Yamaha A-1020 Needs TLC

[Bratwurst7s]

1st Class workmanship!!

Did you already re-cap the right channel and just leave the transistors original?

Perhaps after the customer has it for a few weeks, they will bring it back to have the large power supply caps replaced, and perhaps the rectifier even though my EE friend says the difference is inaudible, it should reduce ripple.

Also the greater capacity of the newer caps should add a little more punch, especially on the bass.

Well, first and foremost, this has been a group project. Without the advice and moral support from you, Karl, and my foreman/work friend this simply wouldn't have gotten this far. Just not.

All of the caps except the 2 47µF/16v BP caps in the phono section (which I screwed up with and ordered polorized caps for) and the big filter caps were replaced in the first step.

Imprtant point (to me anyway), the owner isn't a customer. This is strictly non profit. The speakers he gave me are going to a daughter, and the amp that he said that he will be giving me (AX-8??) will be going to a young friend that just bought a house and has never had a real 2-channel setup.

It will be very interesting to hear this amp with some good speakers. And mhjmhjones will be able to profit from what happens there because the owner has another pair of (larger) MB Quart 4 ohm speakers and fully intends to hook them up to this amp. And to be honest I fully expect it to perform.

James

 

[mhjmhjones]

This is all great!

I'm still in the process of diagnosing my own set of issues here so I'll probably start my own thread but will be following this closely. I look forward to reading how the owner makes out with the 4ohm speakers.

Here is the back of mine-mine says 6 where yours says 8 and the manual says 4!

 

[Karl vd Berg]

Great work, James! Congrats! :tresbon:

 

[Karl vd Berg]

This is all great!

I'm still in the process of diagnosing my own set of issues here so I'll probably start my own thread but will be following this closely. I look forward to reading how the owner makes out with the 4ohm speakers.

Here is the back of mine-mine says 6 where yours says 8 and the manual says 4!

[picture]

Hi Jones,

At a very basic level, if we look at James' amp at post #132, we see that it's a 580W of power consumption under 220V/240V, EU mains. Yours is rated at 450W and yours has also a 580VA transformer for 120V (US mains) and for the 2 switched available inlets (other components). At page 3 of HifiEngine's manual it's in the specs at left.

So, through your 120V amp there's higher current running and would be dangerous to drive 4 ohm loads. According to the SM, your amp should have a fuse for 10A, and James' amp, a fuse for 4A or 5A... If you open your unit it will show the actual fuse's value.

Again, this is at very basic level. Of course, many other American models can drive easily 4 ohms speakers...

 

[Bratwurst7s]

Great work, James! Congrats! :tresbon:

Again, I wouldn't have gotten this far without help from you, Mark and my friend at work. I'm greatfull.

Cheers
James

 

[tubed]

I have a pair of Infinity RSII hooked up to the A-1020.
Very good synergy.

 

[Bratwurst7s]

I have a pair of Infinity RSII hooked up to the A-1020.
Very good synergy.

Good to know. I would guess that your Infinity's are more of a load for the amp than the AR-3a or MB Quart's. I take it that you haven't had any problems?

Cheers,
James

 

[tubed]

Good to know. I would guess that your Infinity's are more of a load for the amp than the AR-3a or MB Quart's. I take it that you haven't had any problems?

Cheers,
James

I suppose they are a load but nary a problem with the A1020( Direct Source Switch is a bit funky), it runs easily at realistic listening levels.
In fact none my Yamaha amplifiers have come close to exhibiting any strain powering my big Infinitys such as the QLS-1.

 

[Bratwurst7s]

Yesterday I made the Mouser order. Included are the remaining parts for this amp:
Nichicon ES Muse NP 47µF caps that I ordered incorrectly earlier,
8ea 1k trim-pots for this and 3 other amps (A-500, A-520, AX-700),
KSC1815YTA transistors (25 ea),
and since they are listed as EOL I went ahead and ordered 25ea of the 2SA1145-O transistors.

Also caps for the A-520 and AX-700,
resistors for the A-520,
and just for fun 3ea LME49720NA & 1ea OPA2107AP op-amps for my PC sound card.

By evening here Mouser reported that the bulk of the order had shipped. Some of the caps for the AX-700 & A-520 are back-ordered. If there aren't any problems this amp could be finished within a week.

Cheers,
James

 

[Bratwurst7s]

My latest Mouser order arrived today. A few items for my other projects are back ordered but everything that I need to finish the A-1020 is here. Workload permitting I'll finish the amp tomorrow.

Cheers,
James

 

[mhjmhjones]

Sweet. Then you'll be ready for me to send you mine.

 

[Bratwurst7s]

Sweet. Then you'll be ready for me to send you mine.

OK. Shipping cost might be a bit high tho...

Cheers,
James

 

[Bratwurst7s]

Today was the day. I finished the 1020 and delivered it to it's now happy owner.

First the 2x 2SA1145-O transistors got replaced with new Toshiba parts, then 7x 2SC1815-Y with Fairchild KSC1815YTA parts. Then the 2x 47µF BP Black Gates in the phono section were replaced with Nichicon ES MUSE parts, and lastly the idle trim pots were measured and replaced with the new Vishay trim pots. There was a complication with those parts as the legs as provided are fairly short and I had to make an extention on the middle wiper leg to reach the mounting holes. The Vishays were set to approx the values of the old pots before installing.

After that I turned it on and tweaked the pots to as close to 8mV as I could get. After about 15 minutes the amp surprised me in that the idle current slowly dropped to around 7mV. I had expected it to rise. After tweaking them again and letting it set for 10 minutes I switched to class-a. Both channels rose slowly to about 46mV and stayed there. After about 15 minutes there I switched back to class-b and the idle dropped to about 5.8mV, and then slowly over a couple of minutes rose to ca 7mV-7.2mV. Another tweak and repeat, class-a was the same 46+-mV and then down/up to 7.8mV-8.2mV after the dip.

After that I closed it up and hooked up a pair of disposable Akai speaker thingys. There was no possable way to tell if the amp sounded good with those pos things, but it did make some German Blues come out of them. The total cost for parts came out to just over €54.

OK. Now an apology. I had fully intended to take IR photos of the outputs of both channels before replacing the right channel with new parts so that we could compare the heat output of the originals with the replacements. But I got so caught up in the excitement of the moment after seeing the sucess of the left channel that I completely forgot to do that before replacing the right side. I'm sorry. I think that that would have been a usefull comparison and I screwed up. Opportunity Lost.

But I do have some audio porn for you with the finished amp. Not every shot turned out good but here are 3 that did. I used the laser pointer function of the camera to check all 8 output transistors and worked to find the hotest spots on each. In class-b no-load they were all within 1° of 40°c. After switching to class-a no-load and letting it sit for 5 minutes they were all within 1.5° of 65°c.

So that's it. That's all that I have for you until I get the report from the owner. Thanks so very much for the help guys, I wouldn't have made it without you. I learned a lot and had a lot of fun.

Cheers,
James

 

[Bubo]

Nice!!

I look forward to your parts list, old and replacements when you have time to update it.

 

[Bratwurst7s]

Nice!!

I look forward to your parts list, old and replacements when you have time to update it.

Will do. I'll try to get that done by the end of the weekend at the latest.

Cheers,
James

 

[Bubo]

James,

Perhaps you can borrow this and put your initials in the middle to go under your Signature in future posts.

 

[Bratwurst7s]

James,

Perhaps you can borrow this and put your initials in the middle to go under your Signature in future posts.

Thanks. But I didn't concour, we did it together. Really, I wouldn't have gotten through it without the help that I got from you, Karl, and my work pal. No way.

James

 

[Karl vd Berg]

...

First the 2x 2SA1145-O transistors got replaced with new Toshiba parts...

... and lastly the idle trim pots were measured and replaced with the new Vishay trim pots. There was a complication with those parts as the legs as provided are fairly short and I had to make an extention on the middle wiper leg to reach the mounting holes. The Vishays were set to approx the values of the old pots before installing.

...The total cost for parts came out to just over €54.

So that's it. That's all that I have for you until I get the report from the owner. Thanks so very much for the help guys, I wouldn't have made it without you. I learned a lot and had a lot of fun.

Cheers,
James

Hi James,

One question, did you replace the Toshiba's 2SA1145-O with same PNP or another Toshiba sub? I'm just curious because I have a bunch of these and believed they are pretty good trannies.
If you replaced them, which other ones did you use?

Nice to know everything went well. I too have to modify the PCB quite a few times to place new components, like new trim pots.

The total of €54 in cost was not that bad considering a mighty A-1020 is running again. :yes:
No idea the retail price of the amp back in 1985, but being TOTL might cost a lot then.

-------------------------------------------------------------------

Now, are you ready for another vintage amp?? :thmbsp:

--

 

[Bubo]

Hi James,

One question, did you replace the Toshiba's 2SA1145-O with same PNP or another Toshiba sub? I'm just curious because I have a bunch of these and believed they are pretty good trannies.
If you replaced them, which other ones did you use?

Nice to know everything went well. I too have to modify the PCB quite a few times to place new components, like new trim pots.

The total of €54 in cost was not that bad considering a mighty A-1020 is running again. :yes:
No idea the retail price of the amp back in 1985, but being TOTL might cost a lot then.

-------------------------------------------------------------------

Now, are you ready for another vintage amp?? :thmbsp:

--

A-1020 B,S -€ 715 85, 86, 87



Result using dollars, you can convert to Euro

The equivalent of 715 USD on 31/01/1987 is 1 548.54 USD on 05/03/2015

Brent crude in dollars bbl 1985-2015

Yamaha modern equivalent integrated amp

http://www.amazon.com/Yamaha--S2000BL-Natural-Stereo-Amplifier/dp/B001L19FBC/ref=sr_1_18?s=electronics&ie=UTF8&qid=1425517071&sr=1-18&keywords=yamaha+integrated+amplifier

 

[Karl vd Berg]

A-1020 B,S -€ 715 85, 86, 87



Result using dollars, you can convert to Euro

The equivalent of 715 USD on 31/01/1987 is 1 548.54 USD on 05/03/2015

Not bad the 54 Euros in parts, then! :thmbsp: