Silvertone 1485 - Output Transformer advice

[sonoflee]

I recently picked up 2 extremely beat up silvertone 1485 heads cheap from a guy who had done some ...interesting... mods.  To refresh your memories, these are 4x6l6 amps that used two (wimpy) O.T.s, each running three 10" speakers (a 2.6 ohm load for each transformer) in a massive 6x10 cab. Schematic below.

Schematic (PDF)

Apparently, he had killed one or both of the OTs in both amps, and used some interesting methods to "fix" them.    

In the first head, he took out both OTs and used a single (massive) OT from an old RCA theater amp. After a couple of replaced tubes, that seems to work fine, and the wiring pretty much makes sense to me.

The second head is more of a head scratcher, though.  One of the OTs is fried, and he apparently hooked it up so that the remaining OT is running all of the output.  This does not seem right to me, but I'm trying to figure out the best way to proceed... My goal is to be able to use the amp with one of my existing cabs (all 8 ohm, various configurations) if possible.  

Option A: replace the dual OTs with a single, higher powered one - maybe a Fender twin OT?  This is pretty much what he did with the first one, and I think it would work fine - except I'd have to make a new cabinet for the head, because I can't think of a high-enough powered transformer that would fit in the space vacated by the two smaller ones.  If anybody has any ideas on one that might fit, please let me know!

Option B: Replace the one busted OT (or just do both) with the Silvertone-specific replacements from Weber or Mojo.  These would fit the chassis, and have a better option in that they're tapped for 4/8 ohm, but I'd still be stuck with the issue of putting together a new cab (or at least of rewiring an existing one to handle the separate/dual 4 or 8 ohm loads).  I was wondering if there could be a reasonable way to tie the dual OTs together to run into one cabinet?  AND, if so, how would that change the output impedence (i.e., if I could tie the two OT's together at the 8 ohm tap, would that make it need a single 4 ohm load)?

Thanks!

[eleventeen]

Tough choice. At first, I thought "how the heck can a real OT (like a Twin) not fit....into a cabinet that holds 6L6 tubes?" Now I see, it is not VERTICAL space you are lacking, it is HORIZONTAL space. I have to tell you I do not see a clean solution. I would not be eager to link the two output trannies together in any way. There's big volts there and I could see evil consequences.

Have you considered the possibility of yanking out 2 of the 6L6's and converting to a Super Reverb (or a Bassman) ? That would possibly allow you to install a normal OT of normal footprint.

[moonbird]

Sonoflee -

Apparently the Silvertone 1484 was a fav amp of Ted Weber (may he rest in peace). He had a clone made of the OT and sells them now. Check a bit over halfway down this page. Look in the far right column for the phrase ... "Better known as that funky Sears Silvertone Output transformer, I just had to do this one after I heard a Sears Silvertone 1484 ..."

https://taweber.powweb.com/store/magnetic.htm

Not sure if the 1485 is just the head version of the 1484 -- but I thought I would offer it up.

[PRR]

It's a mono amplifier. The four 6L6 are fed in pairs. You should be able to tie pairs of plates together (47r 2W resistor in each plate lead is very wise precaution) to a 2K:8 OT such as a "100W" Fender or Marshall repro-replacement. Dunno if one 100W will fit in the place of these two tall-stack OTs.

[SoundmasterG]

The 1485 is basically the same as the 1484, except it has two output sections, each using two tubes and their own output transformer, connected to the 2.6 ohm tap to run three speakers. The head box is the same size on either amp and the wiring and layout is a mess on both. The 1484 used a single pair of output tubes connected to one output transformer, and uses the 4 ohm tap to a pair of speakers. There isn't much room in the 1485 head box or chassis to add a large enough output transformer to run all four tubes, but it can be done, as you noted in your example of the other 1485 you have.

You could get a Weber replacement transformer or two and run the amp through those with only one pair of output tubes at a time....then you would essentially be using a 1484 with the 25 watts or so of power that these are, and with the Weber transformer, you would have the option of an 8 ohm output. You could also build two cabinets, each with an 8 ohm load, and when you need more power, you put the other two tubes in and run the output of each pair to a separate speaker cabinet.

Greg