Fender Combo Amp cabinet roof foil. Foiled again!!

[nevetslab]

I have a pair of Fender Deluxe Reverb re-issue combo amps here in the shop. Both with blown fuses, but I'll address that later. The first one from a steady client was up first. I went to remove the chassis from the cabinet, having removed all the securing hardware and unplugging the cables, and tried to carefully slid it out. Not a chance. The bottom of the front panel label, hanging down a bit below the chassis, wouldn't clear the baffle. So, had to pull everything from the cabinet....lower rear panel, reverb tank, front speaker/baffle, after first securing the chassis back to the roof. Went to remove it again, and it was still tedious to pull out, but did get it out. Moved it over to the service bench onto my lab jacks. I then felt up front on the roof inside, and felt the gaffer's tape and staples from a previous outing, having been there before. I hadn't checked my database for prior servicing.

I finally set this amp aside today, and moved on to the other Deluxe Reverb, this one belonging to Centerstagng where my shop is. After first replacing the rectifier tube for starters, and powering it up, all came up ok. But, the Normal Ch had loads of hum. Input jacks are not grounding, so the chassis has to come out to address that problem besides checking for why it had blown fuses.

Removed all the hardware again, went to slide the chassis out. No such luck Felt the front panel & baffle, but not an interference fit issue on this one. Looked thru the back panel to see if I could see daylight or obstruction anywhere, such as the start of the roof foil rolling up to halt any chance of removal. I didn't see that, but, it wasn't budging. I slid a 1/16" panel thru the front to the rear and then slid it from the input side on down to the opposite end, encountering some resistance. Roof fol issues again. I left the panel in place, and was able to work the chassis on out, removed it.

With it came rolled up and torn roof foil....just ripped to shreds! I lost a good 1/5 of the roof foil on this one.Yeah, I probably should have just screwed the chassis back in, gutted the cabinet as I did on the other Deluxe, then release the chassis and try to go back in and repair the damage.

I'm getting SO TIRED of Fender's shoddy adhesive roof foil installation jobs. That adhesive does NOT bond to the Tolex covering that is wrapped around from the top , then front edge of the sloped cabinet, then onto the roof of the inside. The Knife edge of the front chassis lip works just like a chiesl, and does an excellent job peeling up and rolling up the foil, locking it up and preventing any further removal, and now the damage has already begun!

[Enzo]

As an aside. If I have to fight a chassis, I often turn the amp on its side, so I don't have to fight gravity. The chassis now is standing on end and I can "lower" it towards the cab bottom and it will stay in position.

[nevetslab]

With the DR chassis sitting in the service cradle, letting the amp run under drive to see if the rectifier tube dies & blows a fuse, I turned my attention to the roof of thie combo case. Torn foil at both ends, and no real way to salvage it, so I ripped the rest of the foil out. Unrolled the 8" wide aluminum flashing roll I bought (0.15" thick) and rolled out enough for the full inside width and marked it off. My Roto-Trim shear from my darkroom assets is here to cover light duty cutting tasks, and I sheared off a 22.6" long sheet, then after securing the springy roll, I trimmed it to fit, being 22.4", with just a touch of slop so I could slid it in without fussing. I trimmed the 8" dimension to 7.1", leaving around a 1/4" of Tolex at both front and rear inside surfaces. Then, marked the locations of the chassis holes relative to that set-back, those being on 4" centers. and set back from the inside wall by 3/8" Noted the placement on the one end from teh front, and transferred that to the other end with my machinist square, and marked that end, with calipers to set the 4" mtg centers. With the machinist square reset for 3/8", I scribed the intersect lines for the chassis mtg screws, then center-punched those hole ctr's and punched 1/4" dia holes with a Whitney punch. Did similar marking for the three rear flange mtg holes, being set in 2.8" from each end and teh middle hole at 11.2". Set the adjustable square to the mtg holes in the cabinet, re-positioned the new sheet for alignment with the chassis holes, and marked & ctr-punched those 3 holes, and then punched them with the Whtney pnch (1/4" dia hole, so there's enough clearance if anything moves during fastening.

Once the sheet was set for best hole alignment & squared up, I stapled it into place along the four edges, then pounded the staples in flush.



I still have to clean off the residue from the fiberglass tape that left it's gummy stuff behind when I unraveled the roll of flashing. The Whitney punch can't get into the actual corners due to the side cleats, but the four corners are laying stiff and flush to the roof.

Still a PITA operation each and every time the roof foil gets peeled away by the chassis upper lip and rolls it up, locking the chassis up, and leaving you with foil damage to contend with!

[stokes]

What Enzo said,sometimes I actually turn it upside down,not just on the side,and lift the chassis a bit so I dont catch the shielding.On the rare occasion I do tear the foil I replace with copper foil tape that has a conductive adhesive.I havent had enough problems to think its an issue at all.I've had more problems with old Ampegs that have the tin sheets like the flashing you describe,but again,not so much that I would consider it an "issue".Just gotta be a bit careful when removing a chassis.

[Enzo]

I always had a selection of shim stock to slide between chassis and shield before sliding out, just to prevent it catching.

[Steve A.]

I've used aluminum flashing on some amps but I use rubber or contact cement in addition to staples to eliminate possibility of any metal vibration noises.

Speaking of Fender amps I always liked how you could stand up a BF/SF chassis with a 2×4 under the power transformer... I'm sure that Leo designed it that way to make them easier to service.

Steve A.

[nevetslab]

Checking my database service records, I had last opened this chassis in Jan 2015, and not having made any notes as to foil damage, it was still intact. I suspect someone else along the way attempted to pull it apart, and finding what I found, being unable to remove the chassis, may have fought with it and put all the screws back in place and made no mention of it. I bring up this foil issues, as I have to open up so many of them monthly, and the regularity of foil coming undone and getting rolled up by the front of the chassis is seems to be getting more frequent. The majority of them I'm able to restore, but, it requires gutting the cabinet so you can get the chassis out without further foil damage.