A question for B-2 owners

[Bronal]

I've just taken delivery of a restored 100V Yamaha B-2 amp.  As far as I know it isn't earthed.

 

Has anyone connected a B-2 to earth and, if so, were there any problems?

 

Also, what is the purpose of the Ground terminal on the back,  just below the inputs?  The manual says it should be connected - presumably to another piece of equipment?.  

[Ooogh]

Vintagejapan would be your man bronal. Grizzly might have an idea too.I would put in a link but I don't know how!

 

I have a B2 but never tried to connect the ground to anything, post your results if you go experimenting!

[Guest]

On 15/05/2018 at 12:50 PM, bronal said:

I've just taken delivery of a restored 100V Yamaha B-2 amp.  As far as I know it isn't earthed.

 

Has anyone connected a B-2 to earth and, if so, were there any problems?

 

Also, what is the purpose of the Ground terminal on the back,  just below the inputs?  The manual says it should be connected - presumably to another piece of equipment?.  

 

Not sure about the grounding, but make sure all of the smaller transistors on the driver boards have been replaced. I discovered that the hard way...

[Bronal]

16 hours ago, Ooogh said:

Vintagejapan would be your man bronal. Grizzly might have an idea too.I would put in a link but I don't know how!

 

I have a B2 but never tried to connect the ground to anything, post your results if you go experimenting!

It was Vintagejapan who sourced and restored the amp for me!

[Guest]

24 minutes ago, bronal said:

It was Vintagejapan who sourced and restored the amp for me!

Mine is open right now, I'll check tonight whether the earth terminal is connected inside the IEC connector

[Guest]

Ok so my B2 is earthed to the chassis.

[Darryl]

22 hours ago, Ooogh said:

Vintagejapan would be your man bronal. Grizzly might have an idea too.I would put in a link but I don't know how!

 

I have a B2 but never tried to connect the ground to anything, post your results if you go experimenting!

@Ooogh

 

Type @ followed by a space followed by the name of the person you're tagging

 

[Ooogh]

@ Darryl

 

 

[Ooogh]

Oh no it didn't work. Let's try again

@Darryl

 

Bingo! 

 

Cheers Amigo

[Bronal]

1 hour ago, Grizzly said:

Ok so my B2 is earthed to the chassis.

Do you mean it was already earthed or you earthed it yourself?

 

If the latter, did the sound suffer?

[Bronal]

1 hour ago, Ooogh said:

Oh no it didn't work. Let's try again

@Darryl

 

Bingo! 

 

Cheers Amigo

Any difference?

[Guest]

Do you mean it was already earthed or you earthed it yourself?
 
If the latter, did the sound suffer?

I haven't done anything in there. It always sounded sublime to me. Knowing where yours came from I would suggest yours is virtually identical to mine.

[Ooogh]

4 minutes ago, bronal said:

Any difference?

False alert bronal, I only worked out how to do the link, not earth the B2. That was enough of an achievement for one day.

[vintagejapan]

Hi Bronal,

 

By design the B-2 power wire has 2 prongs. The IEC connector installed for convenience has 3 prongs. You can choose the connect the 3rd prong to the chassi. If you run the B-2 with a isolation transformer will not make much of a difference, if not then you will be connecting the earth of B-2 to every other noisy power supply you have at home. 

 

The earth connection available on the on the back of the case is to be connected to (if available) the earth case connector of say your preamp. That is in case you have hum noise. If there is no hum I would leave things as they are. 

 

Hope this answers your question and that you are enjoying your B-2. 

 

 

 

[Colin Rutter]

Do you mean it was already earthed or you earthed it yourself?
 
If the latter, did the sound suffer?

It will only suffer if it creates a ground loop which is an audible hum
You can have too many earths
They should all end up at one point or "star earth"

[Bronal]

Thanks to everyone who replied on this topic.

 

I must admit I remain a little nervous about using the B-2 without an obvious earth, so have decided to get it properly earthed, subject to one thing - is it possible that it is double-insulated?  How would anyone know?  Was Japanese equipment double-insulated in the late 70s?  Nowadays you can tell by the 'double square' icon on the back of the equipment.  Perhaps the Sansui boys might like to chip in on this - what do they do with two-pin equipment?

[BATMAQN]

28 minutes ago, bronal said:

Thanks to everyone who replied on this topic.

 

I must admit I remain a little nervous about using the B-2 without an obvious earth, so have decided to get it properly earthed, subject to one thing - is it possible that it is double-insulated?  How would anyone know?  Was Japanese equipment double-insulated in the late 70s?  Nowadays you can tell by the 'double square' icon on the back of the equipment.  Perhaps the Sansui boys might like to chip in on this - what do they do with two-pin equipment?

Straight into the Tortech my BA-F1 no trouble so far.

[stereo coffee]

The requirement for earthing when the B2 was made

was not as stringent as it is now.  Which does not

magically excuse like seatbelts in early cars, the B2 from

correct earthing.

 

The requirement is chassis earth is wired to IEC safety earth.

The theory being that if a transformer or other voltage component

lets go it will touch chassis earth, and as well tripping a circuit breaker

will assist to, ( rather than not assist,  if not earthed) to 

protect the person who might happen to touch the chassis, 

http://sound.whsites.net/earthing.htm

 

   

[Guest]

18 hours ago, bronal said:

Thanks to everyone who replied on this topic.

 

I must admit I remain a little nervous about using the B-2 without an obvious earth, so have decided to get it properly earthed, subject to one thing - is it possible that it is double-insulated?  How would anyone know?  Was Japanese equipment double-insulated in the late 70s?  Nowadays you can tell by the 'double square' icon on the back of the equipment.  Perhaps the Sansui boys might like to chip in on this - what do they do with two-pin equipment?

 

If you had Alex restore yours then I'm confident it already has the earth pin wired to the chassis. Use with an isolation transformer and you'll be sweet.

[Bronal]

2 hours ago, Grizzly said:

 

If you had Alex restore yours then I'm confident it already has the earth pin wired to the chassis. Use with an isolation transformer and you'll be sweet.

Alex didn't earth my B-2.  He recommended against it.  However, it does have a three-pin power cord to a three-pin IEC socket.

 

From what I've read, an isolation transformer doesn't provide any protection against a component going 'live'.  It isolates the component against a bad mains supply.  Therefore, the only way to establish an earth is to have to component itself properly earthed.

 

The B-2 was sold in Australia (there was a 240V B-2 recently advertised on SNA) so I'm guessing it must be possible to earth it quite easily.  If there is hum, then the earth can be disconnected.

 

 

[JoshG]

Hey Guys,

Sorry for highjacking the thread, though it could be related. My B2's VU meters have been acting up, I doubt it's related to poor earthing (Not running external earth - B2 into isolated Tortech).
They seem to be fine, but after perhaps around an hour of playing start to go a bit crazy.
See the image, this is actually with no input of music, though the left channel VU is still dancing around, also i have not even come close to pushing this thing loud so it's not like it was cranked loudly and got stuck at that point.
Anyone seen this? COuld it be earthing? There's a very slight hum from the unit but barely noticable and nothing from speakers.

Cheers.
Josh

[Guest]

1 hour ago, JoshG said:

Hey Guys,

Sorry for highjacking the thread, though it could be related. My B2's VU meters have been acting up, I doubt it's related to poor earthing (Not running external earth - B2 into isolated Tortech).
They seem to be fine, but after perhaps around an hour of playing start to go a bit crazy.
See the image, this is actually with no input of music, though the left channel VU is still dancing around, also i have not even come close to pushing this thing loud so it's not like it was cranked loudly and got stuck at that point.
Anyone seen this? COuld it be earthing? There's a very slight hum from the unit but barely noticable and nothing from speakers.

Cheers.
Josh

I had something similar which was accompanied by some speaker noise. Turned out to be a dodgy driver transistor which failed and took out one channel. Don't use the amp and get it checked soon!

[vintagejapan]

The usual culprits on meter board are a few 2SC458 transistors that fail. 

 

Could be more serious though so yeah, just to be safe you should check the amp just in case...

vfets=unobtainable

[JoshG]

Damn.... I was afraid of this, I only imported it from Japan around 8 months ago, had it checked by Kimil as soon as i purchased it for a check over and some adjustments (That's all it needed) - so yeah this is a bummer. Anyone know of someone in Vic who's got a good understanding of something like a B-2? I don't want to have to package up 26kg's again and ship it off

Cheers.

[stereo coffee]

On 24/05/2018 at 3:09 PM, bronal said:

Alex didn't earth my B-2.  He recommended against it.  However, it does have a three-pin power cord to a three-pin IEC socket.

 

From what I've read, an isolation transformer doesn't provide any protection against a component going 'live'.  It isolates the component against a bad mains supply.  Therefore, the only way to establish an earth is to have to component itself properly earthed.

 

The B-2 was sold in Australia (there was a 240V B-2 recently advertised on SNA) so I'm guessing it must be possible to earth it quite easily.  If there is hum, then the earth can be disconnected.

No , you need to locate instead the error in your audio system that is causing

hum. Safety earth as you point out in your second paragraph is there for

very good reason and should not be bypassed, need I say it under any circumstance.

On 24/05/2018 at 3:09 PM, bronal said: