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Solid State Amplifiers => Amplifier Discussion => Topic started by: paolone on January 16, 2021, 01:43:50 PM

Title: Rocktron Rampage R80 - No Sound problem
Post by: paolone on January 16, 2021, 01:43:50 PM
Hy to all of you

My Rocktron Rampage R80 sounds quite well, but sometime if i switch it off and then i switch it on it doesn't sound anymore my guitar.

I hear the the normal knoch when i switch it on
If i insert the footswitch i heard the speaker noises
If i pump up the  master volume i hear the presence in the speaker

What can be?

I saw the two green capacitors in the pre amp section... can they be the cause?

Do you have the electric schematic of this amp please?

Who can help me please?

Thanks

Paolo
Title: Re: Rocktron Rampage R80 - No Sound problem
Post by: paolone on January 16, 2021, 02:58:20 PM
Hy

I send you the photo of the 2 mainboard of the R80 amp

Now, after one hour of sleep the amp is working...
I don' t know why.

Some more information:
The sound, for an 80watt amp is very low, with the master pot set to half the volume is normal (with my fender mustang 2 - 40watt - with the master pot sert to 1/4, the volume is higher...)
The reverb pot don't change anything in the sound if i set it to 0 or to 10.
The volume is quite double in the distorsion mode respect than in clear mode. There is too much difference...

Let me know if someone of you have the electric schematic, please

Thanks

Paolo
Title: Re: Rocktron Rampage R80 - No Sound problem
Post by: dmeek on January 16, 2021, 07:39:14 PM
Please post photos of the foil side of the 2 boards and another of the power amp board with the ribbon cable moved to the side.
Title: Re: Rocktron Rampage R80 - No Sound problem
Post by: paolone on January 17, 2021, 07:51:35 AM
Hy

Thanks for the interesting.

Here is the photos of the 2 sides of the power board
And the photos of the Accutronics reverb

Paolo
Title: Re: Rocktron Rampage R80 - No Sound problem
Post by: paolone on January 17, 2021, 08:20:26 AM
Hy

Here is the pre pcb front and rear

Problem are:
- after some hours of use (random), if you switch it off to make a pause and than you switch it on, there is no sound of my guitar.

- if you wait some hours (random), than it works but there are the problem listed below (THIS PROBLEM THERE ARE ALWAYS, Also on the first switch on):
- no reverb even if you turn up or down the reverb pot
- low volume level in clear mode, better volume ievel in distorsion mode
Title: Re: Rocktron Rampage R80 - No Sound problem
Post by: dmeek on January 17, 2021, 03:48:56 PM
Plug a cord from Effects Send to Effects Return and see if it works. It could be the Effects Return jack switch.

Title: Re: Rocktron Rampage R80 - No Sound problem
Post by: phatt on January 17, 2021, 09:27:07 PM
Quote from: dmeek on January 17, 2021, 03:48:56 PM
Plug a cord from Effects Send to Effects Return and see if it works. It could be the Effects Return jack switch.
Dmeek beat me to it,, Yep FX loop is the most likely culprit. they are *Switching sockets* the switch terminals corrode and give the symptoms you are describing. 
Also looks like it may have a Preamp out and Poweramp input,, which is another fail point. link them as well.

As to reverb not working,,pull the RCA plugs and clean the pins.
Also flip the tank and use a DMM to check you have continuity of the little transducers,, there are 2 of them. if no reading look close for broken wires.

As for the big difference in Volume between clean and dirty,, well that is how most of them work,, Normal. ;)
Phil.
Title: Re: Rocktron Rampage R80 - No Sound problem
Post by: dmeek on January 17, 2021, 11:03:29 PM
Here is a rough schematic of the preamp output. Another possibility for the reverb is the input and output jacks might be reversed.

Title: Re: Rocktron Rampage R80 - No Sound problem
Post by: paolone on January 18, 2021, 01:05:32 PM
Hy

Thanks to all of you.

@dmeek  I've just make a test with a cord between effect send-return, The sound is more noisily.

@Phatt  I have test the reverb box (Accutronics 1EB2C1A) with a multimeter:
IN = 57 ohm
OUT = 196 ohm
Reading the instruction in the pdf i think it's ok...

@dmeek  the cord that starts from the board pin "IN" goes to the reverb box pin "OUT" (cord colour: RED). Impedance misured from cord pin 100 ohm
the cord that starts from the board pin "OUT" goes to the reverb box pin "IN" (cord colour WHITE). Impedance misured from cord pin -LO-


I have cleaned the 2 boards and the terminals with the electronic components cleaning spry.
Do i have to use the sand paper?

Now that i have all the boards unmounted, do i have something other to do before to remount and test them? (check capacitors...)

Thanks

Paolo
Title: Re: Rocktron Rampage R80 - No Sound problem
Post by: dmeek on January 18, 2021, 02:34:40 PM
The wire from CN2 IN on the preamp board is the reverb send. It plugs into IN on the reverb unit. OUT goes to CN3
Title: Re: Rocktron Rampage R80 - No Sound problem
Post by: paolone on January 19, 2021, 11:13:06 AM
Ok,
Thanks for the clarification.

This night i mount all the board and test the amp

Tomorrow i will tell you if it's OK.

Thanks

Paolo
Title: Re: Rocktron Rampage R80 - No Sound problem
Post by: paolone on January 20, 2021, 07:52:00 AM
Thanks to all of you

The amp is still working. Let's see in the next week...


REVERB IS NOT WORKING.
Is like if the reverb pot is broken, (I have test the impedance of the reverb tank and it was good).

How can i test the board and the pot with a multimeter please?

Thanks

Paolo
Title: Re: Rocktron Rampage R80 - No Sound problem
Post by: dmeek on January 20, 2021, 12:15:21 PM
Connect a wire on the board like this. It will bypass the reverb pot.
Title: Re: Rocktron Rampage R80 - No Sound problem
Post by: paolone on January 20, 2021, 02:30:30 PM
Hy

I have tested the resistance of the pot with a multimeter (red sonda on the center pin, black sonda on the lateral pin, in both the way)
It shows 0 to 44,8 kohm turning the pot from a side to the other
The pot is ok
There something else to check please?

Wich is the way on the board of the electric current from the reverb pot to the reverb tank and the continue?

Thanks

Paolo
Title: Re: Rocktron Rampage R80 - No Sound problem
Post by: dmeek on January 20, 2021, 05:49:40 PM
The reverb pot is after the output of the reverb unit.
If you hit the reverb unit do you hear the springs rattling through the speaker?
Unplug the 2 RCA plugs, set reverb pot and master on 10, touch the tips with your finger. One will cause hum in the speaker. That one goes to the OUT jack
Check the voltage on IC 11 pin 1. Should be 0V
Make sure nothing is plugged in the footswitch jack. If the ring connection is shorted to ground it will cut the reverb.
Title: Re: Rocktron Rampage R80 - No Sound problem
Post by: phatt 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.
Title: Re: Rocktron Rampage R80 - No Sound problem
Post by: paolone 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



Title: Re: Rocktron Rampage R80 - No Sound problem
Post by: dmeek 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.
Title: Re: Rocktron Rampage R80 - No Sound problem
Post by: paolone 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
Title: Re: Rocktron Rampage R80 - No Sound problem
Post by: paolone 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
Title: Re: Rocktron Rampage R80 - No Sound problem
Post by: dmeek 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.




Title: Re: Rocktron Rampage R80 - No Sound problem
Post by: dmeek 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

Title: Re: Rocktron Rampage R80 - No Sound problem
Post by: Jazz P Bass on January 29, 2021, 11:40:49 AM
Nice work!
Title: Re: Rocktron Rampage R80 - No Sound problem
Post by: paolone 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
Title: Re: Rocktron Rampage R80 - No Sound problem
Post by: dmeek 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.
Title: Re: Rocktron Rampage R80 - No Sound problem
Post by: phatt on January 30, 2021, 10:18:41 PM
Quote from: paolone 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

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.
Title: Re: Rocktron Rampage R80 - No Sound problem
Post by: paolone 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



Title: Re: Rocktron Rampage R80 - No Sound problem
Post by: dmeek 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.
Title: Re: Rocktron Rampage R80 - No Sound problem
Post by: paolone 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
Title: Re: Rocktron Rampage R80 - No Sound problem
Post by: paolone 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
Title: Re: Rocktron Rampage R80 - No Sound problem
Post by: dmeek on February 08, 2021, 04:43:51 PM
C6 and C7 are part of the compressor in the overdrive channel.

Title: Re: Rocktron Rampage R80 - No Sound problem
Post by: paolone on February 09, 2021, 03:53:21 PM
Hi



Today I have tested all the 7 pots
In the photo you can see the min and max impedance misured between pin A and B and between pin B and C.
Some pot don't increase the impedance even if you turning it up or down and some pot increase the impedance too low or not untill the max quote, turning it left or right.
Only 3 pots are OK.

I'm gonna change them.

Thanks

Paolo
Title: Re: Rocktron Rampage R80 - No Sound problem
Post by: phatt on February 10, 2021, 06:04:59 AM
If you are taking pot measurements while they are still in circuit you will get false readings as other parts are still connected.
You have to remove them from circuit to get accurate readings.
If pots don't make noise when turned then it's likely they are fine.
Phil.
Title: Re: Rocktron Rampage R80 - No Sound problem
Post by: dmeek on February 10, 2021, 01:24:49 PM
Sometimes the terminals get loose. Check them after they're removed from the board. If the terminals can be moved side-to-side at all, crimp them or just replace the pot.
I had a Vox amp a while ago where almost all the pots needed to be crimped
Title: Re: Rocktron Rampage R80 - No Sound problem
Post by: g1 on February 10, 2021, 02:17:27 PM
Quote from: dmeek on February 10, 2021, 01:24:49 PM
Sometimes the terminals get loose. Check them after they're removed from the board. If the terminals can be moved side-to-side at all, crimp them or just replace the pot.
What techniques/tools do you use for recrimping pot lugs?
Title: Re: Rocktron Rampage R80 - No Sound problem
Post by: dmeek on February 10, 2021, 02:38:40 PM
I posted this photo at mef a few years ago: https://music-electronics-forum.com/forum/amplification/guitar-amps/maintenance-troubleshooting-repair/44114-possible-to-repair-a-loose-potentiometer-leg/page2

I ground out these pliers to use for AC cord strain relief installing/removing. They work very well for that, so when I was looking for a crimper the tool was at hand. I have to be careful not to squeeze to hard. It can easily break the wafer.

Title: Re: Rocktron Rampage R80 - No Sound problem
Post by: willpirkle on February 10, 2021, 05:33:36 PM
dmeek — now *that* is awesome. I want one!
Title: Re: Rocktron Rampage R80 - No Sound problem
Post by: paolone on February 13, 2021, 07:06:02 AM
Hi
@dmeek
Today i'll buy an used oscilloscope (a kikusui 538a, yes old but still working...)
Can you tell me how and what i have to test in the amp?
What kind of input i have to use in the amp?

Thanks

Paolo
Title: Re: Rocktron Rampage R80 - No Sound problem
Post by: paolone on February 13, 2021, 03:27:37 PM
Ok

Now i have an oscilloscope:
Kikusui 538a

Here is the manual
https://manual.kikusui.co.jp/NUMERIC/538A_E.pdf

Title: Re: Rocktron Rampage R80 - No Sound problem
Post by: dmeek on February 13, 2021, 07:02:08 PM
You need a stable tone of some kind. There are many oscillator apps for phones and computers or you could use a keyboard organ sound, just tape one key down.
Plug the tone generator into the input and check its level with the scope. Set the vertical gain for about 1 division amplitude on the scope, then move the probe to
IC6 pin 1. the amplitude should be about 5 divisions. Turn the Clean Gain full up, move the probe to the center terminal of the gain pot. The level should be the same 5 div.
Move the probe to IC6 pin 7, should be more than 5 divisions amplitude.
Title: Re: Rocktron Rampage R80 - No Sound problem
Post by: paolone on February 14, 2021, 09:36:33 AM
Hi

I have download NCH Tone Generator (free for 5 hours, only for test the oscilloscope, now i have to find another software...)
https://www.nch.com.au/tonegen/index.html

I have gerated a tone "A" (musical note LA) in 599Hz
and i have connect the ground of the sonda to the ground of the sound cable (channel R) of the output of the computer and the positive of the sonda to the positive of the sound cable (channel R) of the output of the computer.

The software can produce sine, triangle, square wave.

I have posted the photo.

Now that I know that my oscilloscope is OK, i can test my amp.

Thanks

Paolo
Title: Re: Rocktron Rampage R80 - No Sound problem
Post by: paolone on February 14, 2021, 12:20:26 PM
Hi

Before to start the test i have change all the 10 "1uf 63v capacitors" in the board.

Let's start the test:
I have found another easy and free Tone generator directly in the Microsoft store: "PC Revue Tone Generator"
https://www.microsoft.com/en-us/p/tone-generator/9wzdncrdhjqn

I have generated a tone of 30Hz on the frequency of 500Hz. (Photo 2)
I have connected the left channel to the amp and i have started the 4 test that @dmeek  told me:
1- Plug the tone generator into the input and check its level with the scope. Set the vertical gain for about 1 division amplitude on the scope
    OK - Photo 3
2- then move the probe to IC6 pin 1. the amplitude should be about 5 divisions.
    For me is 4 Division, not 5... - Photo 4
3- Turn the Clean Gain full up, move the probe to the center terminal of the gain pot. The level should be the same 5 div.
     For me is always 4 Division, not 5... - Photo 5
4- Move the probe to IC6 pin 7, should be more than 5 divisions amplitude.
     For me is only 2 Division, not 5... - Photo 6

What can be?

Here is the datasheet of IC6, I think is that right JRC 072D:
https://www.mouser.com/datasheet/2/294/njr_njm072_njm072b_njm082_njm082b_e-547738.pdf

Thanks
Paolo

Title: Re: Rocktron Rampage R80 - No Sound problem
Post by: dmeek on February 14, 2021, 03:12:23 PM
If the overdrive channel is OK, the problem in the clean channel must be R44 100K, or Q4 2SK30A, or R41 10k
All ICs in your amp are dual op-amps like this

Title: Re: Rocktron Rampage R80 - No Sound problem
Post by: paolone on February 14, 2021, 03:46:03 PM
Thanks dmeek,

How can i test them, with the oscilloscope?

Or i have to desoldered them?

Thanks

Paolo
Title: Re: Rocktron Rampage R80 - No Sound problem
Post by: dmeek on February 14, 2021, 04:51:35 PM
Try the amplifier with Q4 removed. The clean channel will be always on even when switched to overdrive but you can see if there is a difference in gain.
You can measure the resistors after desoldering one end.
Title: Re: Rocktron Rampage R80 - No Sound problem
Post by: paolone on February 15, 2021, 02:07:54 AM
Hi dmeek

You say "...if the overdrive channel is OK..." but I haven't test it. I have tested only the clear channel with the oscilloscope, following your note.

Can you please explain me how i have to test with the oscilloscope the overdrive channel, as you have explained me how to test the clear channel?

Then i'll test the R44, Q4, R41 desoldering them

Thanks

Paolo
Title: Re: Rocktron Rampage R80 - No Sound problem
Post by: dmeek on February 15, 2021, 12:07:50 PM
If the overdrive channel sounds like it should with a guitar you don't need the check it with the oscilloscope.
Leave the amp switched to the clean channel and remove Q4. See if there is a difference with or without Q4
Title: Re: Rocktron Rampage R80 - No Sound problem
Post by: paolone on February 15, 2021, 03:42:42 PM
Hi

I have some time now so i have made the test with the oscilloscope without the Q4 transistor
1- check tone on the input jack and set to 1 division amplitude
    (Photo 2)
2- IC6 pin 1 must have 5 division amplitude
    Now is correct (Photo 3)
3- clear pot full up, check central pin, must have 5 division amplitude
    Now is correct (Photo 4)
4- IC6 pin7 must have more than 5 division amplitude
    NO - only 3, the same with or without Q4 (Photo 5)

5- photo 6 is the test 3 with overdrive mode on
6- photo 7 is the test 4 with overdrive mode on

What is the SVR1 of 100k in the Photo 8?

Thanks
Paolo

Title: Re: Rocktron Rampage R80 - No Sound problem
Post by: dmeek on February 15, 2021, 04:08:54 PM
SVR1 is to set FET bias for the compressor. Don't touch it. I don't know how to set it.

I guess Q4 is not the problem. I'm running out of ideas. Are you sure there is something wrong with this amp? It's normal for the overdrive channel to be louder.
Title: Re: Rocktron Rampage R80 - No Sound problem
Post by: paolone on February 15, 2021, 04:15:38 PM
Hi

I have played a little now without the Q4 but is the same than with Q4...
I have resoldered the Q4. Nothing has changed. 
The problem is not that the clear mode is lower than overdrive...
The problem is that the clear mode of a 80watt amp at max master volume plays lower than a Fender mustang 2 amp that is a 40watt amp, set to half master volume pot...
This is the real problem... I have an 80watt amp that sounds like a 20watt amp...

IMPORTANT:
I have forgot to tell you that sometimes before start this tests and also this night, the overdrive starts by itself and the red light switches on while i am using the clear mode. Then it switches off.

When the reverb is more than half pot you can hear a noise that disappears under half pot
Title: Re: Rocktron Rampage R80 - No Sound problem
Post by: phatt on February 15, 2021, 10:44:45 PM

The 40 Watt Fender might have a High SPL speaker while the Rockton maybe much lower.

This is measured in SPL (Sound Pressure Level)
So a speaker that is rated at 102 Db SPL will be twice as loud as one that claims 98 db SPL.
All these things can be very confusing as there is no straight line in these numbers,, i.e. 1+1 =5  :duh
A lot of electronic equations are log curves.
Just like Earthquakes where an 8.2 on the richter scale is x10 more powerful than a 7.5

Maybe connect the Fender speaker to the rockton and hear if there is much difference?

Number 3/
The Rockton circuit may not have the same preamp gain and so is not as loud. Also the Input sensitivity of the power amp section may not be as high as the Fender power stage.
Number4/
        The power supply voltages may be higher in the fender which will give it more output power.


It's likely the Rockton is ok except for the switching,
Re switching Amps in general;

Keep this in mind when buying multi channel amps.
I've repaired quite a few amps over the years and I can tell you this,,, more often than not the Audio path is actually working fine,, it's the switching crap that breaks. 8|
Phil.
Title: Re: Rocktron Rampage R80 - No Sound problem
Post by: paolone on February 16, 2021, 03:11:05 AM
Ok thanks
Fortunately i have paid this amp quite nothing...

To fix the autoswitch on overdrive channel what i can do, please?
Which component do i have to control?

To lower the noise on reverb mode what can i do please?

@phatt Here is the spec of Rocktron R80:
https://www.manualsdir.com/manuals/get?doc=741170&h=ab70cfc2039ffb26499851bd19caf4f5daec0c23&open=1
Title: Re: Rocktron Rampage R80 - No Sound problem
Post by: phatt on February 17, 2021, 12:25:48 AM
Hi Paolone,

Sadly without a schematic of the switching setup it's impossible to tell what is wrong.

I should ask,
If the channel switch changes as per normal and it's only the led not lighting then maybe leave it.
Some amps have a front panel channel switch as well as a foot switch, so be aware that the pedal might be causing faults.

So Q.  With pedal disconnected, Does the channel switch work normally?

IF not,, then the front panel Switch maybe faulty.
Some of those push button switches are prone to not making proper contact due to the poor cheap design.
Many times I have replaced Push switches with Toggle switches which are less prone to poor contact.
Either way as I mentioned those switching circuits are often the first thing to fail.

Regards to Reverb adding noise to the signal.
If you have checked that all the RCA leads are making good connection then you have a well know problem of poor design. The biggest issue is the DRIVE circuit is poorly designed and does not have enough Drive to excite the Springs. So to compensate they turn up the Pickup circuit gain which makes the reverb PU very prone to picking up any stray hum from the mains.

Also Check how close the PU end of the tank is to the mains transformer. Some times just by repositioning the tank to keep the PU end away from mains can help reduce the noise.

Re the Rockton Manual;
Look at the last page, it states 80 Watts.
Sadly without stating what load that amp is driving it's meaningless number.
Could mean 80watts of bananas :duh

Here is a rule of thumb for power.
it's likely that 80Watts is based on a 4 Ohm load which is 40Watts into 8 Ohm
and 20Watts into 16 Ohm.

When looking for Meaningful specs for wattage look for something like this;
     *80Watts RMS into 8 Ohms*

Remember the power output the circuit is capable of producing is governed by the Power supply NOT how many watts the transistors are capable of producing.
Phil.
Title: Re: Rocktron Rampage R80 - No Sound problem
Post by: paolone on February 17, 2021, 10:15:00 PM
Thanks to dmeek and phatt for all your help

@phatt
When the amp has the drive mode selected, it works fine, I cannot go over 1/2 master pot and over 1/2 drive pot or there is too much volume.
When the amp has the drive mode deselected (clear mode on), it works bad, sometimes it switch by itself on drive mode for 1 or two seconds and the re-switch by itself on clear mode. There is NO footswitch inserted.
But the real problem is not the auto switch, is that if you're playing in clear mode, you have to set full up the master pot and the clear pot to hear quite well and if you switch on drive mode you have to reset to half master pot or less... it's quite impossible while you're playing...

@dmeek
I have re-check with the oscilloscope the amplitude on IC6 pin 1. With Q4 is 4 division, without Q4 there is 5 division (right division, as you shows = 5).
On the center pin of clear pot with Q4 there is 4 division, without Q4 there is 5 division (right division = 5).
On IC6 pin 7 with a Q4 there is 2 division, without Q4 there is 3 division (right division = 5)

Conclusion:
- With Q4 there is a loss of 1 division, maybe there is a bad component between the Q4 and ground.
- the amplitude on IC6 pin 7 is still under the right division, maybe there is a bad component between the clear pot and the circle circuit of IC6 between pin 7 and pin 6.

Questions:
- How does it work IC6? There is pin 5 on ground and pin 6 from center pin of clear pot. The other circuit of IC6 pin 1 don't have any pin 2 - 3 on ground... From the datasheet of IC6 https://www.mouser.com/datasheet/2/294/njr_njm072_njm072b_njm082_njm082b_e-547738.pdf i can see that the pin 6 is the negative input and pin 5 is positive input...

- dmeek can you please deepen the wiring schema of this point of the circuit (the clear pot and the circle circuit of IC6 between pin 7 and pin 6) to expose all the components, so i can test them one by one with the oscilloscope or with the multimeter after desoldering them, to find where the right amplitude decreases? I have try to do it but i find some different from yours... maybe my is wrong...


Thanks for all your help

Paolo
Title: Re: Rocktron Rampage R80 - No Sound problem
Post by: paolone on February 21, 2021, 04:17:06 PM
Hi
While i was testing the amp, in the clear mode it start to schratch.
I've put a registration here.
https://s105.123apps.com/aextractor/d/s105mmRrQsfE_mov_9pT25cro.mp3

Dmeek i think there is something other to find... can you help me?

Some other test with the oscilloscope?

The scratch noise i think is a cap broken... right?

Paolo