Sony BVH2000PS tension adjustment.

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karol96
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Re: Sony BVH2000PS tension adjustment.

Post by karol96 » Sat Mar 10, 2018 6:56 am

Hello
And I have also solved problem with movable guides. Pin was broken in socket connector on reed switches board.
After replacing the socket, guides are working properly.
I have a question about something different.
How is it with audio quality in this machine?
I know, this is a video recorder, but some people say that the sound quality is very good, even better then in some Studer machines.
What do you think?
Karol

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PID_Stop
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Re: Sony BVH2000PS tension adjustment.

Post by PID_Stop » Mon Mar 12, 2018 7:28 am

You're really making some excellent progress with that machine!

It's hard for me to be objective about the audio quality because I tend to compare it against other analog VTRs. It's much better than the 2" Ampex machines we used to have, and also much better than the U-matic 3/4" machines that we were using for news back in the 1970s and 80s. On the other hand, I think the specs aren't as good as Beta SP... and once we started with digital formats like DVC-Pro, there's no contest. The BVH-2000 was our first machine that gave us really good video quality, decent stereo audio, and really good editing capability -- so it was a big step forward at the time.

The BVH-2000 gives this for audio specifications:
• 50Hz to 15kHz +1.5dB, —3.0dB
• Signal to noise: >56dB (at 3% distortion level)
• Distortion: <1% at operating level

I'm not really familiar with Studer decks, but here's how it compares with my 1970-vintage Ampex AG440B machine (1/4", half track stereo):
• 40Hz to 15kHz +/-2dB (7.5ips), 30Hz to 18kHz +/- 2dB (15ips)
• Signal to noise: >63dB at peak record level
• Distortion: <0.4% at peak record level

So while the Sony wasn't really up to the standards of professional audio recorders at the time, it was quite good for a VTR -- and considerably better than the rest of a typical broadcast plant.

Jeff

karol96
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Joined: Fri Feb 09, 2018 11:27 am
Location: Poland

Re: Sony BVH2000PS tension adjustment.

Post by karol96 » Tue Mar 13, 2018 2:51 pm

Hello
As the machine is happier, I'm also happy.
I was making some audio recording tests - the quality is pretty good.
But no all tension problems are gone. Tension arms are in my opinion adjusted correctly, but rewind doesn't work well.
After pressing shuttle and turning a knob couterclockwise, reels start rotating, but after a few seconds T-Tension arm suddenly goes to left and an alarm comes on.
But with fast-forward there are no problems.
Here is link to a video I made, where I present, what the machine is doing.
https://m.youtube.com/watch?v=bh8KDvVIHs8
Karol

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Re: Sony BVH2000PS tension adjustment.

Post by PID_Stop » Wed Mar 14, 2018 7:11 am

Good morning,

I just watched the video, and have a couple of ideas you might try. One note: when you get an alarm and the buzzer is beeping, pressing STOP will silence the buzzer. It's easier to concentrate when the machine isn't making so much noise! Anyway, these steps should be done in the order given (sensor calibration first, then reel amplifier offset, then reel torque. Order doesn't matter for the sensor arm calibration (which you've already done).

1) Both supply and takeup reel motors, and the timer roller, each have two frequency generators that send speed information back into the servo system. There are adjustments to make the duty cycle 50%; in volume 1 of the manual, it's section 11-1 (page 11-5). One correction to the manual from the training class: change the third line of the instructions from:

"Mode of VTR: program Jog +3 Times Normal"
to:
"Mode of VTR: variable 10/30"

2) Check the S-Reel amplifier offset adjustment (section 11-22). On the graph showing the relationship between the DVM reading and the rotation of RV2, you want to be closer to 1mV than 0mV. (This probably isn't the problem, but is a necessary step before checking the torque.)

3) Ignore section 11-23.

4) Check the S-Reel motor torque adjustment (section 11-24). It is very important that you use a new (that is, a full) one-hour 9" (228mm) reel for this, because the test is using the mass of the reel as a calibration standard. Also, make sure the end of the tape is well taped down, and that your fingers are well away from the reel, because it gets moving very rapidly! When you're looking at the LED display on the SV-43 board, you're looking for a final reading of "Cx" (x doesn't matter, but if you get it around 7 or 8 -- i.e., C7 or C8, you're in the middle of the range). Turning RV1 on board RA-05 clockwise increases the torque, and therefore lowers the count on the LED display.

5) Check the T-Reel amplifier offset (section 11-25). This is like the S-Reel adjustment, and again you want to be closer to 1mV than 0mV.

6) Ignore section 11-26.

7) Check the T-Reel motor torque adjustment (section 11-27). It's just like the S-Reel torque, but on the other motor.

8 ) Finally, check the S-Reel tension offset (section 11-28).

Ordinarily this will correct any tape handling problems, but if it doesn't, you might find a mechanical issue:
• A guide roller that should be rotating, isn't.
• The timer roller isn't turning as fast as the tape is moving. This could be a problem with the bearings, or the rubber surface is glazed. Give it a really aggressive cleaning with alcohol to improve its grip on the tape.
• If there's something sticky in the tape path, that can create strange problems with motion. A thorough cleaning can help.
• There might be a dead spot in one of the potentiometers for the S-tension or T-tension arms. This is the sort of problem that was very unusual back when the machines were newer, but seems to be more common now that they are closer to 30 years old.

Regards,

Jeff

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