UK Vintage Radio Repair and Restoration Discussion Forum

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-   Vintage Tape (Audio), Cassette, Wire and Magnetic Disc Recorders and Players (https://www.vintage-radio.net/forum/forumdisplay.php?f=35)
-   -   Revox A700 End of tape sensor (https://www.vintage-radio.net/forum/showthread.php?t=160764)

stewartrose 23rd Oct 2019 11:00 am

Revox A700 End of tape sensor
 
Good Morning,

Could someone offer number to search for on Revox A700 End of tape sensor, or offer a place to buy one that is not Australia Please

All the best and thank you from Alan

Michael Maurice 23rd Oct 2019 11:27 am

Re: Revox A700 End of tape sensor
 
The diode mentioned in the manual is MRD148. They don't appear to be available anywhere even Ebay doesn't list them.

I cannot see why you couldn't use any opto transistor. Cricklewood stock SFH 206 which could work, or BPW48N.

Before you do so, check that R69 hasn't disintegrated and C8 hasn't gone short circuit. Also check Q1 by substitution.

stewartrose 23rd Oct 2019 1:02 pm

Re: Revox A700 End of tape sensor
 
Good Afternoon Michael,

I changed the transistor because it was EB short, I am getting 4.78v from the sensor, to R8 which is suppling a hi to the B of transistor pulling the collector down to zero...

Covering the sensor does nothing, so I am assuming it is duff :)

All the best from Alan

stewartrose 23rd Oct 2019 1:37 pm

Re: Revox A700 End of tape sensor
 
Good Afternoon Michael,

The Sensor you suggested SFH 206 I can buy on ebay,

The other one I cant find...

But thank you for the information, most welcome

All the very best from Alan


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