Music turn down after a while... [resolved]

[davidnow]

Hi,
The Eros2 is clearly the best phono preamp i had the chance to listen to. Thank you very much for offering this gem.
My vinyl collection is in a country house so I don’t listen to it very often, let’s say few hours a week every two months.
I am back in the country house now and listened to some favorite vinyl albums. But after an hour or so, the Eros 2 turned down, no more music. I switched it off and waited for it to get cold. When it is cold, it could play again, but stopped again after an hour...
I would appreciate any help to cure this problem...
Best regards
David

[Paul Birkeland]

You'll need to post your voltages when the Eros is on but not able to play music.  There's one component in the Eros that is mounted to a heatsink that will turn itself off if it gets too hot, and that's the 1085 regulator.  Make sure it's tightly mounted to the heatsink.  If you don't have the rubber feet on your wood base, that could also be enough to overheat things.

[davidnow]

Thank you Paul, my Eros is mounted on the rubber feet. i will check the regulators and post voltages when i can check them.
Best regards
David

[davidnow]

Hi,
i had the opportunity to check the voltage at last... But i could not!
When the Eros turns down, i put it upside down to check voltages but i have not enough time to do so, i can see the diodes and the tubes glowing again.
So when the music turns down, the tubes and the diodes (the four under the 12AU7 and the eight under the 6922) stop glowing, and when i turn the Eros upside down, they all glow again after few seconds...
I should also tell that the 1085 heatsink is not warm at all.
Maybe i should try to change this 1085...
Kind regards
David

[Paul Birkeland]

You very likely have a loose connection in your Eros.  When you are moving it, it's moving the loose connection and bringing things back to life.

Definitely do not just guess that the 1085 is bad and replace it.  This may just cause more problems.

[davidnow]

Yes maybe a loose connection, I will check it.
But the Eros also gets down when I just let it on for 20 mn without moving it.
Anyway, I will check the connections and let you know.
Thank you very much for your help.
David

[kgoss]

Heat is likely causing the loose connection to expand and loose contact.  Also when you said you didn't have the problem with the amp upside down it is either because gravity is making the connection solid or the connection does not get hot enough to cause the problem.

I would reheat the solder joints paying particular attention to the power supply since you said the tubes stop glowing when the problem happens.

Paul will get you going again.

[Deluk]

Also check that all of the hardware nuts and bolts are tight. This can affect the earthy side of the circuit.

[davidnow]

Hi everybody and thank you for your advices.
I visually checked the connection and could not find out a loose one.

How mad i am about me! while trying to mesure the voltages from power supply board, i made a connection between A5 and A6... now some diodes don't glow anymore. Before this stupid accident, they were all glowing or anyone were.

So i checked the voltages and now here it is :

from power supply :
256VDC instead of 275VDC
6.3VDC OK
115VAC instead of 135VAC
8.3VAC instead of 9VAC

From C4S :
IA 216V
IB 105V
OA 162V
OB 103V
OC 96V
OD 96V
OkA 97V
OkB 95V
OkC 1.6V
OkD 2.3V

Hope i can get my eros playing music again someday!
David

[Paul Birkeland]

The low voltage on IB means the first step would be disconnecting IA and IB on that front C4S board, then performing the voltage checks on the board above the 12AU7 socket to unsure that it's working properly.   

[davidnow]

i removed IA and IB from C4S board and measured voltage on both MJE5731A : 217V on one and 154V on the other...
Thank you for your help
David

[Paul Birkeland]

Pull the 12AU7 and redo that check.

[davidnow]

Without the 12AU7, both are 340V

[Paul Birkeland]

With the 12AU7 in, what are your Kreg voltages?

[davidnow]

One is 2.94V, other is 0.09V