RG100ES Noisy Effects Loop

[Deancfh]

Yea so when I turn the pot to around 6, there is no change. Around 7-8 it like kicks in with no gradual gain. It goes from clean, very slight overdrive, weird scratchy pot noise and boom max gain.

[Deancfh]

So I went ahead and poked around and got nothing, but the gain still sounds like it is dying immensely. What should be my approach?

[Deancfh]

I just swapped the potentiometer, it was terrible. That fixed the gain fortunately, but now I am back to the noisy effects loop.

[DrGonz78]

Take a close up picture of the solder side of the board and make sure the pics show good clarity of the solder joints. Just want to see if there are any regions of the board that need solder. I am suspecting something related to the pots grounding might have cracked solder. So pay especially close attention to those joints. You did spray out the pots? Could be a combination of bad conditions and the pot itself is suspect.

edit: oh I missed the part where you swapped the pot and fixed that part. Nice work

[DrGonz78]

Just got to add that if this amp is RG100es then the effects loop is a simple passive circuit. In fact it is merely two jacks in series. So you said that the noise in the preamp goes away with a patch cord from effect send to the return jack. Did you clean those jacks with the switch contacts? Also would be good to figure which side the noise is coming from, before effects send jack or after return jack. Run the amps pre into another amp, does it sound healthy? Input guitar signal into effect return jack directly, any snap crackle pop? So we need to know if it’s a preamp issue or power amp. Got to conquer and divide.

[Deancfh]

So, with no patch cable, it is hit or miss whether the amp will pop and crackle or function accordingly. With a patch cable, there is never an issue. If I run the flanger doubler in front of the amp, it is beyond quiet. If I run the F/D into the effects loop of another amp, it is extremely quiet. It is only the effects loop of the RG100es where it is beyond noisy.

As for your suggestions, help me understand. For the preamp testing, I would take the send of the amp, put it into the F/D and the output of the F/D goes into the return of another amp? Then for power amp testing, I would do the send of the other amp I have and put it in the return of the RG100es?

Also, my RG100es is 150w and the only other cabinet I have can run 75w and the other effects loop is a 25w amplifier. As long as it is low volume, there should be no issue swapping heads and cabs as long as the ohm rating correlate right?

[DrGonz78]

Input guitar signal like normal then take effect send (preamp out) and input that cable to input of another amp. The other test is simple plug guitar directly into effect’s return (power amp in) and play. The first test will be louder as the second test removes preamp from the equation.

[Deancfh]

Alright, I did some testing and got some results.

Within the first test, I ran the guitar straight into the return of the amp. It is unpredictable, but sometimes it would work, sometimes it would have volume swells or cut in and out. If no cable if plugged into the return of the amp, it will pop like crazy and will stop when I plug a cable in. I then ran the guitar into the F/D and the out of the F/D when into the return of the amp and there was volume swells with or without the F/D engaged, however after turning the amp on and off a few times, it all worked BUT the source of the noise coming from the F/D engaged was present and loud as hell.

https://youtube.com/shorts/eZpUSZDhExo?feature=share POWER AMP TEST VIDEO

For the preamp test, here is what I found. I put my guitar in the front of the amp and the send of the RG went into the front of my tube amp. When I turned the RG on, the effects return having no cable plugged in popped like crazy, but the effects send into the other amp was fine. I then plugged the send of the RG into F/D and then into the front of the tube amp and it sounded perfect. The preamp of the RG100es had the perfect doubling or flanging tone and was amplified in the other amp with very little to no noise at all. All the knobs of the F/D were at noon so when I run it at my normal settings, it would be a lot quieter in the preamp test video.

https://youtube.com/shorts/Zw1L-Khn0y0?feature=share PREAMP TEST VIDEO

Conclusion- The unbearable white noise when the F/D is engaged comes from the power amp. The preamp is fine and works as I'd hope into other amps with the F/D engaged. The return jack crackles and pops with no cable plugged in.

2 HOURS LATER- I went to do more testing and the gain no longer works. The pot I swapped shows signs of levels changing and the return jack I swapped was perfectly working which means no more popping yay! I did not do anything and the gain just stopped working. When I swapped the pot for the gain, it was working perfectly for hours until it randomly stopped working again.

https://youtube.com/shorts/xPJtqHpIXfk?feature=share GAIN FAILURE