AW 15 Amp Problem

[Joe Miller]

I just started on an AW15 restoration and found that my Amp is not wired per the schematic that I am using from EH Scott Google Docs: https://drive.google.com/drive/u/0/folders/0B0K3TBSz_27rNjMzYzk3Zjc...  

On this schematic item 22 is noted as a "No. 2496 Audio Choke" but is shown as an interstage transformer with split windings on the primary and secondary.  The secondary measures 266 ohms and 268 ohms measured separately to ground.  I only see 4 leads coming out of #22, two of which are tied to ground, the other 2 connected to the to the 500 ohm resistors (#5, #8).

When attempting to measure the primary from pins 5 and 6 on the Jones connector I measure 57K ohms.  When I try to measure each section of the primary from pin 4 to 5 and pin 4 to 6, I show an open.  Further investigation reveals that pins 5 and 6 are connected to the 28k resistors rather than connected to the interstage transformer.  That is why I am measuring 57K for the primary (pins 5 and 6 are not really connected to the primary). So I am guessing that my schematic is wrong.  

Is there another schematic for this amp or am I missing something?  Also, not sure what the 28K ohm resistors are doing.

Any assistance would be appreciated.

Thanks,

Joe Miller

PS: I may have a bad power transformer too as it measures less than 5 ohms

[Kent King]

Oh...the AW15: every set built by Scott seems to be different. There are at least 7 major variations of the tuner and probably close to that many different power supplies. And we don't have schematics for most. I would strongly recommend drawing out a diagram of what your supply looks like, including noting the open items and such. From that, I suspect myself and a few other restorers can ID your particular power supply. 

Now for the good news: I have many parts chassis here, and I may be able to provide parts you need. We just need to find out which supply and parts you need. 

Kent

[Joe Miller]

10 4, Thanks Kent. Will let you know what I find out.

[Joe Miller]

Hi Kent,

I've attached a sketch of my as found condition. Looks like it should work.  This version does not use the interstage transformer.  Instead it has an "audio choke" 533 ohms with center tied to ground. Have you seen this version before?  I would like to find an actual schematic for it.  Unfortunately, my power transformer has a shorted primary (it measures one ohm.  It blew the fuse when i tried to slowly power it up for test.  Do you have any spare transformers?

[Kent King]

[Kent King]

Try this schematic. I will check on a power transformer as soon as I can - getting tangled up in holiday busy-ness...

Kent

[Joe Miller]

Thanks for the schematic. It looks close. I'll go through it and mark up any differences in my amp as found. No hurry on the check for power transformer. Merry Christmas, my friend.

[Norman S Braithwaite]

One ohm DC is not unrealistic for the primary winding of a higher power radio transformer.  Try removing all tubes and dial lights and see if the fuse blows when bringing the line voltage up to around 100-VAC (reduced due to no load)

Norman 

[Bruce]

could the schematic that differs from the rider version be for the aw12 w/6pin jones?

[Scott Seickel]

I am with Norman.  1 ohm is definitely not unrealistic.  I would power the transformer with no load and see if it draws excess current and heats up. 

[mike hadley]

The earlier schematic that Joe was refering to was the result of not having the correct diagram for my aw15,

https://ehscott.ning.com/forum/topics/allwave-fifteen-schematic

I put it together from the Riders documentation and included a decent image of ther underside of the chassis.

The diagram is correct as it ties up with another restoration here,

https://ehscott.ning.com/forum/topics/1934-aw-15-electrical-restora...

As Kent mentioned Scott was a custom builder so expect to find that no two sets are the same.

Mike

[Joe Miller]

Thanks Norm, will give that a try.

[Joe Miller]

Bruce I'll check. Thanks