Help needed to repair Rumble 500 V3 bass amp

[jab_bass]

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]

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]

Here they are, thanks

 

[Delta Prime]

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.



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?

 

[kellys_eye]

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!

 

[kellys_eye]

high frequencies have gone.

or your hearing has......

 

[jab_bass]

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]

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?

 

[Delta Prime]

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.

 

[Delta Prime]

I believe further inspection is required!

 

[jab_bass]

I believe further inspection is required!
View attachment 61273

Inspected, it is just some glue

Attached you can find the Solder side PCB Power amplifier

 

[Delta Prime]

Inspected, it is just some glue

Thank goodness. A game of light and shadows because this looks
Damaged.

Thank you for the updated photos.

 

[jab_bass]

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

 

[Delta Prime]

Confirm please..this is not a crack.

 

[Delta Prime]

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

Sounds good.

 

[jab_bass]

Confirm please..this is not a crack.
View attachment 61289

confirmed, it is not a crack, and I am now reviewing the rest just in case

 

[Delta Prime]

When you get her up and running, play a little something, I would like to hear it.

 

[jab_bass]

Remove suffix zip (it is not zipped just added.zip at the end) to the mp3

 

[jab_bass]

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]

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.

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