Does anyone have any suggestions for tube replacements? It looks like I have all 6 original tubes, 1-5AR4, 2-6L6GC, and 3-6SL7's.
I wood like to put NOS tubes in it. Also, I get distortion at any volume level when I hit an E note any place. Any ideas?
Tube Replacement for 67 Portaflex B15N?
Moderator: jingle_jangle
Tube Replacement for 67 Portaflex B15N?
Buy it before someone else does.
You shouldn't get distortion any any level no matter how bad your tubes are unless they are glowing cherry red (power tubes) and are ready to blow a fuse or transformer at any moment, even then you shouldn't get distortion at any level. Do they say Ampeg on them? If not they are likely not original.
Bob, all the powertubes are original, and they do say Ampeg. I think the rectifier and the preamp tubes are not but still very old. Any other thoughts about the distortion? Maybe my speaker needs reconed. It's the original square magnet CTS. $120 for NOS 6L6's. maybe I don't need NOS tubes after all. 
Thanks for the link Jeff.
Thanks for the link Jeff.
Buy it before someone else does.
Yes they don't give them away, that's why I don't have any. Believe it or not but I've bought used GE 6L6's on ebay for 20 bucks before for my old Ampeg and they still seem better than a lot of the new tubes. A blown speaker will give a rubbing sound which is often more noticable at low volumes than high unless the speaker is completely gone, then it's very obviously a mechanical rubbing sound, it's a different sound than amp disortion. Can you hook a different amp up to the speaker? How about a different speaker to the amp? With a vintage B-15 I wouldn't change the speaker or recone it unless I was certain that it was bad. Rectifiers either work or they don't, I wouldn't change that unless the filiment burns out. Could be a bad pre amp tube, that would make an amp distort at all volumes if it were bad, but you could most likely eliminate that if both channels sound the same as they have different pre amp tubes. Another way to check your speaker is to carefully push the cone out with equal pressure on both sides, it shouldn't rub except at the end of it's travel path. Even better take it out and move the cone in and out carefully with equal pressure, it shouldn't rub that way either if it is good unless you force it beyond it's excursion travel. (new term) Was this a gradual thing or did it happen quickly? The best way to check though is hooking the amp up to a different speaker and the speaker to a different amp.
Tap the preamp tubes, if you hear a dinging sound that increases in volume as you turn up the volume they are microphonic and need to be replaced. A really bad power tube can also do that but it won't increase in volume with your volume control. The tubes in your amp are still readily available new and NOS.
I have a 1959 Ampeg Bassamp, was made before the B-15, is similar though, one 15" and 35 watts but it has separate preamp and power amps like a little SVT, sounds really good. It has both bass and treble like yours haha!.
Tap the preamp tubes, if you hear a dinging sound that increases in volume as you turn up the volume they are microphonic and need to be replaced. A really bad power tube can also do that but it won't increase in volume with your volume control. The tubes in your amp are still readily available new and NOS.
I have a 1959 Ampeg Bassamp, was made before the B-15, is similar though, one 15" and 35 watts but it has separate preamp and power amps like a little SVT, sounds really good. It has both bass and treble like yours haha!.
Wow, thanks Bob of all of the troubleshooting advise. I will try what you suggested. The amp does make the same distorted sound on both channels at any volume, but only when playing an E note. Other than that, it's sounds great. I just bought the amp about a month ago from Bass Northwest. I have had this problem ever since I received it. I got a good deal I thought, everything appears to be original and all was in really good shape, except for some small rust spots and pitting in the chrome. I need a new handle, and new speaker cover however. I bought the dolly and one latch from Fliptops, plus the weird screwdriver. They seem to have everything.
Thanks again.
Thanks again.
Buy it before someone else does.
Any E note, even a high E? It's not a resonance is it? If not it could possibly be the speaker, that's kind of wired though. Another thing, crank it up so that all notes distort, is it the same sound as the E note sound or different? Check for loose connections also. But I'd switch amps and speakers first if I could.
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soundmasterg
- RRF Consultant
- Posts: 1923
- Joined: Tue Oct 01, 2002 1:06 pm
Check the speaker screws to make sure one isn't loose. They aren't supposed to be reefed on, just make sure they are slightly more than hand tight. If the speaker is loose, that could account for the noise you are hearing on the low E string. Also check to make sure all the chassis and cabinet screws are tight and not missing.
For tubes, don't bother replacing the GZ34...as long as it works, it is most likely just fine. If you did have to replace that one, I would go with a Weber Copper Cap instead of the tube anyway. They sound just as good and won't ever go bad, and they are cheaper. For the power tubes, you could get some Winged C or JJ for modern manufacture. Both sound very good and last awhile. For the preamp tubes, NOS isn't too expensive, but for some of those types NOS is microphonic. I believe EH makes some decent new manufacture 6SL7's. Most, if not all of those tubes you can get from Antique Electronics Supply.
For tubes, don't bother replacing the GZ34...as long as it works, it is most likely just fine. If you did have to replace that one, I would go with a Weber Copper Cap instead of the tube anyway. They sound just as good and won't ever go bad, and they are cheaper. For the power tubes, you could get some Winged C or JJ for modern manufacture. Both sound very good and last awhile. For the preamp tubes, NOS isn't too expensive, but for some of those types NOS is microphonic. I believe EH makes some decent new manufacture 6SL7's. Most, if not all of those tubes you can get from Antique Electronics Supply.
Greg, and Bob thanks for all of your help.
I just got an email from the man himself Jess Oliver, and he suggested the same things you guys have.
Here's his email, and I will try everyone's advise.
"Hello Bob Scott,
Thanks for the nice things you say about my a B15N. it doesn't sound like a tube problem. I have some good tubes I can sell you., but let's fix the other thing first.
First make sure the nuts holding the speaker are reasonably tight. Or it could be a sympathetic cabinet buzz. Have somebody else press on different places of the unit, even the chassis or the grill cloth. If you find nothing helps, remove the speaaker from the cabinet, being very carefull not to punch any holes in the paper cone. If you see any cracks in the outer rim of the cone it needs to be reconed. In that case send it here, I'll make it sound better than it ever did".
Best,
Jess Oliver
P.S.: You may want to read Keith Rosier’s interview with me:
http://www.keithrosier.com/jess.asp
I just got an email from the man himself Jess Oliver, and he suggested the same things you guys have.
Here's his email, and I will try everyone's advise.
"Hello Bob Scott,
Thanks for the nice things you say about my a B15N. it doesn't sound like a tube problem. I have some good tubes I can sell you., but let's fix the other thing first.
First make sure the nuts holding the speaker are reasonably tight. Or it could be a sympathetic cabinet buzz. Have somebody else press on different places of the unit, even the chassis or the grill cloth. If you find nothing helps, remove the speaaker from the cabinet, being very carefull not to punch any holes in the paper cone. If you see any cracks in the outer rim of the cone it needs to be reconed. In that case send it here, I'll make it sound better than it ever did".
Best,
Jess Oliver
P.S.: You may want to read Keith Rosier’s interview with me:
http://www.keithrosier.com/jess.asp
Buy it before someone else does.
Yes he's a very nice man, he sent me a schematic for free for my old Ampeg, I had been looking everywhere for one. I was actually a little intimidated asking him, but he was very gracious with me.
I didn't think of the speaker screws, did you say it was only the low E or all E's? I thought you meant all E's.
I didn't think of the speaker screws, did you say it was only the low E or all E's? I thought you meant all E's.
I was thinking if it is all E's that it was probably a resonant vibration. I once bought an SVT cab really cheap because it had a bad vibration in it on certain notes. It took me a while to figure it out but it turned out to be one of the baffle boards that isolates each pair of tens from the others. It was supposed to be glued to the front baffle board and it came unglued. When the cab was played loud it vibrated against the front baffle board and made a horrible noise. After I glued it and screwed it it sounded great.
