• TalkBass has been independent since 1998. Add your voice.
    Create a free account to reply to discussions, view embedded media, and browse with fewer display ads.
    Join free Log in
    Want zero display ads or expanded classifieds tools? Compare plans.

pics of ampeg svt4-pro guts?

downneck

downneck

Sep 23, 2006
347
1
east village, manhattan, nyc
fsaadd.com
#1
so...a "friend" of mine took apart my semi-fried svt4-pro in anticipation of fixing it, which he never did.

i managed to replace the fried cap and resistor myself, but now i've no idea how to get it back together.

so i'm begging for someone with one to pop it open and post a good pic of where all the wires go, specifically the ones coming from the power switch, transformer, breaker, etc. or maybe a list of what goes to what ... like "left most orange wire on transformer goes to j22"

i know it's a long shot, but i'm hoping there's a kind soul on here with too much time on his/her hands and a really good camera :)

-dave
 
#2
You say you replaced the "fried" components but keep in mind, they fried for a reason. Have you had the amp repaired or did you just replace the failed parts.

Without properly fixing what caused this you'll be right back to where you are now or possibly damaging the amp even more. :crying:
 
#4
5not4 said:
You say you replaced the "fried" components but keep in mind, they fried for a reason. Have you had the amp repaired or did you just replace the failed parts.

Without properly fixing what caused this you'll be right back to where you are now or possibly damaging the amp even more. :crying:
Click to expand...

we traced the problem back to two probable external issues: the amp was in a rehearsal room and someone plugged the speakon cable into the "power amp a" jack and then took it off mono-bridge. they then plugged it into a non-grounded two-bladed power socket with an adapter. nobody caught this for a couple days and ka-blooie.
 
#5
Thor said:
If the schematic diagram for the SVT 4 pro would help you
(and it should), I have it and can email it to you, send me
your email addy through the email link on the board and I will
happily forward it along.
Click to expand...

thanks, although i already have it...i've gotten most of it back together after some careful reading of the schematics, but i can't find the connection information for the board with the 3 speakon jacks. my only guess at this point is i'm missing a page in the schematics or i'm reading the darn thing wrong. i'll send you my email, i'd appreciate being able to look at your copy of the diags
 
#7
Actually, neither running power amp A, nor using an ungrounded outlet should do anything bad. Naturally, grounded outlets are recommended.

Now I surely hope you didn't mean they plugged the SPEAKER into the ungrounded outlet ..... nor that they plugged the speaker cord back into the amp input :eek:

Sounds like there might have been one or two other haoppenings that you don't know about.

Actually, if you plugged the speaker cord into the amp input, it might possibly only fry the "high frequency load" on the output, depending on how fast it was noticed....
 
#8
Jerrold Tiers said:
Actually, neither running power amp A, nor using an ungrounded outlet should do anything bad. Naturally, grounded outlets are recommended.

Now I surely hope you didn't mean they plugged the SPEAKER into the ungrounded outlet ..... nor that they plugged the speaker cord back into the amp input :eek:

Sounds like there might have been one or two other haoppenings that you don't know about.

Actually, if you plugged the speaker cord into the amp input, it might possibly only fry the "high frequency load" on the output, depending on how fast it was noticed....
Click to expand...

unfortunately i wasn't around when it happened so i couldn't say for sure, but that's what i was told. perhaps they left it mono-bridged and tried to run just power amp a?

further info, for those of you with schematics. this is exactly what went (all on the power amp board):
c110, r218, and q202 all needed to be replaced. c110 blew its cap off and blew fur everywhere i'm guessing this was insulation in the cap? r218 melted, and q202 had broken one leg and looked like it had blown a chip out of itself.

either way, i've got those three parts replaced with fresh components and would love to test, i just can't figure out where a couple of the wires reattach to
 
#11
downneck said:
see last post, i edited it to include what, exactly, blew :)
Click to expand...

Speaking of fried, my SVT 3 Pro stopped working in our last gig, I managed to tune my bass on mute and then when I took it off I could only hear a faint sound out of it.

I took the cover off last night and noticed some scorching around one of the electronic components on the board with the output tubes (the 2 tubes, rather than the 3). The amp started up okay and seems to be working.

The "sound man" for the gig hooked up the XLR line out, and I'm wondering, is there any way that phantom power from the board could have done this?
 
#12
If C110 on the power amp blew like that, you have more troubles than you think.

It is a 35V cap, and it was across the mosfet bias (gate) lines, meaning it should not have had more than about 8V max on it.

Methinks that the output mosfets got fried, I can't imagine how they could be good after whatever did that.

Obviously somebody got very creative with the connections, in a way that deserves a dope slap, or maybe a severe kicking.... Sounds like they may have cost you some money, unless the unit is under warranty.

As far as the 3 pro, most of them, all the recent ones at the very least, have transformer isolated DI, so I see no good way for the phantom to do anything bad.

A very severe ground issue between board and unit , if the ground wasn't lifted might mess up the ground lift switch.
 
#13
Jerrold Tiers said:
If C110 on the power amp blew like that, you have more troubles than you think.

It is a 35V cap, and it was across the mosfet bias (gate) lines, meaning it should not have had more than about 8V max on it.

Methinks that the output mosfets got fried, I can't imagine how they could be good after whatever did that.

Obviously somebody got very creative with the connections, in a way that deserves a dope slap, or maybe a severe kicking.... Sounds like they may have cost you some money, unless the unit is under warranty.
Click to expand...


first off, thanks for all the helpful commentary man, i really appreciate your taking the time to help out. being that it's not under warranty, my options are: send it in for repair (if they'll even take it), pulling all the mosfets and replacing them, replacing the entire unit, possibly replacing the power amp board on its own (is this even possible?). any recommendations, is it worth pursuing or should i just start scouring craigslist for some used gear?

i've got it mostly back together but without the speakon daughterboard attached and i can't get sound out of it although it does power on and the preamp tubes heat up ok. fan doesn't appear to spin on poweron but i don't remember if it was supposed to spin on poweron or if it's temperature controlled, although it does twitch (1/16th of a spin or so) on poweron/poweroff.
 
#15
Bottom line. The amp was used and/or abused without you being around. The people using it should buy you a new one and then they can have the old one fixed themselves. If they refuse try the old Louisville installment plan method.

To answer your last question, yes. That's what the effects loop is good for. Run the "send or out" into the input of the power amp, but I think you really ought to think about replacing the unit entirely until you get it repaired, or you use it as a floatation device on the people that jacked it up to begin with.
 

Latest posts

Top Bottom
Back