CJ

Carvin ST4000 Guitar Amp
« on: June 17, 2017, 02:44:19 PM »
anybody have a schematic for this?

here is the ST2400 which is similar>

http://carvinimages.com/schematics/st2400_schem.pdf

this 4000 has 200 watts at 4 ohms, on paper at least, one main difference is the germanium power transistors, Delco  DTG 110B

which go for 36 bucks a pop on evilbay if you can find them,

If I can't fix it, I can fix it so nobody else can!
Frank's Tube Page: www.mif.pg.gda.pl/homepages/frank/vs.html
Guitar Amps: http://bmamps.com/Tech_sch.html


CJ

Re: Carvin ST4000 Guitar Amp
« Reply #1 on: June 17, 2017, 02:46:20 PM »
these transistors seem to be ok so far, and even match up pretty well,
If I can't fix it, I can fix it so nobody else can!
Frank's Tube Page: www.mif.pg.gda.pl/homepages/frank/vs.html
Guitar Amps: http://bmamps.com/Tech_sch.html

CJ

Re: Carvin ST4000 Guitar Amp
« Reply #2 on: June 17, 2017, 02:49:00 PM »
there go the guts, installed fresh caps and a heavy duty bridge, had an exploded .047 pwr line cap, first time we have seen that,

If I can't fix it, I can fix it so nobody else can!
Frank's Tube Page: www.mif.pg.gda.pl/homepages/frank/vs.html
Guitar Amps: http://bmamps.com/Tech_sch.html

Gus

Re: Carvin ST4000 Guitar Amp
« Reply #3 on: June 17, 2017, 04:45:10 PM »
Looks somewhat like the VOX amps.
Have you looked at geofex.com for information about the VOX amps?

CJ

Re: Carvin ST4000 Guitar Amp
« Reply #4 on: June 19, 2017, 02:52:06 PM »
here is the pwr section  for the ST400,

If I can't fix it, I can fix it so nobody else can!
Frank's Tube Page: www.mif.pg.gda.pl/homepages/frank/vs.html
Guitar Amps: http://bmamps.com/Tech_sch.html

CJ

Re: Carvin ST4000 Guitar Amp
« Reply #5 on: June 19, 2017, 02:54:22 PM »
and the reverb section, everything else looks like the 2400,

there might be extra filter capacitance which we upped to 4700 uf anyway

If I can't fix it, I can fix it so nobody else can!
Frank's Tube Page: www.mif.pg.gda.pl/homepages/frank/vs.html
Guitar Amps: http://bmamps.com/Tech_sch.html

PRR

Re: Carvin ST4000 Guitar Amp
« Reply #6 on: June 19, 2017, 04:49:37 PM »
> somewhat like the VOX amps.

And one/two of the Rhodes' amps, and quite a few others.

We called it "the Delco". Delco didn't invent it. But I have a feeling Delco promoted the heck out of it, with wish-list application suggestions (featuring Delco parts, natch) and maybe even kits with transistors, transformer, heatsinks (Delco made those by the millions for car-radio), for prototyping and maybe even for production.

It works OK. If the transistors are good, there is no reason to mess with it. If transistors are gone bad, it's a problem. Those old Delco Ge power parts no longer grow on Delco trees. Some of them were beefier than most modern Si parts (being derived from 40A-100A car alternator rectifier dies). Si parts will be woefully mis-biased.

This *particular* amp, if the output were toast, I would think about parallel LM3668. The output stage has gain near 600, more than LM3668 is intended for, so it may need a small booster to bring 50mV up to 1.2V. It would be very inappropriate technology. It would put the player back in business.

CJ

Re: Carvin ST4000 Guitar Amp
« Reply #7 on: June 20, 2017, 01:29:06 AM »
looks like they force the bias to 4.7 ohms/ 300 ohms = .01566 * 36 V = 0.564 V for the ST2400 silicon

and 3.3/600 = .055 *36 = 0.198 volts for the ST4000 Germanium

Carvin shows that this amp is no longer in their system files.

the amp is back in the box and ready to go, here is the data on the car radio transistors>
If I can't fix it, I can fix it so nobody else can!
Frank's Tube Page: www.mif.pg.gda.pl/homepages/frank/vs.html
Guitar Amps: http://bmamps.com/Tech_sch.html