Sunn Sonaro 1x15 combo
40 watts
EL34s
Low output, I can talk over the amp at full volume. I have a 50 watter that is loud as shit.
What I have done to correct the problem..
New filter caps
New power tubes, biased
Replaced the tube rectifier with some good old diodes
replaced the bias bleed resistors
checked the speaker for ohms
tried different cabs
all voltages are right around where they should be
It is pretty close to what it should be, I haven't been able to find an actual schematic
http://music-electronics-forum.com/atta ... _jun67.gif
What is next fellas?
Sunn Sonaro low output troubleshooting
Moderators: pompeiisneaks, Colossal
-
gui_tarzan
- Posts: 607
- Joined: Thu Jan 16, 2014 3:10 am
- Location: The 26th State
Re: Sunn Sonaro low output troubleshooting
Don't get close, get exact. If you can. Are you sure it's supposed to have EL34s?
Here you go. I've got a Sentura II and a Spectrum so I'm pretty familiar with the component side of them. I'm still working on the troubleshooting part.
[Edit] While I'm thinking about it, the switching output jack is a logistical nightmare if it gets wonky. You might take a close look at those two jacks.
Here you go. I've got a Sentura II and a Spectrum so I'm pretty familiar with the component side of them. I'm still working on the troubleshooting part.
[Edit] While I'm thinking about it, the switching output jack is a logistical nightmare if it gets wonky. You might take a close look at those two jacks.
You do not have the required permissions to view the files attached to this post.
Last edited by gui_tarzan on Thu Oct 16, 2014 12:51 am, edited 1 time in total.
--Jim
"He's like a new set of strings, he just needs to be stretched a bit."
"He's like a new set of strings, he just needs to be stretched a bit."
Re: Sunn Sonaro low output troubleshooting
Was this originally a 6550 model? Is the sound distorted?
-
Stevem
- Posts: 5144
- Joined: Fri Jan 24, 2014 3:01 pm
- Location: 1/3rd the way out one of the arms of the Milkyway.
Re: Sunn Sonaro low output troubleshooting
I have the same head and I do not think you can get the bias low enough to get EL34s out of cut off with out bleeding some of the bias voltage off as these heads where made to run 6550 output tubes !
You need to get the bias voltage down to about -36 on on pin 5 for those tubes and I would bet that your plate voltage is above 500 in this case.
If you have the needed -36 bolts of bias then do this check out.
Hook a meter set for ac volts across pin. 5 on both output tubes and play with the amp cranked, if you read over 25 volts on the meter then all is well but for the output transformer.
Another way to check this is to install 1 ohm 2 watt 1% resistors in series with pin 8 of each output tube to ground, this will let you set a meter for dc volts and directly read how much current the tubes are pulling.
If you play thru the amp and see this current go up far above idle, then this confirms that the OT is toast also!
While you are in there you should also rewire the standby switch so that it's after the choke.
You need to get the bias voltage down to about -36 on on pin 5 for those tubes and I would bet that your plate voltage is above 500 in this case.
If you have the needed -36 bolts of bias then do this check out.
Hook a meter set for ac volts across pin. 5 on both output tubes and play with the amp cranked, if you read over 25 volts on the meter then all is well but for the output transformer.
Another way to check this is to install 1 ohm 2 watt 1% resistors in series with pin 8 of each output tube to ground, this will let you set a meter for dc volts and directly read how much current the tubes are pulling.
If you play thru the amp and see this current go up far above idle, then this confirms that the OT is toast also!
While you are in there you should also rewire the standby switch so that it's after the choke.
When I die, I want to go like my Grandfather did, peacefully in his sleep.
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Re: Sunn Sonaro low output troubleshooting
Sorry guys I've had a helluva week and haven't had time to post. The sound isn't distoted till I get to 9 on the volume pot. Then it gets fuzzy.
The combo version of the Sonaro supposed to have el34s for sure.
The combo version of the Sonaro supposed to have el34s for sure.
-
Stevem
- Posts: 5144
- Joined: Fri Jan 24, 2014 3:01 pm
- Location: 1/3rd the way out one of the arms of the Milkyway.
Re: Sunn Sonaro low output troubleshooting
Hook up a meter set for ac volts across the speaker and when it goes sound goes south at 9 report back with the voltage you read and the impedance the amp was driving into, and also what the plate, screen and bias voltage is at that point.
When I die, I want to go like my Grandfather did, peacefully in his sleep.
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!