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B2

I just fitted new speaker terminals from this lot; https://speaker-terminal.com/en/?s=yamaha+b-2 Very happy with them except I think the contacts at the back shorted on the metal plate as they were too long. Blew a pair of NS-1000 tweeters and the protection circuit went permanently on. I nearly fainted with grief. The tweeters will have to go to Holland for re-winding. Thank goodness I have two pairs of NS-1000's. However, I fixed the B-2, took the button switches out for a good clean, checked power supply voltage, bias, dc offset and idle. Found everything spot on!

Now, while I was doing all this, within a few hours, all the little white bulbs blew and they were only around four years old fitted by the Glasgow guy. I've ordered replacements and am wondering if there is anything I can check before installing them, please?
 
David Litman said:
I just fitted new speaker terminals from this lot; https://speaker-terminal.com/en/?s=yamaha+b-2 Very happy with them except I think the contacts at the back shorted on the metal plate as they were too long. Blew a pair of NS-1000 tweeters and the protection circuit went permanently on. I nearly fainted with grief. The tweeters will have to go to Holland for re-winding. Thank goodness I have two pairs of NS-1000's. However, I fixed the B-2, took the button switches out for a good clean, checked power supply voltage, bias, dc offset and idle. Found everything spot on!

Now, while I was doing all this, within a few hours, all the little white bulbs blew and they were only around four years old fitted by the Glasgow guy. I've ordered replacements and am wondering if there is anything I can check before installing them, please?
Click to expand...
:yikes:
You're one lucky dude for not blowing the V-FET's! That would have been an extremely stressful situation for them and a true testament to how rugged they are. Poor tweeters though. :(

Regarding the bulbs, I would confirm that the 12V is still 12V.

Something else to note about the bulbs in the B-2. A few years ago I ordered what were supposed to be OEM bulbs for a B-2 I was reconditioning for someone. About 2 weeks after it returned to the owner it kept blowing the fuse for the 12V; he called me about it because he blew 3 fuses in 1 month and was almost ready to ship it back to me. After lots of bald head scratching I decided to measure the bulb current on the spares I bought. Turns out they were 20mA higher per bulb at 12V's which was enough of an additional load to take the fuse out after several power ups ...
 
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Got it. Thank you very much. When I get the bulbs from the USA I'll let you know what I find.

Of course it was my stupid mistake. I had measured the depth but must have made an error. I put in some insulation to guarantee it won't happen again.
 
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Theres no arc suppression capacitors on the 'General Model' 240v European UK/AU. B2 might explain why there're so heavy on Petrick mains switches, the first one I changed while it was still in 5year warranty. Didn't give it a thought then till this problem popped up again.
 
IMG_2969.jpg View attachment 2188301 View attachment 2188301 IMG_2968.jpg I got my little lights and replaced the duds no problem having checked 12v. Actually, it was 11.68v which I thought was OK. Beautiful!

I took this opportunity to replace the relays (as recommended) with https://www.digikey.co.uk/product-d...PYNIiknUjvd1Ems_L2b2Ao2_abSRtS91IUtORX9l8wnwZ

I got the above link from somewhere on AK B-2 forums. The swap seemed straight forward but, at first the new ones wouldn't give that audible click when I power up. I left it in disgust and half an hour later, tried again (illogical) but, to my surprise they clicked. The delay between flicking the power on and the click is about 2 seconds. Longer than the originals. Do these things need wearing in?

Lastly, a pic of the speaker posts I mentioned earlier in this thread. I read somewhere it was good to swap the wire in NS-1000 for 12 gauge from speaker posts to crossover. Would that idea be good for a B-2? As in, from driver boards to speaker posts?
 
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David Litman said:
Would that idea be good for a B-2? As in, from driver boards to speaker posts?
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David, you are blessed to have one very nice B-2 that is working after you already had a vfet or two replaced.
first off: do not lose those rubber boots for the light bulbs. You are using the wrong bulb replacement types and if you ever want to revert to originals, you will not be able to without the original rubber boots.
As far as the internal speaker wires...they do not connect to the driver boards....
I strongly suggest not to mess with your B-2 any further and just enjoy it. There are 10 things that can go wrong with what you are suggesting and ZERO benefits.
Close that beauty up and enjoy it!
 
Rottalpha, thank you for your comments. If there was any gain in beefing up those wires, I would have traced them down to the correct place but, if it ain't broke, don't fix it. I would imagine the 'rubber boots' were discarded by Glasgow man when he replaced the bulbs. I didn't know they existed till recently. The bulb I used is;

https://eu.mouser.com/ProductDetail...sFVwWUc6rig==&countrycode=GB&currencycode=GBP

I bought ten to future proof myself.
 
David Litman said:
I got the above link from somewhere on AK B-2 forums. The swap seemed straight forward but, at first the new ones wouldn't give that audible click when I power up. I left it in disgust and half an hour later, tried again (illogical) but, to my surprise they clicked. The delay between flicking the power on and the click is about 2 seconds. Longer than the originals. Do these things need wearing in?
Click to expand...
To my thinking the protection circuit delay has more to do with the time it takes for the drive circuitry to reach equilibrium than the relays used. If it's taking longer now than before it might be that you need to recheck that the DC balance is still set properly.

It could also be an indication that the stress of the shorted outputs caused some changes to the drive circuitry. Hopefully not.

Like Rott says, button that beauty up and enjoy! :)
 
Many thanks Brinsmead and Vint Age, I did check everything. With vfet replacement by clinic-audio and all of you guys help, I managed to restore my B-2, something I thought I could never do as I know very little about electronics. Believe it or not, this journey has been over four years since Glasgow man first took it in for a recap and destroyed the vfet's. As this is the only forum I've dabbled in, I've also learnt a lot about forum's! Thank you Audio Karma!

Incidentally, this last round of tinkering was mainly to clean the button switches which were dodgy. I took the boards out and just chucked them whole, into an ultrasonic cleaner filled with Cillit Limescale cleaner for five minutes. Pressed input button and speaker on/off button once, changed speaker output and gave them another 5 mins. A quick rinse in water and medium heat dry. Finally giving them a vigorous slosh in pure alcohol. They now work like new. I gave the C-2 same treatment on all the pots. That is now also glitch and crackle free.

So, thanks again to all who gave info on this web site. The world can be a beautiful place even, online. Now, I have a problem with one of my Meridian 105's ;)
 
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Vintage, I checked the resistance of x 2 original Yamaha B2 12v lamps they have a resistance of 22ohms coming in 0.545Amps each lamp.

Some cheap Chinese low current 12 volt- 40-60ma lamps that I have here, have a resistance cold of 15 ohms making them 0.8amp by x4 lamps……. so there we have 3.2 Amps total in rush current on startup for those cheapies. Thats a fair wack through the regulators on startup, I realise that the resistance of the lamps will go up and regulate lower current when they heat up.

So its a good idea to get the best lamps available from a reputable source and watch those fuses !
 

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Some of you guys may be using a Variac for a variety of reasons, I was going to mention my use of the Variac with the B2 which I talked about earlier, was to it main use is to lower the mains voltage.

Ive been using this practice below for sometime, with my B2.
After I’ve had it off for an extended period, to charge capacitors with a lower mains voltage with a resulting in a modest input current then bringing it up to 220 Vac.
I really don’t know if its had any effect on the longevity of the 18000’s but you live in hope. We’ll see when I get into them .

A quote from… Nelson Pass… in construction of his VFets Amp.

“If you have a Variac for this, you will want to use it, but keep in mind that it is only useful for providing a relatively low inrush current to the power supply capacitance – you cannot raise the AC line voltage too slowly or you risk having the VFETs draw too much current while the bias voltages are being established.

I suggest that you raise the AC line to voltage over a period of less than 5 seconds. “
 
brinsmead said:
A quote from… Nelson Pass… in construction of his VFets Amp.

“If you have a Variac for this, you will want to use it, but keep in mind that it is only useful for providing a relatively low inrush current to the power supply capacitance – you cannot raise the AC line voltage too slowly or you risk having the VFETs draw too much current while the bias voltages are being established.

I suggest that you raise the AC line to voltage over a period of less than 5 seconds. “
Click to expand...

Brins, it's Interesting to see how Nelson finally discovered what we already knew 40 + years ago regarding V-FET's and Variacs; Nelson Watt took you so long! ;)

Also, does your B-2 you have this option as shown on the Sch? If so you could select the 240VAC winding to better match the recent changes to your mains ...
B-2 220 - 240 AC.jpg
:)
 
Yes Vintage I’ve also used the Variac for Amplifier repairs in the industry for over 40 years.

When working with Yamaha , I replaced many Yamaha Power transformers in Amplifiers that had either open primary or open built in fuses which by the way was impossible to dig into to repair …Bando I think was the brand Yamaha used in the mid 80’s on or there abouts, these were the iron cored ones. They opened up for indeterminable reasons but this was not output transistor related circuitry.

This has stuck in my mind and I’ve now transferred this concern to the the B2 transformers especially with our high mains voltage, thank you for waking me up , I know our Australia mains is 230vAC + or - 10 % which brings their allowable mains to swing to over 250Vac.That means the B2 would be working within its own transformer limitations.

Thankyou so much, I missed that that was an easy fix, the B2 is now switched to the 240Vac tapping and I’ll continue to run it at 220vAC through the Variac. ( I changed this tapping over many years ago to accomodate my low mains voltage, then forgot about returning it to 240vAC position when the Mains voltage went up considerably.)
 

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I posted this before, but in complete article, just in case it was to long to read, noted American Engineer, Leonard Feldman and technical publisher to all leading magazines in the 70’s and 80’s summed the VFets up with this statement.

We won’t speak to the converted but any one thinking of a valve amp this is definitely a substitute you should consider you’ll get much more power out with a VFet Amp..





Leonard Feldman Conclusion of VFets Amps.jpg
 
not to muddy the water, but I think the same statement is valid today.....in other words, all TOTL modern and older amps are fair game for comparison with the 70's vfet amps.
In a recent listening session between a set of C1/B2 combo and a reference tube Pre and SS amp from AR, I will say that the vfet combo was no slouch and that in terms of depth of field and listener engagement, it took the cake away from the AR combo. AR makes exceptional equipment and I have no intent take anything from them...it is just that the C1/B2 combo is that good.
 
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