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Ampeg SB-12 Serial Number Location and starting restoration thoughts

billdeg

billdeg

Supporting Member
Mar 12, 2006
47
61
#1
Where is the serial number for a 1967 Ampeg SB-12? I believe it's a '67 because the schematic on the inside says 9/66, assuming they then produced and sold it in 1967. It has the speaker on the left side when facing from the front.

Also...just getting started to restore it. It has all original tubes so I want to at least see if the 12AX7's are the reason it can't take much of a signal before breaking up, especially when using a bass guitar lower notes. The volume is ok. Using a theremin through it (as a sine wave tester) works fine. Anything plugged into the bass jack can barely be heard. There are likely solder joints that need TLC, etc. It's a little rough in there but not as bad as I have seen. The light bulbs work, lights up the glass Ampeg plate.

I already fixed the wires to the speaker, the ground wire is just dangling and needs to be extended to the plug (Or I may come up with something internally). Seems like the speaker is intact, not ripped but I have read here where people say they can't handle the input from a modern bass guitar. Sounds great at low volumes. I could always just mic it I guess.

Not sure if I will sell, trade or keep yet. I take in these strays...and that's why I have too many amps. :-)

Bill
 
#2
Check out the TB Portaflex Wiki: Ampeg Portaflex Wiki | TalkBass.com

There is an extensive SB-12 cabinet restoration in the restoration section.

The best way to estimate the date of manufacture is to look at the pot date codes, a code starting with 137. Most ‘67’s had a black cabinet with a silver inlay around the front. There’s an image of a ‘67 in the model’s page of the wiki.
 
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#3
With a bass with typical Fender vintage-style output, it should start breaking up right around 11:00 on the volume dial. And bear in mind it's only 22w.

Serial is usually located inside the cab and under the head, though it's entirely possible they disappeared. And that ground wire unhooked may be at least partially the reason for your problems, though it's impossible to diagnose over the internet. That's more Beans' speed anyway, so just do what he tells you :D
 
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#4
thank you. Funny I cleaned up the amp and put alligator clips on a few broken traces to get it to produce a sound, not expecting much. Although it was a rough you could really hear a beautiful bass thwump sound especially in the midrange when not pushing in too much of a signal.
 
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#5
billdeg said:
thank you. Funny I cleaned up the amp and put alligator clips on a few broken traces to get it to produce a sound, not expecting much. Although it was a rough you could really hear a beautiful bass thwump sound especially in the midrange when not pushing in too much of a signal.
Click to expand...
SB-12 is just as kickass as any of them.
 
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#8
beans-on-toast said:
Check out the TB Portaflex Wiki: Ampeg Portaflex Wiki | TalkBass.com

There is an extensive SB-12 cabinet restoration in the restoration section.

The best way to estimate the date of manufacture is to look at the pot date codes, a code starting with 137. Most ‘67’s had a black cabinet with a silver inlay around the front. There’s an image of a ‘67 in the model’s page of the wiki.
Click to expand...

Then it must be a '66.
It looks exactly like this (but not as nice):
https://images.reverb.com/image/upl...90,w_620/v1505256708/xlezqqvhxqpnm1x1mxvg.jpg
 
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#9
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#10
I have '66 SB-12 and it is a beautiful sounding amp. It is almost as loud as my B-15. The latches complete the circuit for the speaker... that's cool.

Rich, warm, deep bass tone. I've never heard another 1x12 bass amp that comes close.
 
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#11
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#12
The schematic has "9/66" printed on it, and so the earliest it could have been sold was 9/'66. It has the 1966 design though, but it might have sat in the show room into 1967, who knows. I could not find anything else that had a date, no serial number anywhere. Did not check the date on the potentiometers, I'll disassemble the head again at some point soon and check. Sounds like Cream bass Disraeli Gears
 
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#14
shadven said:
I have '66 SB-12 and it is a beautiful sounding amp. It is almost as loud as my B-15. The latches complete the circuit for the speaker... that's cool.

Rich, warm, deep bass tone. I've never heard another 1x12 bass amp that comes close.
Click to expand...

I did an outside house party gig once and the owner of the house had an SB-12 for the bass and I couldn't believe how loud and good it sounded, kept right up with the rest of the band, nice punchy tone.
 
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#15
JimmyM said:
Pretty sure there were some 67's made with blue diamond as I don't think they transitioned at the top of the year but you're probably right. At any rate, there were no major changes between them other than cosmetic that I know of.
Click to expand...

Had a blue diamond 67 single baffle B15, definitely no cut and dry dates when it comes to ampeg (or most manufacturers for that matter).
 
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