Can this amp be fixed?

[Mick Bailey]

the last one of those I had with similar problems turned out to be a bad master volume control, it had some mechanical slop in it that rarely showed up, but when it did. nothing. I replaced the MV and it's been fine ever since. so, know that a tleast one blackstar had a defective MV pot.

Just done a HT Club 40 with these symptoms and replaced the pot. Fixed. Not a very old amp either. The track had started to break up and would sometimes cut out then work for weeks.

[shaggyrun]

Is there an easy way to check the master volume pot. Of its it just replace it and see if it persist?

[km6xz]

First off, forget specific solutions others had for problems, they will usually get you fixated on one imagined solution.
Start over again. Isolate any variable that could have an impact and clearing determine the symptoms. A clearly defined set of symptoms will often be 80% of a diagnosis.
You say it goes dead but that is not clear to any tech what that means. The lights go off? Sound stops(no hiss or any noise at all with ear up to the speaker), Signal stops( hiss when turned up but no input signal reaches the speaker?

Has it ever happened with other instruments, other effects/no effects, with different external speaker, in other venues and power/heat conditions.
The amp is fairly complex with a microprocessor, several cable connectors and potential points of failure. If you focus on suggestions for fixes instead of conditions where the problem occurs, and what exactly are the symptoms you might waste a lot of time and money throwing parts and labor at it.
I can understand a rush fee but not a repair charge unless a repair is completed. Did he say he found some reproducible cause and repaired that, or did he say he just did not get the problem to occur again?
As with any repair, the odds of a successful reasonably priced repair is being a good customer....identify what the symptoms really are, hints of how you reproduced it and under what conditions. The sure way to become frustrated is to just drop it off and say "just check it out". If there is any special use setting that is present when the problem occurs, be sure to describe it, that can make the difference in him seeing the problem on the bench or not.

Combos lead a hard life, like living on a shaker table and seldom last as long as the same chassis configured as a head. EVERYTHING suffers from vibration, especially tubes, heavier lead mounted parts and connectors.
Since there is a good chance that that complex signal change in the loop is the cause, be sure to take all your effects, cords interconnetions and power supplies for them.
One question, why have an expensive amp that has a characteristic tone when you crush that tone with a dozen time and amplitude distorting stages. You could do just as well with a cheap, reliable solid state power amp if you are feeding it such altered signals to start with. The audience would appreciate it more since it would not be cutting out and it makes no difference to the sound in the audience.

So give your tech a fighting chance, list the specific symptoms and do not use vague phrases like "is dead" unless it really is dead, no power, no lights, no current consumed, dead cold. Set it up for him in his shop just the way you feed the effects. There is a good chance it is not in the amp at all since he went through that but not the other many connections in your setup.

[Enzo]

Give your tech a chance to get it. It is darn hard to fix something when it is not acting up in front of you. it is easy to say "Oh I'll just resolder the whole thing." But that assumes solder is the issue. You could have a cap with a failing lead connection inside the part. or a resistor.

And you have a bunch of external stuff in your system while playing. Those things may be involved.

[shaggyrun]

Well the amp is back with my tech, and he is going to look it over again, he told me he may have it a while cause he cant detect the problem with out it acting up. He told me if he cant find it by next tuesday then he will get me to bring up my effects pedals and my amp foot controller. And then he would get me to set it up like I use it on stage. I do think I have a good tech he was a master tech for marshall and korg for ove 20 years, so he seems to know what he is doing. Before I left he had already taken the chassis out and was setting up his oscilloscope. When and if he finds the problem I will let you all know.

[Chuck H]

What Stan said!

If you paid attention and have any details about the failure your tech needs to know those specifics.

[Gtr_tech]

These have a really screwey SS drive to the output section. Tell yer tech to pay special attn to that and its supply rails. Loss of/weak signal there and it will sputter out and die.

[Gtr_tech]

These have a really screwey SS drive to the output section. Tell yer tech to pay special attn to that and its supply rails. Loss of/weak signal there and it will sputter out and die.

[shaggyrun]

ok just thought I would post an update, my tech has had the amp for over two weeks now and he has been running it 6 to 8 hours a day and the amp has not failed yet. he asked if I had my receipt I told him yes and faxed it to him. he contacted Korg and found out my amp is still under warranty, so he has gotten with them to see if they will replace the amp. He told me even though he cant get it to fail he knows it has a problem because occasionally it will hiss and pop then it clears up and keeps working on. I will take a new amp no problem but I kind of wish he could have fixed my amp after a year of playing the speakers were starting to loosen up and they were getting a looser sound to them. oh well just glad he checked on the warranty for me, cause when bought the amp the music store told me it was only a 1 year warranty on it, but they were wrong.

[Chuck H]

If Blackstar will replace the amp they might be happy to send just a working chassis. Mesa did that for me once on an amp that I bought used!!! They're reasoning was that they had enough problems with that model that they didn't want the bad rep. I'm sure Blackstar wouldn't mind subtracting the expense of the cabinet and speaker. Not to mention the added shipping weight and bulk.

[RockinJay]

In a case like this, it may be wise to just re-solder the entire amp.
Thermal intermittent solder connections do not always show themselves as being visible or obvious.
It actually saves time just to re-solder it. Rather than hunting for "1" bad connection....
at least that's what has proven true.

Jacks also fail, because they contain switches, which become oxidized. When the switch fails to close, the amp stops working.
Jacks will also cause a problem like this, and frequently...

So, I take a more aggressive approach, rather than "waiting" for the failure to occur, I try to MAKE it fail.
I knock on it, heat it cool it, run it to full temperature, flex the board, pull on the wires, and abuse it in any way possible to MAKE it fail.

Then after I fix it, I try to make it fail again and again, to make SURE it keeps working.

Although this may seem UN-conventional, the approach has worked better that 99% of the time, in ALL intermittent failures.....

HI, I'm new to this forum and found this post when searching for a schematic with the GOOG, for a Rouge amp. I'm an experienced engineer and repair technician for many years.

I couldn't find a schematic (even on this forum where somebody above acknowledged seeing a schematic [with no download link] )

The SoundGuru has very valid points and I'd like to add some value to what he is telling you guys. {I fixed the distortion problem I was having}

Audio equipment is constructed with single sided circuit boards. The boards are put through a wave solder machine and sometimes it seems as if the boards are NEVER inspected before they are mounted into the chassis. MOST FAILURES ARE DUE TO COLD SOLDER JOINTS.

He's absolutely right when he tells you guys that you probably can fix it with a soldering iron, without a schematic, or even an ohm meter.

As I attacked the amplifier board with my iron, it was immediately obvious that the 2 amplifier transistors mounted to the large heat-sink had bad connections. Out of the 6 legs of the 2 power transistors, 5 solder joints had come undone. I could wiggle the 2 power amp transistors and see they were flopping in the breeze. NO WONDER WHY THE AMP WAS DISTORTING, CONNECTIONS WERE BAD.

We can spend years learning electronics, but audio equipment - most of the time - can be fixed by an armature with a soldering iron.

[olddawg]

HI, I'm new to this forum and found this post when searching for a schematic with the GOOG, for a Rouge amp. I'm an experienced engineer and repair technician for many years.

I couldn't find a schematic (even on this forum where somebody above acknowledged seeing a schematic [with no download link] )

The SoundGuru has very valid points and I'd like to add some value to what he is telling you guys. {I fixed the distortion problem I was having}

Audio equipment is constructed with single sided circuit boards. The boards are put through a wave solder machine and sometimes it seems as if the boards are NEVER inspected before they are mounted into the chassis. MOST FAILURES ARE DUE TO COLD SOLDER JOINTS.

He's absolutely right when he tells you guys that you probably can fix it with a soldering iron, without a schematic, or even an ohm meter.

As I attacked the amplifier board with my iron, it was immediately obvious that the 2 amplifier transistors mounted to the large heat-sink had bad connections. Out of the 6 legs of the 2 power transistors, 5 solder joints had come undone. I could wiggle the 2 power amp transistors and see they were flopping in the breeze. NO WONDER WHY THE AMP WAS DISTORTING, CONNECTIONS WERE BAD.

We can spend years learning electronics, but audio equipment - most of the time - can be fixed by an armature with a soldering iron.

Yep ... The old "re-solder the everything" approach sometimes works with intermittent problems. But there is a plethora of things that cause intermitances. My favorite is a component that is internally intermitance under certain conditions. There are techs that live by the resolder the everything approach and use gallons of freeze. Personally, with 30 years bench experience, I would much rather trouble shoot the problem than cross my fingers and hope I got it..... But sometimes that's all you can do in a timely manner.

[Jazz P Bass]

If it looks like a duck & quacks like a duck, it's a duck.

The first place the board builders cut a corner is the 'preheat time' of the wave solder machine.

Oh, the board will work.
But it will not last.

And this is by no means limited to 'audio equipment'.
By the way, some manufacturers do use double sided boards.

[Mick Bailey]

The boards are put through a wave solder machine and sometimes it seems as if the boards are NEVER inspected before they are mounted into the chassis.

Well, in the main they aren't inspected. How long would it take on a production line to inspect each board thoroughly? They go through ATE and if they pass they get assembled. No one looks at them. But ATE isn't a quality-assurance process and a badly-soldered board can still pass. I've had plenty of Blackstar amps where components can easily be pulled right off the boards - particulalry the wirewound resistors.

I had some amp modules recently (from another manufacturer) where one of the electrolytics had been inserted backwards in each unit. Brand new, direct from the manufacturer. When I spoke to their engineers it turns out their ATE tests at millivolts and a reversed cap could pass.

Many audio boards are actually double-sided and poor thermal control means that the solder doesn't flow around or through the plated holes. The problem is worsened by lead-free solder. To further compound problems you get many hybrid boards that are a mixture of through-hole and SMD components, and when these are badly manufactured it can be really hard to spot the problems.

I disagree that most of the time a repair on audio equipment can be done without any knowledge. Try repairing a class D amp or SMPS and you'll quickly find that approach doesn't work.

[pdf64]

I couldn't find a schematic (even on this forum where somebody above acknowledged seeing a schematic [with no download link] )
...
We can spend years learning electronics, but audio equipment - most of the time - can be fixed by an armature with a soldering iron.

There were software problems with the forum a while ago and message attachments were lost, so the response may have been valid at the time, but the file is no longer available.

I'll have to look into this armature method!