measuring torque

[jwrosenthal]

Greeting guys,

I had posted a couple weeks ago about my newly acquired Tandberg 4000x having problems on the take-up reel with heating up and a rubbing noise. I took it to my service tech and he quickly diagnosed that there was a problem with the clutch alignment on the right hub that was rubbing (hence the noise). He did a CLA (as best as he can as these machines are not his forte), by taking apart the hub, cleaning and dressing all the moving parts, and running to test function.

I ran it last night, and indeed the machine is much quieter (as quiet as an idler driven tape machine can be), but the right hub still gets very hot after an hour of play. I also noticed that when running the machine in forward fast, the right reel pulls very hard, and the left reel lashes (as if it is freewheeling without enough resistance to keep the tape taught).

Before I gave him the machine, I played with the plastic set screws under the hubs thinking it would get rid of the rubbing. There are 3 adjustment screws per hub. One is for the brake distance (which is pretty obvious), one is for the spring tension on the bottom of the hub (where it meets the chassis), and the third is for the distance between the lower plastic spool (where the belt rides in a slot) and the upper hub. I am afraid I screwed with the factory settings for tension and torque and the SM gives very specific measurements for that.

What tool or "trick" do I need to measure the torque and tension on the hubs (and how do I use it) so I can get this thing right, rather than screwing it up further? The service manual gives measurements at the inside and outside of the top surface of the hub and has a picture of a little gauge....what is that?

EDIT: I forgot to mention...what also has me thinking that I have a torque setting problem on the take-up reel is that last night when I was recording, I hit the record buttons, and engaged the joystick (which engages the motor, capstan and roller assemblies), but had the "start/stop" button off as I was cuing up the track to record. The tape was creeping slowly forward and I could hear the take-up reel stressing as it wanted to move forward, but the start/stop acts as a pause...so the clutch is partially engaged. My tech is a wizard at tube equipment and he can solder and bias his ass off, but I know he did't reset the tension screws as he just put it back together and tested to see if it worked and if is was silent. I could take it back to him to fine tune, but that could take weeks for him to do, and he'll probably just adjust the screws as I could do.

James R.

 

[jwrosenthal]

Need to revise my statement....the adjustment screws are: 2 for brake distance, and only 1 to move the lower pulley from the upper hub. When the hub is stopped, the lower pulley keeps going at full speed until the mechanism is engaged to bring the lower and upper together. While the tape is running, the upper is "slipping" against the lower pulley to maintain proper speed (this is normal function), but you can "hear" the lower pulley slipping against the upper while under load (i.e while running at play speed, or stopped on pause).

I adjusted the screw for the 2-part hub distance, and when you move them apart, the noise stops, but there is no contact, hence no torque. When I turn the screw down, the torque resumes (and if you go to far, you hear a chattering, hence you back off to get it in the "sweet spot"), but you then get the rubbing noise (hence the heat). The service manual says to adjust the spring at the base of the hub, but doesn't say how to get to it. I thought it was one of those screws, but it apparently is not.

James R.

 

[fortycoats]

It's a spring gauge -- one of those hang-up weighing scales basically. I haven't done it myself but the SM for my Teac describes the same thing where you wind some string around the reel and tie the end to the gauge (which is anchored to something), start the machine and see how much force registers on the scale.

 

[jdurbin1]

James,

Is there still friction material left on the take-up clutch surface? Or is this down to metal on metal?

John

 

[jwrosenthal]

James,

Is there still friction material left on the take-up clutch surface? Or is this down to metal on metal?

John

There appears to still be about 1/8 inch material all around. This machine doesn't look like it was used all that much, but that damn rubbing is killing me! I can't see where it's rubbing as when you disengage the clutch, it completely disengages, and when it engages, it does it as it should. I guess I have to keep at this until I die trying.

James R.

 

[JonL]

Spring tension gauges as mentioned in post 3 can be purchased from McMaster-Carr (mcmaster.com) in a variety of ranges.