Official Ampeg Portaflex Club

[PapaJohnBass]

Welcome and nice looking amp. At first glance, I thought that you traded a 69 Plymouth for it. I like old cars with AM radios.

I find baltic birch is often available at wood stores that sell high end wood, as opposed to hardware stores. They list baltic birch at this place:


David

Thank You Very Much Beans, You Are The Man. I wanted the amp but I was not willing to trade my 1969 RoadRunner for it, just the AM radio. I went high tech and installed an AM 8 Track Radio. I wish I still had the RoadRunner! (I had to remove the link reference in order to post). I will call them tomorrow and I may have to take a ride to Annapolis (or Frederick). I have some info to post that may be interesting to some. I wanted Green lamps to illuminate the Logo and didn't want to spend $12.00 for LED replacements. I have plenty of LED's in my personal stock and used a portion of a RadioShack PC board and a very simple circuit to make a board with 3 Green LED's on it. It takes its power from the 6.3 volt filament string. It is totally reversible as the connections are soldered to the pilot lamp connections. I also bought two 60mm x 10mm 12 volt fans from an infamous auction site and screwed them on the tube cage to keep the heat away from the power and rectifier tubes. I used 4-40 screws and I did not have to drill holes in the cage. I use an external 12 Volt 1 Amp supply to power the fans. They are quiet and would only need to be turned off in a live recording session. I can post pictures and a schematic if there is any interest.

 

[JimmyM]

Thanks. I have been reading TB for over a decade and I really wanted to rebuild the B15NC. It was through this site that I finally decided to to the jopb. I have gathered enough info from the members to build the cabinet. I have purchased an Eminence Delta 15A this week and I am gathering some of the hardware to build it. Tough to find 13 ply Baltic Birch in my neck of the woods but I will keep trying until I get a sheet. I will post pictures of the cabinet when it is complete.

Good speaker choice! Sounds like a fun project.

Doubt your amp needs fans, but cooling a tube amp isn't usually thought of as a bad thing. Beans might have some thoughts to add, though. He's the dude you should listen to here, not me

 

[PapaJohnBass]

Good speaker choice! Sounds like a fun project.

Doubt your amp needs fans, but cooling a tube amp isn't usually thought of as a bad thing. Beans might have some thoughts to add, though. He's the dude you should listen to here, not me

Thanks for the info Jimmy. I chose the Eminence Delta 15A because it seemed like a good choice from reading the posts here. As far as Beans and others, I am all ears. I have an electronics background as a hobby since I was 12 years old but I am not a know it all and always open for thoughts, suggestions and advise. I thought that getting the heat away from the tubes would not be a bad thing and it was very low cost, simple to implement, low noise and easily reversible by removing just 4 screws.

 

[beans-on-toast]

Like Jimmy said, the tubes are designed to run hot. Having said that, heat kills other things like capacitors. Removing the heat doesn't hurt and what you did sounds like it would do a good job. It never hurts to experiment and see what happens. Some rubber grommets between the fan and the tube cage would prevent any vibration. Depending on where the fans are located, you might not be able to flip the amp into the speaker cabinet with the fans in place.

I have an old fashioned cooling solution. I sometimes blow a small desk fan (http://www.amazon.com/Honeywell-HT-900-TurboForce-Fan/dp/B001R1RXUG) into the back of my amps. In the case of the B-15, the tubes run cool enough that you can touch them.

 

[beans-on-toast]

A friend of mine had a 69 Roadrunner with a hurst shifter that used to be able to lay down some rubber. I held on to my Nova for 25 years.

 

[BassGen]

How long should a set of pre-amp tubes last in terms of actual in-use time? My amp is an SVT6-Pro and IIRC it has 6-12ax7's in the pre section.

 

[Apex_speed]

After the brutal winter that some of us experienced this year, perhaps it's the nice weather.

It would be interesting to know if postings are down since the new TB software came online. Even though it is nice and all, people get put off by change. Maybe that's why most of my musical instrument amps are old. Even the newer tube amps are heavily based on the old designs.

I think it is the new format as posting appears to be down in al threads to me and responses to classifieds are way down as well. I also still hear people complaining that they are not getting notifications but maybe that is corrected.

Just Signed up, This is my first post. I have what I believe to be a 1964 B15NC head with all of the original Ampeg branded tubes but without the speaker cabinet. Some pots are dated 62 and others are 63 and the FP can electrolytic is dated 6404. Even though the amp had no discernable hum, I decided that because the cap is 50 years old it was best to replace it. It is cathode biased with a 5AR4 and utilizes eyelet board wiring construction. It does not have named input jacks (Guitar, Bass, Accordion) or a serial number on the chassis under the power cord or anywhere else.
I acquired this amp back in the mid 1970's from the manager of a band I was with at the time. I traded a 1969 Plymouth AM car radio for it.
When I got it home after rehearsal I noticed that I did not have 6.3 volts as the filaments and the Lucite logo lights were not on.
I got out my voltmeter and began checking voltages. As I was probing, when I touched the filament string on the first 6L6GB the Lucite logo lights flashed. I got out my Weller gun and touched up the solder joint and it came to life. I replaced all of the caps with Orange drops. I removed the Ampeg tubes, put them away in tube boxes and replaced them with Sylvania tubes that I had laying around. Now that I have electronically restored the amp, my next project is building the speaker cabinet. I have attached a picture of my B15NC. Jimmy, I would like to join the discussion group.

Very nice and a cool story!

 

[JimmyM]

Jeez, the answer could vary between 20 years from now and tomorrow. There are so many different scenarios for usage, and such variation in tube quality these days, that you just can't predict it.

 

[vistacruiser]

How long should a set of pre-amp tubes last in terms of actual in-use time? My amp is an SVT6-Pro and IIRC it has 6-12ax7's in the pre section.

BassGen I think the answer is, until you get tired of them and decide to try to find better sounding pre amp tubes. I can't say I've worn out any yet, but I'm happier with the sound of the amp since trying several different 12ax7's and finding some I like better than the original Sovtek 12ax7WA.

 

[coreyfyfe]

How long should a set of pre-amp tubes last in terms of actual in-use time? My amp is an SVT6-Pro and IIRC it has 6-12ax7's in the pre section.

Good tubes? Years at least. I'm not sure where you can find the numbers, but people usually say things like 10-20,000 hours (or more) for certain old tubes. With modern production tubes even if the life is 2000 hours that's about 3 years of playing 2 hours a day assuming normal operating conditions. An amp or position in an amp that really pushes the tube probably less.

 

[BassGen]

Thanks for the comments guys. I've never pulled the cover on my amp so I don't know what tubes are in it. I can't complain about the sound though. AFAIK it's a US built Svt6-pro if anyone happens to know what make of 12ax7's that Ampeg was using in them.

 

[96tbird]

Russian. Most brands come from two Russian factories.

A few come from China.

Brands mean little these days, internal valve architecture is the main difference between valves. The brands only have selection parameters the maker follows to select for branding.

 

[jdubbass38]

Please do, and let us know how the two heads compare through the same 2-15 cabinet!

jdub, are you or have you ever tried using a solid state rectifier in place of the 5ar4 tube in your B25b?
I like the effect it gives. More punch and stronger attack, it actually feels like it adds headroom. It's a simple as pulling the tube and putting the ss recto in it's place. When I put the ss recto in my B25b I saw a voltage increase of 3% at pins 3 and 4 of the 7027A's. From 505 and 499 up to 520 and 514. I took it back out after a while when I noticed my old Sylvania power tubes were not well matched. But plan to re-install it at some point when I re-tube with a matched pair of Sovtek 7027's that are stashed away.

I should have time this weekend to A/B the cabinets with the v4b head.

To be honest I am not sure if my head is using a tube or solid state rectifier, I will check tonight. My b25b rig does seem to have a punch to it but that's interesting to know by changing it out you can get different results.

 

[beans-on-toast]

Whatever can go wrong with a software upgrade, will.

I haven't figured out how to use the iPhone app yet. When I go to any thread, it takes me to the first post. I click on the header at the top and a table comes up, I select the last page and it goes there. Then I need to click on the three dots at the top and select refresh. Then I get to see the most recent posts. I never log on while using my phone, maybe that's the problem.

 

[Ric Vice]

Thanks. I have been reading TB for over a decade and I really wanted to rebuild the B15NC. It was through this site that I finally decided to to the jopb. I have gathered enough info from the members to build the cabinet. I have purchased an Eminence Delta 15A this week and I am gathering some of the hardware to build it. Tough to find 13 ply Baltic Birch in my neck of the woods but I will keep trying until I get a sheet. I will post pictures of the cabinet when it is complete.

Good luck with your restoration, many years ago my father in law built me an Electro Voice Thiel cabinet out of 13 ply baltic birch, it sounded nice, but you have to know what you're doing to work with that stuff. Having owned several Bag End 15's, I applaud your skills.

Ric

 

[JimmyM]

Thanks for the comments guys. I've never pulled the cover on my amp so I don't know what tubes are in it. I can't complain about the sound though. AFAIK it's a US built Svt6-pro if anyone happens to know what make of 12ax7's that Ampeg was using in them.

Most likely Sovteks.

 

[PapaJohnBass]

A friend of mine had a 69 Roadrunner with a hurst shifter that used to be able to lay down some rubber. I held on to my Nova for 25 years.

I wish I had all of the money that I wasted on tires and 29.9 cents per gallon gas and speeding tickets.

 

[RutherfordBrave]

Thanks. I have been reading TB for over a decade and I really wanted to rebuild the B15NC. It was through this site that I finally decided to to the jopb. I have gathered enough info from the members to build the cabinet. I have purchased an Eminence Delta 15A this week and I am gathering some of the hardware to build it. Tough to find 13 ply Baltic Birch in my neck of the woods but I will keep trying until I get a sheet. I will post pictures of the cabinet when it is complete.

Just FYI, I'm awfully close by (Ellicott City), and if you're interested in building more than one I'd be happy to offer a second set of hands. I have a '64 that I haven't brought myself to re-cover, but have a couple yards of tolex squirreled away for a project just like you're talking about. Send me a PM if you're interested!

[Invalid or Expired Link Removed]

 

[PapaJohnBass]

Like Jimmy said, the tubes are designed to run hot. Having said that, heat kills other things like capacitors. Removing the heat doesn't hurt and what you did sounds like it would do a good job. It never hurts to experiment and see what happens. Some rubber grommets between the fan and the tube cage would prevent any vibration. Depending on where the fans are located, you might not be able to flip the amp into the speaker cabinet with the fans in place.

I have an old fashioned cooling solution. I sometimes blow a small desk fan into the back of my amps. In the case of the B-15, the tubes run cool enough that you can touch them.

Thanks to Beans On Toast for providing me with a source for the 13 ply Baltic Birch that I picked up this morning. The shop owner was kind enough to cut the sheet 2 times so it would fit in my car. When he asked how I heard of his business, I told him TalkBass. I have many reasons for the fans, the primary one is my 3 year old Granddaughter who loves to play with the cool stuff in Papa's room including HOT amplifiers. The 6L6GC's are running 300ºF and the top of the cage gets HOT. You would not want to touch the cage after the amp has been on for several minutes. I positioned the fans to cool the power tubes and the rectifier. When the fans are turned on, the top of the cage is cool to the touch so there will be no burned little fingers. Also I thought that since I just put in a new electro with the 5AR4 rectifier a half inch away from it, it may prolong its life a bit and keeping the tubes cooler may not hurt as I replaced the 5AR4 (JJ) and the 6L6GC's (Tung-Sol). The three 5691's I put in it really don't get that hot. I did not need to (yet) put any isolation between the fans and the cage as they are quiet and really don't vibrate, time will tell the whole story. Also the $1.77 ea. fans are only 10mm thick and the fuse holder and hum pot stick out farther than they do. Still, care WILL be excersized when removing and installing the amp in the cabinet. If you look closely at the Side View picture between the amp and the plank you can see a sheet of 18ga. sheet metal peeking out that greatly reduced hum and noise. Pics below. The plank that the amp is mounted on was just something I had laying around in the 1970's. When I do the cabinet build this weekend with my neighbor's help (he has the table saw with the correct blade, a router and all of the other needed tools and builds kitchen cabinets with Baltic Birch). We will also cut the correct size amp base and cabinet cover. I guess I will have to buy the amp shock mounts as well. So far with all of the parts, speaker, Ampeg Scroll Logo and wood I bought I have spent less than $200.00 I still need a 2' x 2' - 1/2" plywood, Handles, Corners, Tolex and Grill Cloth. I can't wait to get started (and finished). I'm gonna celebrate by playing some Pink Floyd and some Led Zepp and........!

 

[Pentatonic]

Whatever can go wrong with a software upgrade, will.

I haven't figured out how to use the iPhone app yet. When I go to any thread, it takes me to the first post. I click on the header at the top and a table comes up, I select the last page and it goes there. Then I need to click on the three dots at the top and select refresh. Then I get to see the most recent posts. I never log on while using my phone, maybe that's the problem.

The app settings include some options for selecting the desired read order behavior. I find "first unread" works best.