Driver Tube Questions Stock ST-70

Running an updated, stock ST-70 with Sylvania 7199s, an NOS International Servicemaster made in Japan GZ34, and 'real' SED Winged C EL34s.

Could someone tell me the symptoms of a bad driver tube? Not a tech and don't have a tube tester. Trying to determine what my problem is and with limited knowledge.

Seems like my left channel is lower than the right. first changed preamps but that was not it. swapped output tubes to opposite channel. other steps also.

this is just to eliminate a 7199 as a possibility. I have a couple things I still want to check. My apartment living room wall is not ideal for speaker placement which is a nagging thought I am hoping is not the issue after all.

Some general thoughts would be appreciated. Happy holidays and New Year to all...     R

raudio44 wrote:Running an updated, stock ST-70 with Sylvania 7199s, an NOS International Servicemaster made in Japan GZ34, and 'real' SED Winged C EL34s.

Could someone tell me the symptoms of a bad driver tube? Not a tech and don't have a tube tester. Trying to determine what my problem is and with limited knowledge.

Seems like my left channel is lower than the right. first changed preamps but that was not it. swapped output tubes to opposite channel. other steps also.

this is just to eliminate a 7199 as a possibility. I have a couple things I still want to check. My apartment living room wall is not ideal for speaker placement which is a nagging thought I am hoping is not the issue after all.

Some general thoughts would be appreciated. Happy holidays and New Year to all...     R

Leave the amp to Your favorite amp technician, he will hook it up to a sinus generator
and artificial load. He will tell you if anything is wrong and also suggest how to correct.

Did you swap the 7199 tubes to see if the situation changed to the other channel?

peterh wrote:

raudio44 wrote:Running an updated, stock ST-70 with Sylvania 7199s, an NOS International Servicemaster made in Japan GZ34, and 'real' SED Winged C EL34s.

Could someone tell me the symptoms of a bad driver tube? Not a tech and don't have a tube tester. Trying to determine what my problem is and with limited knowledge.

Seems like my left channel is lower than the right. first changed preamps but that was not it. swapped output tubes to opposite channel. other steps also.

this is just to eliminate a 7199 as a possibility. I have a couple things I still want to check. My apartment living room wall is not ideal for speaker placement which is a nagging thought I am hoping is not the issue after all.

Some general thoughts would be appreciated. Happy holidays and New Year to all...     R

Leave the amp to Your favorite amp technician, he will hook it up to a sinus generator
and artificial load. He will tell you if anything is wrong and also suggest how to correct.

Don't have a local tech. It was gone over / updated a few years ago by a reputable tech. Just determined the amp is fine, the problem turned out to be uh, me! rechecked a couple things and seems fine now. thinking it was a speaker binding post issue. thought i did that before but?? thank you for your reply. have a great new year.

Brap wrote:Did you swap the 7199 tubes to see if the situation changed to the other channel?

That was going to be my next move; was looking to see what a bad driver tube would exhibit as a problem to watch for. I think I found the issue as you can see in my last post here. still would like to know about the driver tubes. Thank you for your reply, very much appreciated. Happy holidays and new year.