EH Scott Radio Enthusiasts

The Fine Things are Always Hand Made

Sunday I'm looking at an AW12 1 dial with single speaker in an early Tasman- the short leg cabinet. Seller says the speaker cone is damaged. What is the going rate to re-cone something like that? That will be a factor in how much I offer him. It's also missing the escutcheon.

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I must say that set has the best installed dial scale I have seen.  Except for a couple NOS dial scales that I have, I have never seen an original dial scale on the AW-12 Deluxe that has retained the blue color.  They are usually faded to grey or completely faded to amber.

Norman

Sorry, it's a repro.

Indeed.  I forgot I had posted high resolution scans of the NOS dial scales to accommodate reproductions!  It looks great.

Norman

AS for the underside photo of a larger transformer style object - probably yes. Trace the wiring and determine if it connects to the plate pin of the 2nd  AF tube.

I too have have acquired  AW-12's and AW-15's Wunderlick tube sets with other blue glass Arcturus tubes like the 56 and 58. So have some other folks. I have an AW-12 receiver in which I now have a complete set of blue glass tubes, just for kicks.

Here's an update on the speaker re-cone. It seems to be going well and I'm almost done. I used plastic shims to center the voice coil when I attached the spider to the frame. I trimmed the old cone so the new one could be glued to it. I used glue I had left over from a previous woofer repair. I glued the new cone to the voice coil while keeping the shims in place. Then I glued the rim of the cone to the speaker frame. I also attached the new rim gaskets and clamped them in place.

Looking really good, I hope that it plays as well as my aw15 speaker does.

Looking good.

By now you should have checked that both field coils are OK. One is in the B+ circuit. The other is in the grid bias circuit for the 45 output tubes. Every AW-12 pedestal speaker I have had good field coils.  But on the AW-15 pedestal speakers (also custom by Jensen), I am batting about 50%.  Go figure. 

Yes, I checked everything on the speaker itself and all was well. I finished it and it sounds great using the RCA jack to feed a CD signal. Now I need to see why the Wunderlich filament won't stay lit. Someone glued the base so it make me wonder if it has an intermittent open. The socket contacts test ok.

I have also have a bad Wunderlick as a display tube. Tested fine but in less than a minute of operation it winks out.

Make sure the tube pins make good contact in the socket. Expansion as the tube heats likely triggers  the problem. Next, reheat the two filament pins and try to introduce some additional solder into the pins for a possible fix. Also, the globe tubes don't support the innards like the later shouldered tube envelope would. Look carefully at the tube to see if the innards lean to the side - a sign the tube was dropped.  If so, slam the tube against your hand a couple times to try to straighten the innards to perhaps fix the problem - has worked for me on a couple other globe tubes and nothing really lost if slamming finishes off the intermittent tube. Slamming to straighten the innards once fixed a dud globe 27 tube.

I can supply  a good used tested Arcturus Wundelick that I have test run in my AW-12.  dcp944@ yahoo.com.        They also appear on eBay with unknown condition, as few sellers have tube testers with settings for a Wunderlick (but I have an early 1930's Supreme that does). You need the 2.5 volt version, not the 6 volt.

The unusual Wunderlick tube was the first modern tube designed specifically for detection. Has two inter wound (co-cylindrical) grids around the cathode sharing the same plane. Designed to be a full wave push-pull detector and also amplify the  detected audio signal and, at the same time, provide potentials for automatic volume control from the center tap of the final I F transformer secondary. Scott's use is an example off using fringe technology for leading edge performance - seen in the later AW-12 production you have and early production of the AW-15.

If you want to search eBay for the tube, spell it Wunderlich.

Norman

I re-soldered all of the leads and it works ok. Audio comes thru the phono jack amplified loud and clear. Still no tuner action. Time to break out the signal generator.

Thanks Norman. I have to fight to remember it ends with an "H"  not a "K"

The Wunderlich tube is ahead of the audio phono input circuit. So the Wunderlich tube is not a factor in using the phono input. You do need a working Wunderlich tube for radio reception.

A temporary substitute is a 55 tube as follows. Short length of insulated solid wire, stripped at both ends. Use fine sand paper or steel wool to clean the #4 pin of the 55 tube and the grid cap of the 55 tube. Tightly double wrap one end of the wire to the 55 tube pin 4 (one of the two diodes in the 55 tube). Tack solder the other wire end to the grid cap of the 55 tube. Insert the 55 tube in the Wunderlich tube socket. Not optimal, but you should get some radio reception and at least allow you to continue with trouble shooting and alignment of the IF stages.

Although there is also a Scott factory recommended conversion  to use a 55 tube involving a circuit change and drilling a hole for a grid cap wire, I believe performance suffers. One of my AW-15's has this change. Wunderlich tubes had became unavailable, hence this factory alteration. But Wunderlich tubes do how up these days and I recommend using one in you set.

 

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