resurrecting a DC3 (a.k.a. C.S.I. Dc3)

[guitarman1860]

Hey guys

I have just arrived in the forum and need your help. I have a Mesa DC-3, with the 1993 board and Black Shadow speaker. I live in Brazil and down here there is neither Mesa dealers nor authorized service. So this forum is my last hope to fix my problem.

My original El84 power tubes ran off in 2002. I took it to a technician that swapped the tubes, made some adjustments and done. But the amp sounded different even with the original 12Ax7. After this other 3 guys did the same thing. And nothing. I gave up last year. I tried some other amps from Rectifiers, to Carvins and Blackstars but no one sounded so good and versatile as the deceased DC3 (r.i.p.).

As i read previously here that the first DC3s have different biasing, I kind of discovered what is going on. The technicians here don’t know how to adjust this amp. I would like to ask if someone with a similar DC3 could help me. I mean if someone could explain me in details which are the main differences between the internal voltages of the old DC3s and the later ones so I can go to a technician here and say “that’s what I want you to do” instead of waiting for a misdiagnostics from him.

What makes me think you should help me resurrecting my amp? Well, if you do not, the amp will be finally buried and turned into dust and ashes (I am tired). And this image, for those who once heard a Dc3 in full throttle, may be as sad as a death of a dear friend. So please guys let’s save an old friend of us.

thanks

 

[Pilotltd]

Bias at -11v with a plate voltage of 400v is standard. Look for posts on bias mod.

 

[bendo]

And get super cold JJ EL84s. 19-21 rating should hold up.

 

[guitarman1860]

Pilotltd, when you say “standard” you mean the standard values for specifically these early Dc3s or the standard for all Dc3s in general ?

I once read a great debate here in the forum about biasing an early DC3 but could not find it anymore. It must be in some other topic.


Bendo, thanks for providing the JJ ratings - that’s the kind of accuracy I have been searching for years


Thanks, guys

 

[Pilotltd]

Pilotltd, when you say “standard” you mean the standard values for specifically these early Dc3s or the standard for all Dc3s in general ?

I once read a great debate here in the forum about biasing an early DC3 but could not find it anymore. It must be in some other topic.


Bendo, thanks for providing the JJ ratings - that’s the kind of accuracy I have been searching for years


Thanks, guys

By standard I mean factory setting. The -11 is way too hot for modern valves - better around -14v. Look for a post called DC-3 issue on May 23 2013, Bendo's advice on the piggy back resistor mod is recommended unless you want to keep replacing valves regularly. Even cold JJ's don't live long and recently the quality of JJ's has deteriorated in my experience.

 

[guitarman1860]

By standard I mean factory setting. The -11 is way too hot for modern valves - better around -14v. Look for a post called DC-3 issue on May 23 2013, Bendo's advice on the piggy back resistor mod is recommended unless you want to keep replacing valves regularly. Even cold JJ's don't live long and recently the quality of JJ's has deteriorated in my experience.[/quote]




Now that you mentioned, I must say one thing about JJs

In general, it is said that JJ is the best tube today (kind of a dogma). Ok, it must be... electronically (in its construction). When it comes to sound, to my ears, both JJ’s power and pre amp tubes generate some harsh resonant frequency in the “treble domain” that, in a clean channel, produces initially an illusion of brightness. But some minutes later your ears are exhausted (for that was not brightness, was an illusion)

And, in a dirty channel, that damnn frequency simply kills the sound. I tried different amps,guitars,pickups,compressors,eqs, speakers... but it is no use. That frequency remains intact, it is always there. And worst. JJs seem to give a non linear output of the guitar. The bottom E has an output. D and G strings have another. And higher frequencies (from the7, 8th. fret of high E on) have another. It is like having 3 different sections of an instrument in your hands. Bottom line: JJs and I have never gotten along.

How I miss the old Sovteks! Those were great tubes for DCs. Even their smell running hot were different from today’s.

I read the post you talked about. I’m really into making the bias pot mod.

Thanks again

 

[Vigo1999]

I live in Brazil and down here there is neither Mesa dealers nor authorized service.

Já mandou seu ampli pro Pedrone?? ele é meio que autorizado pela Mesa a fazer alguns reparos. todos os meus amplis só ele que mexe. ele com certeza vai resolver o teu problema.

senão manda uma mp para o andy (monsta-tone) falando do problema e ele pode lhe tentar passar a solução e vc conversa com o Pedrone sobre o que o Andy falou (eles já se conhecem, eu os apresentei).

Boa sorte. qualquer coisa não dando certo me manda uma mp que tentamos ver algo. 8)

 

[guitarman1860]

o Pedrone foi o primeiro cara a mexer no ampli e não achou nada, foi aí que vi que o negócio era complicado

estive fora de sp desde o natal, somente agora estou voltando à normalidade e acabei de ler sua mensagem

obrigado por responder

vou dar uma mexida no ampli aqui e depois te aviso...pode ser até que eu pense em vender o ampli

grande abraço