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Author Topic: Rocktron Rampage R80 - No Sound problem  (Read 4834 times)

phatt

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Re: Rocktron Rampage R80 - No Sound problem
« Reply #15 on: January 21, 2021, 02:07:47 AM »
Don't forget to check you have continuity on each of the reverb cables.
Those plastic RCA plugs are a common fail point.  :trouble
Phil.

paolone

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Re: Rocktron Rampage R80 - No Sound problem
« Reply #16 on: January 21, 2021, 03:00:21 PM »
Hy


I have made the homework:
OK - If i hit the reverb unit (with the amp switched on) i heard the springs rattling through the speaker.
OK - With reverb and master pot set on 10, touching the white RCA tip (connected to CN3 and to the OUT of the Reverb unit), I heard the noise in the speaker.
OK - No footswitch connected
OK - checked the continuity on each reverb cable

How can i check the IC1? Red sonda on pin 1 of IC11 and black sonda on ground?

NOW THE AMP WORKS
AND REVERB SEEMS WORKING... “seems working” because for me the reverb level is too low...

I put here a PDF with my project to read easily the circuit board.


Thanks

Paolo



« Last Edit: January 21, 2021, 03:02:54 PM by paolone »

dmeek

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Re: Rocktron Rampage R80 - No Sound problem
« Reply #17 on: January 21, 2021, 06:00:58 PM »
How can i check the IC1? Red sonda on pin 1 of IC11 and black sonda on ground?  Yes

There are 3 electrolytic caps that could affect the reverb C31, C35 and C36 all 1uF. Try replacing them.
« Last Edit: January 21, 2021, 06:06:58 PM by dmeek »

paolone

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Re: Rocktron Rampage R80 - No Sound problem
« Reply #18 on: January 22, 2021, 12:41:02 PM »
Hy

Testing IC11 there was -0,07v between pin 1 (near the circle inpressed on the top of Ic11) with red sonda and the ground (the chassis) with black sonda. I have turned the master and reverb pot on 10.

Tomorrow i’ll test the 3 caps.

Thanks

Paolo

paolone

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Re: Rocktron Rampage R80 - No Sound problem
« Reply #19 on: January 28, 2021, 02:15:23 AM »
Hy

I’m waiting that the 1uf caps arrive from internet, so i can change them.

Which component is the colprit of the master volume’ low level?
Maybe some other caps?

@dmeek do you have the electric schematic of my amp please?

Thanks

Paolo
« Last Edit: January 28, 2021, 02:17:21 AM by paolone »

dmeek

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Re: Rocktron Rampage R80 - No Sound problem
« Reply #20 on: January 28, 2021, 12:18:23 PM »
Here is an update of the preamp output ad the power amp schematics. In the power amp C1 and C5 could affect the gain. You will probably need to trace the signal to find the problem.
Q1 is for power-on muting. You could try removing it temporarily to see if that makes a difference.




« Last Edit: January 28, 2021, 12:58:19 PM by dmeek »

dmeek

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Re: Rocktron Rampage R80 - No Sound problem
« Reply #21 on: January 29, 2021, 11:18:55 AM »
I seem to have a lot of time on my hands lately. Here is the rest of the schematic

« Last Edit: January 30, 2021, 10:42:26 AM by dmeek »

Jazz P Bass

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Re: Rocktron Rampage R80 - No Sound problem
« Reply #22 on: January 29, 2021, 11:40:49 AM »
Nice work!

paolone

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Re: Rocktron Rampage R80 - No Sound problem
« Reply #23 on: January 30, 2021, 02:57:40 PM »
Thanks dmeek, good job with the schematic.

Since i’ve remount the amp, it goes.
I’m waiting the 1uf caps to resume the reverb...
But my problem is still the same:
The clean mode has too much low volume.

Dmeek you told me to change also the C1 and C5 caps to resume the clear mode, correct?

I’m gonna buy the 2 caps to test it.

Thanks
Paolo
« Last Edit: January 30, 2021, 03:02:50 PM by paolone »

dmeek

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Re: Rocktron Rampage R80 - No Sound problem
« Reply #24 on: January 30, 2021, 09:44:49 PM »
If the only problem is that the clean channel is low volume, the only capacitor it could be is C26. Though the problem could be caused by something other than a
capacitor like a bad volume pot or maybe Q4.

phatt

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Re: Rocktron Rampage R80 - No Sound problem
« Reply #25 on: January 30, 2021, 10:18:41 PM »
Thanks dmeek, good job with the schematic.

Since i’ve remount the amp, it goes.
I’m waiting the 1uf caps to resume the reverb...
But my problem is still the same:
The clean mode has too much low volume.

Dmeek you told me to change also the C1 and C5 caps to resume the clear mode, correct?

I’m gonna buy the 2 caps to test it.

Thanks
Paolo

I don't know how many amplifiers you have used but I'm yet to find one of those small medium practice amps that have the clean as loud as the OD channel.

So IME this is how they normally work,, OD is always louder than clean. 8|
But I'm aware that some I've encountered have quite a large difference between the levels of the 2 channels and maybe your amp is extreme, in which case the circuit would need some modification to balance that problem.
At a quick glance at the Schematic (Thanks to Dmeek :tu:) you could lower that 18k resistor at IC6 to boost up the clean. ~~ maybe try 4k7??
Phil.

paolone

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Re: Rocktron Rampage R80 - No Sound problem
« Reply #26 on: January 31, 2021, 11:27:08 AM »
Thanks dmeek and phatt

I’m not talking about the difference between the clear and the distorsion mode...

I have also a fender mustang 2 v2 amp (40watt)
The clean mode of fender amp (40watt) at 3 (volume pot 1-10) is higher than Rocktron R80 (80watt) at 10 (volume pot 1-10).

Another important information is that the volume of clean mode in Rocktron R80 increases after 10/15 minute of use, but is always under or like the fender...

Do you have any idea or C26 is the culprit?

List of caps to change as soon as they arrive from internet:
C31  1uf 63v
C35  1uf 63v
C36  1uf 63v

C1  4.7uf 50v
C5  47uf 35v

C26 1uf 63v


Thanks
Paolo



« Last Edit: February 01, 2021, 11:37:48 AM by paolone »

dmeek

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Re: Rocktron Rampage R80 - No Sound problem
« Reply #27 on: January 31, 2021, 01:06:52 PM »
C1 and C5 would affect the overall volume, so they are not the problem. It might be C26 or it could be something else.  If I had this amp I would plug a 500Hz oscillator in the input and trace with an oscilloscope or signal tracer which is basically a small amp and speaker with a probe connected to the input. The "shotgun" approach of guessing and replacing parts often leads to frustration,
at least in my experience. On the other hand you might be lucky.

paolone

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Re: Rocktron Rampage R80 - No Sound problem
« Reply #28 on: January 31, 2021, 03:05:11 PM »
Thanks dmeek

But I haven’t an oscillator and an oscilloscope...

If there is some other test with a multimeter i can do it...

In other hands... i must only use the shotgun approach...

Can you help me try to locate the real cause?

Thanks

Paolo

paolone

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Re: Rocktron Rampage R80 - No Sound problem
« Reply #29 on: February 08, 2021, 03:24:46 PM »
Hi to all of you

The caps are arrived today.
I have desoldered the old ones.
Tomorrow i will resolder the new update ones and then i will test my amp.

All the caps except one show 960nf
Only one shows 1040nf
The right is 1uf = 1000nf

Tomorrow we will see...

But i saw the C7 capacitor in the PRE PCB (in the photo) that has a nose on the upper side and the esr tester don’t recognize (the same cap: C6 instead is recognized)

I don’t find it on your schematic. But i think that is in the preamp gain section...
Can you please show it on your schematic?


Thanks
Paolo
« Last Edit: February 08, 2021, 04:12:26 PM by paolone »