Eros 1 left channel not functioning [resolved]

[Ascari]

A few months ago my Eros 1 failed after years of service.   I started to trouble shoot it and then decided to upgrade to the Eros 2 which is now in my system.    Just today I got back the the Eros 1.   Resistance checks are fine throughout.   When I checked voltages the right side was all in spec.   There is one (1) discrepancy on the left side.   The OA voltage is supposed to be 170 Volts and is only reading 102 Volts.   I replaced all of the transistors on the board except for the 4250A's since I do not have any.   This far nothing has worked and the voltage at OA is still 102.   I did find that the 220K ohm resistor was only reading 170K ohms so I swapped that out and three is still no change in the voltage at OA.  Ideas?

[Paul Birkeland]

Do OA and OB on that PC board both measure about 102V?  You could have some pins touching on the socket or a shorted 6922 tube.  I would not replace any components unless they actually don't measure properly.  For transistors, you set your meter to beep when the probes are touched together, then see if any two pins of any of the transistors measure as a short when you test them.

[Ascari]

Thank you Paul.   I will check and let you know.   I suspect a transistor, but was not sure how to check.     PS, the Bepree is working great now.
 

[Ascari]

OA and OB both measure the same.   102 volts.   I did double check the transistors and could not find any that have shorted out.

[Paul Birkeland]

I would try a different 6922 just to be sure.  Did you also double check the 2N2222 transistor on that channel?

[Ascari]

Yes I did check the 21222 again.   I third check would not hurt.    I  have a few other 6922's   I will swap that out and let you know.

[Ascari]

I changed out the 6922 and the problem resolved itself.   So much for the quality of my ancient tube tester.   Thanks Paul

[Doc B.]

Yup, tube testers generally make a pretty basic check of tube vitals. The problem is that even the more sophisticated transconductance testers don't necessarily create the exact operating point that the tube may run at in your amp. That's why the very best tube tester for a tube in a particular amp is the amp itself.

[Ascari]

That makes sense.    None the less, live and learn.

Thanks Paul