Parasound A21 problem

[cwlau5450]

Hi,

Is there anyone here using Parasound A21 or familiar with it?

I've just got a problem Parasound A21 from a friend of mine. He just said cant power on the amplifier.

Tonight I tried to power on the amplifier with only power cord. There are nothing connected at back panel. And there is only a red light appear behind the "P" logo at front panel when pressing power on button. Is it normal? Since the operational manual said blue light should glow behind the power button but never turn on at my Parasound A21.


The settings at back panel are as below:

All input/output are didn't connect
Auto turn on: Auto
Ground: Normal
Inputs: Unbalanced

And I have checked all the fuses didn't blow and all capacitors didn't leaks.

Hope can get some clue here.

C.W

 

[JonSnell Electronic]

If the relays do not pull in, there is probably DC on the output. Check for DC.

 

[cwlau5450]

Thanks JonSnell for your suggestion. I have found that there are no output voltage (AC) from toroid transformer before bridge rectifiers. I will start here and trace back to
line voltage.

C.W

 

[rczetli]

I had an A-23 and when it was set to Auto on "Auto Turn On" it would only come on with either a 12v trigger or an audio signal present at its input.

 

[awkwardbydesign]

I had an A-23 and when it was set to Auto on "Auto Turn On" it would only come on with either a 12v trigger or an audio signal present at its input.

That is what Parasound's specs say! "Auto turn-on by 12v trigger or audio signal, 12v trigger out"

 

[cwlau5450]

I tried to turn off "Auto Turn On" function by switching to manual. I noticed that the only dark red light behind "P" logo. My only question want to know at this moment is that whether any blue light turning on at front panel?

 

[phase]

Can you remove the fuse from one channel or the other and still get the same results?
My HCA-1000a has three lights; plugged in to the wall; standby/protect; and powered on.

 

[cwlau5450]

I have tried to remove the fuses in combination(remove either one channel, and remove both channels). But it still shows red light behind "P" logo. So I will trace between AC in and fuses. Thanks for your suggestions phase.

 

[awkwardbydesign]

I have just bought a new A21. The red light behind the "P" is always on if the power lead is connected. The manual says there should also be a faint blue light behind the power switch; there isn't. The blue light comes on when the amp turns on, and the red light gets brighter.
I don't know if that helps.
Oh, and I am using the auto function which turns the amp on when it detects a music signal, but it is the same with the manual setting.

 

[ManUtd]

Parasound A21

Hi,
I also have this amplifier but with a fault difference to this description.
It behave normal at startup with no DC at output and relays goes on as normal.
It also plays music without distortions or bad sound issues.
But suddenly after 2-3minutes of playing music i can hear a very clear "Spark/tick" in one channel.It sounds like someone turns on a heavy electrical Motor and it gives a spark at startup.What could cause this?
I have measured on the input stage and tried to use this separately from Outputstage and then there is no "spark" after 2-3min.So i believe it must be something wrong in the Output stage on one channel.I have got the scematic of A21 based on AD711 but mine has the TL061ACP.

 

[phase]

Might check the smaller electrolytic capacitors on that channel, also to read what the output is doing during that click/pop event, maybe a burst of dc offset.

The ad711 is only on the schematics from what I have seen with these amps, maybe some model has them(?). I replaced whatever was in there with ad744, replaced the .47uf caps with 1uf styrenes as well on a similar model from that brand.

 

[ManUtd]

Thank You for Your answer.
I already replaced all the 47uF 100v Rubicon with Panasonic low esr type.
Checked the bias voltage across 0,22 Ohm emitter resistor to 20mV at start rising to 30mV after 1 minutes or so.
Do You mean the small Capacitor placed near the Sanken output transistors
rated at 10uF 50v N.P c20,c47 ?

Might check the smaller electrolytic capacitors on that channel, also to read what the output is doing during that click/pop event, maybe a burst of dc offset.

The ad711 is only on the schematics from what I have seen with these amps, maybe some model has them(?). I replaced whatever was in there with ad744, replaced the .47uf caps with 1uf styrenes as well on a similar model from that brand.