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Vintage Tape (Audio), Cassette, Wire and Magnetic Disc Recorders and Players Open-reel tape recorders, cassette recorders, 8-track players etc.

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Old 11th Jun 2017, 6:00 pm   #1
Linnovice
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Default B77 EOT sensor

Hi all, I'm in the process of refurbing a Revox B77 MkII HS machine. The end of tape sensor does not seem to be working but I can't work out if it's the sensor or a component further up the line. Before I try and obtain a replacement sensor, how do I check if the IR is working? If I cover the bottom of the sensor with tape all is well, but I'd still like to check the sensor itself.
Any advice (polite!) would be gratefully received.
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Old 11th Jun 2017, 10:35 pm   #2
Michael Maurice
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Default Re: B77 EOT sensor

In what way is the sensor not working?

You can measure the change in voltage across the sensor depending on whether its 'lit' or dark.
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Old 14th Jun 2017, 5:08 am   #3
Diabolical Artificer
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Default Re: B77 EOT sensor

If its a photo resistor clip your DMM terminals on, resistance range and shine a bright light at it. If a photo diode, use the diode checker and shine a bright torch at it. Or is it a hall sensor, in that case a magnet will change it's parameters.

What ever sort of sensor it is, it's change in condition will probably switch a transistor off/on, which will turn a relay on/off. So if the sensor is ok, check what it's attached to Mike.

Hope that helps, Andy.
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Old 18th Jun 2017, 10:44 pm   #4
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Default Re: B77 EOT sensor

Hi Andy, long time no message. Thanks for the advice, I've not touched it for a couple of weeks. Been too busy. Hope to get back on it this week so will follow your suggestions. M.
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Old 20th Jun 2017, 9:38 pm   #5
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Default Re: B77 EOT sensor

Quote:
Originally Posted by Diabolical Artificer View Post
If its a photo resistor clip your DMM terminals on, resistance range and shine a bright light at it. If a photo diode, use the diode checker and shine a bright torch at it. Or is it a hall sensor, in that case a magnet will change it's parameters.

Hope that helps, Andy.

Its a photo diode and yes it does turn a transistor or two on and off.
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