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In Reply to: RE: Should we send a "representative" to Magnepan? posted by josh358 on October 16, 2011 at 18:46:51
Did you ever do a gauge study?
For example, you have a micrometer. You have 10 sample pieces. You have 3 operators measure each piece 3 times.
Crunch the numbers.
Result? How good is the gauge? Is is 'capable' of measuring your process?
Stuff like that is part of quality.
For electronics: Meters get cal'd on a regular basis. At final test for semiconductors, you have to run known samples on a regular basis to make sure of no drift in measuring tools.....called probers, which check each device for function and 'ink out' those not meeting spec.
If your video heads needed replacement every 200 hours, PMs should be scheduled to 'lead' that time so the tool doesn't go down during use or produce poor quality.
At Magnepan, for example, I'm guessing they go thru a fair amount of Mylar. Now, does Magnepan do an incoming inspection or do there suppliers send the right stuff...every time? Is there an 8d procedure for identifying supplier problems and getting the right stuff? I was part of several 8d efforts and can assure you, it is taken seriously by those who assign the 8d...usually those who received defective or marginal material and those who are responsible for FIXING it. DOES Magnepan have such a procedure in place for resolving systemic failure or problems?
I know Magnepan is a very small company. I like the nice lady who answers the phone.....But, doe they have a dedicated quality program? Is there a training group?
I have bunches of other questions.....but will refrain for now.
BTW, Josh. A Micron? HUGE. I'm used to dealing with Angstroms, of which there are 10,000 in a micron. Thin films of 0.1 micron (1000 angstroms) were routine and I dealt with films down to well below 200 microns. This is why I stress gauge studies and knowing your metrology.
Too much is never enough
Follow Ups:
But you didn't have to adjust within an angstrom by tapping with a screwdriver. :-)
We did routinely send waveform monitors, vectorscopes, and oscilloscopes to Tektronix for recalibration. And spent a lot of time calibrating stuff in house as well, not just the scopes but monitors.
Quad VTR head assemblies were designed to be swapped rapidly when tip projection was too low or a head broke or went out of quadrature. This happened pretty frequently because the head wheel rotated at 14,400 RPM and it could certainly happen during a session, they weren't generally reliable enough to get to the 200 hours or even close. Each machine had to be aligned and checked by a technician in the morning, and adjusted by the tape operator when a new tape was mounted. The routine alignment process typically took about 15 minutes, a soup to nuts alignment much longer. Even when functioning properly, tape interchange was a problem because of changes in track geometry as the head wore. For that reason, masters were recorded with a head that was halfway through its life for maximum compatibility. And you still couldn't count on it working.
All of this was necessary because when the first VTR's were introduced, there was no time base correction so they had to be able to produce a broadcast quality signal mechanically. Amazingly enough, before the development of digital editing, they would splice the videotapes by developing the tracks with an iron oxide solution and cutting and reassembling them under a microscope! The process was so touchy that an old timer who had been around then told me that when a spliced tape played successfully, everyone would cheer.
When color was introduced, limited electronic time base correction made it possible to directly record color subcarrier. VTR's, like 3/4" or 1/2", didn't have the low time base error of a quad, so they had to heterodyne the subcarrier, making them unsuitable for broadcast use. But when digital time base correctors were developed, it was possible to upgrade 1" industrial machines to full broadcast quality, and they replaced the old quads. The 1" machines were much smaller, more reliable, and easier to maintain, though they still required a skilled engineering staff.
But I know a lot more about that crap than making speakers, so the speaker questions will have to go to Wendell. :-)
I don't know much about video OR speaker manufacture.
What I DO know is procedure, specifications and manufacturing TO the spec. If the spec is wrong, get it changed. Changes in the line are managed thru some kind of form where the responsible parties sign off on it and it goes ONLINE as the new procedure of measurable. If training is required, some responsible party has to take the responsiblity and SIGN OFF the operator or whoever does the procedure being changed.
Not to say I never did any wacky stuff. We had photgraphic steppers to put the image of the new layer on the silicon wafer. The wafer had been coated with 'photoresist' which is sensitive to UV light, and the room was illuminated in a yucky yellow. The reticle had tabs glued to it for alignment purposes. The alignment? within a few 10 of microns, but is self aligning within the mechanical / electrical limits of the stepper. The stepper, incidently, is built on a 20" thick slab of granite which is polished and finished to optical flat standards. Anyway, a reticle (kind of a glass negative) had one of these tabs snap off and no replacement was on site. Turnaround was probably a week.....way to long and the lot was waiting. Well, I was NOT a photo tech, but the boss tossed the whole thing at me and said to make it work. HA! I gave myself about 10:1 against, since I knew that it was a lot touchy. Long / Short? I took a razor blade and made a single pass on the tab and the glass. This got off all the old crazy glue. I put a drop on the darn thing and with my hand, clamped the tab back in place and it worked. Much to everyones vast surprise. I was not able to duplicate the fix, and nobody else was able either. The company ended up buying an alignment jig so anyone could do it.
The lesson? While artifacts exist, nothing beats precision and repeatability. Those machines of yours, breaking down at odd times, needed a proper fix with first cause identified for the failure modes. In my line of work, a dead machine invariably resulted in EXPENSIVE scrap.
I'd love to see Magnepan's facility and 'take the tour'. I'd love to make 'em an offer. I work cheap.....maybe a pair of 3.7s for 3 or 4 months work...... I'm now working on my 6S 'belts' and may even get to 'blackbelt' status, which would qualify me to go in and be of substantial help, while saving them some real bucks.
Too much is never enough
Well, admittedly, we had sucky quads, the RCA's rather than Ampexes, which were much better machines. You haven't seen fun until you've seen a machine decide to dump a client's master onto the floor. RCA's broadcast division is a great example of a company that died because of poor quality. So for that matter is Ampex, in its later years. The Japanese, Sony, in particular, ended up taking over, even though the American companies had a significant edge in technology.But, in general, I think that the quads were limited by the technology of the time. Consider that you had a wheel spinning at 14,400 RPM on air bearings with four heads around it. A head would hit 2" magnetic tape moving laterally at 15 IPS and write 1/16 of a field of video. It had to dig into the surface of the tape by a precise amount and when the head rotated off the next head had to start writing the track in precise quadrature, or you'd get "banding" in the image -- it would seem to break into 16 segments (you used to see this sometimes on the air). You could also get minor changes in the phase of color subscarrier at the start of a quad band, called one-line error -- remember how sensitive NTSC color was to phase error? The color time base was corrected electronically but it couldn't correct all errors since its only reference was the brief color burst at the start of a line of video.
The position of the tape and the rotation of the heads were controlled by servo mechanisms, which used a separate control track for course adjustment and then the sync signals in the video signal itself for fine adjustment. A vacuum guide insured that the tape had precisely the right tension around the spinning head wheel. And all of this had to be done to the timing standards of black and white television, despite the fact that you were recording on magnetic tape, a flexible medium that wasn't dimensionally stable. And the tape was open reel, running ideally in a controlled environment equipment area but realistically the environmental control wasn't that good, because the practicalities of a production environment didn't permit it.
What's really amazing is that it worked at all.
The ultimate solution to the cost and reliability issues was basic improvements in the technology. Quad VTR's cost $100,000, were the size of a refrigerator, required an army of technicians, three-phase power, a supply of compressed air, and climate control. Within a few decades, a child could make a high quality digital recording on a cassette the size of a matchbox. But you couldn't have done that when the quad was developed in the 1950's, and all they had was vacuum tubes. The engineers who developed it at Ampex (including a young Ray Dolby of Dolby Labs fame) were doing what had been considered impossible, and what no one else had been able to do, despite significant R&D efforts at RCA. The basic problem was that tape recorders could only record up to 15 kHz or so, but the bandwidth of video was 4.2 mHz! The innovations they came up with to solve the problem were remarkable, everything from the rotating head to FM recording to the nested loop servo system. When they showed the first quad at NAB, there was pandemonium.
Edits: 10/18/11
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