The official Fairchild 412 registry thread!

[Sam Cogley]

The double pulley mechanism can be unscrewed and rotated to adjust belt tension. It's an eccentric design. Also, make sure it's riding in the right spot on the platter.
The very, very early 412s like yours used a ball-tip toggle switch instead of the rotary switch found on most 412s. It had a super-long threaded shaft. Identical switches can still be bought today, except for the ridiculous length to get through the wood panel. You can probably scare one up on eBay, they were used in tons of old electric organs.

 

[Sam Cogley]

For the record, the two motor mounts on the side opposite the electrical panel should have a screw running through each one to adjust the motor angle. They had a metal bar with a threaded boss at each end that the screws thread into. The two mounts on the very crowded side by the electrical panel did not have screws.

 

[adnick]

For the record, the two motor mounts on the side opposite the electrical panel should have a screw running through each one to adjust the motor angle. They had a metal bar with a threaded boss at each end that the screws thread into. The two mounts on the very crowded side by the electrical panel did not have screws.

Sam: Believe you’ve passed that information on before, my storage device just failed

VR
Andy

 

[Madman1]

@doug s.
Hey Doug, anymore updates on belt status? I definitely need the short belt, but I’m going to replace both. I’m looking for the thread, but I know the longer belt needs to be 39.1 there is an eBay seller that says he will have some in stock in a week or so. I know Andy said he tried quite a few before he found the right one and still had to make adjustments after some break in and stretching. That platter is no joke and I can imagine it’s hard on belts and the original cloth would be better suited, but I don’t think mine is salvageable.

 

[doug s.]

@doug s.
Hey Doug, anymore updates on belt status? I definitely need the short belt, but I’m going to replace both. I’m looking for the thread, but I know the longer belt needs to be 39.1 there is an eBay seller that says he will have some in stock in a week or so. I know Andy said he tried quite a few before he found the right one and still had to make adjustments after some break in and stretching. That platter is no joke and I can imagine it’s hard on belts and the original cloth would be better suited, but I don’t think mine is salvageable.

see my last post:

https://audiokarma.org/forums/index...-registry-thread.677977/page-10#post-16599470

i still have not decided whether to try a 40" belt or a 41" belt instead of the 39" belt i bought - i need to get the 3-wheel pulley spindle to move ~5/16" further from the center of the platter, per the pic in my prior post.

re: shorter belt, the 411 only has the one longer belt; no short belt.

doug s.
ps - interested in purchasing a 39" hardly used belt?
https://www.mcmaster.com/products/belts/width~1-4-2/made-to-order-flat-belts/

 

[Madman1]

Well, I ordered 2 sets of belts today from 2 different vendors. We’ll see how they work out. Both sets are rubber not cloth.

 

[doug s.]

Well, I ordered 2 sets of belts today from 2 different vendors. We’ll see how they work out. Both sets are rubber not cloth.

i have a rubber belt that works - sort of - which is why i wanted to try an inflexible belt like the one i ordered from mcmaster carr. the rubber belt seems to want to change platter speed depending on exactly where the 3-wheel pulley spindle is. and i had to order a few before one worked.

doug s.

 

[Madman1]

i have a rubber belt that works - sort of - which is why i wanted to try an inflexible belt like the one i ordered from mcmaster carr. the rubber belt seems to want to change platter speed depending on exactly where the 3-wheel pulley spindle is. and i had to order a few before one worked.

doug s.

PIA!

 

[adnick]

PIA!

Think I’ve pointed this out before but just in case…..here’s a way you don’t have to worry about exact belt size, and yo get multiple speeds too boot

Variable speed adapter for Fairchild 412-1 turntable (basic) | eBay

Also you could get unbelievable stability of any speed of your lovely Fairchild 412 turntable. For sale it’s a device /adapter that can make Fairchild 412-1 single speed (33rpm) to work 4-speed turntable (16-78rpm variable).

www.ebay.com

Andy

 

[doug s.]

Think I’ve pointed this out before but just in case…..here’s a way you don’t have to worry about exact belt size, and yo get multiple speeds too boot

Variable speed adapter for Fairchild 412-1 turntable (basic) | eBay

Also you could get unbelievable stability of any speed of your lovely Fairchild 412 turntable. For sale it’s a device /adapter that can make Fairchild 412-1 single speed (33rpm) to work 4-speed turntable (16-78rpm variable).

www.ebay.com

Andy

this won't help if the location of the pulley wheel spindle causes speed changes... not sure if the 412 has a similar pulley wheel arrangement as does the 411. from what i've seen, some 412's do, some don't

doug s.

 

[adnick]

this won't help if the location of the pulley wheel spindle causes speed changes... not sure if the 412 has a similar pulley wheel arrangement as does the 411. from what i've seen, some 412's do, some don't

doug s.

If I’m understanding your comment, that only would occur if there’s a mechanical issue….different belt sizes that cause a few rpm’s slow/fast aren’t a problem…


Run a more sophisticated speed Control with mine..

Andy

 

[doug s.]

If I’m understanding your comment, that only would occur if there’s a mechanical issue….different belt sizes that cause a few rpm’s slow/fast aren’t a problem…


Run a more sophisticated speed Control with mine..

Andy

yes, there's a mechanical issue w/the pully system and stretchable rubber belts. if the early 412's have a fixed pulley, there there would be no issue once the speed is correctly dialed in. but dialing in the speed won't help if the pulley spindle can move, as it changes the speed of the platter w/a flexible belt.

doug s.

 

[adnick]

yes, there's a mechanical issue w/the pully system and stretchable rubber belts. if the early 412's have a fixed pulley, there there would be no issue once the speed is correctly dialed in. but dialing in the speed won't help if the pulley spindle can move, as it changes the speed of the platter w/a flexible belt.

doug s.

Have a very early 412-1 with flexible belts, and the eccentric idler but the available belts cause it to run too fast, mine doesn’t vary in speed even without the speed control.

The eccentric idler needs attention on occasion, @Sam Cogley has addressed this prior….

Andy

 

[sberger]

yes, there's a mechanical issue w/the pully system and stretchable rubber belts. if the early 412's have a fixed pulley, there there would be no issue once the speed is correctly dialed in. but dialing in the speed won't help if the pulley spindle can move, as it changes the speed of the platter w/a flexible belt.

doug s.

I have a 412-1, and use a VPI SDS with no issues or speed change once speed is set. In fact, I can move the table in and out of my system as I do on occasion, come back, not the past setting on the SDS, and sure enough the table still holds perfect speed at that setting.

I use the SDS with 4 different tables(including a VPI) and it's become one of the better investments I've made.

 

[doug s.]

Have a very early 412-1 with flexible belts, and the eccentric idler but the available belts cause it to run too fast, mine doesn’t vary in speed even without the speed control.

The eccentric idler needs attention on occasion, @Sam Cogley has addressed this prior….

Andy

if yours doesn't vary in speed, then a speed controller would likely be what you need to get the speed setting correct.

doug s.

 

[adnick]

if yours doesn't vary in speed, then a speed controller would likely be what you need to get the speed setting correct.

doug s.

Yes, if I wasn’t clear, I’ve built a more sophisticated speed control, it turns the 412-1 into a 412-3 and like @sberger it greatly enhances the table….

VR
Andy

 

[doug s.]

Yes, if I wasn’t clear, I’ve built a more sophisticated speed control, it turns the 412-1 into a 412-3 and like @sberger it greatly enhances the table….

VR
Andy

well, i am not sure if a speed controller can be fitted to a fairchild 411, but if i can get the right sized non-flexible belt from mcmaster carr, (still contemplating whether i need a 40" or 41" belt to move the spindle 5/16" further from the platter than what the 39" belt positions it), and the speed is slightly off, then a speed controller would work, as the non-flexible belt does provide rock-steady platter rotation speed.

on my oracle delphi, i upgraded to an origin live dc motor kit, and using a lab grade hp power supply, i was able to dial in the speed exactly, with a needle in the groove of a record while playing, so i understand the usefulness of a device like that.

doug s.

 

[sberger]

Per @adnick 's touting of Delrin ball bearings for his Fairchild and other tables, I went ahead an got some for my 412. Not quite sure what improvement I should be hearing, but it does seem to be a little quieter. However what it did do was require me to speed the table up according to the KAB speed strobe I'm using. I also use a VPI SDS controller, and previously it required a setting of just under 59.00 Hz output voltage to lock in at 33. But with the new bearing, I had to increase that to 61.59 Hz. I'm not sure why this occurred. I didn't lubricate the bearing, although there is oil in the well so I would assume that's not it, but maybe I'm wrong.

Table still sounds great, so there's that.

 

[adnick]

Guess it could possibly slow it down but on mine it went up, I’m using ISO 46 oil ….That’s really not a great deal of difference, does your speed control allow voltage change as well? I’ve also found something like 110 volts to have less vibration.

You might pull the ball and make sure there’s not any scratches on the ball, there’s always a possibility that the bottom of the well is worn to the old ball bearing…

The difference (less noise) was noted with a test record silent track playing through the speakers.


VR
Andy

 

[sberger]

Guess it could possibly slow it down but on mine it went up, I’m using ISO 46 oil ….That’s really not a great deal of difference, does your speed control allow voltage change as well? I’ve also found something like 110 volts to have less vibration.

You might pull the ball and make sure there’s not any scratches on the ball, there’s always a possibility that the bottom of the well is worn to the old ball bearing…

The difference (less noise) was noted with a test record silent track playing through the speakers.


VR
Andy

Increased voltage from 72(which is default for VPI tables) to 115(other choices are lower) and that still required a speed increase, but a much smaller amount then the 72 volt did.

I should also not that I sprung for the speed controller that you linked the other day. I have other tables that I use the SDS for , including a VPI, so I'd like a dedicated controller for the 412, especially one that makes it simple to go to 45.