I have wheels under my Bassman RI for obvious reasons. It vibrates quite a bit when rolling it into gigs, sometimes shaking the tube shields off the 9-pin tubes. I have the standard Fender tube sockets with integrated metal shields; the kind with the slots that fit over the little dimples in the base.
Is there anything that can be done -- short of replacing the tube sockets -- to keep the tube shields more securely seated to the sockets?
Thanks.
---------- -Rick Davis
Last Edited by on Sep 18, 2012 2:44 PM
i tried to get 3 different techs to install the spring retainers in my amp no one would do it like my money isnt green? i'll have to do it my self i put a towel on the bottom of the cab just in case one drops
On the larger 6L6 power tubes,or the 5AR4/GZ34 rectifier tube yes,due to the weight of those tubes,and fewer pins securing the tubes to the sockets.
My Bassman went by pickup truck,with me driving,from NY to Califorinia and back,NY to Florida and back twice,and the tubes never showed any signs of being loose or falling out-
Last Edited by on Sep 18, 2012 3:47 PM
Sometimes just tightening up the fit by pinching the narrow bridge at the top of the tube shield cut-outs can be enough, so they are a tighter fit over the dimple.
Sometimes the tube shields get changed out for generic types (softer metal that gets loose quick) or the dimples on the shield holder flatten out. If the dimples are still good, try some new shields (if the pinching trick doesn't work), you often need to buy new sockets but they are cheap.
I usually find amps feedack quicker without the shields. ---------- www.myspace.com/markburness
"Amps Feedback quicker without shields? I've never heard that before. If that's true how much feedback can be eliminated by shields? Maybe a more elaborate shield could be fashioned to prevent more feedback?
I've done what you suggested: taking a pair of needle-nose pliers and crimping the tube shields a bit around the slot that catches on the bump on the tube socket. I think you are right that these shields are softer metal. I'll look for new shields; they are inexpensive.
Rick, do you have removeable casters on them?? If you have removeable casters, before you begin playing, ALWAYS remove them because the vibration will shake not only the shields loose, but more so, the tubes. The newer production tubes, from experience from the days when NOS tubes were what you always bought in a store when I started, they were noticeably more prone to getting loose than the NOs mainly because many of the components for years haven't really been as a good a quality.
I know you make the argument that the NOS stuff ain't worth the money, but this is something I've noticed from day one, and that's not counting the fact that the glass in the newer production tubes isn't as heavy duty and more easily subject to cracking.
You may want to replace those casters with removeable ones so that you can get them off before you begin playing and the louder you push the amp, the greater the vibration becomes.
I'd also auggest that you periodically check both the shields as well as the tubes to make sure they're not getting loose.
If you had the amp in the bottom of those heavy old anvil cases, the wheels on those cases have a wheel lock and the ones you've posted appears not to have this.
The thing about the shields preventing feedback, from my experience, is the truth. ---------- Sincerely, Barbeque Bob Maglinte Boston, MA http://www.barbequebob.com CD available at http://www.cdbaby.com/cd/bbmaglinte
@ Rainman, it's not a massive reduction in feedback, but noticeable. The tube shields confuse the electrons in the tube a little...removing them effectively gives the gain a little nudge up. ---------- www.myspace.com/markburness
BBQbob- I've made the argument that much money is wasted on NOS tubes. The claims one hears from some purveyors of old tubes are just nonsense, and the prices are often absurd as well.
I use NOS tubes, in particular the NOS JAN Philips 5751, a USA-made tube that sells for about $35. I also use NOS Sylvania 5814A tubes that sell for $20.
I do have a nice old GE 5R4 rectifier (not NOS, just old) that I like very much. The power tubes I prefer are new production Tung Sol; very economical and very warm.
The Bassman does not vibrate when sitting on stage being played. It is hard to imagine a 65-pound amp jiggling. The casters are not loose, they are quite rigid: That is why the amp gets shaken up when rolling across rough surfaces. When it is sitting still it is like a rock. ...a very nice sounding rock.
Really not so much with the feedback-there is no notiable difference-you really cant hear it with the RI Bassman,which is the amp in question. Other early tube amps-maybe. But it is mostly unproven with the RI Bassman,or any amps for that matter. Old wives tale-here is an excerpt-http://www.thegearpage.net/board/archive/index.php/t-859318.html
Last Edited by on Sep 19, 2012 9:22 AM
Interesting TMF714, what makes the cathode biased 12A#7 tubes in an RI bassman react differently to the cathode biased 12A#7 tubes in other amps? You are suggesting that a tube can detect the year of manufacture of an amp and behave accordingly, rather than work off the voltages supplied? Amazing!
I have seen more RI bassmans that any other kind of amp, more than you have for sure.
There are other threads on the gear page forum that contradict your off hand, untested, theorising. Perhaps you know more then Ken Fischer did...? I think not.
I say potato, you say poataato...yaaaaawwwnnn. If had a black dog, you'd have one blacker. ---------- www.myspace.com/markburness
I ordered three new black tube shields from Angela Instruments, at $1,49 each. Maybe mine are just old and worn out. They do look like they've been handled a lot.
@Rick Davis-Rick-please let me know if you find any difference tonally of otherwise with the shields off,if you please.
@Joey Anchors-the discussion revolves around a RI Bassman with printed circuit board. Like I said-earlier amps with point-to-point wiring may have a noticable difference.
Last Edited by on Sep 19, 2012 3:14 PM
@TMF714 "the discussion revolves around a RI Bassman with printed circuit board. Like I said-earlier amps with point-to-point wiring may have a noticable difference."
Kindly, using your extensive knowledge of amp circuitry (rather that cutting & pasting/linking other people's thoughts & ideas), explain this. How does a preamp tube know whether it is in a PCB amp or not? How does the wiring/PCB affect what goes on in the preamp tube envelope & with regards to the tube shield?
I know the arguments regarding co-planar boards and capacitance between traces, but you seem to be raising something different altogether here.
I'm all for sensible debate, but your assertion simply stems from your habit of knee-jerk contradiction. ---------- www.myspace.com/markburness
http://www.facebook.com/markburness
Last Edited by on Sep 20, 2012 1:21 AM
"Kindly, using your extensive knowledge of amp circuitry (rather that cutting & pasting/linking other people's thoughts & ideas), explain this. How does a preamp tube know whether it is in a PCB amp or not? How does the wiring/PCB affect what goes on in the preamp tube envelope & with regards to the tube shield?"
You seriously think there is no difference between the pre-amp stages in a RI Bassman and the 1957-60 5F6A?
The sheilds job is to reduce EMI -thats it-on earlier amps you may notice a slight upswing in gain-the earlier tube suppliers QC values were less demanding-the quality was ok-but EMI was a larger issue.
I am also quite sure that pin values were different between these amps-I have never heard of feeback increase due to lack of tube shields-I have built my own Bassman,and been involved with upgrades to many others.
I know, not think, what the differences are between an RI & an original 5F6A (of which there was more than one circuit, the amp design did not stay the same from 57-60). No changes were made to preamp grid, plate or cathode resistor values (nominal, within tolerance, change to V1 cathode bypass cap value, due to more commonly available modern values but also used on many hand wired repros - like your Hoffman board model you had, for example).
"I am also quite sure that pin values were different between these amps" You are wrong. There were at least a dozen component value permutations on the original amps (tone stack, PI tail, & presence control were affected), the 59RI is a copy of the last model made, with revisions to filter cap wiring (main & screen nodes now totem poles for higher voltage handling, preamp filter cap value upped to 44uf, totem pole in the bias filtering), addition of small grid stoppers on the power tubes, addition of virtual heater CT resistors as RI transformer has no centre tap on the filament circuit, bias pot added to RI Ltd.
I can draw the schems & layouts from memory, build to an eyelet board, terminal strips or point to point without reference. I'm sure that there are subjects in this world on which you are very knowledgeable...on this occasion, however, you are out of your depth. ---------- www.myspace.com/markburness
The new shields fit tight on the base. I don't think they will fall off. The original grey aluminum tube shields had gotten kind of soft with all the handling, and they fit askew on the tubes and fell off occasionally. I know it is kind of silly but the new shields also look better.
I gigged the amp last weekend without any tube shields and could not hear any difference in the tone or performance at all.
---------- -Rick Davis
Last Edited by on Sep 25, 2012 2:55 PM
I doubt anyone would in such circumstances. My observations were the result of immediate A/B tests in a controlled environment, which is how a lot of people identify small, but perceptible differences...get enough small things together and you get a bigger more noticable thing.
As ever, nice work cutting & pasting someone else's thoughts & opinions TMF714, you are great at it, you must do it for a living? ;-) Saves you having to do any thinking or make any effort doesn't it.
I saw Rick's last response & took it exactly as it read. I saw no reason or need to comment, or contradict it & thought it might be nice to let Rick have the last word/post on a thread he initiated...seemed like a natural conclusion? However, I didn't account for your inability to let things lie & now realise that was naive hope...so I leave the last word to you TMF714...so go on, take the glory! ;-)
---------- www.myspace.com/markburness
http://www.facebook.com/markburness
Last Edited by on Sep 27, 2012 4:42 AM
@Rick Davis-Rick-please let me know if you find any difference tonally of otherwise with the shields off,if you please.
Rick was simply getting back to me with his findings-I simply responded to Ricks post confiming my thoughts -if you have issues with that, simply don't repsond to my posts.
Last Edited by on Sep 27, 2012 4:31 AM
There may have been a difference but I could not hear it in a loud blues jam setting. It was ridiculously loud at times. I did play a nice 3-song blues duo set with Al Chesis on guitar that was not too loud and the amp sounded great, but the rest of the show was way over the top. The guitar player in my band -- Steve Mignano -- is moving to New Orleans to carry on his career there, and the jam turned into a drunken blow out (except for me: I do not drink).
Here is a sample. Not much harp content. Mostly it's Guitarmageddon.
Note: Randy Ricks is playing harp in the first segment, though his Frender '65 Princeton Reverb RI. It was seriously overmatched here. I'm playing in the second segment.
---------- -Rick Davis
Last Edited by on Sep 27, 2012 6:57 AM
