BVH-3000

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DoctorZW
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Joined: Tue May 05, 2020 9:48 pm

BVH-3000

Post by DoctorZW »

Hi Folks,
I am new to this forum, and appreciate the wealth of knowledge I have read here. Hopefully I can contribute in return. I have a BVH-3000, which works well. It has a part in the transport that I have not found any information about in the manuals and was hoping someone would enlighten me. This part is called the IP Roller, I believe it stands for impedance roller. It seems to have light contact with the tape, it is powered, and rotates both directions. What is this used for?

Thanks for any insight.
jon

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PID_Stop
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Re: BVH-3000

Post by PID_Stop »

Welcome to the forum!

My own expertise is mainly with the BVH-2000 (I attended Sony's two-week training school about 30 years ago and have maintained 2000s, 500s, and 2500s) -- the 3000 is similar in many ways, but the control system is quite different.

You are correct: "IP" does stand for impedance, and the purpose of the roller is to create a stable moving surface between the exit guide and the fixed heads that effectively isolates the rotating upper drum and any bearing noise from guide roller 3 from the audio heads. This isolation reduces flutter in the audio that would come from the constantly changing contact between video head tips and the tape: every spin of the drum means that each of the six head tips (or dummy tips, for machines that don't have dynamic tracking) breaks contact with the tape at the entrance guide, and then re-establishes contact at the exit guide... this not only creates slight impacts with the tape at the exit guide, it also changes the effective circumference of the drum at a roughly 359Hz rate. The roller probably also improves the stability of the control track phase in recording and in playback, but the most apparent improvement would be in the audio.

Interestingly, the manual says very little about the IP roller, and the only adjustments for it are the frequency and voltage balance for the two motor windings. It isn't terribly fussy. I don't know about the BVH-3000, but on a 2000 the IP motor is actually controlled by the timer roller... if you give the timer roller a spin, the IP motor will start running.

Regards,

Jeff

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PID_Stop
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Re: BVH-3000

Post by PID_Stop »

Another way to think about the IP roller -- if you have experience with older Ampex audio recorders like the 350 or 440 series, the BVH's IP roller performs much the same function as the flywheel-coupled roller to the left of the head assembly. Its purpose is to isolate the motion of the tape passing across the heads from variations in the supply reel torque (the capstan and pinch roller perform the same isolation between the heads and the takeup reel).

Jeff

DoctorZW
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Joined: Tue May 05, 2020 9:48 pm

Re: BVH-3000

Post by DoctorZW »

Jeff,
Thanks for the fast response to my question, and the explanation of the purpose of the IP roller. These older VTR machines are incredible and I enjoy repairing and tinkering with them.

regards, jon

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