tcd-3014 roller pressure

[Patrik]

I'm looking in the service manual, but can't find any information on the correct roller pressure! Got a tension gauge on order. (Sure takes a lot of tools to maintain tape decks!

[tapetech]

Many service manuals for cassettes do not list that spec. The pinch pressure is supplied via a spring and it's quite rare for a spring to "go bad" or change it's tension.

Say your deck is skewing tape (common in Tandbergs) and it stops skewing tape if you manually apply more pinch roller pressure. That does not automatically mean that the pinch roller pressure is too low. Often, the problem is elsewhere (there are numerous causes for tape skew).

There is also the possibility that Tandberg chose a spring that was not strong enough to begin with in their original design. In that case it would be ok to increase the spring tension. Just eliminate other causes of tape skew before you go changing springs.

-NAK 300 manual states 270 to 370 grams for the takeup roller and has no spec for the supply roller.

-REVOX 215 manual states 490 gm for the takeup roller and 300 for the supply roller.

-Pioneer: 350gm to 450gm for both rollers is specified.

-

[Patrik]

Thanks for the reply!
I did increase pressure a bit some time ago by installing a second spring next to the original one. This was to lower wow.
No skewing issues, but wow is still a bit high towards the end of the tape.
I got the gauge primarily to check the B215, as it's too has quite high wow at the end of at least some tapes.
Regards

Many service manuals for cassettes do not list that spec. The pinch pressure is supplied via a spring and it's quite rare for a spring to "go bad" or change it's tension.

Say your deck is skewing tape (common in Tandbergs) and it stops skewing tape if you manually apply more pinch roller pressure. That does not automatically mean that the pinch roller pressure is too low. Often, the problem is elsewhere (there are numerous causes for tape skew).

There is also the possibility that Tandberg chose a spring that was not strong enough to begin with in their original design. In that case it would be ok to increase the spring tension. Just eliminate other causes of tape skew before you go changing springs.

-NAK 300 manual states 270 to 370 grams for the takeup roller and has no spec for the supply roller.

-REVOX 215 manual states 490 gm for the takeup roller and 300 for the supply roller.

-Pioneer: 350gm to 450gm for both rollers is specified.

-

[tandberg]

Don't know about 3014, but the older TCD 300-400 series had 1,2 /0,6 kilo each. Same rollers as in 3014.
If you increase pressure you'll probably increase bearing-wear as well.............

[Patrik]

Don't know about 3014, but the older TCD 300-400 series had 1,2 /0,6 kilo each. Same rollers as in 3014.
If you increase pressure you'll probably increase bearing-wear as well.............

That's massive pressure!
That's about twice the Revox B215 pressure, which I believed was considered very high.
Good point about the bearing wear. Another reason to get the pressure just right!

[perry]

If you can HEAR ANY wow at the end of a tape on a B215, then something is very wrong. If you mean you measure increased wow at the end of certain W&F/Speed tapes, but not others, then the tapes must be very different lengths, and the take up motor needs work or adjustment. On the B215 and B710, both take up and supply spring pressures are very, very adjustable, and are sensitive to even a few turns of the nut to have a significant effect on the readings. You should not have to be at either extreme at all. In the past, I've put in the W&F tape so it plays at the end where (almost) any deck has higher W&F (another notch for the Dragon, which is very insensitive to tape spool size) and moved the nut on the take up to slighter higher tension to isolate it further from the effects of the take up reel, which also brings it's speed slightly closer to ideal, as all the Revox decks run faster than they should. At some point there is no reduction in W&F or the tape starts to travel, and I back it off a half turn or so.

On normal decks, the torque the take up reel can apply is reduced significantly by the larger spool on the take up so this "trick" is often helpful. The Revox decks, especially the B215 (it's design is a bit different in exactly this aspect from the B710) are NOT normal decks. Revox designed the torque to the reel motors to differ based on their relative rotational speeds so it applies less torque when it is in the beginning of the tape and more towards the end on the take up and the opposite on the supply motor. Because of this, if you go too high in spring tension on the take up roller to minimize W&F, you will find the torque is unable to correctly pull at the beginning of the tape! On the B710, this ratio is adjustable to some extent via a pot, but it can actually cause all sorts of issues, where FF or REW is SO fast that the counter doesn't even count! I spent a LOT of time rewinding and FF because of this. Forewarned is fore armed.

[Patrik]

Thanks for the input!
I have to admit that I find it a bit hard to understand why the takup reel affects wow towards the end of the tape. I mean, at that point the force on the tape is lowered by the large spool size. (The Revox may be different due to applying more torque towards the end -so is this a Revox specific thing?)

If you can HEAR ANY wow at the end of a tape on a B215, then something is very wrong. If you mean you measure increased wow at the end of certain W&F/Speed tapes, but not others, then the tapes must be very different lengths, and the take up motor needs work or adjustment. On the B215 and B710, both take up and supply spring pressures are very, very adjustable, and are sensitive to even a few turns of the nut to have a significant effect on the readings. You should not have to be at either extreme at all. In the past, I've put in the W&F tape so it plays at the end where (almost) any deck has higher W&F (another notch for the Dragon, which is very insensitive to tape spool size) and moved the nut on the take up to slighter higher tension to isolate it further from the effects of the take up reel, which also brings it's speed slightly closer to ideal, as all the Revox decks run faster than they should. At some point there is no reduction in W&F or the tape starts to travel, and I back it off a half turn or so.

On normal decks, the torque the take up reel can apply is reduced significantly by the larger spool on the take up so this "trick" is often helpful. The Revox decks, especially the B215 (it's design is a bit different in exactly this aspect from the B710) are NOT normal decks. Revox designed the torque to the reel motors to differ based on their relative rotational speeds so it applies less torque when it is in the beginning of the tape and more towards the end on the take up and the opposite on the supply motor. Because of this, if you go too high in spring tension on the take up roller to minimize W&F, you will find the torque is unable to correctly pull at the beginning of the tape! On the B710, this ratio is adjustable to some extent via a pot, but it can actually cause all sorts of issues, where FF or REW is SO fast that the counter doesn't even count! I spent a LOT of time rewinding and FF because of this. Forewarned is fore armed.

[studeb]

interesting about how you got to a revox from a tandberg...

anyways, at the end of the tape the take-up reel has a large radius, thus would be pulling the tape with a larger force, if the motor torque is constant. Any motor cogging would be amplified as well in the same way.

[Patrik]

interesting about how you got to a revox from a tandberg...

anyways, at the end of the tape the take-up reel has a large radius, thus would be pulling the tape with a larger force, if the motor torque is constant. Any motor cogging would be amplified as well in the same way.

Yeah, I just realized this now is a Revox thread.. But the discussion is probably valid for most decks.

The larger the diameter, the smaller the force at the perimeter, given the same torque at the axle.