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Ampeg SB12 authentication

#21
Raw N Low said:
Not to derail the thread but, would you happen to have a how-to guide on how to tear down the SB-12? I have a lightbulb out and would like to change it. I have no clue on how to disassemble the head to make the repair.
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Ric Vice said:
Take off the tube cage, carefully unscrew the two chrome bolts to detach it from the floating cabinet shelf, carefully turn it upside down, find the bulb in it's socket, twist slowly until the spring loaded bayonet socket pushes the bulb out. Sometimes, it takes a little Deoxit 5 to loosen the white build up around the socket.
Click to expand...

Ric described the process, the two big screws on top of the chassis have to be removed to release the chassis. The schematic should be below.

You might find this article of interest. They focus on an early revision of the SB-12. Also attached is a 1967 SB-12 manual.
 

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#22
As a low volume bass amp, SB-12's are the shizz. As a guitar amp, SB-12's are the shizz. At $700 I'd totally hit that thing and I wouldn't give a crap about what's original or not. But as someone with a little practice de-rattling Portaflex cabs, they can all be de-rattled, though sometimes it might take you a while to figure out where that last rattle is coming from :D
 
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#23
Raw N Low said:
Not to derail the thread but, would you happen to have a how-to guide on how to tear down the SB-12? I have a lightbulb out and would like to change it. I have no clue on how to disassemble the head to make the repair.
Click to expand...

I recently put a pair of LED bulbs in my B15. If the green coloring has worn away on your plexi logo as they often have you can get green ones (or a number of other colors).

2SMD Bulbs
 
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#25
I had an SB-12 with a 15" in it. It was tight, and sounded as great as my B-15's. Used it for a couple lower volume gigs and it was one of the best bass sounds I have heard.
 

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#26
Thanks for the support! I rolled it into the studio today! In my quiet studio it's even more ballsy. I noticed like a buzz at idle with volume down coming from the power tubes so not sure if this is normal or an adjustment or amp tech visit is needed. Didn't notice it in the noisy environment when I tested it.
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But it's imperceptible when you are playing. Clean tones are so full and warm. Crunch is so authentic anywhere from halfway to dimed on a guitar. Thrilled and from an ego standpoint it looks very cool in the studio!
 
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#27
If the trans
thegrapeguy said:
I looked closely at transformers and their numbers indicate 682 651 and 682 639. Based on an SVT document I read this means the Electrical Windings Company (682) and the 51st and 39th week of production in the year 1966. SO would it be a safe bet to assume this is a 1967 amp?
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That looks earlier than a 67 to me. That thing looks to be in really nice shape. I played at an outside gig once with one of those or the other bass amp with the 12", forgot the name of it, it sounded great. The guy who owns it said Chris Squire used to use it for his bridge pickup in the studio on his Ric, he didn't know which albums though. He's an engineer and studio owner so I believe him.
 
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#28
Ric Vice said:
Take off the tube cage, carefully unscrew the two chrome bolts to detach it from the floating cabinet shelf, carefully turn it upside down, find the bulb in it's socket, twist slowly until the spring loaded bayonet socket pushes the
bulb out. Sometimes, it takes a little Deoxit 5 to loosen the white build up around the socket.
Click to expand...

beans-on-toast said:
Ric described the process, the two big screws on top of the chassis have to be removed to release the chassis. The schematic should be below.

You might find this article of interest. They focus on an early revision of the SB-12. Also attached is a 1967 SB-12 manual.
Click to expand...

That was so easy I feel like a moron. Looks like this amp dates back to 1966. One of the bulbs gave up the ghost.
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#30
I liked at the '67 manual that beans on toast attached and the picture of the '67 looks nothing like mine. It seems a model change took place. But with the production of the transformer being almost last week '66 and my serial number (which I found finally) (056560) it seems this amp dates to a 1967. Perhaps in early '67 they were making the '66 still...
 
#31
thegrapeguy said:
I liked at the '67 manual that beans on toast attached and the picture of the '67 looks nothing like mine. It seems a model change took place. But with the production of the transformer being almost last week '66 and my serial number (which I found finally) (056560) it seems this amp dates to a 1967. Perhaps in early '67 they were making the '66 still...
Click to expand...

The look of the '67 with the face inlay was short lived, towards the end of the year. The pot codes will also help you to date the amp. Look for 137 followed by a year and week of the year code.
 
#32
Raw N Low said:
That was so easy I feel like a moron. Looks like this amp dates back to 1966. One of the bulbs gave up the ghost.
View attachment 3654952 View attachment 3654953
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Good going, it never hurts to ask if you aren't sure.

Best to change both bulbs, they are inexpensive and rated so many hours. Service life varies with model.

Nice clean schematic. It never hurts to grab a high resolution image of it for ur records.
 
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#33
beans-on-toast said:
Good going, it never hurts to ask if you aren't sure.

Best to change both bulbs, they are inexpensive and rated so many hours. Service life varies with model.

Nice clean schematic. It never hurts to grab a high resolution image of it for ur records.
Click to expand...

Forgot that the previous owner kept the original paperwork. This was shipped to Colorado in the '69-'70? The only thing I'm missing is the badge that sat on the front of the grill.
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#35
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#36
Ampegs online manual and schematic library is pretty good where they are available. I know the troubleshooting guide is in the wiki as well.

here is the SB12 user guide
[Invalid or Expired Link Removed]

manual (dated 8/67 on top)
[Invalid or Expired Link Removed]

And some schematics
[Invalid or Expired Link Removed]

[Invalid or Expired Link Removed]

love the old warranty cards and stuff too. Always cool to see.

Here's the support menu
Index of /support/files
 
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#39
A sad day yesterday. I returned the amp to Guitar Center (where I got it). Lucky for me when I bought it - it wasn't labeled "vintage" (because of the changed out baffle and speaker) so I had 45 days to return. When I got to GC and wheeled it in a customer who is a "regular" there remembers the amp and knew something about the history. Apparently the previous owner bought the aftermarket portaflex cabinet (which explains why the tolex looked so good). SO my cabinet wasn't original and whatever original cabinet came with the amp was long gone. I knew the speaker and baffle was changed out but I was told everything else was original. You guys helped me authenticate the amp which was cool. Lucky for me the GC salesman said had it been labeled "vintage" I would have only had 3 days to return it.

But I had decided before this to return it for these reasons. It needed a trip to the amp tech to probably recap it, service it and solder in the 3-prong chord. There were lots of inherent noises at idle, pops now and then, lots of rattles in the cabinet when I played bass through it, etc. It still sounded great at a low volume though. With guitar it was nice and clean and then turned up it was a beast, I liked it. But I found myself not playing very much at that loud distorted volume even though I liked the tone. So for all those reasons I returned it. Honestly if a perfect example of this amp were to be available I would get it again. The ability to play bass in this amp and get a great clean tone and then turn up a guitar and get this authenticate blues tone is extraordinary. But the amp would have to be tender lovingly cared for and invested in. Someday...
 

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