Refurb: 50s Sano Excelsior 25W

[xtian]

Awesome craigslist day today! Got a Harmony standalone reverb unit, handfull of old 12ax7's, a nearly full set of TRW carbon comp resistors, and the most awesome old Excelsior!

Has missing fuse and missing 6L6 tube. The full complement: 2 @ 6L6, 5U4, 6SL7, 2 @ 6SN7GT.

Schematic???

In decent shape. Look at that 15" Gold bell!

This is going to be a fun refurb!

Can someone help me decipher the speaker code: 106752-1


[IMG:800:598]http://www.monkeymatic.com/pub/ebay/excelsior1.jpg[/img]
[IMG:800:598]http://www.monkeymatic.com/pub/ebay/excelsior2.jpg[/img]
[IMG:800:598]http://www.monkeymatic.com/pub/ebay/excelsior3.jpg[/img]
[IMG:800:598]http://www.monkeymatic.com/pub/ebay/excelsior4.jpg[/img]
[IMG:800:598]http://www.monkeymatic.com/pub/ebay/excelsior5.jpg[/img]
[IMG:800:598]http://www.monkeymatic.com/pub/ebay/excelsior6.jpg[/img]
[IMG:800:598]http://www.monkeymatic.com/pub/ebay/excelsior7.jpg[/img]

[Firestorm]

Can someone help me decipher the speaker code: 106752-1

I think that's just the cone code and I'm not sure how decipherable those are. But the amp is definitely a Sano and the speaker is definitely a Utah PA15R; alnico "Public Address" speaker, pretty much standard in the larger Sano amps. You might take the bell cover off the magnet and see if there's an EIA code under there.

[Bear]

The Fender Pawnshop Excelsior has some visual echoes of this, doesn't it?

That looks all sorts of cool, especially the Coke-bottle 6L6's.

[xtian]

You might take the bell cover off the magnet and see if there's an EIA code under there.

328601

[Firestorm]

So: Utah, 1956 (it looks more '56 than '66 doesn't it?), 1st week of January. You could get another date code off the filter cap can, which is probably original.

[gingertube]

Great Score.

Best to do a circuit trace but to get you started.
Sub 6SL7 for 12AX7 and 6L6 for output tubes in this and you priobably get a big head start.
http://www.webphix.com/schematic%20heav ... l_1959.pdf
Cheers,
Ian

[Structo]

Cool amp!

I love the spatter paint and grill cloth!

That should sound killer when you get done!

[xtian]

Played my 18 watt head thru this amp's 15" Utah AlNiCo. Sounds GREAT! Very clear and articulate, as you'd expect from a PA speaker, but not spikey or unpleasant. Far less bass than my 12" Celestion Blue, though that may be the cabinet. Very happy with the speaker.

Found a schemo that's a lot closer to this amp. Attached. Includes the buss wires from amp to control panel.

Powered up with light bulb limiter, then with full tube complement. Very loud hum as soon as it warms up--could it possibly be the 60-year-old caps? Didn't blow the fuse.

Time to order parts.

[xtian]

Please observe the "death cap", lower left, large yellow 0.1uF cap. It's connected from one leg of the 110vac primary to ground.

Is it recommended to remove the death cap, install a three-conductor power cord, and ground the earth wire to the chassis? Is that all, to solve the death cap?

[xtian]

And while I'm replacing caps, should I

A) just do the power filters first and see if it sounds OK
B) replace those Astron coupling caps at the same time 'cause they're probably too old

[Firestorm]

Keep the Astrons if you can, but be prepared for them to be leaky.

[xtian]

In the 50s and 60s, manufacturers are building these tube amps with multi-section cap cans, riveted into place, with the tabs securely bent and soldered.\

Did they not know or care that the caps would have to be replaced?

Man, what a pain.

[Phil_S]

Maybe you are already familiar with removal of the old can caps. Yes, it is a PITA. Do you have a Dremel tool? If you are very careful, you can use a cut off wheel to remove the tabs. There may be some other tool tips that work well, too. It depends on what you have and your manual skills.

If you don't have a Dremel, then wiggle and twist those tabs with a very large pliers or vice grips until they break off. You will need the leverage from a large handle pliers. If you are lucky, they will break clean enough to make removal possible.

Drilling out the rivets is not difficult, but they should just be holding the mounting plate, so leave them alone until you are sure you need to remove them. The caps should come free once you remove the twist lock tabs.

Whatever method you employ, take your time. Time invested on the front end will pay dividends in what doesn't need fixing up after removal.

Save the death cap. It could very well be a good replacement for a similar leaky cap.

As to the power cord, though it would break my heart to do it, I'd clip it close to the strain relief on both sides, leaving maybe 2". Then, you can probably fish out the inner wires with a pliers (pull hard). Once you have the inner wires out, the insulation should pull out. Then, the strain relief will be loose and easy to remove. If everything is too tight, you can clip close to the chassis and run a drill bit in there to get things moving.

I don't get it, there are two unused never-been-soldered octal sockets and a terminal strip in the chassis? And they used a socket instead of a terminal strip for terminating the power transformer wires? On second thought, I guess they used the socket for transformer wiring so they could relay filament voltage to the tubes in the control panel?

[xtian]

Good advice, Phil. Thanks.

I don't get it, there are two unused never-been-soldered octal sockets and a terminal strip in the chassis? And they used a socket instead of a terminal strip for terminating the power transformer wires? On second thought, I guess they used the socket for transformer wiring so they could relay filament voltage to the tubes in the control panel?

The empty sockets are for Tremolo and reverb (not used on this model). and the socket in the corner carries heater, B+, and switching wires to the front panel where the preamp section lives.

[xtian]

I took everything out of the cab except the speaker, and reseated the speaker to make sure it wasn't rattling. Then I fed the cab some low tones to see where it's making noise. Turns out the glue holding on the paper covering (I don't think it's vinyl) has lost it's stick, and the paper all around rattles against the plywood! I can stop it with my hands, and then it sounds pretty rock solid.

Can one inject glue thru small holes in the covering? Will cyanoacrylate do the trick? Anything else might be too viscous.