Swiched to class A opration, and the problems started

[cremona]

hi there

I tryed putting my new c+ in class A operation while in clean channel, the differece was there, and sounded great , but when i looked at the back of the amp the two outer tubes where now glowing purple blue.

I thourght okay, sound is still good no problems , but when i put it back in simul class , the blue light remained, that was not the case before, before the all had the yellow glove.

here is have it behaves When i flick it out of standby, al tubes give a blue glimps, but only for a sec , then the two outer tubes glow blue and the two in the middel are yellow , but now with a faint blue colure in the middel of the glass.

When i put in in lead channel i could hear the sound had changed, changed to the worse, not catastrofic but worse none the less.

What could the probme be ?

BTW When i got my old c+ , it also started to make the tubes turn blue, and sortly after that the died, the fix was new tubes sockets, and it never did it again.

The tubes are all sylvania 415 str, and are not exactly cheap, so i wanna saurght this out quick

One more problem, the EQ swich only works in clean channel, but is has been like that ever since i got it

I will take it to the doctor soon, but i might as weel get some tips here first

Thanks

 

[MrMarkIII]

Normal. Don't worry, be happy.

 

[JOEY B.]

One more problem, the EQ swich only works in clean channel, but is has been like that ever since i got it

I will take it to the doctor soon, but i might as weel get some tips here first

Thanks

There were two different switches used for the EQ, if I remember correctly. Is it a 3 position switch? Are you saying that you can't cut the EQ off in the lead channel?

From the C+ guide:

"The early “Pull Deep” plates had a dark gray EQ face and the EQ toggle order is –

Top – Auto
Middle – Out
Bottom – In

The Later Plates had light gray EQ face, which scratched much easier. The change in toggle order is probably by customer request or a change in the availability of the switch.

The EQ toggle order is –

Top- Auto
Middle - In
Bottom – Out

"

The faceplate has a 3 position switch that is only labeled as a 2 position. Someone may have put in the wrong switch during the last 26 years.

Don't worry about the "blue haze" in the power tubes. It's that "lightning in a bottle" that will get you.

 

[cremona]

One more problem, the EQ swich only works in clean channel, but is has been like that ever since i got it

I will take it to the doctor soon, but i might as weel get some tips here first

Thanks

There were two different switches used for the EQ, if I remember correctly. Is it a 3 position switch? Are you saying that you can't cut the EQ off in the lead channel?

From the C+ guide:

"The early “Pull Deep” plates had a dark gray EQ face and the EQ toggle order is

Top – Auto

Middle – Out
Bottom – In

The Later Plates had light gray EQ face, which scratched much easier. The change in toggle order is probably by customer request or a change in the availability of the switch.

The EQ toggle order is –

Top- Auto
Middle - In
Bottom – Out

"

The faceplate has a 3 position switch that is only labeled as a 2 position. Someone may have put in the wrong switch during the last 26 years.

Don't worry about the "blue haze" in the power tubes. It's that "lightning in a bottle" that will get you.

Hi Joey

I tried swapping the tubes, so the outer ones are now in the middel, that removed the blue glow, the sound is still a bit different.
Also one thing i noticed yestoday, was that about 3/5 sec after i have turned the amp of the was a strange fading noise ,like biiiibeeeeeob.
Is the outer tubes going bad ?

The face plate has the same colure as the mark III`s (luckely mine only have some minor scratches

The EQ is always on in the Lead channel, nothing happens when i flick it

The seller stated in the ad , that just prior to the sell , he had it by a guitar tech shop because the eq swich was going bad, so it was replaced, and the tech did a pretty horrible job replacing it, because the swich is smaller[shorter] and the thread sticks out of the faceplate ,plus it only has two possitions. this one of the things i want to change so it looks stock again, and works

So that proberly explains why the eq dossnet behave like i should.

Thats why i wanna take it to the mesa service center here in denmark , because i wanna turn it back to have it was from the factory back in 85 and hopefully the can orderd the right swich from straight from boogie.?

The can also measure the tubes and see if the work as the should

BTW The other eq swiches on this long head c+ are longer then the ones that where on my short head c+.

 

[JOEY B.]

BTW The other eq swiches on this long head c+ are longer then the ones that where on my short head c+.

Definately get the correct swich from MESA or elsewhere. When I replaced the standby switch on a long chassis Mark III, I discovered that there are 3 different toggle or "bat" lengths for the same standby switch.

 

[peterc52]

Hi,

Where do you get your Mesa's serviced here i DK?

 

[cremona]

Hi,

Where do you get your Mesa's serviced here i DK?

Aage is the importer, so the can supply the parts

regards

 

[Boogiebabies]

The EQ switch is most likely wired wrong and it defaults to EQ Auto for Lead and Out for clean.
As for the outer sockets, if you pay very close attention the glow may increase in class A. You are
cutting the voltage ad current draw from two tubes so the plate voltage and bias go up when you
switch out the center sockets. It's not a big deal unless your tubes are too hot and draw too much
natural current. If they did, they would most likely go into cutoff and you would hear nothing but a faint signal
from the power amp in Class A. Since you don't the tubes are probably fine. Remember Joey's advice and get
pins 1 and 8 connected on the outer sockets and you will rarely ever have an issue with the Class A sockets.

As for the odd blurbs and flatulent noises on power down, 90% of these amps do this if you don't use the master volume
over 2 or play for a short period and shut down. The sound is the filter caps draining to ground and through the speaker and they are unusually louder when you
do not give them a chance to be discharged naturally by using the power section. New filter caps may or may not fix this problem. If you don't
want to hear it, strum an E Chord before you turn off the standby and then go to standby. Turn the Master volume up while the chord is still ringing.
This will bleed the caps and will usually prevent the noises on power down, otherwise you will have to play over 2 on the Master and over 20 minutes.

You mentioned that you want the amp to be like it left the factory in 85. Other than the EQ toggle switch, it is.
Nothing else has been changed.

 

[cremona]

The EQ switch is most likely wired wrong and it defaults to EQ Auto for Lead and Out for clean.
As for the outer sockets, if you pay very close attention the glow may increase in class A. You are
cutting the voltage ad current draw from two tubes so the plate voltage and bias go up when you
switch out the center sockets. It's not a big deal unless your tubes are too hot and draw too much
natural current. If they did, they would most likely go into cutoff and you would hear nothing but a faint signal
from the power amp in Class A. Since you don't the tubes are probably fine. Remember Joey's advice and get
pins 1 and 8 connected on the outer sockets and you will rarely ever have an issue with the Class A sockets.

As for the odd blurbs and flatulent noises on power down, 90% of these amps do this if you don't use the master volume
over 2 or play for a short period and shut down. The sound is the filter caps draining to ground and through the speaker and they are unusually louder when you
do not give them a chance to be discharged naturally by using the power section. New filter caps may or may not fix this problem. If you don't
want to hear it, strum an E Chord before you turn off the standby and then go to standby. Turn the Master volume up while the chord is still ringing.
This will bleed the caps and will usually prevent the noises on power down, otherwise you will have to play over 2 on the Master and over 20 minutes.

You mentioned that you want the amp to be like it left the factory in 85. Other than the EQ toggle switch, it is.
Nothing else has been changed.

Hi BB

Thanks for the excelent replay and teaching. :shock:

You are right at the given time i have the master under 2 .

Regarding the tubes, the are proberly fine , but the thing that puzzels me (proberly because i dont understand tube behavior) is that there colure suddenly changed, before the all ran with the yellow light, now the are blue.

 

[Boogiebabies]

The power tubes can appear different due to the amount of actual light in the room.
If you ever want to really see them operate, turn the lights off.

 

[cremona]

The power tubes can appear different due to the amount of actual light in the room.
If you ever want to really see them operate, turn the lights off.

Im fully aware of this, the room the amp is in have curtains that fully blackends the room ( because i cant sleep if its to bright )

The glow blue now and did not glow blue before , secondly the amp dos not sound like it did when i got it, its much more harsh and the bass has lost its focus. espicialy when i have played for a littel while.
Untop of that the seller stated in the ad that the tubes where worn out , and where only put with the amp so it can be sold as working.

I will buy a new pair of sylvania 415 str and the sylvania 6ca7 should be here next week.

 

[dodger916]

Good luck. I hope that fixes it.