allwave 12

[thomas higgins]

Hello:  Client asked me to work on comatose radio inherited from grandfather.  I have worked on dozens of philcos telefunkens RCAs GEs and such but this is first time tackling a EH Scott.  The turntable is a electromatic with horseshoe magnetic cartridge.  The power amp n supply chassis had no tubes and when I put some spares I had in there the audio from "phono" input came through.  Right now nothing in the way or tuned radio from its own massive tuner.  One thing I don't get is why a 9 pin mini tube was cobbled in underneath near the AF output tubes?  Might be a 12ax7?  I got the platter to turn.  I found a schematic but it is for the record cutting version which this is not.  The speaker cone is rather shot to hell.  There was a guy here in tucson that would do those but now he is gone.  Any ideas on where to send this thing?  Thank you. 

[thomas higgins]

Updates:  the blue tinted wunderlich in here has open filament.  The 6dj8 was put in to perform some detection.  We are abandoning this electromatic record changer.  The client wants a modern turntable for 33 n 45 which will drop in here.  If I have a 55 tube laying around I might try and put it in here and remove the 6dj8.  Because this new thing is a twin triode I wonder (wunder?) if we are getting much AVC action.  It is detecting at least.  Thank you. 

[Kent King]

I can probably help with a 55 or even a Wunderlich (I need to check what I have)...

Please don't throw out that turntable - the early ones are hard to find - I would be very interested in it, even if not working.

Kent

[thomas higgins]

Hello Kent:  I will not literally trash the electromatic.  If the client does not want it, we can find a way to get it you.  It does turn 78 and even 33 and it tries to cycle when manual reject command thrown but it will not auto trip into cycle at end of the record.  Looking underneath I suspect a spring came off or a piece of something is gone.  The cartridge had zero output; the suspension is completely stuck.  In the course of trying to disassemble the magnet pole piece and coil structure, I broke the coil.  It is unwinding itself and is open. 

Right now it is tuning and detecting with this 6dj8 in place of the wunderlich.  The meter is not open but will not deflect.  The voltage drop across it is around 14V and only varies a half a volt on strong vs no station tuned in.  It had been shunted across but I put the wires back on though no action is observed.  Is this a current meter on the plate circuit of the wunderlich now 6dj8?  Thank you. 

[David C. Poland]

The Wunderlich tube design and application for detection and automatic volume control was developed by  Norman E. Wunderlich. The first tube designed for AVC  was put into production by the Arcturus Radio Tube Company which explains the blue glass, as cobalt blue glass was a signature of Arcturus tubes into the early 1930's. 

I have seen a clear glass shouldered example, also Arcturus, but production must have been short lived.

Scott redesigned the 12 tube Allwave Deluxe to introduce AVC using the Wunderlich tube in December 1932 and through 1933 into 1934. And continued its use with the Subsequent 15 tube Model FIFTEEN for several months in 1934. then Scott evolved the Model Fifteen to employ the 55 tube in later 1934.

The 55 tube introduced later is a triode with 2 diodes, and is not a direct substitute without a wiring change and, in my opinion, is only a so-so substitute, having a Scott Model Fifteen with the factory modification to use a 55 tube.

In addition to the 2.5 volt Arcturus globe 6 pin tube yours use, there is a 5 pin version with a grid cap and a 6 volt version, both curiosities with no known application. In addition to Scott Radio for for aver a year, there was a Crosley radio early 1930's the used the same 2.5 version. I know of no other manufacture using the tube. There was a magazine article of a Scott automobile radio using the 6 volt version, but am  unaware of any ever turning up

[thomas higgins]

The only schematic I have found provides no voltage information.  Whoever put this 6dj8 in also put in a little 6VAC filament xfmr just for it.  This wunderlich has no plate cap and is not marked as A or B.  Incoming B+ to the tuner from the power amp n supply cable is 242V.  The main filament buss is 2.7VAC.  I did read up on the wunderlich.  Since someone before me unknown modified this to use 6dj8 I am not reinventing that wheel especially since the radio does work nominally.  The only choice now is to bypass the unresponsive current meter or reconnect it to get some voltage drop.  The 6dj8 does not seem to care either way.

[Kent King]

The B+ is a little high (should be 225-230VDC), but today's higher line voltages probably increase it some. If there is a Hi/Lo switch on the PS, be sure to set it for High voltages. Check to be sure the B+ divider resistor is good all the way down too...check each lead, the full B+ is first, then you should read about 100V less at the next contact and about another 50V less at the last divider point. Ground should be at the other end. If those are all good, the set should be ok, voltage-wise.

There are manuals and info here too, check the "Scott Info Archive" link above, Set Folders > Allwave Deluxe and you should find more info.

Kent

[thomas higgins]

Hello and yes I am sure that switch is set for higher incoming but will double check that.  And yes the big resistor drops down each step to zero at the bottom.  I had not thought to look on here in archives for more data.  Thank you. 

[David C. Poland]

With today's higher voltage, the high-low switch should be which ever position dims the dial lamp a bit. Hence, the low position  keeps the B+ at a desirable lower voltage by maybe 15 volts or more. 

If Kent does not have a good Wunderlich tube, I am sure I have a good used one. This tube is in a low stress environment and should last well, and long as it is treated gently when out of the chassis - so do not drop it nor bang it.

[David C. Poland]

From the info archive here, print off an owners manual to give the owner. There is several versions. Each has a tube layout for the receiver about in the middle. fFnd one that has the same 1st detector as yours - either showing a 57 or 58 tube. Also, one that shows which front left control you have - either a 3 position or 5 position sensitivity switch.

The "high" position is for higher house voltage 115 to 130 volts, and dims the tubes and dial lamp.

[thomas higgins]

David I must think hard about this wunderlich business.  If I got one, and I appreciate that you might provide one, I would have to undo the modification done by previous person.  Right now the radio is tuning and receiving and sends line level baseband through on the "phono" connection strap.  I always weigh the risk of an operation for what it offers in benefits against the possible risk of something failing or breaking or another hidden failure being revealed.  The guy actually as an original manual for this radio as it has been in his family from day one.  But yes I can certainly send him a pdf if he desires.  Tomorrow I shall confirm the volts position switching and I am rather certain the sensitivity switch is three positions. 

I left the SW optimizer control in the cabinet which is across town.  When the thing all gets put back together, I will hope that part works OK.  RIght now it is barely receiving anything but hash and noise on the other three higher bands. 

[Kent King]

Test SW at night, and use as long a wire as you can for the antenna. It should pick up AM stations on the first SW band at the low end (it starts about 1.5MHz), there should also be stuff in the 6-10MHz range. Tune SLOWLY, the small SW unit in the cabinet is virtually indestructible, it will be working - I have several of them, never had to do anything but clean them up. It is just a small coil and pre-tuning capacitor.

If SW still doesn't perform, it may need to be aligned, or the previous work reduced the set performance.

Kent

[thomas higgins]

I am getting our uppermost AMs here on the low SW band even without the optimizer connected.  One should be able to get the WWV at 5 10 15 n 20 mhz is that right?