[QuadList] Headwheel blower questions

[Don Norwood]

After Wayne's reply, I had a look at the VR-1000 manual.  There was a blower that supplied cooling air to the head channel electronics housing, but it was totally separate from the headwheel cooling blower.  The exhaust from the headwheel blower simply exited into the bottom of the console cabinet.

One other thing that I had not considered....on the Mark-3 head, there is a shroud over the headwheel itself that is connected to one of the head blower ports.  Remembering that the head "blower" is actually pulling air from the head assembly, this shroud acts as a vacuum cleaner for any tape fragments or oxide that might be shed as the tape passes the heads.  For this to be effective, you would need a good bit of vacuum, and so perhaps that was more of the reason behind the powerful system than the need to cool the motor. 

Don 
  ----- Original Message ----- 
  From: Wayne Watson 
  To: Don Norwood ; Quad List 
  Sent: Friday, January 28, 2011 11:42 AM
  Subject: RE: [QuadList] Headwheel blower questions


  The recall is a bit foggy but in the VR-1000 there were tubes, (mounted upside down as I recall) and the cooling was needed for them. If the blower quit the tubes got so hot and the heat went up to the base causing them to melt right out of their sockets. One head channel would be lost per tube and you would find the tube in the bottom somewhere with the base still in the socket. So perhaps that is why the VR-1000has much more air????

  Or was there a separate blower for the headwheel???

   

  Wayne Watson

  Broadcast Systems Technology

  wayne.watson at sait.ca

  (403) 284 7079

  SAIT Polytechnic

  School of ICT

  Room G239E

  1301 - 16th Ave. N.W.

  Calgary, Alberta T2M 0L4

   

  The SAIT BXST program and WABE need your help to recruit maintenance techs to join our industry. If you want to help please email info at wabe.ca

  For information on the SAIT Broadcast Systems Technology Program, check out http://broadcast.sait.ca

   

   

   

   

  From: quadlist-bounces at quadvideotapegroup.com [mailto:quadlist-bounces at quadvideotapegroup.com] On Behalf Of Don Norwood
  Sent: Thursday, January 27, 2011 8:32 PM
  To: Quad List
  Subject: [QuadList] Headwheel blower questions

   

  I recently dealt with a problem that led me to discover something I had never thought much about before, the various schemes used to provide cooling air for the video headwheel, and what the requirements were for cooling the headwheel motor. It's something that had just always worked. Aside from cleaning filters, I never thought much about it. Now I realize that there was an evolution in this process, and it's caused me to wonder about several things.

   

  The original head blower on the VR-1000 was an incredibly heavy-duty device. It was built like a vacuum cleaner inside of a very thick-walled canister. The same assembly was used on the VR-1100. If you measure the vacuum at the head-cooling ports on the transport plate, you'll see that it pulls about 20" of water! 

   

  By comparison, measuring the cooling port on a VR-1200 indicates only about 2" of water, and then, there's the AVR-2 with no head blower. I haven't checked the AVR-1 or AVR-3, but I don't think they used any cooling air either. Of course, the AVR series machines use different head assemblies than their predecessors.  RCA machines had fairly substantial head blowers too, from the TRT-1 up through the TR-70. Don't know what was done in the TR-600.

   

  I have some Mark-3 heads which I never noticed running hot, but then they were run on VR-1100's with the massive air flow. All newer 1100's were spec'd for the Mark-10 head, and there was obviously no cooling problem with that combination!  But the VR-2000 and 1200 still had warning lights for the cooling air, even though the flow was much reduced. 

   

  So, did the original headwheels really run hot and need the cooling, or was this just "good engineering practice"? And a service question too..... does anyone know the proper setup procedure for the airflow warning switch in a 1200?  I have the procedure for the 1000/1100, but can't find anything for the 1200, and they are very different.

   

  Don
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