6 Track Mag Head Maintenance

[Ryan Gallagher]

The booth I worked at the Telluride Film Fest this year would pick up static/buzz from our
digital walkie-talkies if we stood within several feet of the sound rack, but this was only a
problem when running 35mm. (Optical sound through a CP-65 which fed into a CP-750)
I'm sure it was a shielding issue, as the rack wasn't the neatest job I've encountered. The
festival folks have promised to look into it before next years shows. There were VFD drivers
on those projectors for running silent stuff, although this year we were only running 24fps, but
I was running an archival print of a 1940's movie, so I had programmed a 3sec ramp-up
time into the VFD's to protect the print, but we didn't have any noise from the VFD's.
(TB-Woods "E-Trac X2C" VFD's - almost every venue at Telluride has them. Never heard of
any RFI or noise problems in the 15 years I've worked there)

Yeah our new digital radios reak havock with the little PC speakers we have plugged into the 8ch mixer for monitoring intro mics and pre-show music. Thankfully have not heard anything in the house along those lines... but I'll make a point of getting a co-worker to key a radio near all 35/70mm stuff soon.

It's worth adding we had issues with vintage guitar amps onstage too, when radios were keyed 30-50ft away. We had our radio supplier come back out and turn down our handset transmit power. That helped a good deal, now you have to be standing near them to get the same effect.

[Scott Norwood]

For those saying "star-quad": do you mean microphone cable? (Canare L-4E6S, etc.) Or is there a different sort of cable with similar properties for mag heads?

[Steve Guttag]

That or its foil shield version. I've used both Canaire and Belden (1172A). And yeah, it's microphone cable (and very limp stuff too...with braided shield). The jacket is a little fatter.

[Ryan Gallagher]

Hah, so previously I was not aware of the 6-track head "cover", because one of ours lacked it (the Teccon), and the other had it and said Ampex on it, thought it was a single piece and spoke of it as if it was for sure an Ampex previously. After being told to replace the Ampex I stopped troubleshooting.

In revisiting this subject Brad was suspicious that we might have a Teccon under that cover I was unaware of. But nope. We have a rare original Ampex that was still seeing occasional use until I called it last year with noise problems on that projector.

Here is that rare bird in situ, confirmed AMPEX, in case you haven't seen one in a while!

thumbnail_IMG_6208.jpg

I'm endeavoring to replace it with a Teccon. My partner Teccon has a p/n 29800 on the Teccon label.

I've got a line on 3 Teccon that have p/n 76200. Are those going to be a different sound-head brand mount but same mag-head? Am I needing another Century mount or is the one the Ampex is mounted to equivalent and could be re-used provided I source a mag-head? I'm aware they were originally sold as kinda a "kit" with mount and rear termination posts etc, so swapping just the reader across mounts might create more work than I am comfortable with. That and all the A-Chain I'd have to learn to finish the install. But without endeavoring to do it, 6-Track 70mm is dead in our booth for now. So no time pressure. (Unless our programmer ignores my status warning and books one anyway).

[Steve Guttag]

According to our Teccon sheet, the 29800 is a 70mm 6-track head for Ampex/Century. It is mounted on sub base.

76200 are not in my Teccon parts lists (nothing that begins with a 7, for that matter) for either studio or theatre heads. Either there is a typo or they were something custom or simply not in the normal catalogs. Pricing wise, Teccon always priced by the number of channels. So a 6-track head for a Simplex was the same price as one for a Century as one for a Norelco. It didn't matter to them.