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Messages - paolone

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1
Amplifier Discussion / Re: Rocktron Rampage R80 - No Sound problem
« 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

2
Amplifier Discussion / Re: Rocktron Rampage R80 - No Sound problem
« 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

3
Amplifier Discussion / Re: Rocktron Rampage R80 - No Sound problem
« 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

4
Amplifier Discussion / Re: Rocktron Rampage R80 - No Sound problem
« 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

5
Amplifier Discussion / Re: Rocktron Rampage R80 - No Sound problem
« 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


6
Amplifier Discussion / Re: Rocktron Rampage R80 - No Sound problem
« 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

7
Amplifier Discussion / Re: Rocktron Rampage R80 - No Sound problem
« 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

8
Amplifier Discussion / Re: Rocktron Rampage R80 - No Sound problem
« 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


9
Amplifier Discussion / Re: Rocktron Rampage R80 - No Sound problem
« 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

10
Amplifier Discussion / Re: Rocktron Rampage R80 - No Sound problem
« 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


11
Amplifier Discussion / Re: Rocktron Rampage R80 - No Sound problem
« 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

12
Amplifier Discussion / Re: Rocktron Rampage R80 - No Sound problem
« 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

13
Amplifier Discussion / Re: Rocktron Rampage R80 - No Sound problem
« 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

14
Amplifier Discussion / Re: Rocktron Rampage R80 - No Sound problem
« 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

15
Amplifier Discussion / Re: Rocktron Rampage R80 - No Sound problem
« 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




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