Ampeg SVT-450 schematics

[Brian Swatton]

Hi,

I've been through most of the links in the Ampeg section, but have either missed it or it's not there. Can anyone help with schematics for the SVT-450 please?

Thanks

[Enzo]

Here

[Brian Swatton]

MEF to my rescue again, thanks Enzo. I was trawling through links for ages without success.

[anticpunk]

I'm looking for these schematics too, but the above links don't work for some reason.... Any way you could email them to me or repost them?

Thanks!

Jay

[mozwell]

try this one

[Jazz P Bass]

Thanks Moz!

[anticpunk]

Thanks for that. Do you have a schematic for the preamp/eq section?

What I'm up against is a head that is in constant use in a studio/rehearsal space that can't be taken out of service but needs new sliders and pots. I have extremely limited access to it, so I'm trying to get a parts list together without the amp in hand.
The amp works great, but 3 pot shafts are broken and every slider is missing its tab, so I need these values, etc.

Thanks again,

Jay

[Enzo]

The power amp is all there is in the SVT450 file. Isn't the preamp the same as the SVT350?

You don't need values, you need part numbers. On the broken shaft rotary pots look on the pot body. Is there a number like 70-133-01? That is a 50k linear, which is what I think you need. I think all five are the same. That 70-xxxxxx is the part number, and LoudTech Inc or an Ampeg parts seller will source it by that number.

I believe the sliders are all 70-104-21, which are 100k linear. Again, use that part number.

[Jazz P Bass]

Flip Tops has them both.
100k Ohm Slide Pot, OEM# 70-104-21 - Product Details
50k LInear Taper Mini Pot OEM 70-133-01 - Product Details

[J M Fahey]

As of:

What I'm up against is a head that is in constant use in a studio/rehearsal space that can't be taken out of service but needs new sliders and pots.

all I can say is f*ck them (excuse the French).

Idiotic customers are always asking for such things.

If maintenance *is* needed (and it is), the broken unit must be taken off service until repaired, a spare/backup unit used instead, and replaced when ready.

I always get such unreasonable requests, and they always get the boot.

Why does, say, a mechanic (no need to mention Doctorts, Lawyers or whatever) earn more than we do, and in practical terms command more respect?

Because a typical dialogue sounds like this:
Me (on Thursday): "here's my car, I need it ready tomorrow, I'm going on vacations on Saturday"
him: "I'm full of work, bring it next week"
- "but I'm going on vacations on Saturday"
- "bring it next week"
.........
repeat as many times as needed to get the idea in MY head that MY Vacations are a big deal for ME; but for the mechanic it's "just another job".

Rant mode off.

[anticpunk]

I gave them hell and got the amp in hand.

P/Ns are 70-503-70UQ, 70-133-70 PQ

Sliders they don't want to replace......

These pots are junk, I want to upgrade to 1/4" shaft pots. Just need to decode the values.
Looks like 50K by fliptops, but I need to be sure before I get a set of Alphas and they aren't right....

Thanks!

Jay

[Jazz P Bass]

What is junk about the pots?
They're mini pots.
Not too sure about replacing them with 1/4".
They may not line up with the front panel.
They may not fit the front panel hole.
The knob will be different.
The customer will break them just like he broke the mini's & sliders.

[Enzo]

Pots don't break off because they are junk, they break off because they are abused. Someone props a guitar on the amp, and it falls over. ANd when it does, it whacks the little knobs and breaks the pots. Use a guitar stand. Of Ronnie Roadie tosses things in with the amp while loading, and the drum case lops off a couple shafts. Those are cheaper pots, sure, but they will work for decades if you take care of them. And as a shop tech, I sure have changed out my share of 24mm pots with broken off shafts.

These are 16mm pots. They have a 1/4" bushing and 3/16 shaft. The shaft centerline sits about 18mm above the board. Your standard 1/4" shaft pot has a 3/8" bushing, and while you may find some 16mm pots with that, I suspect most are the larger 24mm size. You need to consider that size. First, they must be far enough apart on the panel that they fit. You may also find you don't have room under the pot for its legs. Plus the legs will not line up with the holes. In fact a 24mm pot should have about 12mm radius on the body other than where the legs are. That might just fit over the board if you mount it upside down. But then you'd have to run flying leads down to the board.



I'd buy some extra and put them in a jar labeled "so and so's SVT450" and stick them on the shelf. If they break the new ones, bring it back next year for new ones ...and a fresh repair bill.

[plec.22]

Been asked to look at one of these svt450's...fault report from the last tech is.. power's up but, when played it's all distorted at the o/p so better to scrap it!!

So it's going to be one of them starts to the week of seeing whats been done or not done....