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Fairchild 412-2 owners, a question...

Sam Cogley

Sam Cogley

Last of the Time Lords
Subscriber
Could any of you (and I know there are a few around here) take a picture of the idler mechanism that connects the two belts? I'm looking for a side view of the assembly, but primarily the bottom half of it. I've been looking over pictures of the speed changer mechanism on the few 412-2s documented online, and it appears to act on the lower belt, not the upper. None of the tables documented online show the bottom side of the idler mechanism very well, so I can't figure out exactly what that lever system is doing to change speeds.
 
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Going by memory here, but I believe the motor uses a stepped pully to get 33/45. The lever moves the belt between the pullys. Not sure if anything is going on with the transfer pully.

Remembing this being a real bear to to get to work properly.
 
Bueller...? Bueller...?

Sold my 412-2 years ago.

Here's the best the web can do.

fairchild-412-turntable_1_c92aea73da14684555a09c9297f020d4.jpg
 
OK- I looked through the 27,000 photos on my desktop. Here's a pic of the 412-2 I sold.

It appears that motor pulley and the transfer pulley are stepped. Hard to tell.

There are two levers as part of the mechanism.

33275145876_565e434d19_c.jpg
 
Interesting. The only 412-1s I've seen with that base plate under the transfer pulley were the shallow-chassis later models.
 
Maybe this is unrelated to the O.P question, but did Fairchild ever produced (50 Hz) export versions of their 412 (non- ED) series turntables ? Up to recently I was pretty sure they didn't until I bought a 412-2 from a french seller who was very confident that it worked at the right speed in Europe on 50 Hz mains. I was sceptical but after closer examination (I put it side by side with another US 412-2 I have for comparison) I found he was right: the motor was a 115V/60Hz version but the upper side of the intermediate pulley has a larger diameter to compensate for the lower motor speed. Of course, the platter speed was spot on. This was the only difference I found and the pulley looked original, not a rebuilt one.
All the (5) other Fairchild turntables I have are (US) 60 Hz versions and runs too slow in Europe but I built a stand alone replica of the (tube) 412-ED electronic drive which allows me to accurately adjust for the correct speed without needing any modifications to the mechanical design.
 
Selmerdave said:
Wow, is there a thread about that?
Click to expand...

No, never thought about it... but I will post a few pictures of the unit very soon (or start a new thread as I don't want to spoil this one with unrelated topics). It's very close to the original (Fairchild) circuit with same tubes complement, except that as I don't have 78 rpm records the version I built is only 2 speed (33/45) Yes, a 100% tube turntable motor drive !
 
I've thought about building my own ED unit for one or both of my 412-1s. It would be interesting to do it as a solid state design, but I'm not an electrical engineer.
 
Sam Cogley said:
Could any of you (and I know there are a few around here) take a picture of the idler mechanism that connects the two belts? I'm looking for a side view of the assembly, but primarily the bottom half of it. I've been looking over pictures of the speed changer mechanism on the few 412-2s documented online, and it appears to act on the lower belt, not the upper. None of the tables documented online show the bottom side of the idler mechanism very well, so I can't figure out exactly what that lever system is doing to change speeds.
Click to expand...
 
Their are two diameters if the lower section of the idler mechanism and two different diameters on the motor pully. When you change speeds the short belt between the motor and the idler is moved on both the motor pully and the lower portion of the idler
 
That makes sense and thats how I remember it.

Getting the belt switching mechanism to work is a real balancing act. If you don't adjust it correctly, it will only switch the belt on one pulley, instead of both at the same time. I seem to remember that you can adjust the lever positions to get it working.

I'd be curious to see if the speed stays true in both positions when switching.
 
Tubologic said:
No, never thought about it... but I will post a few pictures of the unit very soon (or start a new thread as I don't want to spoil this one with unrelated topics). It's very close to the original (Fairchild) circuit with same tubes complement, except that as I don't have 78 rpm records the version I built is only 2 speed (33/45) Yes, a 100% tube turntable motor drive !
Click to expand...
 
Hello
The 412-2 speed change.
The motor and transfer pulley each have 2 steps. Or at least mine did.
The belt is moved up or down changing to which ever step on both the motor and transfer pully.
The 412-1, long chassis will have a socket with a cheater plug. This is where the electronic speed controll plugs in. Creating a 412-4
Some are short chassis single speed, no electronic speed controll provision.
Every 412-1 i own or have seen runs a bit fast, has anyone found good belts for this model ?
I also have seen some with a fabric belt like the belts on rek o kut tables.
One thing to know is if the belt tension using this belt is not right the belt will sing or vibrate.
This is audible in a very quiet system.
Bob
 
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