Gain from one channel is spilling over to another? :(

[Bonez]

Ok ive got this stupid problem with my rhythm channel where i hear my nice clean sound but faintly in the background i hear distortion, like tow guitars playing one clean one distorted.

but today i tryed somthing out.

the lead channel gain is spilling over into the rhythm channel, if i turn down the gain on lead channel to zero the distorsion that was in the background of the rhythm channel goes away and i have a nice clean sound for once.

any idears and to whats stuffed in my amp?

other post with images that went nowhere untill today when i found out the cause of it
http://forum.grailtone.com/viewtopic.php?t=29448&start=0&postdays=0&postorder=asc&highlight=

 

[tetsubin]

Time to take it to a tech. Bring the original schematic and he'll easily be able to undo the mods.

 

[Monsta-Tone]

Yeah, it needs a doctor visit.

I don't think anyone can help on the board because the amp has been modded. It's hard to say what the guy did without tracing the circuit out.

Ordinarily, I would say that the LDR's are not switching off completely. I had this happen to me on a DC-3. But, it is possible that the modder did something that is causing a little bleed through.


Is there a good Mesa guy in your area?

 

[Bonez]

Do'h yeah i think you's are right, didnt sound like a simple fix i just know a tech is gonna take me to the cleaners and charge me heaps hehe , thanks for help though guys.

 

[Restless Rocks]

Tech Bench Charge:

$40.00 per hour

If you have advice for the tech:
$50.00 per hour

If you want to watch:
$75.00 per hour

If you tried to fix it yourself: (If you used fuse from under dash of your car: new fuse $50.00)
$100.00 per hour

If you think speaker attenuators and variacs are the greatest thing since you discovered getting high on catnip:
$125.00

If your freind tried to fix it:
$150.00 per hour

If you or your freind tried to Mod the circuit:
$200.00 per hour

And we deserve every penny.

 

[Monsta-Tone]

:lol: :lol: :lol:

I charge $40 an hour too. If you can't find a good guy in your area, you are welcome to ship the chassis to me.


I have owned 10 DC's and currently own 4. It's safe to say that I can navigate them fairly well.


While it is in the shop, it would be a good idea to have the filter caps and bias caps changed. This is a great preventative measure and will insure that your amp's power supply will function properly for many years to come.

 

[trey85stang]

Yeah, it needs a doctor visit.

I don't think anyone can help on the board because the amp has been modded. It's hard to say what the guy did without tracing the circuit out.

Ordinarily, I would say that the LDR's are not switching off completely. I had this happen to me on a DC-3. But, it is possible that the modder did something that is causing a little bleed through.


Is there a good Mesa guy in your area?

Id still say an ldr problem and start with testing them, I dont know much about the mesa in general but ldr's never completely turn off and depending on the mod it could be pushing more voltage through one side of the ldr causing a leak.

 

[Bonez]

i live in australia and there is no mesa guy in my area or this country lol gonna take it to my local tech and get a estimate.

About the caps do ya need to replace them with original mesa's if theres such a thing or just normal caps?

 

[Monsta-Tone]

Any decent quality electrolytic will do, but make sure that the voltages are matched. For instance, 220 mf @ 300 v. You can always go up in voltage rating, but never down.

Sometimes the larger voltage ones are physically larger too, so you have to watch for that.

I usually just use caps from Mesa. This way, I know I'm getting quality, and my customers love that it still looks factory fresh under the hood.

They are glued down with silicone, so your tech will have to gently pry the old ones out. I usually use a mild clear silicone to hold the new ones in place and eliminate vibrations caused by large loose parts.



Like I said, make sure he replaces the Bias capacitors too. I failed to do this on a cap job when I 1st started working on amps. Less than a month later, I had an angry customer because his prized '68 Marshall Plexi had develloped another hum.


Also, if one LDR needs replacing, I will almost always replace them all just for good measure.

Hope this helps.

 

[Bonez]

(UPDATE)

MY tech says he dosnt think is even has ldr's and its sounding like thats a normal thing for my amp to do because its got so much gain :twisted: yeah right lol to have a two channel head but only be able to switch between them if your close enough to turn down the gain on the other channel quick enough during a gig lol ooook!

 

[Monsta-Tone]

:lol: That guy doesn't sound like he should be changing your strings. :lol:


You should call Mesa and see if there is a guy in your country. I'm not listed on their website because there is not enough warranty work in my area. In fact, I probably own 30% of all the Mesa's in my area. :lol:


I bet there is a guy in Aus. that has the same problem and is just looking for a good Mesa project.

 

[hugsy41]

i live in australia and there is no mesa guy in my area or this country lol gonna take it to my local tech and get a estimate.

Whereabouts are you? I live in Sydney, and there is a Mesa qualified tech in Canberra that works on site for 'Pro Audio'. He saw to my DC-5 back in March. 'Pro Audio' are the distributors for Mesa in Australia, so it's only fitting they have a qualified technician on site. I'm sure he could fix this easy.

chris.

 

[Monsta-Tone]

:lol: :roll: :lol: He doesn't think it has LDR's! :lol: :roll: :lol:


Sounds like a call to Pro Audio is in order!

 

[trey85stang]

for sure, find someone else to work on it.

 

[Bonez]

cool i told him to call 'Pro Audio' and they told him the Go about the amp, so now even he thinks there is a problem, aparently he didnt even open it to cheak :shock: im in victoria and this place is the only place near me that will touch a mesa. so now that hes gonna have a good look at it it might get fixed.

 

[Monsta-Tone]

I wouldn't let him touch my amp if I were you. A good tech would have listened to you in the 1st place. An arrogant tech would have told you exactly what he said. This sounds like the kind of idiot that will "Bench Test" it for you instead of giving it a run for it's money.

 

[Bonez]

GOOD NEWS! for me atlest its fixed 8)

bad news! i will no longer be using my local and only tech in my area, the #%^$ only replaced 1 of the 3 ldr's in my amp saying "it could only be that ldr that could possibly be the culprit if infact it wasnt what that model was spost to do" :shock: lol

well $200 later and my amp exactly the same as when i gave it to them, i went along with all of your answers still thinking it was infact an ldr problem i set about to replace the one ldr right next to the other he replaced, i mean 1mm next to lol and it fixed my problem what a knob! lol

+ almost killed myself learning how to discharge them caps!

oh well all good now, thanks guys you saved me almost throwing the thing out my window. 8)