on the bench, Airline 62-9052 built by Valco

[terminalgs]

This an Airline 62-9052 that Montgomery Ward contracted with Valco to build.  It is very similar to the Supro S6699.   Valco closed in 1969.  The CTS pot date to '6921' so this is one of the last ones.


You can review the schematics below (the S6699 is better quality) to see some of its oddities.  most notable is the dual OT setup, each with a pair of 6L6's.  They share a phase inverter.  The OT secondaries are also wired to a stereo output speaker jack.   I suspect this was the demised of many 62-9052's and S6699's.  the amp doesn't say "warning do not use mono speaker plugs with this amp".  The evidence of exploding and burning is all over both output sections on this particular amp,  and,, all transformers are gone (2 OT's, 1 reverb OT, and 1 PT all missing).


Also, valco switched to using hammond tanks at some point, and this is a "4F" reverb.   The driver is a 6973.  compared to valco builds from ten year before, this one still uses Z5U ceramic caps everywhere, but they increased the use of shielded wire quite a bit.  Even the mains 120V is routed from the back fuse to the front switch via shielded cable...


62-9052:





S6699:





damaged power amp sections,,  on both sides, one of two octal sockets were replaced.  some resistors not really connected...








preamp area looks pretty clean:





here's the entire gut shot:





bigger image @ http://i.imgur.com/chUkFzE.jpg


immediate plans:


ClassicTone still makes this OT (!!) I've had one on the shelf for 4 years and now it'll finally be put to use.


I have a 305V (no CT) PT from a red knob Fender "The Twin" that I might use, at least to see if it'll all work without a ton of re-working.  the S6699 calls for a 320V secondary, but 305V should be enough to test things out.  Sourcing an exact PT might be a trick.   6.3V filament requirements at 5.5A minimum.  The PT needs to be no taller than 3.5".   I also need to keep the total possible value of the amp once fixed in mind (what I suspect to be somewhat low).


I'll replace the octal sockets, repair 6L6 section with new caps & resistors.  install a single OT, and for now, isolate the other 6L6/OT section from the circuit effectively making this a one-legger instead of a two-legger.  I'll also use a mono speaker out!


If that all works, I rework the reverb section to use a 6CZ5 or EL84,,  or maybe a 12AT7.


It is #3 in this advert:

[eleventeen]

Well, nobody can accuse you of supplying a non-comprehensive post. LOL. Got the product photos, everything.


You may end up in that odd situation with that choice of Power trans...with no CT, you of course need to use a bridge rectifier and that should probably produce 1.4* 305 more like 425 volts.


Looks like a neat project. Sorry you have to replace all the trannies, that kind of sucks.

[eleventeen]

Maybe you should consider a new toroid power transformer considering your size requirement. Just a thought.

[terminalgs]

Maybe you should consider a new toroid power transformer considering your size requirement. Just a thought.

excellent idea! I'll consider that for sure.


Without that picture of the Cryan' Shames jamin out of these Airlines for Montgomery Wards (I wonder in MW also sponsored the cool threads...),  I'd have little motivation to rebuild!!!

[Willabe]

In the 60's as a kid I listened to WCFL (AM) in Chicago and the Cryan' Shames were big back then. They were a good 60's AM pop band.

I still once in a while listen to them on youtube and others for memories.



                  Brad        

[eleventeen]

re: the toroid possibility---you'll of course check both dimensions, height and diameter. You may well have a problem with the horizontal   space (eg; footprint) such a tranny requires.


I am assuming you have a stand-up transformer since I see no horizontal cutout on the gut shot. You may have to find an old Scott amplifier or something similar to get something really squat. Or, you may have to move to a transformer that *does* require a rectangular cutout and I'm sure you would prefer not to do so. Point being, replacing your power transformer could be a mild challenge. Furthermore, you have the additional restriction of your stiff 6.3 volt current requirement as you pointed out. That's definitely bigger than normal. I could see you needing a separate "auxiliary" 6.3 transformer, or, choosing a tranny with two 6.3 windings. 

[jjasilli]

 

[DummyLoad]

seems to be the same circuit or close to the gretsch fury 6169 and gretsch chet atkins 6163.


http://www.swingcitymusic.com/wp-content/uploads/2014/03/Front-Gretsch-6169-Fury.jpg


http://vintagegretschguitar.com/files/2010/09/-23013602994928400.jpg




--pete

[terminalgs]

update:

I've decided to install only one of the two output sections. If someday someone wants to install the second it will be easy enough (add OT, sockets, tubes and cathode resistor).   

 The PT that I thought was a Fender "The Twin" unit is actually from a Fender Super 112.  It fits the cabinet, but I don't think it has the filament capacity for all these tubes, so I've added a small Hammond filament transformer for three of the preamp tubes.  The original schematic calls for a 320V secondary, and the Fender PT is 355v.  All B+ voltages in the circuit are increased (of course!),  but I'm surprised to see how much higher the voltages are compared to the original circuit!  Original schematic has 360V at the OT,  I've got 470V!!). For everything except the first reservoir caps, cap voltages are under the 450V ratings (The first caps are 20V over  ).    my 355v PT must be closer to 390v....




So I either need to find another PT, or upgrade a few caps.  I ordered a 320V toroidal PT, so I'll be giving it a try.
I had to seek out the shortest 6L6GC I could find to fit that cabinet.  Standard sized 6L6s do not really fit.   I ended up with some TAD 6L6WGC's.
some mods:

• elevated heaters.
• moved the power switch to the rear
• twisted heater wiring where possible.
• converted 6973 reverb driver to a 12AT7 driver.

[terminalgs]

 more about the reverb 12AT7 conversion:

The 62-9052A uses a 6973 as the reverb driver (Valco commonly used this tube in this capacity). Rather than source the pricey tube for the workaday task of driving a reverb transformer, I converted the circuit to use two parallel 12AT7 triodes.  The typical AB763 fender circuit is as simple as it can be, and is a perfect fit.

I left the R12-470K grid stopper (as well as R113,R114,R115) in place, and replaced R116-330 cathode resistor with a 2200ohm-1W resistor. 

The Fender circuit includes a 500pf coupling cap out front of the driver, but it isn't necessary in the valco circuit.  The original valco screen grid supply is no longer needed (filter cap re-purposed, or disconnected).
The original transformer was long gone, but a Classictone TF103-48 makes for a good bolt-in replacement.
Here are some pictures:


Original circuit:

fender circuit:

socket wiring before filament hookup: