Triple Rectifier 2 channels

[etrium]

Hello to all of you!
I am Giuseppe and I write from Italy...I got a mesa boogie triple rectifier head 2 channels model...I changed the old transformer (an artigianal one that produced near 100 watts instead of 150 )with a new one that produces all the 150W, but there is a hum problem that was there even before but that I think now is accentuated by the more power...so I had a look at the inside of the head and by comparing it with the inside of a dual 2 channels ( I found some pics on web) and with the schematics of the dual 2 channels I noticed some strange things in my head...I searched for the schematics of the triple but I can't find.
Now I'd like to ask to the owners of a head like mine a great help...could you post some pics of the inside of the head so I can compare with mine?It would be great to have some pics from a european 2 channels triple rectifier with no mods.
Thanks a lot!

 

[YellowJacket]

How old is this amp?
Have you checked all the tubes?
If the tubes checked out fine, have you checked out the filter capacitors?

 

[etrium]

The amp is from early 2000 and yes I also changed all the tubes (both pre and power tubes)
Are the filter capacitors the 2 on the power supply board? if yes, I checked them and are ok.

 

[cradlefish]

what are you looking for or comparing from the inside of the triple rect?

 

[etrium]

I think there could be some missing or wrong things on my main board so I'd like like to see another head like mine to correct them

 

[boss4]

I think tremoverb94 is the guy that can help you (about knowledge and fiding the problem, about the pictures I dont know)!

 

[etrium]

These are the pics of the main board of my triple 2 channels

I temporally removed C91 cap(2200microfarad 25V) , the black wire that comes from the power supply board and goes to the main board where there is written BK near C91 (do you know what is this wire for?) the brown 12V wire that should be connected to D9(the diode near R503) and a silver bare wire (visible in the pic)that goes from where the black wire is connected to the chassis.

Looking to this pic

that is from "How to install a bias pot in a Rectifier" mikey383 topic
I noticed that this triple 2 channels misses R332 resistor that instead is present in my head...I think that this resistor was added on my head when it came in Europe (my head is an american one with a 220V transformer), because the european version of this head needs this resistor...am I right?
I'm saying this because I saw this in the dual 2 channels schematics, where I also noticed, if I understood well, that in european model R282 ( a 82K) should be removed, while is present in my head., but I don't know if these things are for both dual and triple.

As I said before there is a hum problem on my head so I woukld like to ask you firstly if you notice something wrong on the main board or if it's all as it should be and then what could be the problem.
Thanks

 

[msi]

The PCB's and components of the triple and dual rectifiers are identical. The only difference is the addition of the two power tubes and the single rectifier tube. Everything else is the same. I have both and I promise that. So find the pictures that focus on the areas you have questions with and compare those. If you can't find them specify which section and I'll see what I can provide. I have a triple rectifier with the revision g board. It's a us version so I can't help you with a 220v transformer.

 

[skoora]

Does the hum get louder with volume like a ground/tube issue or could it be more mechanical like some tranny's hum but you can only hear it when playing very quiet or when you're not playing.

 

[etrium]

it gets louder with volume, at low volume is louder than what I'm playing, it desappears by removing the 5th preamp tube, if I put a noise gate in send return the hum is still there...

 

[94Tremoverb]

(Got your PM)

I'm not quite familiar enough with troubleshooting these amps to give you a definite answer, but if the hum goes away when you turn down the Loop Active Master or pull the 5th preamp tube (phase inverter), the problem is most likely in the preamp HT supply, particularly the filter cap stage that feeds the phase inverter. It *is* possible it's a power stage issue getting back into the phase inverter via the negative feedback loop, but if the problem occurs in Modern mode on the Red channel, it isn't this because that mode disconnects the feedback loop.

For Europe, R332 should be fitted and R282 removed. These alter the bias to compensate for the different voltage produced by 50Hz vs 60Hz - 60Hz is slightly more efficient through a half-wave rectifier, so the bias needs to be reduced slightly in the US, whereas it needs to be raised in Europe. If your amp has the US resistor set, it will be biased a bit too hot, and may hum as a result - but I would not expect that to be affected by the LAM setting, although it might be in other than Modern mode.

C91 is part of the filtering for the LDR switching supply, put it back!

 

[etrium]

thanks a lot for your kind answer...
the hum is really big only in modern mode on red channel

 

[etrium]

and the hum is there even with all knobs to zero just going from stanby to on

 

[94Tremoverb]

*Only* in modern mode is likely to mean it's the phase inverter filtering, because the phase inverter is inside the negative feedback loop which is turned off in Modern mode - the feedback loop reduces the effective gain from the PI and power stage.

But, get the bias right first because it could just possibly be an effect related to that, if the hum is being suppressed to an extent when the feedback loop is engaged. (Yes, I know this is something like the opposite what I said earlier! I thought about it some more .) It's important to fix the bias just from a tube life point of view anyway.

 

[etrium]

Can somone of you post a pic of a triple 2 channels like this that shows from the power supply to the main board?(I mean something like this)

please help me...as you can see from the pic there are some problems in this part.
For example I think that the main ground on my head is in a different place from where it should be but I don't know where.
(My head is an american triple 2 channels Rev G from 1998 with a new transformer to use it in Italy).

 

[boss4]

I'm no tech, but that sh!t doesn't look right...

 

[etrium]

could u tell me what's wrong?

 

[boss4]

Like I've said before I'm no tech, but somehow... it seems like an homemade job, not very professional. But it just appears so, there's many specialized people here in the forum that can help you. Good luck!

 

[etrium]

Ok thanks...so I hope someone will help me

 

[mikey383]

I'm no tech, but that sh!t doesn't look right...

Yeah, the melted part of the power supply board is what tipped me off. :?

This is a perfect example of why you shouldn't go messing with you amp unless you know exactly what you're doing.

Since it's obvious that you have now fried the amp, I suggest you stop what you're doing right now before you totally wreck it, if it's not already. Take it to a tech or someone who knows who they're doing.