Jess Oliver's legacy - AMPEG PORTAFLEX CLUB part 9 - Page 31

**ddbassGA** · #**601** 12-23-2012, 10:22 AM

I used a 2 cab B-15 stack back in the day (66-69). Yeah, wheeled 'em in, took the dolly off the main cab and fastened the lid of the ext cab into the bottom of the main cab with the dolly's knobbed bolt and fastened them together with the lid clips. I skipped the fasten once and it fell off, so from then on every time. I cant put a number on it, but adding the 2nd B-15 cab made a huge difference, made my bass audible among 2 guitars with Twin Reverb amps, a Farfisa playing through a Gemini II and a flashy drummer (think Dino Danelli). It also helped me and the others to have some sound coming out closer to ear height. My local idol worked at Ampeg in Linden and had the same stack with a B-18 head (before the ND was marketed). He used to be known as the loudest bass player around. (He sold me my ext cab for $25! I always wondered if it was hot). Remember, this is all prior to FOH support for instruments - if there was a PA it was for vocals only, at least at the club level - and prior to the 100+ watt amps, V4, SVT, Sunn etc. You couldn't get by with the B-15 once the guitarists started going to Marshalls and heavy distortion or keys went to B3 through twin Leslies ( my next band).

Today I have B-15s, B-18 head etc. And I use them mostly in the studio or practice room, occasionally a light gig. My regular gigging amp is a PF500/PF115E and I stack a 2nd 115 when I need more umph. At 61 I like light, simple.

jnewmark · #**602** 12-23-2012, 11:47 AM

^ Hmmm, not really sure what you did there with the two cabs. Did the ext cab have a threaded hole on top or something ? Or did you turn the cab upside down so the cabs' latches met up together ? I just can't picture this somehow. I assumed that, once you take the dolly off the main cab, it just sat on top of the bottom ext cab, no ?

JimmyM · #**603** 12-23-2012, 11:54 AM

Boy oh boy, that sounds like a lot of work! I just got a piece of closed cell foam and I stick it on top of the bottom cab.

beans-on-toast · #**604** 12-23-2012, 12:10 PM

Getting a cab up to ear level makes a big difference when playing. I sometimes stick my single cab on top of a Leslie to get the height. I use a gramma isolation riser to prevent any vibrations. The Leslie cabs can be wobbly. Seems to work out well.

jnewmark · #**605** 12-23-2012, 01:27 PM

Quote:

Originally Posted by JimmyM

Boy oh boy, that sounds like a lot of work! I just got a piece of closed cell foam and I stick it on top of the bottom cab.

I was kinda thinking the same thing. The one I just got has chrome ball type feet on it. I could do the old small glass ashtray trick !

**ddbassGA** · #**606** 12-23-2012, 03:08 PM

Quote:

Originally Posted by jnewmark

^ Hmmm, not really sure what you did there with the two cabs. Did the ext cab have a threaded hole on top or something ? Or did you turn the cab upside down so the cabs' latches met up together ? I just can't picture this somehow. I assumed that, once you take the dolly off the main cab, it just sat on top of the bottom ext cab, no ?

The ext cab had a removable lid just like the main cab, but no amp. Screw the blank lid of the ext cab in place of the dolly on the main cab. Stack and then clip the clips. Worked well, not that much work, just a bit of ritual. Had to take dolly off to stack anyway. I figured this was the way the B-15ND dual cabs connected.

jnewmark · #**607** 12-23-2012, 03:25 PM

Quote:

Originally Posted by ddbassGA

The ext cab had a removable lid just like the main cab, but no amp. Screw the blank lid of the ext cab in place of the dolly on the main cab. Stack and then clip the clips. Worked well, not that much work, just a bit of ritual. Had to take dolly off to stack anyway. I figured this was the way the B-15ND dual cabs connected.

How do you screw the blank lid in to the bottom of the top cab, there is no hole in the blank lid to do so, at least none I've ever seen .

**ddbassGA** · #**608** 12-23-2012, 03:32 PM

Quote:

Originally Posted by jnewmark

How do you screw the blank lid in to the bottom of the top cab, there is no hole in the blank lid to do so, at least none I've ever seen .

You drill a hole. And you can add the threaded hardware, like the dolly has.

coreyfyfe · #**609** 12-23-2012, 05:18 PM

So I've pinpointed either a cause or symptom of why my B15 is blowing fuses. There is a small indentation on the heater winding for the power tubes that can be seen in this picture. When I fire up the amp with a fresh fuse I'm getting a spark between approximately this point and the terminal on the fuse casing. Is it possible for the casing on the wire to wear through, or is this indicative of a short somewhere in the wiring or some kind of fault in the transformer? Can it be repaired or reinsulated to prevent these shorts in the future or does the transformer need to be replaced? All of the wiring impedance checks seem to be ok based on this troubleshooting guide.

christw · #**610** 12-23-2012, 06:13 PM

Quote:

Originally Posted by ddbassGA

I figured this was the way the B-15ND dual cabs connected.

That was how the '66 BT-15 extension cabinet I had connected.

beans-on-toast · #**611** 12-23-2012, 06:39 PM

I can't see where the problem area is in your image. Bad eyesight.

If the insulating sheathing is cracked or burnt due to soldering the wire is exposed, it can short as you described. Fix the insulation and the problem will go away.

I think that this is the source of the problem. A problem somewhere else in the transformer wouldn't cause it to short somewhere else. Electricity finds the shortest path to ground. It sounds like it is arcing between two uninsulated circuits in close proximity.

If you can, it would be a good idea to move the heater wire away from the fire terminal. Be careful moving these old wires, they can be brittle and break. One way to fix the affected area is to slip some heat shrinkable tubing over it and shrink it into place with a hair drier. You can also use teflon tubing to reinforce the insulation, available by the foot at Surplus Sales of Nebraska.

Just to be sure, the green wires are for the 6.3V heater; the yellow wires are for the 5V rectifier tube heater; the red wires are high voltage B+, the red yellow striped wire is the high voltage center tap. The AC wire pairs should be twisted to reduce noise.

I see some cracking on the red wire in the lower left. This is typical of old transformer wires that are exposed to heat cycles. If the bare wire came in contact with the chassis, it would cause a problem. Having that splash of solder on the other red wire next to it isn't a good idea either. Easy to clean off.

coreyfyfe · #**612** 12-23-2012, 06:46 PM

I was hoping you'd pop back in David

I'll start with insulating the filament wires. The red wire in the background has some kind of fiber on it, it actually all over the inside of the amp. When I bought the amp there had clearly been some kind of mess inside, maybe failure in a cap at some point, there was some kind of mess on the circuit board, some areas that looked like they were a little burned and cleaned up, and fiber everywhere. I can't tell if its from the insulation in the cab (its more of a dark orange) but I've been cleaning it up as I've checked out the amp. Didnt see the solder drip though, I'll be sure to clean that up.

Hopefully some heat shrink will take care of it, I'll keep you posted.

beans-on-toast · #**613** 12-23-2012, 06:46 PM

Quote:

Originally Posted by ddbassGA

You drill a hole. And you can add the threaded hardware, like the dolly has.

I've always thought that that this is how some extension cabs were built. Not all extension cabs that I've seen have this but some do. Somehow I'm thinking it was used by Ampeg towards the end of the 60's.

beans-on-toast · #**614** 12-23-2012, 07:09 PM

Quote:

Originally Posted by coreyfyfe

I'll start with insulating the filament wires. The red wire in the background has some kind of fiber on it, it actually all over the inside of the amp. When I bought the amp there had clearly been some kind of mess inside, maybe failure in a cap at some point, there was some kind of mess on the circuit board, some areas that looked like they were a little burned and cleaned up, and fiber everywhere. I can't tell if its from the insulation in the cab (its more of a dark orange) but I've been cleaning it up as I've checked out the amp. Didnt see the solder drip though, I'll be sure to clean that up.

Hopefully some heat shrink will take care of it, I'll keep you posted.

Yes let us know how it goes.

If the gunk was all over the amp, chances are it is from a blown cap as you said.

In general, a lot of types of insulation has been used over the years. In the earliest days it was bare wires laid out like you see in the knob-and-tube wiring in houses. Braided cloth was common in older amps. Sometimes there was a plastic coating over the braiding that would break down with time and shred. Hard to believe but some companies used braided asbestos as insulation over the wires. I'm not aware of Ampeg doing this. I would try to remove as much of whatever it is with a Q-Tip soaked in alcohol.

beans-on-toast · #**615** 12-23-2012, 07:39 PM

**ddbassGA** · #**616** 12-23-2012, 09:09 PM

Quote:

Originally Posted by beans-on-toast

I've always thought that that this is how some extension cabs were built. Not all extension cabs that I've seen have this but some do. Somehow I'm thinking it was used by Ampeg towards the end of the 60's.

My old ext cab lid came with the hole, but I don't recall if it had the threaded hardware.

jnewmark · #**617** 12-24-2012, 09:28 AM

Quote:

Originally Posted by ddbassGA

My old ext cab lid came with the hole, but I don't recall if it had the threaded hardware.

I never knew this, but I hardly ever see an " authentic " B15N extension cab come up for sale, anywhere. I occaisionally see an empty B15N cab, but never just an extension cab meant for the B15N. I'm on the hunt !

RobJ · #**618** 12-24-2012, 09:50 AM

Merry Christmas to my fellow Portaflexers!

(or Happy Holidays if you prefer).

jnewmark · #**619** 12-24-2012, 11:20 AM

Having some fun this Christmas Eve, noodling around with my new to me, B15N, '71 style, portaflex. It's been over 40 years since I played an Ampeg with the Ultra High and Low, rocker switches. Can someone refresh my memory on what position engages the effect; is it when you " rock " the switch to the left, so that the sort of triangular , thick shape of the switch is on the right side ? There is definitely some tonal changes there when combining them both, even a jump in apparent volume , but I'm not really sure what I'm supposed to be hearing. Also, Channel Two seems to be a tad louder with it's volume knob at same position as Channel one. I'm also kinda digging the Bright channel with a P bass. Have'nt tried my Jazz yet. It's also a different kind of feel, tone wise, to the '67 B15N I had. Interesting.

59Pan · #**620** 12-24-2012, 12:07 PM

Here's a '63 B-12-N that I just brought back to life:

It had no dolly, but I found an original that was in good shape. It's not the blue diamond checker, but black. But, sure makes it handy to roll with no handles on it.

I am presently working on a '64 B-12-XY, that was very in a bad way, in the chassis. I have gone into detail on that one, in a troubleshooting thread that I posted over in the Amps forum.

I'll post pictures of it when I'm finished working out the hum. Have a good one.

Jack