A-1000/A-1020 info/repair thread

That is a great help, thanks James. I had a service shop diagnose the amp and they said three of the transistors were bad and the estimated it would be $250 to replace them all. So, I'm considering doing it myself!


If you mean the output transistors the one that I worked on had 2SA1265 (PNP) and 2SC3182 (NPN), 2 pairs per channel for a total of 8 outputs. I used ON-Semi NJW0302G and NJW0281G.
https://www.mouser.de/ProductDetail/ON-Semiconductor/NJW0281G?qs=sGAEpiMZZMshyDBzk1/Wi9NZvtrCxX3LQxpSknG8TRg=
https://www.mouser.de/ProductDetail/ON-Semiconductor/NJW0302G?qs=sGAEpiMZZMshyDBzk1/Wi9NZvtrCxX3LH9AISc2zENc=

The driver transistors were 2SA1306A and 2SC3298A. I used ON-Semi MJE15033G and MJE15032G.
https://www.mouser.de/ProductDetail/ON-Semiconductor/MJE15033G?qs=sGAEpiMZZMshyDBzk1/Wi/PUgtclNldlWYDF5lWmMkM=
https://www.mouser.de/ProductDetail/ON-Semiconductor/MJE15032G?qs=sGAEpiMZZMshyDBzk1/Wi/PUgtclNldlIbxeXkBE6a0=

For the other assorted transistors I'd have to look, it's been a while.

Cheers,
James
 
How many of each transistor does one need? I'm guessing eight (8) each of the first two listed?

4 each of the 2SA1265 (PNP)/NJW0302G and 4 each of the 2SC3182 (NPN)/NJW0281G. They are arranged with 2 of each type (NPN/PNP) per channel.

1 of each type (NPN/PNP) of the drivers for each channel for a total of 2+2.

Normally one would expect that if 3 of the outputs are bad then there will be other damage as well, drivers, resistors etc.

Cheers,
James
 
I agree with James both with his parts recs and in saying it will likely need some additional parts replaced.

Look around the bad channel for any of those standing up green resistors and see if the have a brown or burned band around them. They are fusable and will open up. Sometimes the damage is hard to spot and looks very much like a color band so a magnifier may be of help.
Those you can replace with flame proof carbon or metal films.

Also check the other channel for loose or cracked solder joints. My driver transistors were completely loose in their board along with many other cracked joints. Again, magnifier is helpful here.
 
ere is the Seppl (Berni) from Franconia,
have already noticed that you are a Yamaha A - 1020 specialist.
I found one from my youth in the basement. I think he would need a recap set or set of electrolytic capacitors power supply and audio ELKOS.
Do you have a list or pictures which should be changed, that would be super nice.
I read something from Nichicon KZ MUSE Series.
Or you can recommend something more appropriate. Are there tips on what to do first or where to watch out?
Thanks in advance Berni
 
I had mine blow up, changed the output and driver transistors with the same model and blew up again. Found the 100ohm resistors near the driver connectors also burned. Measured everything in the area and everything seems fine. If the driver boards and output transistors are not connected the rest of the amp seems to work fine. What could be the issue?
 
I had mine blow up, changed the output and driver transistors with the same model and blew up again. Found the 100ohm resistors near the driver connectors also burned. Measured everything in the area and everything seems fine. If the driver boards and output transistors are not connected the rest of the amp seems to work fine. What could be the issue?

Which amp are you working on? Did you use good replacement transistors? I've heard of people using eBay stuff which promptly fail and nukes their work all over again.
Otherwise, there's got to be something you're missing that's causing the failure. I've never had one of these go without taking out quite a few more parts than just the outputs and drivers.
 
With the A-1020 that I worked on the idle current trim-pot for the right channel was shorted from a nicotine/dust paste and let the idle current run off-scale-high, burning resistors and transistors.

Cheers,
James
 
I am so frustrated, it's the 3rd time I schange the transistors. I also checked resistors, replaced all zeners, checked all diodes. The only thing I am seeing wrong is the voltage from the transformer. It should be 91.5 ac on the secondary between red and red. I'm getting 103. 16v is 18.3, and 18v is 19.5. Is the transformer bad? Is there something that I'm missing? I so love this amp but I am at the end of my patience. +B- R 115v, B+ B- 137v, B- - R - 20v, E - B+ 68v, E - B- - 68v
 
I had mine blow up, changed the output and driver transistors with the same model and blew up again. Found the 100ohm resistors near the driver connectors also burned.
I am so frustrated, it's the 3rd time I schange the transistors.
I also checked resistors, replaced all zeners...
:wtf:
I counted 11 x Zener Diodes on the circuit diagram (there may be more...).
There is no conceivable electronic fault that would destroy ALL 11 x Zener Diodes inside the amplifier.

Following Internet forum advice (possibly including this...) and randomly replacing semiconductors will ensure that the amplifier is destroyed beyond economical Internet repair: i.e. It may be more economical to purchase a new amplifier.
Examples.

Replacing 11 x good parts with 11 x parts of unknown provenance has increased the number of fault variables as follows;

(n+original fault)², where n=the number of new parts.

If the parts were sourced from a supplier of 'fake' parts, the formula changes as follows;

(n+original fault)³, where n=the number of fake parts.

Free advice.
Do not replace any parts unless they are defective and watch this. Then build a current limiter or a current limiter (there are many examples in this forum) if you wish to continue your repair attempts. Select components that are appropriate for your country's mains voltage (currently undisclosed).

If you decide to troubleshoot the pre-existing and introduced problems, disconnect ALL external cables (except the power cord), set the volume control to 0 (zero, minimum), tone controls bypassed and input to AUX.

When seeking assistance, ALWAYS state the DC supply voltages and their polarity (if powered-on) and use the component references in the circuit diagram: e.g. TR102,;) TR104, TR106, R108, R110, C232,;) D218 etc.

So far, you've replaced some unknown transistors three times, 11 x Zener diodes and a 100R resistor somewhere. You have also reported a high transformer secondary voltage, but you haven't reported/measured the primary input voltage or provided pictures of the voltage selector switch (if present) on the rear of the amplifier.

More free advice.

Good Luck! :lurk:

N.B. Apart from the Yamaha badge, the A-1000 and A-1020 are completely different amplifier topologies - Class G and Class U™ respectively, where U™=UNSTABLE!

Class U™=Tone controls in the feedback loop of the power amplifier - a cost-cutting exercise at the expense of stability! :crazy:
 
I just got a mostly functional Yamaha A-1000. Two slight problems.

The A-1000 used to pop when turned on and off, and then would only stay on for a few minutes and then shut off. My father and I poked around and re-soldered several joints around the relay. Seems that now, it will not pop when turned on and stays on and plays great! However it pops when turned off and instead of just shutting off the LEDs slowly darken and it just fades away. We CANT FIND THE RELAY in the on-line repair manual. We see it on page 7 that is a picture of the main board, it's RY101, great, but the actual schematic diagram on the following pages seems to be cut off or missing that section where the relay is. We want to see where it's powered from and check connections over there. Yes, i have read the several threads on here about this problem. Id rather not re-flow 100+ soldering joints on the bottom.

Problem 2: Class A does not work in the right channel. I had a tech take a look, he was kinds enough to show me how to measure for that and tell me that it's not worth 300+ dollars of labor to pull out all the transistors on the main board and test for the one bad one. I'm fine with doing that but i am wondering if someone has done the same before and can narrow it down to a few resistors that i should pull version the 20+ on the board.

Later in the year i plan on doing a full recap minus the 4 big boys. How do i separate the cable from the phono impedance selector on the board to the tone control in the front?
 
The protection / relay part is visible in the service manual available for free download on hifiengine.

Sounds like you may have a problem with the protection area transistor/s.
If that is the problem, you can replace those 2SC2603 with a higher rated transistor like 2SC2383 from mouser.
The transistors I would check are TR167, 168, 169, 170.

Yes, i have read the several threads on here about this problem. Id rather not re-flow 100+ soldering joints on the bottom.
The general recommendation to reflow all solder joints isn't a blind one, the amp is a hot runner and ~37 years old. If you plan on keeping the amp and using it regularly, removing the corrosive glue / damage and resoldering the main board is a must. However if you'd rather not, just be aware that the amp may decide it'd "rather not" keep working - possibly in a more drastic way than it currently has.

I suggest using a dim bulb tester (100W bulb) on first power up after doing any work in case you make mistakes.
 

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  • A-1000 protection schematic.png
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So is the box in the diagram you shared the relay? I saw that when i downloaded it from hifiengine but it's not the ry101.

I do plan on removing all the glue since i ordered a re-cap kit. That will be a project for later in the year.
 
but it's not the ry101.
Yes, it is.
There is only one relay in this amp, it's for speaker protection, and the part of the schematic I posted correlates to that exact relay.

TR167-170, C177 (22uF / 16V), C178 (220uF / 6.3V) are parts relevant to its operation.
I wouldn't buy replacements for anything off ebay, especially not transistors. Use mouser or digikey.
 
The recommendation would be to test before replacing (read Hamish's post), if you have a transistor tester which can measure gain.

I already recommended a transistor you can use here, the stock ones are a little undersized:
KSC2383 NPN from mouser (for 2SC2603, TR167,168,169,170)
https://www.mouser.com/ProductDetai...rchild/KSC2383YTA?qs=JV7lzlMm3yJNKQVlvFWlyg==

The capacitors are likely still fine, but if you need a replacement you could use these:
220uF: https://www.mouser.com/ProductDetail/Nichicon/UHE1V221MPD6?qs=TV4h2c8HJqd8pF%2Be6DlzzQ==
22uF: https://www.mouser.com/ProductDetail/Nichicon/UPW1E220MDD1TA?qs=iiPS6W94Qthw0O0WRCNEoA==

Please heed my advice on building / using a dim bulb tester for first power up (100W bulb wired in series), otherwise it may all end in tears.
Be mindful of polarity and careful to not make solder bridges. There's a lot of wiring above those joints which you don't want to disturb much.
 
Ok, one more question. In looking at the phono/equalizer board there is a long flat cable between the tone control board and the phono board.

I can see how to remove the phono/equalizer board. But how do i separate the cable?
 
But how do i separate the cable?
Mini%20Electronic%20Pliers%20Diagonal%20Cutting%20Pliers%20Wire%20Cutter%20Nipper%20Hand%20Tools.jpg



Just kidding......:biggrin:

Post a photo of said cable..
 
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