HELP - Something Blew on my Stereomour

[drewh1]

My Stereomour has been working great since Sunday -Now everything sounds distorted, like a fuzz tone.

All resistances and voltages check out fine - except that I have no voltage when I test the hum pot outputs.

It started when I switched to my Shunyata Power cord. I plugged it in with power off and when I powered on, the problem started. I checked the cord and everything seemed fine.

Any ideas what fried?

 

[Doc B]

It doesn't seem likely that all the voltages would be OK except what you are referring to as the hum pot output, which I presume is the center lug of the hum pot that connects to the 2A3 cathode resistor. Check the resistance reading from that center lug to ground (should be around 1200 ohms), and also recheck the voltage at A1 and A4 which should be around 57VDC.

 

[drewh1]

I checked the hum pot output at the speaker terminals per the manual - it had been set with the hum pots to .9 mv. 

I just happened to have a new driver tube waiting to be installed. I tried it and everything is fine. Apparently the stock tube failed.

Is that a coincidental failure?  I don't see how switching power cables could have caused it.  Please let me know so I don't blow another one.

 

[Paul Birkeland]

It is very unlikely that the power cord adversely affected your amp, this is more than likely just a coincidence. 

 

[Doc B]

OK, you were talking about measuring the hum level at the speaker output, got it. If voltages are all good the problem is not in the power cord, power connection, power supply or the tubes. That leaves the signal path, that is the signal is not making it out to the speaker for some reason. Check to make sure the input selector switch is set to the correct source and that your speaker cables are making good contact with the binding posts.

 

[drewh1]

Hey Doc - I bypassed the switch, only use one set of inputs.

Anyway - it was definitely the driver tube - I replaced it with a JJ ECC81 Gold Pin - Not a subtle difference, my bass is back in spades, I have more volume, everything sounds more defined.

i am guessing that driver tube was faulty from day one and was causing me to have less fidelity - This amp just keeps getting better and better.

Any chance you can send me a replacement tube, just so I have a spare?

thanks,

drew.

 

[Doc B]

Yup, the best way to get a tube is to email us at replacementparts@bottlehead.com. That will get it in the queue for the next day's shipments.

 

[drewh1]

Got my backup tube today - thanks so much for the quick response.

In the meantime, I was trying a JJ gold pin. Now that I have the stock tube, I like it better than the JJ. Although Doc has said that tubes are really tone controls, I notice more detail with the stock tube. The JJ was a bit flat a lifeless and lost detail without providing better bass. This was my experience in any case.