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Discussion in 'Shock Brother's DIY Amps' started by King Fan, Jul 22, 2019.
And while we're on the topic of silicone, I've used it for other amp purposes in the past (eg, MuchXS told me how he uses it to lock under-board wires in place). But I hated how there was no easy way to clean the extension nozzle *and* no clear way to re-cap the tube without silicone setting up inside the tip.
Researching silicone now, I see this tip about storage in the Permatex tech data sheet:
"Create a “Silicone Plug” by allowing excess material to extend beyond the extension nozzle or aerosol tip to cure, sealing and protecting the remaining product from moisture. For reuse, simply remove the cured product from the tip."
Having built my own bypasses for 2-way powered boxes where solder melts hot glue might do in an amp for Forbon boards or phenol as long as it's far from the tube mounts but RTV is a bit better IMO, plus as noted it sticks to metal a bit better but can be peeled off.
I made wooden blocks with screws for terminals and the bypass caps I hotglued ended up flopping on the wires.
I measured the temp of the circuit and the trannies over hours and not the tubes or the spaces in between.
The circuit temp seems to peak out around 150 F with the rectifier and cathode cap being the hottest.
Thanks, Pete. So this was the temp of the wires themselves? I'm wondering slightly about the chassis temp (which must vary by location) and even more about the air temp (which I'm guessing tends to equalize across the space due to convection).
Should be able to measure air temp. Hmm, need a fairly high-reading remote sensor or a sensor probe you could sneak into a buttoned-up chassis. Of course, I'm guessing it also varies by amp -- 4x6L6, an overworked PT, etc.
Remember, King Fan, an engine block can hit 250+, and it doesn't degrade the silicone!
You're totally right. Plus, as far as the chassis and my filter caps, they'll be some distance from the PT and tubes. So it was partly just curiosity. But...
To detour my thread a second, I was also thinking about a different aspect of this restoration. I'm thinking about re-stuffing new electrolytic bypass caps in the old 20uF paper tubes, and in some experiments and reading it sounds like you can refill the ends of the stuffed tubes with melted beeswax. But beeswax has a nominal melting point in the 140s.
Sorry, I feel a new thread coming on.
I did measure the chassis, near the PT and opposite of the PT. After 3 hours the open champ chassis only got up to 90 F near the PT. I don’t think the space in between can get (much) hotter than the hottest things in and around that space. Silicone should hold up.
A tube on the counter says, "sensor safe, temperature range from -85F to 500F, oil resistant, and designed to be used on any engine".
Hot melt glue is liquid at 400F, if your chassis gets that hot you've probably already got something else on fire...
FWIW, I've used hot glue to secure filter caps to the chassis in two builds and it worked well and seemed to be securely attached.
There exists low temp hot melt glue, and so, if silicone doesn't spin your fan, double-check the hotmelt in your gun isn't left over from the Xmas decorations that someone used low temp on. Whether the 375F glues will damage any of the components you use it on is another issue.
They make muffin trays/cake pans out of silicon these days.... ovenware...
it should handle the inside of an amp...
Yep, I have silicone barbecue mats -- they go right on the grill.
I appreciate all the reassurance about silicone heat, and I deserve it for dragging in my "how hot" curiosity. Just to be clear, I wasn't worried about heat to start with, just if silicone would give enough grip on slippery shiny caps and slippery shiny paint.
I've now tried it (nothing beats empiricism ) and it grips really well, as a number of you said it would.
Yes! I had a Marshall DSL401 where someone repaired the PCB near the power tubes and put hot glue over the repair. It reflowed when the amp got hot. I had to cut the tubes out of the amp! Good silicone is a much better choice.
That happened to me ... someone tried to anchor the tube sockets on a Blues Jr with Low Temp glue stick, and when I helped them change their tubes, there was glue all over them. Had to let it warm up just to get the tubes out.
Your picture demonstrates a common problem I’ve encountered with the self adhesive tie wrap hold-downs. The adhesive fails a lot! One of yours here is lifting off.
I found gardener-bender to make the best I can find, but even those fail. When I do use these, I clean off the original adhesive and glue them with Gorilla glue. That’s never failed, but I expect those mounts to be basically permanent.
Good info. Nothing like sticky real-life facts. Location location location -- hot glue (especially the high-temp kind) may work fine to stick filter caps up somewhere on the chassis. But the low-temp kind is not good near the tubes or other very hot components. Heck, I don't need to ask how hot *tubes* get...
Good point, Bob. Adhesives on fasteners are at least as likely to fail as any other stickum, and maybe more so. Remember waking up with the poster you stuck to your dorm wall lying on your face?
In regards to location and adhesive type, my source, Doug Hoffman, notes that in the doghouse "you can secure the caps to the metal can with double stick tape, glue or RTV silicone." I hope the doghouse isn't too hot. Of course, so does the dog.