Revox B77 - Questions. - UK Vintage Radio Repair and Restoration Discussion Forum

Courtney Louise · 29th Dec 2017, 9:37 am

Hey all.

I have just aquired a lovely B77HS MkII Half Track and am having a few issues with it. All 4 Rifa Caps have been changed but for some reason if you touch the metal reel, while the machine is in stop mode, you can feel a slight current through it if you run your finger over it. I have experienced a similar thing in Apple laptops that are aluminium when the charger is plugged in.

Also I was testing the B77 and playing my Fiio X5 lossless player using the line out on the player to the line in on the Revox and everything was going fantastic, the sound quality was superb so I thought I would stop the recording and see what it was like at 15ips.

I stopped the recorder and touched the Fiio (aluminium cased) and all of a sudden the Fiio stopped playing and now wont turn on.

What is wrong with it?

Courtney x

Ted Kendall · 29th Dec 2017, 9:58 am

Sounds like the chassis was seeking a path to earth. Some leakage is not unknown - usually the Revox would be earthed through connections to an amplifier. Was the Fiio connected to anything else at the time? I hesitate to use words like "zapped", but fear something in it has gone pop...

Courtney Louise · 29th Dec 2017, 10:04 am

erm yeah it was sitting on the cooker, cooker would have been earthed

Ted Kendall · 29th Dec 2017, 10:15 am

OK. I'm not particularly familiar with the Fiio - are you able to remove and replace the internal battery without losing data? If you can I'd try it, as some sort of hard re-set.

Michael Maurice · 29th Dec 2017, 10:20 am

I presume it was the Fiio that was sitting on the cooker as the Revox has a plastic casing.

A lot of static can be generated whilst winding and rewinding, maybe thats what you were experiencing.

John Caswell · 29th Dec 2017, 4:52 pm

As an aside to this but possibly relevant,
Back in my servicing days one of the simpler methods of checking for a live chassis was to lightly rub the back of the fingers across the chassis. As the hairs there are quite sensitive it was easy to determine a live chassis by the very slight tingling noticed.
I would add that as the workshop was a concrete floor we had duckboards to stand on, but there was enough leakage current through you/boards to make things noticeable.
The downside was as I was the gofer, Friday night was my "cleaning under the duckboards" night.
I suspect that what Courtney is feeling was leakage through the "X and Y" capacitors. This is certainly enough to "splat" any µprocessor control circuitry.

John

Michael Maurice · 31st Dec 2017, 1:05 am

The only X2 cap in a Revox on the mains side is across the mains, there are no Y class capacitors between mains and chassis.

Courtney Louise · 31st Dec 2017, 3:28 pm

Hmmm, I used X2 caps also on the reel size board and the motor control board as they required AC, won't hurt will they?

Courtney Louise · 31st Dec 2017, 3:28 pm

The Fiio did a hard reset of itself, came back on after an hour or two.

Ted Kendall · 31st Dec 2017, 3:36 pm

Good show! Might be a good idea in these circumstances to earth the Revox, by connecting to an earthed amplifier, for example.

Courtney Louise · 1st Jan 2018, 11:05 am

Hi Ted, once in proper use it will be.

C

29th Dec 2017, 9:37 am	#1
Courtney Louise Octode Join Date: Sep 2005 Location: Welshpool, Powys, Wales Posts: 1,327	Revox B77 - Questions. Hey all. I have just aquired a lovely B77HS MkII Half Track and am having a few issues with it. All 4 Rifa Caps have been changed but for some reason if you touch the metal reel, while the machine is in stop mode, you can feel a slight current through it if you run your finger over it. I have experienced a similar thing in Apple laptops that are aluminium when the charger is plugged in. Also I was testing the B77 and playing my Fiio X5 lossless player using the line out on the player to the line in on the Revox and everything was going fantastic, the sound quality was superb so I thought I would stop the recording and see what it was like at 15ips. I stopped the recorder and touched the Fiio (aluminium cased) and all of a sudden the Fiio stopped playing and now wont turn on. What is wrong with it? Courtney x __________________ *33, 45, 78, around and around they go...*

29th Dec 2017, 9:58 am	#2
Ted Kendall Dekatron Join Date: Jul 2008 Location: Kington, Herefordshire, UK. Posts: 3,670	Re: Revox B77 - Questions. Sounds like the chassis was seeking a path to earth. Some leakage is not unknown - usually the Revox would be earthed through connections to an amplifier. Was the Fiio connected to anything else at the time? I hesitate to use words like "zapped", but fear something in it has gone pop...

29th Dec 2017, 10:04 am	#3
Courtney Louise Octode Join Date: Sep 2005 Location: Welshpool, Powys, Wales Posts: 1,327	Re: Revox B77 - Questions. erm yeah it was sitting on the cooker, cooker would have been earthed __________________ *33, 45, 78, around and around they go...*

29th Dec 2017, 10:15 am	#4
Ted Kendall Dekatron Join Date: Jul 2008 Location: Kington, Herefordshire, UK. Posts: 3,670	Re: Revox B77 - Questions. OK. I'm not particularly familiar with the Fiio - are you able to remove and replace the internal battery without losing data? If you can I'd try it, as some sort of hard re-set.

29th Dec 2017, 10:20 am	#5
Michael Maurice Moderator Join Date: Feb 2006 Location: Wembley, Middlesex Posts: 7,224	Re: Revox B77 - Questions. I presume it was the Fiio that was sitting on the cooker as the Revox has a plastic casing. A lot of static can be generated whilst winding and rewinding, maybe thats what you were experiencing. __________________ Forum Moderator http://www.michaelmauricerepairs.co.uk/

29th Dec 2017, 4:52 pm	#6
John Caswell Hexode Join Date: Jul 2009 Location: Wokingham, Berkshire, UK. Posts: 437	Re: Revox B77 - Questions. As an aside to this but possibly relevant, Back in my servicing days one of the simpler methods of checking for a live chassis was to lightly rub the back of the fingers across the chassis. As the hairs there are quite sensitive it was easy to determine a live chassis by the very slight tingling noticed. I would add that as the workshop was a concrete floor we had duckboards to stand on, but there was enough leakage current through you/boards to make things noticeable. The downside was as I was the gofer, Friday night was my "cleaning under the duckboards" night. I suspect that what Courtney is feeling was leakage through the "X and Y" capacitors. This is certainly enough to "splat" any µprocessor control circuitry. John

31st Dec 2017, 1:05 am	#7
Michael Maurice Moderator Join Date: Feb 2006 Location: Wembley, Middlesex Posts: 7,224	Re: Revox B77 - Questions. The only X2 cap in a Revox on the mains side is across the mains, there are no Y class capacitors between mains and chassis. __________________ Forum Moderator http://www.michaelmauricerepairs.co.uk/

31st Dec 2017, 3:28 pm	#8
Courtney Louise Octode Join Date: Sep 2005 Location: Welshpool, Powys, Wales Posts: 1,327	Re: Revox B77 - Questions. Hmmm, I used X2 caps also on the reel size board and the motor control board as they required AC, won't hurt will they? __________________ *33, 45, 78, around and around they go...*

31st Dec 2017, 3:28 pm	#9
Courtney Louise Octode Join Date: Sep 2005 Location: Welshpool, Powys, Wales Posts: 1,327	Re: Revox B77 - Questions. The Fiio did a hard reset of itself, came back on after an hour or two. __________________ *33, 45, 78, around and around they go...*

31st Dec 2017, 3:36 pm	#10
Ted Kendall Dekatron Join Date: Jul 2008 Location: Kington, Herefordshire, UK. Posts: 3,670	Re: Revox B77 - Questions. Good show! Might be a good idea in these circumstances to earth the Revox, by connecting to an earthed amplifier, for example.

1st Jan 2018, 11:05 am	#11
Courtney Louise Octode Join Date: Sep 2005 Location: Welshpool, Powys, Wales Posts: 1,327	Re: Revox B77 - Questions. Hi Ted, once in proper use it will be. C __________________ *33, 45, 78, around and around they go...*