Quote from Forum Archives on November 18, 2003, 1:00 pm

Posted by: bellis <bellis@...>

Danny Southard wrote:

>I know a little. It sounds like an early '70's model. What a find!
>Anyway, a lot of Portaflex amps were driven by a pair of 7591's, so if
>the schematic is still pasted to bottom of the head, you might want to
>verify that it does use 6L6's. I have the Ampeg book and can date your
>amp, but most likely I'll need the speaker # and/or a potentiometer # to
>do it accurately. The amp puts out between 20 and 30 watts, BTW. It's
>probably a B-15N; let me know if it's not (it could be a B-15S).
>
>
It definantly is using 6L6GC's.. I tore it down first thing and cleaned
everything up. The speaker EIA code is 137742 which seems to place it
either 1967 or 1957, but id guess '67 with the 066252 serial number,
though I can't seem to locate a photo of a mid/late 60's amp that looks
like this one with the black tolex, 'Ampeg' in metal on the speaker
grill cloth, and the gold trim around the faceplate. The speaker is a a
CTS (137742) with a square magnet that has 'custom ampeg design', i
believe in Linden New Jersey Def somewhere in NJ, I cant remember the
name exactly. This again would place it 42nd week of 1967 probably.
The speaker does have a small hole (1/8" X 1/2") in the speaker surround
where some insect or something has eaten through the fiber. It has
black tolex (whats left of it), and a gold trim around the face rim. It
does have the plastic Plexi-lighted 'Ampeg' thing in the middle of the
head.

Sounds pretty great just as is, especially with double bass. At higher
volumes it does buzz a bit, but I expect it might be the cab is leaky,
and is buzzing the loose tolex around a bit, perhaps, because i tore the
cab down and tightened most everything else down, and it seemed to clear
most of the extra noise up. I may try sealing the corners a bit with
wood glue or silicon. I do think its a B15N, but I've not found a
picture that looks exactly like it. However by comparing some of the
schematics to the actual circuitry, it looks real similar (I've not
studied it a whole lot but many of the bias resistors, etc are the same)
to a late 60's b15N schem that I have with 6L6GC's.

Thanks for the info!
-b