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Old 26th Jan 2017, 8:14 pm   #1
yampy187
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Default Sanyo Betacord VTC 9300 Strange fault?

Hello Everyone.

I have recently got my hands on a Sanyo VTC9300. In pretty good order and was pretty much working when i got it.

I treated it to a new belt kit and cleaned up the rubber idler tires so the machine is running mechanically sound and was playing fine. However a fault appears to have appeared. There is a hum bar rolling down the screen constantly and a buzz/hum on the sound regardless weather a tape is in playback or not. it shows up best on the machine's own test pattern.

I have had a look over the power supply and have changed a few crusty looking capacitors to no avail.

I have downloaded the service manual however i have never worked on a Beta machine before and have limited knowledge about them.

Would anyone happen to have a common fault guide of any description?

Regards,

Jan
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Old 26th Jan 2017, 8:45 pm   #2
Vauxfan2k
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Default Re: Sanyo Betacord VTC 9300 Strange fault?

I think the only person on here that has one of these is Fivos. if it's doing it whilst not playing a tape and on the test screen then I'd look at the video pcb. Did you move or disconnect anything on it while you were working on the machine? Could be a dry solder joint that's been disturbed while moving the machine about.

It's all vhs stuff that I'm used to, the oldest being the 3v23 jvc clone that I have. I have a vtc-5000 but haven't looked at it yet as I have no tapes.

Hope you get it sorted.

Steve
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Old 26th Jan 2017, 9:31 pm   #3
Sanbeta
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Default Re: Sanyo Betacord VTC 9300 Strange fault?

Jan

The last and only time I ever saw that was on a Sanyo VTC 5000 that had obviously been plugged in most of it's life. It was the biggest capacitor in the PSU. Cannot remember the value at present.
Maybe the mains transformer is suffering?

......Kevin
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Old 26th Jan 2017, 11:40 pm   #4
jayceebee
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Default Re: Sanyo Betacord VTC 9300 Strange fault?

I've never worked on one of these but I do recall stories about problems in the 12v supply, check the emitter volts of Q702 on the regulator board.
The hum appears to be at 100Hz so unlikely to be a bridge rectifier problem. Also, if the 12v at Q702 is high don't run the set for too long as it could lead to other damage.

John.

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Old 27th Jan 2017, 3:08 pm   #5
dj_fivos_sak
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Default Re: Sanyo Betacord VTC 9300 Strange fault?

Easy fix. Turn off the Test Signal. Btw, I have two VTC 9350's, which is the Middle Eastern version of that.

Fivos
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Old 27th Jan 2017, 3:51 pm   #6
Mooly
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Default Re: Sanyo Betacord VTC 9300 Strange fault?

The 12 volt (was it 12 ? its a long time ago...) supply was troublesome. Replacing the series pass device with either a TIP41 or TIP 42 (can't remember if the original was NPN or PNP now) was always a quick fix. Its on the big heatsink.
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Old 27th Jan 2017, 8:05 pm   #7
yampy187
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Default Re: Sanyo Betacord VTC 9300 Strange fault?

Hi everyone!

Thanks for the suggestions. I shall have a look this evening and report back.

Kind regards.

Jan
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