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Yamaha B-1 Quickie

Mr. Yamaha said:
Little side question here. @Beau Geste , when you do it like that, between which legs are you measuring the value? Because you can measure 2 values: between 1 and 2 and between 2 and 3. Both willl give you different values. This becomes even more interesting when you replace a for instance original 2.2 kOhms pot with a 2 kOhms pot (when 2.2 kOhms is not available).

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Red test lead on Nr 2 and black misuring other 2 .So get two values for more accurancy .No trimmer is ever at full stroke. In the case that you indicate the value to be taken is that from Nr.1 to Nr. 2 being the trimmer of 2K and not of 2.2K :-)
 
Mark B said:
I've got an RU-1 you can borrow.
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thank you for the offer Mark. I will let you know if it is needed. I briefely looked at the manual, and I initially got the impression that I would need the cable, which would be silly. Clinic and VintAge, think I don't and they know better.

Yamaha USA must have used a 1970 version of Google Traslate when they put the B-1/UC-1 service manuals together.
 
Easy job. No need for any cable. trim pots available form the top once top outer casing for UC-1 is removed.
IMG_20171229_232536493_HDR (1).jpg

I do not have time to go for the UC-1 Quickie yet. Will do adjustments only this time around.
 
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I ran across this unusual main cap mode today:
195004-yamaha_b1_yamaha_uc1.jpg
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anyone here done this?

I guess it works but the PSU is no longer dual-mono. He essentially has the transformers and bridges in parallel in order to use the two caps in series. A bit of a mind bender but it looks like it worked.
 
this is the add for the amp:
http://www.canuckaudiomart.com/details/159813-yamaha_b1_yamaha_uc1/

observaton:
to me, what he is saying is not correct; "..one transformer supplying the positive rail and the other the negative rail"
to me it looks like both transformers supply both rails. Is just that before they were doing it separately, now they do it in parallel....or am I wrong?
There would be a way to do it the way he describes it, but I do not see it that way based on the whiring.

At any rate, while this is clever, it defeats the dual-mono design of the PSU
 
Finished the UC-1 adjustments. It needed it and the adjustment procedure worked like a dream. One of the meters adjustments was way out (2dB).

Again, thanks to @avionic for the UC-1 service manual:beerchug:
 
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I should have mentioned...going back to the UC-1 adjustment...
while I was in there I did do a load test to max output for the B-1.

here are the results:

<210W @8R, @1kHz

Both channels are just about the same and both start clipping just after 41v.

one interesting thing is that the mains power meter has consumption at nearly 1kW
Depending on which B-1 version you look at, Yamaha rates the B-1 440W or 700W. I am assuming is all the same, just erroneous print...However, even at 150W factory rated power, the unit consumes about 760W. So I can confidently say that the rear panel power consumption for any B-1 flavor, is wrong.

Anyway, B-1 data is relatively scarce on the net so I figured I'd share the additional trivia.

IMG_20171231_112922964.jpg

IMG_20171231_112911717_HDR.jpg

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Very nice! Now just for fun see how it behaves with a square wave. :)

This pic from a B-1 review back in the day. Pretty impressive don't you think?

B-1 S W Response.jpg
 
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Vint Age said:
Very nice! Now just for fun see how it behaves with a square wave. :)

This pic from a B-1 review back in the day. Pretty impressive don't you think?

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it sure is impressive. when was this test done. I am looking to see if it was done with a new unit (or relatively new unit). I did not pay attention. Is it from the manual?

the square wave test will have to wait until next time. Beastie is rocking upstairs already.

Yamaha rated the unit at 150W as continuous use probably. Is nice to know we have the additional headroom, tho. Not that I will ever get there..... :D
 
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to elaborate more about my question above to whether the test was done it was done with a new unit or not, while this top end test I did was only with a 1kHz wave, if you look at the THD reading of the analyzer, is still right about 0.016%
but even at 0.15% @200W is still very impressive.
 
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