Film-Tech Forum ARCHIVE: bulk tape eraser recommandations

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Posted by Scott Norwood (Member # 30) on 11-05-2002, 09:02 PM:

I know this is a bit off topic for Film-Tech, but I'm sure that I'll get some good responses here, so....

I'm in the market for a bulk tape eraser. This will be for 1/4" audio tape on 10" and 7" reels as well as radio "carts." It would be nice if it worked on videotape, cassettes, DAT, DLT, etc., but none of these are critical. Cheap is good. This is for occasional home use, not full-time professional use. What should I buy? Is there anything to avoid buying?

I've been borrowing a little handheld model that works OK, but now I'd like to purchase something for myself.

Posted by James R. Hammonds, Jr (Member # 673) on 11-05-2002, 09:20 PM:

get one like the ones they used in Fight Club.

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Posted by Brad Miller (Member # 2) on 11-05-2002, 09:38 PM:

The Rat Shack makes one for about $20 that does the job. It's not perfect, but it works. I've used it before and found that I commonly had to do it twice to completely erase everything. Obviously I prefer the professional models that look like a bulk candy scale, but it sounds like the $20 one will suit you just fine. Do note the Rat Shack model has a limited service time. Something like 15 seconds on and a minute off.

Posted by Paul G. Thompson (Member # 655) on 11-05-2002, 09:53 PM:

I never had much faith in bulk erasers. They generally leave "something behind." That in itself is no big deal, because the erase heads in both reel-to-reel and cassette machines will clean it up during the recording session of new material.

However, bulk erasers for carts are a different story. There is no erase heads I know of in BE and ITC Cart Decks, and I am sure that condition probably exists with other manufacturers as well.

For cart bulk erasers, I usually seen the best results obtained from those that look like a clothes iron. If those styles are used, move the eraser further away from the cart before securing the power so the flux field will not leave its impression on the tape. Otherwise, you will hear a low-key "shhh shhh shhh" during quiet spots on the tape.

As a passing thought, keep the heads clean and in perfect alignment. If not, the machines may never see the Sec tone, the Tertiary tone, or the Stop tone. It is a total disaster if the "stop tone" is not read properly. The machine will continue to cycle until it sees the tone, or until the machine is manually shut down.

All three tones are recorded on a separate track from the audio. If the heads are out of alignment, you might hear the tones in the audio, and other tones from the audio track might be heard by the control logic causing false shutdowns and false triggering of an on-coming cart machine.

Cart decks are great Hi-Fidelity machines....but they require much more TLC in servicing and cleaning than the average reel-to-reel or cassette.

Posted by Gordon McLeod (Member # 33) on 11-05-2002, 11:58 PM:

MagnaSync made a great one and I think MTE now makes the same unit contact ICECO in miami

Posted by John Pytlak (Member # 331) on 11-06-2002, 09:05 AM:

I bulk my tapes using an old loudspeaker field coil (from the days when loudspeakers didn't have permanent magnets). Powered by 220 VAC, the magnetic flux density is so strong that it's tough to pull the tape away from it! Use is limited to about 5 minutes, as it starts to heat up.

here Field Coils

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e-mail: john.pytlak@kodak.com
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Posted by Paul G. Thompson (Member # 655) on 11-06-2002, 11:30 AM:

Scott, if you can get a eraser/splice finder for the carts, do so. You'll never regret it. The eraser portion works well for cassettes, too. Just stuff it in there and push the button. You'll know when it is done.

The eraser electronics is almost as strong as an armature growler.

Posted by Tim Reed (Member # 137) on 11-06-2002, 12:06 PM:

I never had a problem with the old Fidelipac erasers. They were heavy-duty tabletop models, with a plexiglas guide on the edge, to bulk carts. The trick is to slowly pull the cart away on the last swipe, before you release the button. That's effectively what the splice-finder/erasers do; they ramp the voltage down on the erase coil after a few seconds, leaving a nice, thumpless "bulk".

The Fidelipacs should be available on the used market, I would think, since cart useage has waned in broadcast.

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Better Projection Pays!

Posted by John Pytlak (Member # 331) on 11-06-2002, 12:28 PM:

My technique with the AC-energized field coil is to wipe the cassette in a circular motion around the center of the energized coil for a few seconds, then flip the cassette and wipe again. Then slowly pull the cassette away from the magnetic field with the same circular motion. You can actually feel the cassette held by the strong vibrating magnetic field.

The field is so strong that I get noticeable deflections and color impurity on a CRT display a few feet away. (The field coil makes a great degaussing coil too).

Posted by Paul G. Thompson (Member # 655) on 11-06-2002, 10:57 PM:

Tim said:

quote:
"The trick is to slowly pull the cart away on the last swipe, before you release the button. That's effectively what the splice-finder/erasers do; they ramp the voltage down on the erase coil after a few seconds, leaving a nice, thumpless "bulk".

Tim is absolutely correct.

John said:

quote:
"My technique with the AC-energized field coil is to wipe the cassette in a circular motion around the center of the energized coil for a few seconds, then flip the cassette and wipe again. Then slowly pull the cassette away from the magnetic field with the same circular motion."

John's method is very effective if you are not blessed with the bulk erasers such as Tim and I suggested.

I always get a laugh out of these guys who slam the tape down, turn on the power, shove it around for a few seconds, turn off the power, and then pick up the tape. They they scratch their lower posterior trying to figure out why all the "thumps" and "shhh shhhh shhh" noises are still on the tape!

As I look at John's quote, It could have a whole new meaning if it read like this:

quote:
"My technique is to wipe in a circular motion around the center for a few seconds, then flip and wipe again. Then slowly pull away with the same circular motion."

John, that sounds like a wad of toilet paper doing its job with the Klingons encircling Uranus in Star Trek.

Posted by Bruce McGee (Member # 131) on 11-07-2002, 09:28 AM:

FWIW: The Ampex owners group recently had a discussion on this subject.

Some degaussers can leave sub-auditory 'thumps' in the oxide on the tape that the erase heads on the vcr/reel to reel/cassette deck cant possibly begin to remove/reshape. This means that there may be some degradation in the recording.

They never really decided what type of degausser was the best.

We have a big one at work (30 amps, 220 volts) that pulls the medium through on a conveyer belt. When it comes out the exit side, I flip it over, and run it through again. The end.

I can possibly get the information off of it this weekend if anyone is interested.

Posted by Paul G. Thompson (Member # 655) on 11-07-2002, 12:59 PM:

Bruce, please do so. It might be helpful.

I have also observed the phenomena you discribe....I just thought it was improper bulking techniques. I guess I was wrong.

Posted by Scott Norwood (Member # 30) on 11-07-2002, 01:25 PM:

Who decided that cart machines don't need erase heads, anyway? It seems odd, since every other type of tape recorder that I have ever seen has them....

Anyway, thanks for the recommendations so far; please keep them coming.

Posted by Tim Reed (Member # 137) on 11-07-2002, 08:04 PM:

Paul quoted:

quote:
wipe in a circular motion around the center for a few seconds, then flip and wipe again.

I'm ROLLING!
Also, I apologize, Paul. The description of my "technique" is essentially the same thing you said earlier.

YES! I remember that same guy, whose spots always went "shh-shh-shh"! He never had a clue!

Bruce, yes, that'd be interesting to see the conveyor belt jobbie. I remember seeing ads for those things. Always looked like they could double as microwave ovens, and at 30 A, maybe they could!

Scott said,

quote:
Who decided that cart machines don't need erase heads, anyway?

Scott, as far as I can tell, they never had erase heads in order to force bulk erasing, because carts are of differing lengths (and often, more than one cut is recorded on a single cart). That way, you couldn't have a short recording made on a longer cart, with the end of an earlier recording remaining present.

I'm hypothesizing, of course.

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Better Projection Pays!

Posted by Paul G. Thompson (Member # 655) on 11-07-2002, 11:29 PM:

What Tim says is true. That method was used for Liners and Sweepers which made it very handy for the "Go-Cart" machines such as what IGM made along with other companys. However, we never recorded more than one spot per cart.

I might add that since the cart decks were not equipped with erase heads, it allowed for some voice or music lay-overs. That might be another reason why....I don't know.

I just fixed the damn things, I never ran them.

Posted by Scott Norwood (Member # 30) on 11-08-2002, 06:45 PM:

So do cart machines use a standard track configuration? I'm having crazy thoughts about spooling cart tape onto reels, recording stuff on my Otari 2-track 1/4" machine, reloading the tape into the cart, and using the cart machine only to add the cue tones. Would this work?

Posted by Scott Norwood (Member # 30) on 11-10-2002, 11:11 PM:

To (sort of) answer my own question: the audio track on a mono cart machine appears to correspond to "channel 1" on a half-track 1/4" machine. The cue track appears to correspond to "channel 2." Disassembling the cart, winding the tape onto a reel, recording onto the tape with the 1/4" machine, and then reassembling the cart does work, although the cue tones seem to be more reliable if they are recorded in the cart machine (as opposed to using the 1kHz tone generator on the Otari). Also, cart tape is significantly thinner than normal 1/4" tape, which makes splicing more difficult. "Normal" tape apparently doesn't have the necessary lubricant on it and thus won't work in carts.

Posted by Paul G. Thompson (Member # 655) on 11-11-2002, 12:38 AM:

No. It won't work. On a stereo cart tape, one channel occupies two tracks like a standard reel to reel. Reel to reel use tracks 1 and 3 in one direction, and tracks 2 and 4 in the other direction. A cart deck uses squished tracks 1 and 2 for one channel, and 3 and 4 for the other channel as compared to a reel to reel.

The cue track on the cart decks are in the center of the tape between combined tracks 1 and 2, and the combined tracks 3 and 4.

The cart decks have stacked heads. I could be wrong, but I think most reel-to-reel machines have staggered heads. Even if it worked, you will have an undesirable offset between the left and right channels by a couple of milliseconds if there was a difference in head configuration.

Posted by Scott Norwood (Member # 30) on 11-11-2002, 05:14 AM:

Hmm...it works with my mono (only) cart machine. My reel-to-reel is a two-track (aka half-track) machine, not a four-track, and uses stacked heads (each records on 1/2 the width of the tape). It only works in one direction (if you flip the reels, the tape plays in reverse, with the L and R channels swapped) There is a fourth head for playback of 4-track tapes, but I'm not using that. The audio track seems to line up fine (though I'm now wondering if the track is narrower on the cart machine), but if the cue track is in the center, that would explain why recording the tones on the reel-to-reel doesn't work reliably.

Also, this only works at 7.5ips. Supposedly some cart machines can be modified to run at 15ips, but mine isn't set up this way.

Anyway, I'll probably never do this again, since reassembling a cart is slow and painful.

Posted by Brad Miller (Member # 2) on 11-11-2002, 05:18 AM:

quote:
" "Normal" tape apparently doesn't have the necessary lubricant on it and thus won't work in carts."

It's not only the lube, but the thickness of the tape as well as a good backcoating (not found on the cheaper tapes). Loaded and spliced exactly, a thicker mil tape will work just fine in a cart machine. Of course if you splice it off by even a half inch or so from the ideal loop size, it will jam.

Posted by Jack Ondracek (Member # 1466) on 11-12-2002, 12:02 AM:

quote:
from Scott N.
So do cart machines use a standard track configuration? I'm having crazy thoughts about spooling cart tape onto reels, recording stuff on my Otari 2-track 1/4" machine, reloading the tape into the cart, and using the cart machine only to add the cue tones. Would this work?

This could be done, though one would wonder why you'd want to?

As for how it all works (Paul covered a lot of it), cart tape only travels one way... therefore, there's no need to allot track space for the reverse trip.

The monaural configuration is much like the 2-track stereo setup you'd find on an Otari or Ampex broadcast machine. In the case of carts, the audio is recorded on one track (I think it's the top one... 50% chance of being right here!), and the cue tones are laid on the lower track. Accounting for guard bands, the head (with stacked poles) therefore uses both halves of the tape.

For broadcast stereo, the cart configuration is a little wierd, and relatively unlike reel-to-reel. Again, since the tape only travels in one direction, there's only need for 3 tracks... 2 for left & right, and the third for the cue tones. There was an effort at one time to matrix L+R / L-R on cart tapes, so as to minimize high frequency phasing problems. A company called Ramco Research tried real hard to get some market share out of this... and I think ITC may also have given it a shot. I don't think either company was very successful, and I never heard why.

Anyway... as for cue tones... you could do a monaural recording on one half of a 2-track setup, then reload the cart... and your audio would be OK. The tricky part would be getting the cue (stop) tone in exactly the right place. In the real world, there's a small time period between the start of the actual tone, the time it takes for the electronics to validate it and the mechanics to release the capstan roller, thereby stopping the tape at the beginning of the recording. This is why production people had to put a slight delay between hitting the record button and actually sending audio to the cart recorder. Even if you had a machine that would lay the 1000 hZ cue without biasing the audio track record head, you'd have to have pretty good timing to get it in the right place. In the case of secondary and tertiary signalling tones, most cart recorders were capable of laying them down in record or playback mode.

There is an issue regarding cart tape lubricant. The graphite will get all over your reel-to-reel, so if you actually do try this, be prepared to give your deck a good cleaning afterward.

A side note regarding the thumping sound with bulk erasers... I was able to get good results with just about every eraser out there. The trick for me was NOT to wiggle the cart around when pulling it away from the eraser. The circular motion was fine for getting around all parts of the cart... but moving it around a lot while separating it from the eraser seemed to be the cause of some residual noise issues I used to have.

If you guys REALLY go back aways, here's a question for you... Did any of you ever put a bulk eraser to a MaKenzie cart?????? Really??

If so... you tell your story first!

And finally, for Paul... there IS a type of cart machine (by ITC, Gates, MaCarta, Sparta[ick], ATC, etc) that DOES have an erase head on it. (Jeopardy music goes here).... what kind is it?

Posted by Bruce McGee (Member # 131) on 11-12-2002, 12:55 PM:

OK I'm a little late in my response. I will get the brand, model, etc, when I go to work this weekend.

No pics though!

This unit is built with the degaussing coils suspended over the conveyer belt. It really does a good job. I have never had a problem using degaussed tape on my high-speed VHS tape duplicators.

Posted by Bruce McGee (Member # 131) on 11-18-2002, 09:18 AM:

The degausser at work is a Garner 1600. It runs on 220 volts, and draws 15 amps. The nameplate is on the bottom of the unit, and since the machine is bolted to the table, I cant see where it was built. I hope that this helps you.