Jess Oliver's legacy - AMPEG PORTAFLEX CLUB part 9

[JimmyM]

Originally Posted by stiles72

I've been using some yellowish 1" foam in my '63 since I got it, and prefer it over the insulation in my '66 cab. I think just like Marks updated latches or using felt on the baffle board, using an alternative to insulation is a good idea.

Yepper! I'm glad I finally did it for sure!

[beans-on-toast]

I oversize the lining a bit which helps keep it snug. The felt material that I use is stiff enough that it doesn't need any tape to affix it. It looks like Clint's acts the same way. The bottom and sides are lined the same way. I keep an extra piece that I arc over the top when playing. Not sure how much of a difference the extra lining makes but I figure that it doesn't hurt.

Like the B-15, the old Leslie organ cabinets were only lined on the surface opposite the speaker. The reflected waves tend to predominantly move backwards. They used a multilayered paper with air between the layers. Very green for their time.

[beans-on-toast]

Amazon has some good deals on Ampeg equipment at this time of year. They have a couple of HB-15's going for around $5K. Nothing special although nice to see that they are available.

Good deal on a Heritage 810E for $794 with free shipping. I wonder if they are demo units.

[Vintage-Blue]

Originally Posted by JimmyM

Has to be cheaper than the stuff the Heritage B-15 uses

At the very least it saves you the labor of covering the insulation with felt.

[JimmyM]

Originally Posted by Vintage-Blue

At the very least it saves you the labor of covering the insulation with felt.

Ah, THAT is why it looked so neat in the cab! Well maybe I'm wrong about the price of what they use

[stiles72]

Originally Posted by beans-on-toast

I oversize the lining a bit which helps keep it snug. The felt material that I use is stiff enough that it doesn't need any tape to affix it. It looks like Clint's acts the same way.

Yes - the piece in back fits nicely and stays in place with no staples, adhesive, tape, etc...

[JimmyM]

Had I used foam and done more than the back wall, I probably could have gotten away without tape. But this Nu-Foam looks like it will fold up or come loose even if you cut it oversized. Could be wrong, but I already had the tape so I used it.

[beans-on-toast]

Nothing wrong with using tape. If the lining gets mucked up, it's a lot easier to change. It's a lot better than the tons of staples that are often used. When the batting is glued in place it makes it even harder to replace.

[jnewmark]

I will soon be getting another B15, pictured below. I believe the design change was around, 1968 ? Is there a definitive way to pinpoint the year on these models ?

[portaflexer]

The blue line graphics were only used until 1972, so that would put it between 68-72. From what I've experienced in the past, the only way to get a more accurate date is to look for the manufacturing codes on the internal components (make sure you look at multiple components because some wear out and get replaced over time). My SB-12 Portaflex is the same series. Last time I had it serviced, the tech guessed it to be a 1970 based on date codes on the pots.

If anyone knows a more accurate way to date them, please let me know. I also have a blue line GU-12 from the same era. That particular model wasn't made until 1970, so it's a little bit of a smaller window. It would be really cool if they were both 1970 models.

[garmenteros]

Anyone else use their b15 for vocals? Ive been using mine for about two months as a vocal monitor because my zeppelin tribute band has been rehearsing in a large warehouse and we don't own a PA. So far it keeps up well against a loud drummer, and the guitarist and my half stacks. It starts to distort some after about an hour so if I really push it but thats normal I guess. One of those times I also ran one of my ibanez fender copies with flats and I got awesome grinding tone even though the drummer and guitarist had to turn down.

[garmenteros]

I also just got a couple of months ago a second b15 that I haven't had a chance to fix or get the other parts for. 150USD for the cab with a destroyed and modded head... Can't remember If I posted pics or not so here they go...

[beans-on-toast]

Originally Posted by garmenteros

I also just got a couple of months ago a second b15 that I haven't had a chance to fix or get the other parts for.

Looks like it'll be a fun project. The amp has had some mods to say the least. It looks like all the guts were removed. Are you planning to use a turret board or do a circuit board? THe cab looks like it will clean up nicely.

The nice thing about that model is that the chassis can be painted and it can look as good as new. Can't do that with chrome. I've done a number of the front gray panels and they turned out well after I figured out to use a zinc chromate primer.

[beans-on-toast]

Originally Posted by jnewmark

I will soon be getting another B15, pictured below. I believe the design change was around, 1968 ? Is there a definitive way to pinpoint the year on these models ?

Very nice j! It looks like it has been well cared for. Always a good sign. Yes, the design change was in 1968.

The easiest way to estimate the manufacturing date is to look under the chassis at the date codes on the pots. They used CTS pots, so code starts with 137. For your era, the following two digits indicate the year, the next two are the week. So 1376824 would indicate a CTS pot manufactured on the 24th week of 1968.

There can be date codes on the larger wire wound resistors.

The capacitor mounted on top of the chassis may have a date code.

If you remove the transformers, there is sometimes a paper label with a date code. This is rare to see.

The four shock mounts that the amp tray is mounted on also have a date code.

You can also check out the speaker for a date code.

There is also a serial number on the chassis of that B-15 revision:

Serial Number Range Year
000001 to 020000 1965
020000 to 049000 1966
049000 to 075000 1967
075000 to 080000 1968
080000 to 092000 1969


Finally, here is an ecopy of the 1968 schematic:

[jnewmark]

Originally Posted by beans-on-toast

Very nice j! It looks like it has been well cared for. Always a good sign. Yes, the design change was in 1968.

The easiest way to estimate the manufacturing date is to look under the chassis at the date codes on the pots. They used CTS pots, so code starts with 137. For your era, the following two digits indicate the year, the next two are the week. So 1376824 would indicate a CTS pot manufactured on the 24th week of 1968.

There can be date codes on the larger wire wound resistors.

The capacitor mounted on top of the chassis may have a date code.

If you remove the transformers, there is sometimes a paper label with a date code. This is rare to see.

The four shock mounts that the amp tray is mounted on also have a date code.

You can also check out the speaker for a date code.

There is also a serial number on the chassis of that B-15 revision:

Serial Number Range Year
000001 to 020000 1965
020000 to 049000 1966
049000 to 075000 1967
075000 to 080000 1968
080000 to 092000 1969


Finally, here is an ecopy of the 1968 schematic:

Thanks for the info, much appreciated. Was this revision also the change to 50 watts ?

[Ric Vice]

Originally Posted by jnewmark

Thanks for the info, much appreciated. Was this revision also the change to 50 watts ?

J Newmark,
To the best of my recollection, the helmet head logo B-15N's were never bumped to 50 watts. The B15-S amps did have that output. The Solid State BT-15's were 50 watts, and in 1967 the they built a B-15ND that used
the B-18N head atop a pair of B-15N Cabinets. Both of those amplifiers precede the redesign of the amp in 1968.

Ric

[garmenteros]

Originally Posted by beans-on-toast

Looks like it'll be a fun project. The amp has had some mods to say the least. It looks like all the guts were removed. Are you planning to use a turret board or do a circuit board? THe cab looks like it will clean up nicely.

The nice thing about that model is that the chassis can be painted and it can look as good as new. Can't do that with chrome. I've done a number of the front gray panels and they turned out well after I figured out to use a zinc chromate primer.

All the guts were removed... Any idea if that stock speaker on this battered one will sound better than the jensen I have for my almost stock working 70s b15? I'm thinking about trying it out but its at my techs shop which is a very long drive and he doesn't normally answer the phone or have one most of the time.

[jnewmark]

Originally Posted by Ric Vice

J Newmark,
To the best of my recollection, the helmet head logo B-15N's were never bumped to 50 watts. The B15-S amps did have that output.

Ric

Here's an article from Bass player mag about the B15N. Scroll down to a brief history to 1968, where it says the B15N was bumped up to 50 watts. I'm wondering if this is accurate info or not.

http://www.bassplayer.com/article/Th...urrection/5175

[coreyfyfe]

Originally Posted by jnewmark

Here's an article from Bass player mag about the B15N. Scroll down to a brief history to 1968, where it says the B15N was bumped up to 50 watts. I'm wondering if this is accurate info or not.

http://www.bassplayer.com/article/Th...urrection/5175

There were versions - the B-15NC and B-15ND which were 50 watt, but they were basically a B-18 head (they used a 7199 PI and 7027 power tubes) on either a 2x15 column (NC) or a 1x15 with a 1x15 extension cab (ND). The change over with the high/low boosts was still only 30 watts as far as I know, it used the same power amp as the B-15N(f) revision. There were also B-12 and B-18X models, but I don't know if I've seen schematics or pictures of a B-15X that is referenced in this article as 50 watts.

[beans-on-toast]

Originally Posted by garmenteros

All the guts were removed... Any idea if that stock speaker on this battered one will sound better than the jensen I have for my almost stock working 70s b15? I'm thinking about trying it out but its at my techs shop which is a very long drive and he doesn't normally answer the phone or have one most of the time.

I can't say which will sound better. Probably a good idea to try them both in that cab and see. Sometimes you'll be surprised by the outcome. I have a Jensen Concert that I really like.