Rebuilding an old 5A3 TV pro Where to mount OT ?

[chopstuck]

I have an old TV pro I got from the Chicago Store in Tucson about 20 years ago.
I retweeded the bare wood cab and got a pretty good Jensen EM 15 speaker, without any mounting points for the OT (from an old Flot-a-tone amp).
One of the things that has been holding me back on this rebuild is, I did not want more holes in the chassis.
Mounting the OT to the cab seemed less than cool when there are no extra holes yet.
None on the chassis either.
Anyone have an idea or simple bracket for mounting an OT on an old Jensen EM 15 speaker ?

Also should the wax dipped caps be tossed as a matter of carcinogen infused badness or should they be tested for leakage one by one ?

[tubeswell]

Huh? I've never seen a 5A5, but the schematic suggests that it has an OT AND a field-coil speaker.

http://ampwares.com/schematics/pro_5a5- ... rected.pdf

So where is the existing OT if your one hasn't got an OT? (Because if it did have an OT, you could mount the new OT there).

[chopstuck]

The original speaker had a mounting boss incorporated into the basket.
This one does not.
I'm looking for an alternative to mount my MM tone clone OT.

[Cliff Schecht]

First off, that retweed looks great and that amp is pretty dang unmolested. Are you going to change out all of those wax caps? I probably would replace them with some Astrons if I was so equipped or something film and of similar vintage. I'm never sure on stuff like this. In the 40's radio that I use almost daily on my workbench, I instantly saw how horrible it would be to replace all of the wax caps in there. The entire radio works as is (with the other basic requisite modern safety improvements i.e. 3-prong cord and fresh e-caps) and so I don't fuss over it, but if you are gigging that amp then it might be a good preventative maintenance sort of task.

As far as your mounting issue is concerned, if I am understanding your post correctly then this speaker isn't original. That gives you a point to work with that won't hurt the value of the amp so much. The trickiest option is to simply drill some holes in the basket. If you tape off both sides of the metal and drill slowly from the bottom (i.e. cone pointing in the air, you under the speaker) then you shouldn't have a problem getting crap in the spider or gap. I'd probably go that route myself and just be very careful when drilling.

You could also try to somehow mount the OT to one of the speaker mounting screws. This might require you to drill one of the OT mounting holes but that's not such a big deal because it's again not a factory component. The other mounting hole could even be screwed into a simple bracket that mounts to another speaker mounting screw.

The only other not-so-intrusive option I can think of is either some sort of badass double-sided sticky tape or a glue that is strong enough to hold an OT without being destructive when removed. For the double-sided tape, I've had fantastic luck with this stuff holding up a LOT of weight, but you can't attach it to paint or it will rip the paint off of whatever it's attached to. I sort of cringe when I think of gluing an OT into an amp, so maybe scratch that thought..

[Phil_S]

If you don't want to drill, maybe you can find 2 existing holes that can be captured for double duty. For example, I see tube sockets that are screw mounted. Also, you might consider drilling out a rivet or two (if there are any) and replacing them with screws.

If you can fashion some sort of metal bracket that can be held by the screws, you can then mount the OT to the bracket. Is there any possibility of using the mounting bolts for the handle? Look for a new way to do things. It may or may not be elegant. If you are clever about it and get lucky finding some existing holes, it just might work.

An alternative may be to mount the OT to the side of the cab. I guess you'll need some sort of system for unplugging it from the chassis. I know this requires a couple of holes in the wood, but they can be filled and repaired whereas a hole in the chassis is there forever.

[chopstuck]

Thanks guys, I so neglected to consider the fact that the speaker is non-original.

I am going to see what the garage hardware fairy can bring me to solve this.

Stay tuned.

[rp]

First off, that retweed looks great and that amp is pretty dang unmolested.

+1

There's no chance the electro bypass caps are still good. IME those pre molded era coupling caps will likely all leak and be off. But since the guts are so unmolested I'd try to save as much as possible. You Probably know all this but if not: Lift one end on all and test for value. If any are way off then it won't matter if they leak. If you have any that are within tolerance, then with the amp powered, test them one at a time - one end lifted up, for DC on the side that should be blocked. Save all those old caps and keep them with the amp, if you have the old power supply electros save those too, and death cap and power cord too. One day soon unmolested non working amps will be worth more than restored working amps.

You could test the resistors too, but can wait on that, once it's working if it sounds good, strong and bright, and your voltages are all good then who cares if the resistors are somewhat off. Those early ccs in values like 250K don't show up anywhere.

As you said, don't hurt the chassis so harmlessly kluge the OT for now. Put the proper field coil model in your ebay favorites and wait patiently for however long it takes (could be years) for one to show up, if it's shot Weber will recone field coils I believe. Will be a real sweetie then.

[Structo]

You can also try and save the E cap paper tubes and insert new E caps inside.
Seal ends with epoxy or high temp wax.