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Yamaha A-1 amplifier thump on power off.

Thanks Athanasios but, no, the thump doesn't happen with the speaker switch off.
My current problem is finding something just right for 'C217 SM states 0.47/50V and MS cap.'
My Farnell link above is for an item for which one has to buy a minimum of 10 units..
Apologies for being so inept but can anyone see a polypropylene PET on:
https://uk.farnell.com/
 
leed spacing may be an issue, likewise with the MKP416 series. An MKP cap would be fine if you can find one that fits. MKS would probably do? Keep it simple, use a Nichicon UPW? For some strange reason I used a Nichicon EP (bipolar, wtf, probably what I had in stock). The cap does take a little bit of a hammering as the supply bounces around so the need for the low impedence? I wouldn't loose too much sleep, UPW.
 
Guys, thank you so much. Athanasios for doing the donkey work of trawling the catalogue and @mbz for background and explanation.
Out of curiosity, I didn’t realise that you worked on an A-1 mbz, any opinions on the machine?
Anyway thanks again and I’ll probably buy both types of cap and see how it goes.
 
Oops!! I didn't realize the lead spacing!!! @mbz .

The A-1 is a very good sounding amp, and its phono stage is also extremely well regarded . That is why it has Pre outs , I tried this with my B-2 amp and it was a wonderful combination. But as a stand alone unit you'd be hard pressed to find a better one for the same amount of $$$.

Athanasios
 
Cheers Athanasios.
Interesting that it worked so well as a preamp. I’d heard that the signal to the pre out actually went via the power section before being reduced by some resistors to the pre out… and so the inclusion of the power section might ‘degrade’ the signal… but all that really matters is that it sounded good to you in practice. Thanks for letting us know your experience of it.
 
Hifibythekg said:
Out of curiosity, I didn’t realise that you worked on an A-1 mbz, any opinions on the machine?
Click to expand...
I've done something of a refurb on one, it's a nice amp, using almost daily waiting for niggles to appear. Seems to have a fuller(?) sound (tones) than the CA-1000 which I also like. Haven't tried phono yet. Seems we are spoilt for choice when we add CA-1010 and CA-2010.

Hifibythekg said:
I’d heard that the signal to the pre out actually went via the power section before being reduced by some resistors to the pre out
Click to expand...
Yeah, red line is for spkr out, blue is for pre-out. Possibly because it's DC design?
upload_2022-9-20_7-39-27.png
 
Nashou66 said:
But as a stand alone unit you'd be hard pressed to find a better one for the same amount of $$$.
Click to expand...
Probably shouldn't say this, will start a rush on them. I picked up a Japanese Junk unit for USD10- (add USD70 surface shipping)
They can be consistently had for under USD30 on the EDIT:Yahoo auction site. Be warned, the amp can bite (main caps hold charge) and being direct coupled it makes troubleshooting "difficult". Voltages at speaker "line" during variac power up can cause concern (10-15Vdc...)

Echo Nashou66, can't beat bang for so little bucks
 
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Will try resist sourcing and working on another one, but nice to hear and very reassuring.

Now C216 on the power board.. SM says 'MS.'
What should I try to use here?
I have a 10Uf/16V Panasonic ECEA1CN100U cap..
https://uk.farnell.com/panasonic/ecea1cn100u/cap-10-f-16v-20/dp/2326008?CMP=i-ddd7-00001003
but it's bipolar... will this be ok?
Polypropylene PET was recommended, aren't these all bipolar?
The cap that's currently sitting there (original) is a blue and black polar electrolytic..
 
On the schematic the code is also used for a ceramic. I looked online and only found that many people say it means nothing :dunno: But I am sure its not the case. I just used a cap good for the power supply and 105c type.

52377906555_45220ee448_b.jpg
 
Hifibythekg said:
Thanks Athanasios.
Silly me, I ordered the enormous
https://uk.farnell.com/wima/mkp1g034706a00kssd/cap-0-47-f-400v-10-pp/dp/1890240?CMP=i-ddd7-00001003

But I also have
https://uk.farnell.com/wurth-elektr...lec-0-47uf-50v/dp/2533737?CMP=i-ddd7-00001003
Can I use this at C217?

At C216 I have a 10Uf/25V Nichicon UPW, will this be ok? (SM says 10Uf/16V MS)
Click to expand...


The Wurth is a good brand and the UPW is fine as well. Going up in voltage is always a good thing if the cap will fit physicaly.
 
Thanks again Athanasios, that’s great.
…following this, on the big Electrolytic Cap Board at C119 and C120 there are two bipolars.
SM says 10Uf/16V, should 10Uf/50V be ok here?
They’re Panasonic ECEA1HN100UB.
 
Thanks again Athanasios.

Now, a query about the ‘Disc’ button…

if I’m playing music via the Aux input (from a CD player) should depressing the Disc button:

  • just affect the sound a little because it’s bypassing the tone controls
  • OR
  • cut out the sound completely from the Aux input (because ‘Disc’ is designed to work in conjunction with the Phono input.)
 
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