series on a 22V supply, if the leds take 2.5V each that's 17.5V,
Leaving 2.5V across the resistor, this will set the Current at 57mA max, and if the leds are 3V each thats 21mA minimum.

Measure the Voltages across the Leds and across the resistor to see the total supply.
 
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