SOLVED Hyped Fuzz - LED not turning on

[guythmike]

Trying to troubleshoot the Hyped Fuzz I'm almost finished up with. Having issues with the LED not lighting. I do not have the 4.7k resistor on the PCB because I'm using a prewired LED that includes the resistor built in (I've confirmed the LED works by powering it directly). So far, my extent of troubleshooting has involved easy fixes like a ground issues and such, so please forgive me if I'm not using the correct terminology in the data I'm providing. This is the first time I've had a failure with the LED and I have yet to verify I'm getting any sound; figured if there's a power issue not much point in continuing on with that test.

Voltage readings are as follows:

DC jack - 9.18v

IC1 TL072
Pin 1 - 4.2v
Pin 2 - 4.3v
Pin 3 - 0v
Pin 4 - 0v
Pin 5 - 0v
Pin 6 - 0.93v
Pin 7 - 4.42v
Pin 8 - 8.8v

IC2 JRC4558D
Pin 1 - 4.42v
Pin 2 - .08v
Pin 3 - 0.25v
Pin 4 - 0v
Pin 5 - 0.25v
Pin 6 - .01v
Pin 7 - 4.42v
Pin 8 - 8.82v

IC3 JRC4558D
Pin 1 - 4.43v
Pin 2 - 0.24v
Pin 3 - .08v
Pin 4 - 0v
Pin 5 - 0v
Pin 6 - 4.43v
Pin 7 - 4.43v
Pin 8 - 8.82v

Q1 BC549C
Collector - 0.52v
Base - 0v
Emitter - 0.51v

Q2 BC549C
Collector - 0.24v
Base - 0.02v
Emitter - 0.24v

Q3 BC549C
Collector - 0.24v
Base - 0.02v
Emitter - 0.24v

Q4 BC549C
Collector - 8.8v
Base - 0v
Emitter - 1.32v

I did solder the transistors into the sockets, but that was only after noticing how loose they felt in there and I originally thought this might have been the culprit for the lack of LED power. Like I said, this is my first real troubleshooting experience, but looking at these numbers makes me suspect the transistors, but if there are any other places I should be taking data from, please let me know. I got the transistors from Tayda (Part A-2571), but I'm hoping it's just a user error. I still have some spares if I need to replace them, but I'm not sure how to go about testing them before installing.

Thanks a lot in advance! I feel I've gotten lucky with the previous builds, and now I get to finally learn some "real" trouble shooting stuff!

 

[DailyDovetails]

Where is the LED and how is it attached to the circuit currently?

 

[Zanshin]

I think you’ll need to put a jumper in place of the PCB led resistor.

 

[guythmike]

Where is the LED and how is it attached to the circuit currently?

I had to remove it in order to make sure it wasn't a faulty LED.

 

[DailyDovetails]

Got it

I had to remove it in order to make sure it wasn't a faulty LED.

I agree with Zanshin. I think you need to jumper the 4k7 resistor without it the connection or the switch is open.

 

[guythmike]

Got it

I agree with Zanshin. I think you need to jumper the 4k7 resistor without it the connection or the switch is open. View attachment 69368

Makes sense. I've used these LEDs before and I've always just put a like value resistor in there and had no problems. I'll give it a shot!

 

[guythmike]

Yep, that was it! Put in a 1k resistor and it's lighting up. Thanks a lot, @DailyDovetails and @Zanshin!