Eros silent

[grosen]

Hi all,

My Eros has been up and running for a couple of years trouble free.  I was listening this afternoon, heard a soft thump and then no sound at all in either channel.  I haven't tried to recheck the voltages yet, but the LED's and the shared tubes are lighting up.  (I think the EF86's are *not* lighting up, but they never glowed all that much before, so I'm not sure.)  Is there something obvious that I should check first?

Thanks,

[Doc B.]

Yes, do the voltage checks.

[grosen]

Solved.  Came back after a couple of weeks' vacation and everything's fine.  Don't know what the problem was ... but I can live with the mystery.

[grosen]

Same problem again.   Thump, then silence.

Resistances are OK, except for C4, which should be open but reads 2.6 ohms.  (I think I noted this on the initial build and was told not to worry.)

The LEDs on both C4Ss are black.  LEDs on the central board are fine.  The 12BH7A should be fine. (I tried two.)

What should I check next?

Thanks in advance.

[Grainger49]

Both channels out points to the common power supply.  Did the voltage readings on the regulator tube come out good?

Since both channels go dead my gut says to check the power supply circuit board when this happens.  You have the common power supply checks in the manual on page 44 and 45 of the manual.  Since this is intermittent it is hard to say if you have the lost channels when you move the Eros and do your checks.  It might be a solder joint that goes bad when it heats up.

[grosen]

Thanks very much for the quick reply. 

When I run the power supply checks from pp. 44-45 of the manual, I get 270V at the right lead of the 270Kohm resistor -- should be 375V according to the manual--, and 6.3VDC at the +6.3V tab.

I'll fish around for a bad solder join in the PS

One more bit of info.  I accidentally plugged the unit in without the 6922, and when I did that I got two LEDs out of 4 lighting up on each of the c4s boards.  The 6922 is lighting up when it's in place, so I'm getting some power from the PS. Don't know if that means anything.

Gideon

[Grainger49]

The 6.3V DC should make all the tubes warm and ready to conduct. 

Well, I mislead you.  The tests on 44-45 are with no current being drawn.  It will be lower with all the circuits and tubes being powered. 

What you need to check is at the bottom of page 77.  Anything that is more than 15% out of spec report back.

Good luck.

[grosen]

Hmm.  The p. 77 voltages were completely off: no voltage at any of the check points until ...

I jiggled the 12BH7 and the 6922 a bit to see if the problem was at the pins and the LED's lit up like a Christmas tree, the voltages checked out and everything is fine.   (kreg is a bit high:  should be 1.0V, measures at 1.5V.)

I can't reproduce the problem now, and the Eros sounds terrific. (I've been listening to CDs since for the past three weeks, and coming back to vinyl after a break reminds me why I bother.)

I'll have to wait for the problem to recur to track down the problem joint, but I still have a question: If jiggling the common tubes restored power to C4S boards, does that tell us something about where the problem might be?

Gideon

[Doc B.]

That means it is most likely to be a bad connection at one of those sockets or bad contact of a tube pin in one of the sockets.

[Grainger49]

As Dan says, touch up all the solder joints on the 12BH7, the 6922 socket and the wiring to the front boards.

Now remove/insert all 4 tubes a dozen times.  Although the sockets are brand new, and at least 3 of the tubes are new nobody knows how many years the have been on the shelf gathering a slight corrosion.

Then settle back for some Sunday listening.  I spent 3 hours listening to mine yesterday, more today.