Tube Amps / Music Electronics
For current discussions, please visit Music Electronics Forum. New: view Recent Searches.
New: visit Schematic Hell!
The sunn still shines online!

Listen to great tunes streaming live right now!

ampage archive

Vintage threads from the first ten years

Search for:  Mode:  
previous: Dean Owens ok, so i took out the board and rew... -- 7/28/2003 2:35 AM View Thread

Re: This is turning into quite an adventure - PLEASE HELP!

7/28/2003 1:42 PM
Re: This is turning into quite an adventure - PLEASE HELP!
Hi Dean, sounds like you are having a lot of fun there. I would call Bruce, he will spend some time with you on the phone. But before you do this, I have a few suggestions which may help, and this information will help Bruce help you.  
First, remove all the tubes and using a meter, do a continuity check of every single connection in the amp using the color coded layout diagram which you can get for free off of Tom Seward's 5E3 site. Also, check out the input jack wiring diagram there as well. You won't be able to get an accurate reading on your jacks once they are wired as they are shorting jacks and tied together, but you can visually verify that they are wired correctly. Don't just check your connections for continiuty, but also check the resistance. It should be less than an ohm easily, a good connection will read about 0.1 to 0.3 ohms. Keep in mind that the oxidation on the surface of a solder joint will prevent good contact, so remember to dig the lead into the solder to get a good connection. Needle point leads work the best for this. Check every single cap and resistor value against the layout. Check every single wire going to every single tube socket and make sure you are sure which pin is which.  
Check your pot wiring, and check your ground leads for a good connection to ground. This is absolutely essential. A bad ground will confuse you to no end. Make sure they are beyond suspicion using your meter. Check your speaker jack wiring.  
Then, when you are absolutely sure everything is wired correctly, insert just the rectifier tube and check your rectified voltage. Write the number down. Then insert the preamp tubes and measure the plate to cathode voltages, and write those down. Next, insert your power tubes and check the plate to cathode voltages, write those numbers down, and then measure across your cathode bias resistor to find out how much idle current is flowing through your tubes. Remember, this number is for BOTH tubes. Then divide your bias resistor voltage by the resistor value to get the current for both tubes, and if your tubes are matched, each tube will be roughly half of the total.  
Again, write all this info on your schematic. If your are still baffled, call Bruce. Good luck Dean, hope this helps.