Author Topic: What can you tell me about This? Motorola SD194AW  (Read 658 times)

vintage cltr

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What can you tell me about This? Motorola SD194AW
« on: September 08, 2017, 05:37:21 PM »
Tube tuner - transistor amp.



Loud and Vintage.... any questions?

Motorola Minion

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Re: What can you tell me about This? Motorola SD194AW
« Reply #1 on: September 21, 2017, 09:34:59 AM »
I have not seen one up close but the tuner circuits may be similar to the ones in my 1964 motorola all-tube console, with the exception of the tuning eye tube.

Since Motorola was a transistor maker, I would expect the early SS amplifier to function well, like a Magnavox or Zenith, who used RCA's transistors.

Tubes - Magical - Tubes

Dave

electra225

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Re: What can you tell me about This? Motorola SD194AW
« Reply #2 on: September 21, 2017, 04:36:30 PM »
Don't let the Magnavox boys know this, but I own two Motorola stereos with a similar tuner setup as the one you posted.  One is a console, model SX196-AW with two four inch speakers and two ten inch speakers.  The other is a table model, model ST82-A with two four inch speakers and two six inch speakers.  Pretty good performers, especially on FM stereo.  AM is pretty weak without using my longwire outside antenna.  Mine both have a 1200 series VM changer with a lightweight cartridge.  My console, in fact, has an issue with the cartridge.  The table model has as good of a changer as I own.  Mine both have a single, eight tube hybrid chassis.  They are actually mostly tube with solid state components serving as a driver for the "stereo" light, in the discriminator/detector circuit, in the FM stereo circuitry, and the rectifier.  They utilize 50HN5 output tubes with a 12AX7 first audio stage.  My understanding of the 50HN5 is that it basically provides a push-pull stage using one tube.  Mine have well-built, solid hardwood cabinets.  Even the bottom is plywood, no particleboard, ala Magnavox.  They do not provide boomy bass, but are quite pleasant nonetheless.  They have a balance control that serves as the stereo/mono switch.  An odd feature of both of mine is that nothing happens if you put the function switch to "FM".  I have to use the "FM Stereo" position.  I don't know if this is normal, or if both of mine have an issue of some kind.  There is a separate stereo/mono switch on both of them, so I'm wondering if that same function switch is used on instruments that do not have the separate control.

I have had the table model stereo for several years.  I found it in the back of a '72 Buick station wagon I had bought for parts.  It had sat out in the AZ sun and heat in the back of that old station wagon for who knows how long.  It was covered by other junk, so it was out of the sun and protected.  It cleaned up and rebuilt well.  The console I found when I was hired to tear down an old garage in a nearby town.  It was under the partially-collapsed garage, protected by the ceiling laying over it.  It was fairly crispy from sitting in the old garage.  The power cord was like barbed wire.  I replaced most of the rubber parts in it, along with the usual electronic componentry.  The suspension in the cartridge is hard, so it does not track well.  I have not taken the time to see if I can get a replacement.  The best part about it is that it came with the owner's manual, the original owner's name and all the other goodies.  I actually contacted the original owner.  He had given the console to his grandson a number of years before.  The grandson had no interest in it, so he put it "out in the garage."  That's where I found it.  I would recommend that you replace the filter capacitors before you use it much.  Both of mine had fried silicon rectifiers due to shorted filter caps.  There is a 6.8 ohm resistor in the B+ circuit that was bad in both of these as well.  They have 100uf caps for filters, so they utilize a well-filtered power supply.  I have pictures of these instruments if you would be interested in them.
If it ain't broke, call me.  I can break it....

Ken Doyle

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Re: What can you tell me about This? Motorola SD194AW
« Reply #3 on: September 22, 2017, 07:33:31 AM »
My understanding of the 50HN5 is that it basically provides a push-pull stage using one tube.


The 50HN5 is a single beam power amplifier tube.  You would need two of them for push-pull.


See:
https://frank.pocnet.net/sheets/202/5/50HN5.pdf

electra225

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Re: What can you tell me about This? Motorola SD194AW
« Reply #4 on: September 22, 2017, 08:24:17 AM »
I stand corrected.   :-[


















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electra225

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Re: What can you tell me about This? Motorola SD194AW
« Reply #5 on: September 22, 2017, 10:12:52 AM »
My previous response to Ken's remarks sounds more snarky now than it did when I posted it.  Sorry, Ken.  I appreciate your input.

The 50HN5 does not appear anywhere in the tube manuals I own.  I tried Google one time, but my "googling" skills are notoriously inept.  Someone on another forum had informed me in the past that the 50HN5 was a triode/pentode.  That was all the information I had and what I passed on with the caveat that it was my "understanding" of the matter.  The 50HN5's in both of my Motorola stereos are Sylvania coded.  I have never had an occasion to change any of them, they still work just fine.  I have spares, so apparently they are not rare.  The paperwork I have for the console shows it was sold new in April, 1965.  Why would Motorola have used a 50HN5 rather than the more common 50C5 or 50EH5, or similar?  Is the 50HN5 a Motorola "exclusive"?  How about the 17C9 in the tuners of these instruments?  It is not in my tube manuals, either.  What is the advantage of the 17C9 over a 17EW8, more commonly used in heater string chassis like this one.
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Ken Doyle

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Re: What can you tell me about This? Motorola SD194AW
« Reply #6 on: September 22, 2017, 12:22:24 PM »
I was hoping that I didn't come across as snarky.


Just be glad you don't have the "push pull in one tube" tubes that I have in my
Grundig console.  The ELL80 / 6HU8 has been rare and expensive for 40 years now. 


Doesn't this adapter look like fun?:


electra225

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Re: What can you tell me about This? Motorola SD194AW
« Reply #7 on: September 22, 2017, 10:25:01 PM »
You were not at all snarky in your remarks.  I feared I was, hence my comment.

I have enough trouble de-ciphering American made electronics.  German electronic engineering is way above my pay grade.  I have a Phillips radio that I got in a bunch of radios at an auction.  It works, but that is about all I can say for it.
If it ain't broke, call me.  I can break it....