Who sells EI Xfmr mounting brackets?

[nevetslab]

I have an EI-125H Core Size power transformer (open primary, out of a Fender Hot Rod Deluxe), and assuming the fault is the open thermal fuse buried inside the windings....which is no doubt parked inside a cardboard tube near the base of the core in the winding, as I've seen before. EI-125H Core is 3.75" x 3.125" outside dimension, with mtg ctrs of 3.125" x 2.500". In the Hot Rod chassis, they cut out the pattern for the lead-breakout end bell. I'm looking to mount this using mtg brackets, either using long L-Brackets, or perhaps short width or length brackets off of the 3.125" or 2.5" mtg ctrs.

I downloaded the Tempel Steel Transformer Core catalog, which helped identify the core size, but, thus far, the only souce I've found for L-brackets was thru Tube Amp Doctor. p/n TFM-96, @ 2.21 Euros ea. There's gotta be more sources than that.

Will I have to contact transformer mfgrs to find someone who has mtg hardware to solve this? Application is on this KT88/6550 Power Tube Test Fixture, being built into a Blackstar S200 chassis. Their power xfmr has the HT winding for above 700V no load, but, doesn't seem to do a good job for the Screen Supply. A separate Screen Supply winding, or two as Hiwatt uses, accomplishes this task quite nicely. This presently-dead HR Deluxe P/T, assuming I can replace the open thermal fuse, would solve that Screen Supply quite nicely, as it's around 430VDC @ idle.

Any suggestions for mtg bracket sources?

[Jon Snell]

https://www.grau-stanzwerk.de/e/prod...formatoren.php
These guys manufacture and sell transformer parts.

[Jon Snell]

A bit nearer to home for you;
https://www.thomasnet.com/products/t...3023001-1.html

[SoulFetish]

I have an assortment of mounting brackets. I'll try and remember to see if I have any that'll fit in the mean time.

[nevetslab]

A bit nearer to home for you;
https://www.thomasnet.com/products/t...3023001-1.html

Looks like all the companies listed via www.thomasnet.com are geared towards supplying materials to manufacturers. Usually not much luck when you're just looking for four mounting brackets for a singular task asI have here.

I haven't tried contacting Pacific Transformer over in Orange County, who I had used for years when working as an engineer at BGW Systems in Hathorne, CA over the years. They were no doubt getting their brackets from another source.

Thanks, Steven

[nevetslab]

I have an assortment of mounting brackets. I'll try and remember to see if I have any that'll fit in the mean time.

I always scavenge hardware from dead xfmrs for such purposes, but I don't have any that are suitable.....at least not in the shop. That would be terrific if you find a set that would work. If they're narrow L-brackets, then I'd need four, while if short/long width brackets as would be used to mount at the base of the core, then two. Redrilling/cutting to size always works to make them fit.

Thanks in advance! Steven

[nevetslab]

I looked on McMaster-Carr, and after checking the mechanical dimensions from the core to the flat portion of the end bells, I have a touch under 1/2". I found some T-6061 1/2" x 1" angle stock, 1/8" thick that would suit for mounting the xfmr in either the horizontal or vertical position with cut/drilled/shaped brackets to pick up the core mounting screws. So, I ordered a foot length of that material for a touch over $3, along with a couple other items. That should solve the mounting problem.

I checked my files from when I had previously taken a Fender Power Xfmr apart that also had an open primary. I thought it was from a Deluxe Reverb, but it turned out to also be a Hot Rod Deluxe power xfmr like this one I have on the bench. I think I still have that one someplace. I did take a series of disassembly and dissection photos showing the steps to get to/extract the open thermal fuse. Hopefully I DID keep that xfmr, and not just chuck it after that exercise. I don't recall tracking down the replacement thermal fuse. I did find that post from recent times:

https://music-electronics-forum.com/...r-thermal-fuse

Onward with the project. HT voltage would be suitable for the Screen Supply of the KT88/6550 Power Tube Test Fixture I'm about to begin building into that Blackstar S200 Chassis and with their power and output xfmrs. I did pick up a 63VA 10A/6.3VAC heater xfmr. I somehow doubt if this Fender HR Deluxe xfmr could handle the heaters of four KT88's plus the four preamp tubes of the Hiwatt DR201 circuit that I'll build this up as, with the rear panel fused test sockets for cathode current monitoring.

[nevetslab]

When I finally got that power xfmr apart and removed the thermal fuse, which was open as I expected, I also discovered not only was IT open, but so was the Primary coil! RATS. So, saved the end bells and mtg hardware, and tossed that out. After digging thru the shelves, I found I had clearly marked the box containing that previous power xfmr that I had done that dissection on to get at the thermal fuse. So, it was where I had left off. I looked in my catch-all desk drawer where I store batteries and other useful items, and was pretty sure I had stashed thermal fuses there, as I sometimes have to use them to restore the coffee pot when those open. I had the same part as I had removed from the Hot Rod Deluxe power xfmr, seeing the same model number on the end bell.

Checked the primary on this one, and it WAS still intact, so I just needed to clean up the mounting sleeve for the thermal fuse. Found an appropriate sleeve to crimp the longer insulated connecting wire from the thermal fuse, installed that, wired the two ends up, then carefully taped up the core, closed the heavy insulation band down and taped it shut, and finally clamped the copper flux band back down.

The 3/4" copper soldering iron tip of the 300 W American Beauty Iron was badly corroded, so I stopped to file it back to bare copper, put it back into the iron, plugged it in and waited for that to come up to temperature. Got the tip re-tinned, then finally got that copper flux band soldered back together.

I had found a pair of somewhat larger mounting brackets and installed those, after putting the end bells back on, and put the hardware back in, closed it all up. I may still change to the aluminum angle extrusion that just arrived from McMaster-Carr.

Powered up the xfmr thru my fused AC interface box, with quick-disconnect breakout leads to plug the xmfr in. Powered up without any issues. 340VAC HT winding, 41VAC Utility winding, 7.1VAC for the Heater winding...all unloaded. More HT voltage than I need, as well as that power xfmr from Blackstar also produces higher HT voltage than I need, so I'll no doubt have to trim the AC Mains to keep the voltage where I need them after I get this project wired up.

So, I have a Screen Supply xfmr to go with the HT xfmr.

There was a core bolt broken off in the Fender xfmr, which was a real PITA to drive out. Frozen stiff in place. Fearing for my left hand while holding a drive pin punch and whacking the head of that punch with a hammer, I finally changed to holding it with my 8" gas pliers and a heavier hammer. That finally succeed in knocking that broken screw out.

[nevetslab]

Yesterday, having received my McMaster-Carr order which contained the 12" piece of T-6061 Aluminum 1/2" x 1" angle extrusion, 1/8" thick, radiused at the inside corner (all that was offered with that 1/8" thickness). I cut two pieces 3.125" wide to mount the xfmr vertically. With the EI-125H Core Mtg holes set in 7/16" (0.3125), that placed the hole a mere 0.1875 down from the inside top of the extrusion. I only had the choice of 1/2" or 1" height, and not wanting to spend the time to hack out a relief, I opted for the 1/2". I did have to file out the radius at the ends with my carbide mill file so I could mount the #8-32 mounting nut & washer flush. The hardware I had was 11/32" hex, so there wasn't enough clearance for my socket wrench, but I was still able to tighten them up. After I had sawn them to length, using calipers and sliding Machinist Square, I scribed the mtg hole locations, center-punched the holes, and mounted them into my drill press vise and drilled them out, first with 1/16" pilot hole, then drilled out to 0.210". I finished the core bolt holes with a #3 Taper Reamer, taking it out to 0.221" for the 7/32" ID mtg holes. At least using T-6061 Aluminum instead of soft aluminum, the drilled holes didn't wander during the drilling process. Drilled clearance holes for #10-32 mtg hardware.

I still will end up cutting the quick-disconnect terminals off, and extending the leads with 600V rated 18AWG PVC. Shame the power xfmr of the Blackstar S200 didn't have traditional heater windings and separate Screen/HT winding for the preamp tubes. Having to add a 63VA heater xfmr for the KT88's heaters, and now this for the Screens, it's going to be a heavy chassis. Already was lop-sided with the two large xfmrs at the one end.