Maker Pro
Maker Pro

Help needed to repair Rumble 500 V3 bass amp

jab_bass

Oct 29, 2023
9
Joined
Oct 29, 2023
Messages
9
Hi,
I am using a Rumble 500 V3 bass amp in my rehearsals and, since recently, I am facing a problem with the quality of sound, it seems to be lost the presence. I will try to explain the problem

- Keeping all the controls flat, and no activating bright button, with no active mode only passive, high frequencies have gone.
- I have tested the horn (tweeter) and it has 6ohms and seems to be working, when I connect a music source to the amp the horn seems to be active although music has a very low volumen in the horn, almost imperceptible but you feel whether it is connected or not.
- Equalizer (Preamp) works, in order to compensate the lack of high frequencies I have to activate BRIGHT button and increase a TREBLE
- The rest of the AMP (Power) works fine.
- It is not a problem of strings (I have changed them few months ago)

I thought that crossover could the reason, so I am looking for the components (cap 1uF and 8.2ohms 5W) to replace them.

Reading in this forum but related to Rumble 150 and another problem, I read a comment from a member of the forum that electrolitic capacitors could be the reason of bad audio quality, so I decided to explain here my problem.

I have the schematics but I see several electrolitic capacitors and I am not sure to change all of them,

Any idea, comment or suggestion will be much appreciated. Thanks in advance
 

Delta Prime

Jul 29, 2020
2,110
Joined
Jul 29, 2020
Messages
2,110
I have the schematics but I see several electrolitic capacitors and I am not sure to change all of them,

Any idea, comment or suggestion will be much appreciated. Thanks in advance
You're welcome prematurely.
Would you care to share those schematics? If you could photos if possible .thank you
 

jab_bass

Oct 29, 2023
9
Joined
Oct 29, 2023
Messages
9
Here they are, thanks
 

Attachments

  • Rumble 40 V3 Schematics-Diagrams.pdf
    630.2 KB · Views: 6

Delta Prime

Jul 29, 2020
2,110
Joined
Jul 29, 2020
Messages
2,110
I thought that crossover could the reason, so I am looking for the components (cap 1uF and 8.2ohms 5W) to replace them
Can you take a photo please.
Do you have a multimeter?
have you verified the test point voltage values on the schematic. Follow the procedure given.

Screenshot_20231029_151254.jpg

The schematics you provided are wonderful ; would you happen to have sheet three and four?
I need to see your power amplifier and support circuitry. take a photo.
Do you have the ability to solder electronic components?
 
Last edited:

kellys_eye

Jun 25, 2010
6,514
Joined
Jun 25, 2010
Messages
6,514
I read a comment from a member of the forum that electrolitic capacitors could be the reason of bad audio quality,
You 'problem' as such would be WHICH capacitors to change. Without test equipment to chase the signal through the amp to find where it's losing quality the only solution is to replace them ALL which can be quite a bind and no guarantee that it will fix the issue.

The capacitor in the tweeter circuit (1uF) would be the first to be changed - it's NON-polarised and readily available and may fix the problem immediately. The tweeter itself, although measuring fine for resistance, could have a distorted cone or other physical issue preventing it operating properly. If you can change this (or swap it out temporarily just to check) then it eliminates another problem.

Do you get good results through the headphone output? This would eliminate much of the signal processing circuitry and give you an excuse to NOT change all the capacitors!
 

jab_bass

Oct 29, 2023
9
Joined
Oct 29, 2023
Messages
9
Hi,

I am able to solder electronic components and also with multimeter

I have not verified yet the test point voltage values on the schematic, I will prepare the set up to do it.

Regarding the schematics, that PDF is the unique one that I got. I think that Power Amplifies is in page 1

Do you want photos from the physical board?
 

jab_bass

Oct 29, 2023
9
Joined
Oct 29, 2023
Messages
9
Can you take a photo please.
Do you have a multimeter?
have you verified the test point voltage values on the schematic. Follow the procedure given.

View attachment 61270

The schematics you provided are wonderful ; would you happen to have sheet three and four?
I need to see your power amplifier and support circuitry. take a photo.
Do you have the ability to solder electronic components?
 

Attachments

  • 2023-10-29 23.47.05.jpg
    2023-10-29 23.47.05.jpg
    188.9 KB · Views: 6
  • 2023-10-29 23.47.23.jpg
    2023-10-29 23.47.23.jpg
    225.1 KB · Views: 6

Delta Prime

Jul 29, 2020
2,110
Joined
Jul 29, 2020
Messages
2,110
Forgive me the fault was on my end. the schematics did not show up until now. We will work our way back from the horn to the amplifier then the front panel display board if need be. So no need to verify test point values unless you want to... it wouldn't hurt. Solder side PCB Power amplifier
photos please. The information you have provided already will be a tremendous help to others so thank you for that.
 

jab_bass

Oct 29, 2023
9
Joined
Oct 29, 2023
Messages
9
Attached the unit of Rear I/O PCB where the cross over is placed, looking at crossover looks fine but probably its capacitor is failing, searching a new one
 

Attachments

  • photo_2023-10-30 18.33.50.jpeg
    photo_2023-10-30 18.33.50.jpeg
    193.7 KB · Views: 3
  • Screenshot 2023-10-30 at 18.35.31.png
    Screenshot 2023-10-30 at 18.35.31.png
    158.8 KB · Views: 2

Delta Prime

Jul 29, 2020
2,110
Joined
Jul 29, 2020
Messages
2,110
When you get her up and running, play a little something, I would like to hear it.
 

jab_bass

Oct 29, 2023
9
Joined
Oct 29, 2023
Messages
9
Remove suffix zip (it is not zipped just added.zip at the end) to the mp3
 

Attachments

  • Standard recording 1.mp3.zip
    1.5 MB · Views: 1

jab_bass

Oct 29, 2023
9
Joined
Oct 29, 2023
Messages
9
I guess that not more clue... I have tested the horn and it works and also de crossover, there is something (no idea where) that makes rumble 500 lack of intensity, of presence, consistency to the sound. I will try to learn how to trace a signal however I would need to know what to expect in each point to understand whether it is ok or not.
Also let’s see if I can find another rumble 500 to compare with.

In any case thanks for the support, and if my files shared could help someone else I will be happy. Best
 

Delta Prime

Jul 29, 2020
2,110
Joined
Jul 29, 2020
Messages
2,110
In any case thanks for the support, and if my files shared could help someone else I will be happy. Best
Thank you for posting this thread. don't give up yet.
I would recommend this site. the more people you have to look at your situation the better. :)

A little tip. To expedite their analysis please post your documentation you have posted here. ;)
 
Last edited:
Top