Tube retainer clips problematic?

[mozz]

I don't think you need the full split tubing ring on top, 4 small pieces would do.

[nevetslab]

Sorry I came upon this thread so late.

Having maintained the rental gear for CenterStaging, LLC in Burbank, CA since 2009, and have seen a lot of tube failure, some from direct contact of the spring joint of hold-down clamps in contact with the tube glass, and causing cracks as well as digging holes into the glass until the tube fails from that, I began using hi temp silicon rubber tubing, purchased from McMaster-Carr to slip over the spring/clamp joints to begin with, then later slitting the smaller OD tubing and fitting that into the open hole on the hold-down 'hat' of the clamp. I see one of my posts was attached : https://music-electronics-forum.com/...358#post794358

Here are some images of hold-down clamps I've done on a variety of tube amps over the years here.



I've found on Fender amps, such as aged Twin Reverbs, Deluxe Reverbs and such, as the tube sockets are no longer so tight-fitting to the tube pins, and even with re-tensioning the socket contacts, they will be a source of noise from vibration. The bear-trap clamps don't do as good of a job as the hold-down clamps, and the addition of the hi temp silicone rubber tubing, my tube glass breakage problems went way down, as well as the complaints from tube rattle noise. And contact is improved from the clamps keeping the tubes pulled in firmly under tension.

The Fender Super Bassman hold-down clamps are a real PITA. They would do well to use the base clamps instead of their clap-trap clamps that challenge anyone's patience in tying to replace tubes in that chassis. I finally found the partial solution to that. First, installing heat shrink tubing to captivate the spring to the clamp hat, then adding the larger dia silicon tubing over that to keep it intact. Then, adding the slit-tubing to fit into the top of the hat, and finally adding tubing onto the fingers to keep the tubes properly cushioned:



The EL84 power tubes and the usual thin spring-wire hold-down clamps aren't one of my favorites, and to use bias probes on those tubes, I have to extract those to fit my Compu-Bias Probes into the sockets. I saw the Belton 50703 EL84 Hold-Down clamps some time ago, and fitted those with some silicon sleeving.



The McMaster-Carr P/N's for the two Hi-Temp Silicon Rubber tubing...5/16" OD/3/16" ID P/N 3038K14, 10 ft @ $12.47 & 7/32" OD/3/32" ID P/N 3038K12 10 ft @ $9.63.

The SVT-CL & SVT-VR Hold-down clamps for the KT-88's & 6550's is where I began back in 2015, and it evolved to this:



On a side note, as i have a large fleet of Ampeg SVT-CL amps in our inventory, I replace the stiff plastic 'garden hose' sleeving with Tech Flex, as it makes servicing these amps far easier, as I have to stand the power amp chassis on it's power xfmr end, along with the Preamp coupled to it. Easy with the Tech Flex tubing, and nearly impossible with the garden hose tubing. I can measure the cathode current across the ten ohm cathode resistors, using the chassis as the test fixture for sorting/matching the tubes.

[Axtman]

Thanks! Nevetslab!

I just ordered tubing.

[nevetslab]

I don't think you need the full split tubing ring on top, 4 small pieces would do.

Back in mid-2021, one of our client's had our rental Ampeg SVT-CL on tour with them, and it managed to get knocked off the top of the Ampeg 810 bass cabinet to the stage floor. Surprisingly it survived the fall without any broken tubes. The stock Fender Super Bassman, prior to it having received the full shock mount treatment I give them, it was dropped by our staff hefting it up to the cabinet, and broke one of the power tubes. Another, a late generation Ampeg SVT-CL that has the base clamps, that tube shown in my post above broke in half cleanly. So, I think there IS something to be said for having the hold-down clamps with full shock mount sleeving to protect the tubes. Since i began using the hi temp silicon rubber tubing, the breakage problem vastly decreased. Still suffer from the normal tube failures, but not from breakage.