Randyshone1
New Member
Hi Folks,
I hope you can help pin point this issue I am having with an Eico ST 70. I have attached a wav file of the sounds coming from the speakers.
I have done some trouble shooting.
1. Clean and lube all the pots and switches.
2. Adjust the the balance pots. (I could not set channel 1 below .303, channel 2 is running at .002
3. Performed bias readings to the 7591 power tubes. (All the tubes are running between 425v to 428v plate voltage. Channel 1 tubes are running between 78v and 75v on the cathode. Channel 2 tubes are running between 24v and 26v on the cathode. Things do seem suspect already in this stage.
4. I have had all the tubes (original Mullard/Eico) tested for shorts, leaks, transconductance, and gas. All the tubes passed and rated good.
5. I have also cleaned all the tube pins and sockets.
I don't claim to be knowledgeable or an expert in electronics or tube equipment. I am learning as I go and am doing a ton of heavy reading to learn this stuff.
Oh yes, the output tubes are JJ's 7591s's. When I purchased the Eico it did have the original power tubes and when I got it home and opened it up about 2 months later BINGO! I found JJ's. Long story short. I am stuck with these for now.
Thank you for giving this a read! I value all your input.
Cheers,
Randy
I hope you can help pin point this issue I am having with an Eico ST 70. I have attached a wav file of the sounds coming from the speakers.
I have done some trouble shooting.
1. Clean and lube all the pots and switches.
2. Adjust the the balance pots. (I could not set channel 1 below .303, channel 2 is running at .002
3. Performed bias readings to the 7591 power tubes. (All the tubes are running between 425v to 428v plate voltage. Channel 1 tubes are running between 78v and 75v on the cathode. Channel 2 tubes are running between 24v and 26v on the cathode. Things do seem suspect already in this stage.
4. I have had all the tubes (original Mullard/Eico) tested for shorts, leaks, transconductance, and gas. All the tubes passed and rated good.
5. I have also cleaned all the tube pins and sockets.
I don't claim to be knowledgeable or an expert in electronics or tube equipment. I am learning as I go and am doing a ton of heavy reading to learn this stuff.
Oh yes, the output tubes are JJ's 7591s's. When I purchased the Eico it did have the original power tubes and when I got it home and opened it up about 2 months later BINGO! I found JJ's. Long story short. I am stuck with these for now.
Thank you for giving this a read! I value all your input.
Cheers,
Randy