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January 20, 2021, 10:48:45 AM

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21
Amplifier Discussion / Re: Rocktron Rampage R80 - No Sound problem
« Last 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.

22
Amplifier Discussion / Re: Rocktron Rampage R80 - No Sound problem
« Last 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
23
Amplifier Discussion / Re: Rocktron Rampage R80 - No Sound problem
« Last 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
24
Amplifier Discussion / Re: Rocktron Rampage R80 - No Sound problem
« Last 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.
25
Amplifier Discussion / Re: Rocktron Rampage R80 - No Sound problem
« Last 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
26
Amplifier Discussion / Rocktron Rampage R80 - No Sound problem
« Last 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
27
Amplifier Discussion / Power supply/ power amp question
« Last post by NPreston on January 16, 2021, 09:42:00 AM »
Hi.  I am attempting to build an amp and learning as I go.  So I have built a simple power supply using a Hammond 166m72 transformer which is spec’d with output 72ct which I understand as 36-0-36 at full load..(correct me if I’m wrong). Anyways the supply after filtering with no load is 53-0-53.  Question is when designing the power amp to determine power dissipation of various parts do I use +/-53v in my calculations??  Not sure how much loading to expect once I actually hook something up and apply signals and loads. 
Thanks!
28
Tubes and Hybrids / Re: Help with Hybrid Design
« Last post by SerpentRuss on January 14, 2021, 05:17:43 PM »
Well, my project is currently a bust.   I finished soldering everything together (without breadboarding, LOL)  and it didn't work.  When I was trying to diagnose the issue, I shorted out one of the LND150s.  I have spares, but I'm going to start over and build the circuit between terminals so I can follow the signal path

I tested by using my phone with a guitar tuner app.  It was supplying 196 hz at 45 mV which I scoped before I connected it.  When the amp was turned on, it produced a 6k tone whether the input was connected or not.  The volume knob seemed to work making the squeal louder and softer.

The heater Voltage was dead on 6.3 volts AC with the tube up to temp.  B+ was a scant 123 Volts DC.  I could not find my test signal anywhere in the circuit, starting at the input jack.  It was being sucked away by some soldering or component mistake.   DC power was clean and steady, but as stated, lower than I expected.  I didn't troubleshoot long before I let the smoke out so I didn't learn much other than the output was quiet as a tomb after I killed the MOSFET.  :lmao: :trouble

29
Amplifier Discussion / Re: Coxx GG-30 with low volume issue
« Last post by joecool85 on January 14, 2021, 08:36:35 AM »
SOLVED!

Sorry for long time without update. I received the LM1875 today, I changed it and the problem was still there   :grr
I decided to remove the surrounding capacitors and measure them one by one. It turns out that C12 was damaged, but not in short so I didn't detect it before. It measured some kohm in resistance and 0,5 uF instead of 4,7 uF. That damned capacitor drove me crazy.
Anyways, I changed it and the amplifier is now loud again.

I would like to thank a lot everyone that helped me, in particular dmeek that made a lot of work with reverse engineering.  :tu: Without the shematics I would have been lost. I hope that these posts will help people with the same amplifer.

Good job!
30
The Newcomer's Forum / Re: Soldering Iron Tips
« Last post by joecool85 on January 14, 2021, 08:15:14 AM »
The Weller tips I use cost more than your iron did!  Not sure what to recommend that would be inline with your budget.
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