REVOX B77 MKII stops after starting to play - UK Vintage Radio Repair and Restoration Discussion Forum

prototype · 20th Apr 2015, 7:51 pm

Hello everyone!!!

All was good and fine...until last week.
I have absolutely the same sympthomes as it's described here in this thread by topicstarter

https://www.vintage-radio.net/forum/s...d.php?p=706269

the main difference that's my tape recorder is REVOX B77 MKII. Therefore it haven't any fader start board.
Now it can "play" "rev" or "ff" only if I keep holding the appropriate button.
The tape of end sensor is alive and working perfectly.
Can you give me some advise which side I shall look for?

thanks...

Michael Maurice · 20th Apr 2015, 9:14 pm

There were several versions of the tape control board, If you can let us have the version, then it will help with looking at the diagrams.

I essence you need to look at the stop line, that is the line that goes from the stop switch to the logic chip.

This is also fed from the edit lever and the End Of Tape sensor.

This line should be at 0V if it is high then you need to isolate whats causing it to go high.

prototype · 21st Apr 2015, 7:35 pm

Well the version of the board is 177.317-11. So I'm really not a big specialist. I'm still need your help

Michael Maurice · 21st Apr 2015, 10:32 pm

On this version, the stop line is fed from the stop switch, the edit block, the end of tape sensor and the remote control (if fitted)

Do you have a test meter?

You need to measure the stop line

On the attached diagram of the tape control board, the stop line is marked in red. It should be at 0V unless either the stop button is pressed, or the EOT sensor shows that a tape has ended or the edit lever is in edit (which cancels when play is selected)

If you dont have a test meter, then either buy one or give the recorder to a professional repairer.

prototype · 22nd Apr 2015, 7:04 am

Sure I have the test meter. I haven't seen any attached diagram. Can you reattach once again?

Michael Maurice · 22nd Apr 2015, 1:56 pm

Sorry my fault

prototype · 7th May 2015, 8:56 am

Hello. After a couple of sleepless nights battling the problem it has been solved. The main causer was a Q11 transistor (BC 307A) in tape end sensor circuit.

20th Apr 2015, 7:51 pm	#1
prototype Retired Dormant Member Join Date: Apr 2015 Location: Kashira, Russia Posts: 4	REVOX B77 MKII stops after starting to play Hello everyone!!! All was good and fine...until last week. I have absolutely the same sympthomes as it's described here in this thread by topicstarter https://www.vintage-radio.net/forum/s...d.php?p=706269 the main difference that's my tape recorder is REVOX B77 MKII. Therefore it haven't any fader start board. Now it can "play" "rev" or "ff" only if I keep holding the appropriate button. The tape of end sensor is alive and working perfectly. Can you give me some advise which side I shall look for? thanks...

20th Apr 2015, 9:14 pm	#2
Michael Maurice Moderator Join Date: Feb 2006 Location: Wembley, Middlesex Posts: 7,224	Re: REVOX B77 MKII stops after starting to play There were several versions of the tape control board, If you can let us have the version, then it will help with looking at the diagrams. I essence you need to look at the stop line, that is the line that goes from the stop switch to the logic chip. This is also fed from the edit lever and the End Of Tape sensor. This line should be at 0V if it is high then you need to isolate whats causing it to go high. __________________ Forum Moderator http://www.michaelmauricerepairs.co.uk/

21st Apr 2015, 7:35 pm	#3
prototype Retired Dormant Member Join Date: Apr 2015 Location: Kashira, Russia Posts: 4	Re: REVOX B77 MKII stops after starting to play Well the version of the board is 177.317-11. So I'm really not a big specialist. I'm still need your help Attached Thumbnails

21st Apr 2015, 10:32 pm	#4
Michael Maurice Moderator Join Date: Feb 2006 Location: Wembley, Middlesex Posts: 7,224	Re: REVOX B77 MKII stops after starting to play On this version, the stop line is fed from the stop switch, the edit block, the end of tape sensor and the remote control (if fitted) Do you have a test meter? You need to measure the stop line On the attached diagram of the tape control board, the stop line is marked in red. It should be at 0V unless either the stop button is pressed, or the EOT sensor shows that a tape has ended or the edit lever is in edit (which cancels when play is selected) If you dont have a test meter, then either buy one or give the recorder to a professional repairer. __________________ Forum Moderator http://www.michaelmauricerepairs.co.uk/

22nd Apr 2015, 7:04 am	#5
prototype Retired Dormant Member Join Date: Apr 2015 Location: Kashira, Russia Posts: 4	Re: REVOX B77 MKII stops after starting to play Sure I have the test meter. I haven't seen any attached diagram. Can you reattach once again?

22nd Apr 2015, 1:56 pm	#6
Michael Maurice Moderator Join Date: Feb 2006 Location: Wembley, Middlesex Posts: 7,224	Re: REVOX B77 MKII stops after starting to play Sorry my fault Attached Thumbnails __________________ Forum Moderator http://www.michaelmauricerepairs.co.uk/

7th May 2015, 8:56 am	#7
prototype Retired Dormant Member Join Date: Apr 2015 Location: Kashira, Russia Posts: 4	Re: REVOX B77 MKII stops after starting to play Hello. After a couple of sleepless nights battling the problem it has been solved. The main causer was a Q11 transistor (BC 307A) in tape end sensor circuit.