The Fine Things are Always Hand Made

Aw15 questions

So i found a aw15 in the abandoned old barn out back. .. now suprisingly the wood isnt too bad given thr age and the fact it was laying in a barn for who knows how long. The good news the top end. Tuner chassis looks ok for the most part. Besides a few stuck controls a broken coil and a bent in "can" lid thing. Plus the external wiring is shot. Have not tested the tuner but have been trying to get the power supply/amp side going. I saw a parts list/location sheet. That page calls for 8 mfd at 450v rating. Apparently these were replaced as it had 2 10 mfds at 600v and 1 double 8 mfd modded to fit and onlt used half of it (a single 8 used) rated at 800v i beleive. That cap gets hot hot. Pops the fuse. But upon testing. There was around 500 volts sitting there. And around 400 at the other 2 caps. And the 2A3 tube specs are at 300 v max to the plates? And theres over 400 there if i remember right. I have been using an adapter made up to adapt a 5U4 rectifier to the 5z3 connection. Not sure if that could cause an issue. Or if this is normal (doubtful). Replaced the caps and still shows the same but at least it hasnt blown another 3A fuse yet.. . . I mean at the worst case scenario maybe i can build a custom chassis to run the power and amp. Unless this can be fixed. Anything is possible on that end. I didnt know the chassis was supposed to be chrome. THATS HOW RUSTED it is. I am honestly suprised i got anything to happen. So far it has a voltage output and the rectifier tube and 1 of the 2A3s glow. Although the 2a3 was dim. I am not sure if those are any good they are old pulls.

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Permalink Reply by Kent King on April 10, 2021 at 6:53am

Cody - Do not power the power supply without it being connected to both the set and the speaker. The voltages will be too high without the load of the tuner and this can easily damage the amplifier. Scott sets must be fully connected before applying power unless you use a Variac transformer. With a Variac, you can test the amp separately at a greatly reduced line voltage to protect the components. I usually replace the caps with 10@450v units.

That said - what is the serial number of the tuner? Can you post some pictures for us?

Kent

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Permalink Reply by Cody Serucsak on April 10, 2021 at 8:00pm

Theres a smudgy spot that could be a 1. After that its D-334. And good to know on the power supply.. so it -might- be ok. I have to rewire the tuner as the external wiring is completely shot. Cut/chewed up etc. I can see if i can get some pics loaded up. Beware that power chassis looks ROUGH. I am actually suprised it is doing anything.. i fear the speaker coil is bad. The paper cone is in tact suprisingly. It does move free but from a light load from another source it doesnt appear to respond to anything. The OT checks out. Along with the audio Xformer within the power chassis. I will see that i can get power running to the tuner chassis at least to check voltages within the power supply. Hopefully it stabilizes where it should be. Luckily the tuner chassis is clean on the inside. Probably the best looking area on the entire unit. I will let my 600v cap in for now. Just in case the voltage doesnt drop where it needs to be.

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Permalink Reply by Kent King on April 10, 2021 at 8:41pm

Thanks...D-334 is the entire serial number. I can't tell you a lot about the date on this set, no info in the D prefix. However, all the AW15 sets were built from March 1934 to about May/June 1935. Also, if you have not found it - the Scott Info Archive (link near the top of the page) has data on all Scott sets. Look in Set Folders, then in Allwave 15 and you can find all the info on your set. WARNING: AW15 sets vary widely - almost no two are the same. You will NOT find an exact schematic. But the general info on the sets is good. The AW15 is the worst for this variability - it was a transitional set from the AW Deluxe to the Allwave High-Fidelity. Many experiments...

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Permalink Reply by David C. Poland on April 11, 2021 at 10:19pm

Note also, the speaker has 2 field coils. One in the high voltage circuit, the other is in the bias circuit for the output tubes.

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Permalink Reply by Thomas Day on April 17, 2021 at 2:50pm

This configuration was used by several companies including Hammond organ, which used two 12inch Jensens with different values for the field coils. They also used the quad 2A3 output tubes. I had one of these amps in a Hammond tone cabinet. Later versions used the same speakers, but with a quad 6V6 set of output tubes. I have one of these in service still.