Hi all: New to this board and here's my first question. I have a Yamaha A-720 integrated amp that doesn't put out any sound any more. It seems to power up ok, but will not make any sound.
I'm "somewhat" familiar with electronics, but am far from an expert, and I'd like to fix this myself. Can anyone point me in the right direction?
Also if schematics (ie service manual) are available for this amp I'd appreciate getting my hands on good quality jpg's or bmp's of it!
Thanks in advance
I'm "somewhat" familiar with electronics, but am far from an expert, and I'd like to fix this myself. Can anyone point me in the right direction?
Also if schematics (ie service manual) are available for this amp I'd appreciate getting my hands on good quality jpg's or bmp's of it!
Thanks in advance
Does the pilot light work?
The lamp is used as a current source for a voltage regulator.
No lamp, no voltage.
The lamp is used as a current source for a voltage regulator.
No lamp, no voltage.
I've had a A1020 and experienced 2 problems.
Too high dc offset on the output, then the some safety system came in and blocked the output, how it was exactly I dont now annymore over 10 years ago. check the dc offset directly at the outputtransistors and keep it below 20-50 mV, mine had over 700 mV.
Another problem was to high bias current in classA mode, a very silent poeff it said and gone were the outputstages of both channels. After installing new outputdevices, Check the bias current if possible or else turn the trimpot as high as possible, this gives very low bias current , and try again.
For manuals go to this website of Yamaha and look for services manuals or manuals. they have quite a lot for free downloadable. Or call the distributor of your country, mostly they are very willing to help. At least in Holand they were😀
good luck
Rob
Too high dc offset on the output, then the some safety system came in and blocked the output, how it was exactly I dont now annymore over 10 years ago. check the dc offset directly at the outputtransistors and keep it below 20-50 mV, mine had over 700 mV.
Another problem was to high bias current in classA mode, a very silent poeff it said and gone were the outputstages of both channels. After installing new outputdevices, Check the bias current if possible or else turn the trimpot as high as possible, this gives very low bias current , and try again.
For manuals go to this website of Yamaha and look for services manuals or manuals. they have quite a lot for free downloadable. Or call the distributor of your country, mostly they are very willing to help. At least in Holand they were😀
good luck
Rob
Thanks for the replies so far! I haven't torn the amp apart yet..... I have an outdoor project on the go right now that my wife and I want to finish. Gotta get that stuff done while the weather is nice.
Anyway, by pilot light, I presume you mean the light that comes on when you push the power button? If so, it does indeed light up.
When I get a chance I'll take it apart and check the things that you've said .
Anyway, by pilot light, I presume you mean the light that comes on when you push the power button? If so, it does indeed light up.
When I get a chance I'll take it apart and check the things that you've said .
If you have DC on the output then you will not hear the output relay click, it was quite distinctive if i remember correctly.
When I turn the amp on, it lights all up as normal, then after a few seconds I hear a distinct click. I recall that the amp always did that........still haven't opened it up and put a meter to anything
Sorry to ask but have you checked the obvious like speaker switches and tape selector. If the relay pulls and you still do not hear anything it is strange. Do you hear a faint noise in the loudspeakers if you turn the volume up full?
Have you tried all sources if it is just one input that is wrong.
Have you tried all sources if it is just one input that is wrong.
jlbosch said:
If the relay pulls with a click then there is no DC-offset present, at least not enough to activate the protection. But when nothing is heard than there is something strange happening. A possibllity is that you have a faulty selector switch for input or speaker. I would check and push all switches and check your tape selector.
Did you check the mute switch.
Is there a signal comming out of the preout plug, at your amp it is called accessory send, if so than the preamplifier is working correctly if not than someting in the preamp is causing the signal not to come through. When connecting the variabel output of a cdplayer to the accessory recieve plug do you hear something? if not then the output stage or a switch is faulty.
Does the amp get warm after let say 20 minutes? If so then somewhere in the signal path their is a crack. If not then there is no power to the outputstage, which means that either a fuse is blown or in the powersupply is something wrong.
You can check a lot before opening an amplifier, nice hè.
As I know the protectionsystem and the rest of the amplifier don't share the same powersupply. Also there is a different powersupply for the preamplifier. I'm not sure if they have separate fuses but check it.
I also included a link to yamaha site with the ownersmanual of the 1020, it looks a lot like the 720 only the outputpower is lower
Look at page 9 there you can see an overview of the signalpath and the important buildingblocks of the amplifier.
good luck
Rob
http://www2.yamaha.co.jp/manual/pdf/av/english/IntA/A-1020.pdf
Thanks Robbie B. I see that you're right about being able to check lots of things before opening up!
Anyway, the first rainy day I get, I'm going to do all the things you suggested and see where I'm at!
Thanks also for the link to the manual: I see it has a schematic which gives me a starting point!
Anyway, the first rainy day I get, I'm going to do all the things you suggested and see where I'm at!
Thanks also for the link to the manual: I see it has a schematic which gives me a starting point!
Yamaha A 1020 problems
Hi guys,
I don't have a solution for the mentioned problems but I was wondering if anyone could help me with a similar problem I have with my Yamaha A1020.
From time to time it just stops producing output and when I firmly close the lid over the controls I hear a clicking sound like a relay and the amp switches on again.
Anyone who has seen this and solved it? I would really appreciate a reaction, thanks in advance.
Bert
Hi guys,
I don't have a solution for the mentioned problems but I was wondering if anyone could help me with a similar problem I have with my Yamaha A1020.
From time to time it just stops producing output and when I firmly close the lid over the controls I hear a clicking sound like a relay and the amp switches on again.
Anyone who has seen this and solved it? I would really appreciate a reaction, thanks in advance.
Bert
Re: Yamaha A 1020 problems
hi Bert,
it looks to me that there is some kind of losse connector or solder crack in the preamplifier part. In your case you will have to open the amplifier. When done so you have to check the printed board just directly behind al the controls.
You will see several switches and potmeters, check those whether they are still stuck firmly to the board. Check also al the "stekker" connections. These small white connectors sometimes come loose, also check the volume potmeter on the rightside.
If this doesn't help them you will have to remove the bottom plate so yo can see the solderside of the board on cracks.
i had more or less the same problem, which was caused by a loose connection of the volume potmeter board
Good luck
😎
Rob
Sveasvea said:
hi Bert,
it looks to me that there is some kind of losse connector or solder crack in the preamplifier part. In your case you will have to open the amplifier. When done so you have to check the printed board just directly behind al the controls.
You will see several switches and potmeters, check those whether they are still stuck firmly to the board. Check also al the "stekker" connections. These small white connectors sometimes come loose, also check the volume potmeter on the rightside.
If this doesn't help them you will have to remove the bottom plate so yo can see the solderside of the board on cracks.
i had more or less the same problem, which was caused by a loose connection of the volume potmeter board
Good luck
😎
Rob
jlbosch - I just got an used A-720 that produced no sound. All lights worked OK.
Traced it to a relay on the main board. This connects/disconnects the speakers from the amplifiers. It clicks on a few seconds after powerup; I guess it's to prevent powerup transients from reaching the speakers.
The relay did click, but my ohmmeter showed no connection. I unsoldered it, cycled it a few times from a 24 V supply, and it then worked. Sound now fine. Time will tell whether it remains reliable . . .
The relay is a vertical plastic black box close to the connector of the cable that takes the signal to the speaker switches. It has 6 pins soldered to the board.
Traced it to a relay on the main board. This connects/disconnects the speakers from the amplifiers. It clicks on a few seconds after powerup; I guess it's to prevent powerup transients from reaching the speakers.
The relay did click, but my ohmmeter showed no connection. I unsoldered it, cycled it a few times from a 24 V supply, and it then worked. Sound now fine. Time will tell whether it remains reliable . . .
The relay is a vertical plastic black box close to the connector of the cable that takes the signal to the speaker switches. It has 6 pins soldered to the board.
Hi.
my A720 is almost working.. right channel is behaving properly: while feeding large amplitude sine waves to subwoofer of proper ohmage and cranking up, the distortion increases without much increase of power consumption from the socket. this for many desibels and then protection kicks in..
the left channel has a habit of agitating the protection well too early without apparent distortion in the sound. with my crude experiment of finding out the how much power i can make the amplifier eat for a channel, the troubled one satisfied with 100+ watts less..
in real life situations the problem was amplified with bass peaks so easily triggering the protection and shutting off both channels.. it may be that low load impedance made the problem much worse.. funktion as a 2 + 2 ohm sub amplifier was miserable..
it has history of being burned and some stuff has been changed to working ones. only non symmetry is in those smaller fets, driving the corresponding bigger pair (or whatever they do..) the replaced one is not exactly type than original.. also, those main ones measure alright (as a diode) and first there was one slightly non symmetric one that i changed to resemble its dual, but this had no effect whatsoever to the above issue..
whether that trimmer on pcb is in original position is unknown.
what comes to my own moddings (of possible importance) i bypassed tune adjustments with now only one input.. and only A speaker out instead of combinations of A, B and C speakers selectable.. coils and capacitors of A output in place the original way, without those the amplifier would have the protection on all the time..
so, enlighting information or elaborate guestimates welcomed, really would like to have this working properly
my A720 is almost working.. right channel is behaving properly: while feeding large amplitude sine waves to subwoofer of proper ohmage and cranking up, the distortion increases without much increase of power consumption from the socket. this for many desibels and then protection kicks in..
the left channel has a habit of agitating the protection well too early without apparent distortion in the sound. with my crude experiment of finding out the how much power i can make the amplifier eat for a channel, the troubled one satisfied with 100+ watts less..
in real life situations the problem was amplified with bass peaks so easily triggering the protection and shutting off both channels.. it may be that low load impedance made the problem much worse.. funktion as a 2 + 2 ohm sub amplifier was miserable..
it has history of being burned and some stuff has been changed to working ones. only non symmetry is in those smaller fets, driving the corresponding bigger pair (or whatever they do..) the replaced one is not exactly type than original.. also, those main ones measure alright (as a diode) and first there was one slightly non symmetric one that i changed to resemble its dual, but this had no effect whatsoever to the above issue..
whether that trimmer on pcb is in original position is unknown.
what comes to my own moddings (of possible importance) i bypassed tune adjustments with now only one input.. and only A speaker out instead of combinations of A, B and C speakers selectable.. coils and capacitors of A output in place the original way, without those the amplifier would have the protection on all the time..
so, enlighting information or elaborate guestimates welcomed, really would like to have this working properly
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Hello everybody,
Sorry to bring this thread back to life again, but i have a problem too with my 720.
There was some problem with the balance for L\R channel, so i opened it up, i fixed part of it, there were still some issues, so i opened it again, and once i ve done what i wanted [i didn't replace any parts] and wanted to test it, there was a spark and it powered down, now it won't power up again...
Is it a easy fix (i know i didn't give much details...)?
Sorry to bring this thread back to life again, but i have a problem too with my 720.
There was some problem with the balance for L\R channel, so i opened it up, i fixed part of it, there were still some issues, so i opened it again, and once i ve done what i wanted [i didn't replace any parts] and wanted to test it, there was a spark and it powered down, now it won't power up again...
Is it a easy fix (i know i didn't give much details...)?
it seems it was just the fuse...i didn't see it was blown..
but i still have issues with the left\right channel blanace, the right one isn't working properly, either doesn't work, or at best after some tunning it works but not a high output as the left channel... does anyone know what this might be?
but i still have issues with the left\right channel blanace, the right one isn't working properly, either doesn't work, or at best after some tunning it works but not a high output as the left channel... does anyone know what this might be?
Have you checked for the usual contact problems? The protection relay in particular is a very common trouble spot.
So hello again,
I just got my fuses delivered, and potential bad surprise, they were t4l 250v instead of t4a 250v, is that a problem?
Anyway, as soon as i try turning it on, it blows the fuse.
Ihave already burned 3 of them.
If there is no problem with using a t4l instead a t4a, does anybody know where the problem might be? (keep in mind i'm a total begginer 😉 )
thanks
I just got my fuses delivered, and potential bad surprise, they were t4l 250v instead of t4a 250v, is that a problem?
Anyway, as soon as i try turning it on, it blows the fuse.
Ihave already burned 3 of them.
If there is no problem with using a t4l instead a t4a, does anybody know where the problem might be? (keep in mind i'm a total begginer 😉 )
thanks
I just got an used A-720 that produced no sound. All lights worked OK. Output relay did click. This amp has output/input for external signal processing. The problem was that the RCA jumpers was missing! Perhaps the jumpers easily get lost during transport. This amp sounds best in class A mode.
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