Sony Betamax VCR Model SL-HF360 pulse or "click" in the HI-FI audio

not

Clean the pinch roller, may have a particle of magnetic material on it if "recorded" on tape (try on another machine)

Is it exaxtly the same click rate at any point in a tape?

Does it change periodicity if you slightly brake capstan motor (more likely) or drum motor with a finger? ie a problem on a commutator contact.

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on

Hello,

While I don't know your model, we once had a Betamax at the shot with an audio problem like this that turned out to be a ground shield that was not mounted properly when the owner cleaned the heads. I'd make sure all shields are in place, along with ground straps, as Sony intended them. Our guess was that the switch mode supply was interfering with the audio board.

Regards, Tim Schwartz Bristol Electronics

Thanks for the responses. The pinch roller was cleaned and it is not worn or slick. The click is constant on all tapes at the same rate. If I slow down the drum or capstan motor nothing changes until the motors are slowed down to the point the video starts to drop out. Then the HI-FI drops out also so I can't tell. I was leaning to a ground problem also as the problem showed up after a move from one city to another. Have looked for loose parts and cracked etches. Could very well be interference from the power supply. Found nothing so far. I will keep looking. Thanks!

Not all that familiar with Beta machines, but I assume the Hi-Fi audio is taken from a set of the rotating heads on the drum similar to the way it is done in a VHS HiFi machine. If so, it sounds to me like you're hearing the dropout where the heads are switched. Most VHS machines had an adjustment for this to switch the heads on-and-off so there was a slight overlap. Hopefully you have the factory service manual and an oscilloscope. Look at the Hi-fi FM envelope on the 'scope (and see if there is a small void in it) and adjust the Hi-Fi switch point according to the spec's listed in the manual. Note this will be seperate from the video switch point, but while you're at it, check (and if necessary adjust...) the video first (as the manual no doubt will specify). The Servo system tells the head amp when to switch heads by comparing this adjustment with a pulse from a sensor on the drum, called PG (Pulse Generator). Many times the service manual refers to this adjustment as "PG Shift" , and on HiFi machines, there are TWO PG shift adjustments, one for the video, and one for the HiFi audio. Keep in mind, the heads could be worn, or something wrong with the tape path that could be causing your problem, in which case adjustment may be futile.

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Nope. Beta HiFi didn't require extra heads. (If I'm wrong about this, my face will be deeply red -- though you won't be able to see it.)