Jess Oliver's legacy - AMPEG PORTAFLEX CLUB part 10 - Page 16

beans-on-toast · #**301** 02-07-2013, 12:58 PM

Bass amps differ from guitar amps in the power supply in that they often have a little more capacitance. This helps, especially in the first node for a good low end. Often the voltage rating of the first node capacitor is rated higher than the others because of the initial spike that you get when you turn on the amp and the caps are discharged. So what is often done is a stand alone cap @575 or greater for the first node, then a cap can at a lower voltage rating for the rest of the nodes. Fliptops sells a B-15 re-cap kit that includes a 30uF @600 for the first node, and then a 40/40/40 @ 525V. If you order this make sure that the correct caps for the bias circuit for the amp that you are working on are selected. Ampeg went with a 30uF for the first node to protect the 5AR4 rectifier from flashover. On some B-15N revisions they had a 40uF in that position. Better low end and headroom with the 40uF. Weber sells a 40uF@600V but they are out of stock. They may have something at fliptops if you ask otherwise go with the 30uF.

With the cap can it is important to use an isolation washer so that the can is not in contact with the chassis. Do not ground the can to the chassis with a wire. Otherwise you will get a ground loop and hum. They sell the washers with the cap cans.

xoir · #**302** 02-07-2013, 06:31 PM

We went from here to here

I thought the B18N had a fixed bias but is self bias

Happy user underway

unbiased -------------------------------------------------> biased

JimmyM · #**303** 02-08-2013, 12:15 AM

Quote:

Originally Posted by kuratacus

My Gf and i have an agreement. i can buy amps, she can buy cook books and kitchen appliances... it's a win win for me, she's a great cook ahhahaha

many a night over dinner "soooo i bought another.........." is over heard

LOL! You gotta respect that. Cool you have a good working relationship there. We sort of have the same deal, although I space out major purchases and she doesn't

Her thing is fixing up the house and adding fences and furniture and that kind of stuff. She works hard, so I don't say a word except a token "Aw, honey, not again?"

kuratacus · #**304** 02-08-2013, 05:40 AM

it helps that i run a rehearsal studio and all my gear, and projects are kept there.

kuratacus · #**305** 02-08-2013, 06:19 AM

my SS 63's new digs, cant tell from the photo but the logo is the same green as the cab.

christw · #**306** 02-08-2013, 06:38 AM

Quote:

Originally Posted by kuratacus

my SS 63's new digs, cant tell from the photo but the logo is the same green as the cab.

Niiiice!

Ras Keita · #**307** 02-08-2013, 06:56 AM

Much as I'd like to grab this up I can't afford it right now...

http://cleveland.craigslist.org/msg/3560321375.html

beans-on-toast · #**308** 02-08-2013, 07:08 AM

Quote:

Originally Posted by JimmyM

LOL! You gotta respect that. Cool you have a good working relationship there. We sort of have the same deal, although I space out major purchases and she doesn't

Her thing is fixing up the house and adding fences and furniture and that kind of stuff. She works hard, so I don't say a word except a token "Aw, honey, not again?"

Females like to build their nest. Males like to protect it against interlopers, hunt (go on gigs), and sing songs of their adventures. What better way to accomplish this than to make a big sound which is precisely what a Heritage SVT is designed to do. All this is perfectly understandable.

beans-on-toast · #**309** 02-08-2013, 07:27 AM

Quote:

Originally Posted by kuratacus

my SS 63's new digs, cant tell from the photo but the logo is the same green as the cab.

That's one cool looking rig. Being so unique, it'll attract attention. I have a red Vox AC-30 that I get asked about all the time.

kuratacus · #**310** 02-08-2013, 10:32 AM

yeah, this is my giging rig here, nice match to the green marshall. usually is sceen next to the bass picture attached as well. though lately the b15 has been getting all the attention

as much as i like my old amps to be original, i dont mind making my modern ones more ummm "original" ahahha but i have 2 micro's so one is still mint

Thunderbucker · #**311** 02-08-2013, 10:36 AM

"With the cap can it is important to use an isolation washer so that the can is not in contact with the chassis. Do not ground the can to the chassis with a wire. Otherwise you will get a ground loop and hum. They sell the washers with the cap cans."

Great info on the caps and isolating the can. Thanks much!

beans-on-toast · #**312** 02-08-2013, 11:22 AM

Quote:

Originally Posted by kuratacus

as much as i like my old amps to be original, i dont mind making my modern ones more ummm "original" ahahha but i have 2 micro's so one is still mint

Keeping it original really is cool. Like the bones on the doghouse.

JimmyM · #**313** 02-08-2013, 11:34 AM

Quote:

Originally Posted by beans-on-toast

Females like to build their nest. Males like to protect it against interlopers, hunt (go on gigs), and sing songs of their adventures. What better way to accomplish this than to make a big sound which is precisely what a Heritage SVT is designed to do. All this is perfectly understandable.

HAHAHAHAHA!!! You are right once again, David!

Kuratacus, love that tailpiece on the upright!

kuratacus · #**314** 02-08-2013, 11:46 AM

Quote:

Originally Posted by JimmyM

HAHAHAHAHA!!! You are right once again, David!

Kuratacus, love that tailpiece on the upright!

thanks Jimmy, my own design. took me a while to carve it but it turned out nice. holds my preamp as well

TheDialog · #**315** 02-08-2013, 01:23 PM

Quote:

Originally Posted by kuratacus

yeah, this is my giging rig here, nice match to the green marshall. usually is sceen next to the bass picture attached as well. though lately the b15 has been getting all the attention

as much as i like my old amps to be original, i dont mind making my modern ones more ummm "original" ahahha but i have 2 micro's so one is still mint

Really great looking stuff you have there.
Did you do the tolex work yourself?

kuratacus · #**316** 02-08-2013, 01:35 PM

thanks....yeah, did all the tolex work myself... sticky job but someone has to do it. have a few other cabinets i recovered as well. and i did all the work on the upright (the tailpiece, finish flames etc...)

wessman · #**317** 02-08-2013, 02:40 PM

Hello,

Are your B15's dead quiet or they are making some constant pitched noise even though your guitar cable is not connected to the amp? Mine is dead quiet while on stand-by mode, but once stand-by switch is in a play mode it starts to make a constant pitched electrical noise . Many thanks for your replies.

BR yeppe

Ps very nice greeny amp 😎

Vintage-Blue · #**318** 02-08-2013, 03:13 PM

Quote:

Originally Posted by wessman

Are your B15's dead quiet or they are making some constant pitched noise even though your guitar cable is not connected to the amp? Mine is dead quiet while on stand-by mode, but once stand-by switch is in a play mode it starts to make a constant pitched electrical noise . Many thanks for your replies.

Was it serviced recentlly? Based on my limited knowledge it sounds like the output transformer primary leads might be reversed.

Apex_speed · #**319** 02-08-2013, 03:57 PM

The Oliver P500 has landed. The amp chassis is all original and excellent, the faceplate looks excellent, and the electronics look original from what I can see. The tolex is rougher than I would like and the grill cloth is far better so I will have to ponder weather or not to do a cosmetic restoration to it. I have the original cart (yet to unpack that) and the cord retractor real works well so that's all good. I'm not sure about the driver yet as I have to figure out how to get into the cabinet to see what it's loaded with (hoping for vintage original).

The good as that I did a quick test and it is pretty obvious that it is beyond the sonic performance of my restored '67 B-15N, B-15R, etc.

The bad is that it hums like a mofo. It has a wicked 60Hz hum with both gains down and no instrument plugged in. Running up the gains with an instrument plugged in adds a bit of higher frequency hum but nothing like the 60Hz hum.

Any guesses? Do you think it is the power supply caps or some larger issue? I was planning to do all the PS caps and new tubes. The only odd thing I can find is that there is electrical tape on two of the wires. The wires are from the electrical plug in the chassis (original) which is wired to the original cloth covered internal wire (one goes to the transformer and the other somewhere else) and has two small wires coming off headed to the front panel hum control knob. There is also a rear panel hum control knob so not sure how that works as a B-15 only has one. The hum control knobs don't do much.

FWIW, I think a B-15 is better built but the P500 certainly has amazing cool factor and at first listen is stunning and can move some serious air.

Thanks in advance for any help!

gjbassist · #**320** 02-08-2013, 08:30 PM

I dissembled the cabinet of my B-15T today to give it a thorough cleaning and replace a couple of broken parts. When I removed the speaker I noticed that it is 8 ohms instead of 4 ohms. All the info I can find on this amp says the EVM 15L speaker in the cabinet is 4 ohms. I find it a little hard to believe that someone would have replace the 4 ohm speaker with the exact same 8 ohm speaker. Is it possible that when it was built they used an 8 ohm speaker on a few of these amps?
Another thing I have noticed is the lack of the Portaflex nameplate under the Ampeg logo. Every image I have found of the B-15T has this. Mine doesn't even have holes where one could have been attached to the grill. I wonder if mine could have been a prototype or very early version of the B-15T?