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Messages - sempri_fi

Amplifier Discussion / 1978 carvin st2500
November 21, 2007, 02:21:55 AM
ok everyone, i've taken on a new project, that is, to restore a carvin st2500 amp to its former working condition. the amp uses 4 2n6254 transistors for power and currently only partially works.

the problem appears to be the age of the amp, being almost 30 years old now, and is quite tired. most of the pots have moderate to severe crackle or will cut out all together. the amp also appears to be stuck in 'distortion' mode, the reverb does not work, but instead adds a tremendous amount of noise to the signal, as does the vibrado effect. the 7 band eq would appear to be functioning normally as it was replaced before the amp cut out. the amp also has a few stuck rocker switches, such that the power drive feature is always on the second channel, and the ground is always lifted.

the extreme distortion and noise appear to be happening in the preamp from what i can tell, though, im not sure if the power amp is bad...

i was wondering, is anyone familiar with such an amp? or at least might know something about the RCA 2n6354 transistors? and what normally goes bad or wears out in amps like this one? and anything else that might be helpful is most welcome.

i also plan to replace the horrible 'gain/overdrive' circuit with something with more of a tube screamer type feel
and hopefully carvin will email me the schematic for it as i have inquired, i will post it here for you all to have a look.

thanks in advance
Jacob t. 
Amplifier Discussion / Re: very large schematic files
October 31, 2007, 03:04:58 PM
alright sweet, i got them posted, flickr lets you post up to 5 meg files, so i only had to cut them down by about half, so they're still readable
Schematics and Layouts / VOX AD 50vt
October 31, 2007, 02:49:21 PM
here's the link to the flickr hosting of the schematics

its essentially the field manual for the amp, i got it directly from korg with the aid of some trixsyness

you cant get these schematics anywhere, i've checked, they dont exist

and with good reason, they are most likely somewhat of a trade secret to vox

at any rate, i would recommend downloading the images yourself, as a backup of sorts
just in case vox finds them and decides to get their panties in a bunch

and as a side note i also have the parts lists, with part numbers for this amp, so if you'd like me to post them as well, ask.
Amplifier Discussion / very large schematic files
October 31, 2007, 02:13:14 AM
would anyone happen to know how to post very large schematic drawings? like super hi-res scanned images.

i recently acquired a full set of schematics for the VOX Valvetronix series of amps and would like to share them with you as i went through hell and high water to get them and would like to help others out that might be looking for schematics...

i know photobucket will take files up to 1meg/1024x768 but when i shrink them down that small they just arent readable, and definitely not printable
Amplifier Discussion / Re: More gain?
December 04, 2006, 07:31:38 PM
see, told you these guys are good
and you never have to worry about getting flamed for not having a tube amp
or being a newbie for that matter
wow! you guys are awesome, adding an external gain stage is perfect because it doesnt void my warranty, so thats what im going to do, but im useing the eclipse tube booster kit from ( its a pretty good deal for a complete kit that has full costomer support behind it. they even finish the enclosure for you.
sorry guys i dont have a schematic to give you, ive looked on google and there is nothing. but i wanted to add another tube because it allready has one 12ax7 that its useing half to preamp and half to power amp somehow so would i just take and wire another tube socket in paraell to it or would i have to do some other mods first? and the signal path gos like this it gos through the moddeling chip, then it goes through the preamp half of the tube then it goes through the effects chain chip that moddels the effects, its then shiped off to the poweramp half of the tube and through the output, then it goes through an additional solid state power section that does most of the amplifying and is pretty transperant, and then it goes out through the speaker.

this problably wont help schematic wise but i think it gives a good idea of what is going on.
it also isnt actually 50 watts, it says it is but it only consumes 52 watts so its problably around 30 ish. i wanted to get a more tube like distortion out of it and i figure adding another tube or tubes woud help, so if you guys have any ideas please tell me.
does anyone know how to modify a vox ad50vt to put out more wattage or maby even add a couple more tubes because ive asked a bunch of people and they all say that you cant mod ss amp which i know is bs so can someone help me???