Second amp build. This one came out nicer than the other one (that sounds great but looks like toddler day at the spaghetti factory). However, I fired it up today and got nuthin. When I check the voltages (which seem OK) I get a wee crackle thru the speaker when the probe is moved. But there isn't even tube hiss. Nuthin, nuthin, nuthin. I first thought maybe the OT was bad and subbed in a known good one, no change. The amp is basically a Matchless Lightning into 6L6 cathode biased output.
Any ideas? Something simple I may have missed?
New build--zip, zero, zilch, nada sound
Moderators: pompeiisneaks, Colossal
New build--zip, zero, zilch, nada sound
Rich Gordon
www.myspace.com/bigboyamplifiers
"The takers get the honey, the givers get the blues." --Robin Trower
www.myspace.com/bigboyamplifiers
"The takers get the honey, the givers get the blues." --Robin Trower
Re: New build--zip, zero, zilch, nada sound
I apologize in advance if this seems obvious and you've done it already, but... from my limited experience, when new builds don't work at first, it's usually something simple. Check the Tube Amp Debugging page at Geofex (http://www.geofex.com/ampdbug/ampdebug.htm). I always think I have that stuff committed to memory, but sometimes it helps alot just to read it.
If that doesn't help, a signal probe is a great and fast way to find problems in a no-sound amp. Got this method from a thread on the old Ampage site. If you don't have a signal generator and a scope, you can cobble together a cable to send a signal to the input jack of the amp from something like a CD walkman. Then make a signal probe. It could be a multimeter probe connected to a 600 V cap (.1uf, value not too important). Connect the probe to a practice amp (the chassis of the amp under test has to be connected to the (-) side of the plug going into the practice amp). Usual warning--be careful--one hand in amp, other hand not... You can check various points in the ciruit, starting at the input jack, until you get to where the signal stops. At this point, look for a part missing, open circuit, signal going to ground, etc. Hope this makes sense. The Ampage thread I got the idea from was quite clear, but I don't remember which forum it was on...
If that doesn't help, a signal probe is a great and fast way to find problems in a no-sound amp. Got this method from a thread on the old Ampage site. If you don't have a signal generator and a scope, you can cobble together a cable to send a signal to the input jack of the amp from something like a CD walkman. Then make a signal probe. It could be a multimeter probe connected to a 600 V cap (.1uf, value not too important). Connect the probe to a practice amp (the chassis of the amp under test has to be connected to the (-) side of the plug going into the practice amp). Usual warning--be careful--one hand in amp, other hand not... You can check various points in the ciruit, starting at the input jack, until you get to where the signal stops. At this point, look for a part missing, open circuit, signal going to ground, etc. Hope this makes sense. The Ampage thread I got the idea from was quite clear, but I don't remember which forum it was on...
Re: New build--zip, zero, zilch, nada sound
Chris,
Thanks for that link to the amp debugging page. I'll check that out this week. I think I may have to make that signal probe. Seems to me I remember something like that in one of Gerald Weber's books. Back in the day, when I used to actually use my electroknowledge, I had access to all kinds of helpful gizmos like O-scopes and such. Darned if that wouldn't be pretty handy right about now!!
I think my next build will have to be a Trainwreck--with so few parts there's less for me to get wrong.......
Thanks for that link to the amp debugging page. I'll check that out this week. I think I may have to make that signal probe. Seems to me I remember something like that in one of Gerald Weber's books. Back in the day, when I used to actually use my electroknowledge, I had access to all kinds of helpful gizmos like O-scopes and such. Darned if that wouldn't be pretty handy right about now!!
I think my next build will have to be a Trainwreck--with so few parts there's less for me to get wrong.......
Rich Gordon
www.myspace.com/bigboyamplifiers
"The takers get the honey, the givers get the blues." --Robin Trower
www.myspace.com/bigboyamplifiers
"The takers get the honey, the givers get the blues." --Robin Trower
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skyboltone
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Re: New build--zip, zero, zilch, nada sound
Hi Rich:
Years ago I built a 5 tube receiver. I checked it against the schematic again and again. That's the first step. I was new to the game and I finally asked an experienced tech for help. He found an extra wire. One that wasn't supposed to be there and carried my detected signal to ground.
So it might be something missing or something added. The signal tracer is the way to go.
Dan
Years ago I built a 5 tube receiver. I checked it against the schematic again and again. That's the first step. I was new to the game and I finally asked an experienced tech for help. He found an extra wire. One that wasn't supposed to be there and carried my detected signal to ground.
So it might be something missing or something added. The signal tracer is the way to go.
Dan
The Last of the World's Great Human Beings
Seek immediate medical attention if you suddenly go either deaf or blind.
If you put the Federal Government in charge of the Sahara Desert, in five years time there would be a shortage of sand.
Seek immediate medical attention if you suddenly go either deaf or blind.
If you put the Federal Government in charge of the Sahara Desert, in five years time there would be a shortage of sand.
Re: New build--zip, zero, zilch, nada sound
You know the old saying - you always find te thing you are looking for in the last place you look for it.
I recently fired up a build that I had checked and rechecked, and there was no sound. I finally had a chance to try out the simple little audio probe that I had read about in Gerald Weber's books.
Axial lead cap (.047, but its value is not critical) attached to a wire attached to the tip of a 1/4" jack.
A second wire attached to the ground of the 1/4" jack, and an alligator clip on the other end. Electrical tapethe cap to a chop stick leaving 1/4 - 1/2" of the cap lead sticking out.
Plug the 1/4" jack into a known working amp, a micro amp, or a stereo, or whatever. Plug a sound source into the amp you want to test.
Now, touch the cap lead to various points in the amp circuit, starting at the input jack, and wokring your way through the signal chain. If the part of the circuit you probe is working, the swound will come out of the other amp. Move on to the next point in the signal chain. When the sound stops, you know that you have moved past the problem.
In my case, it was a "too long" wire attached to a bright switch that was grounding out. I got sound coming out of my "known" working amp when I probed the input jack, the plate of V1-a, etc, but once I probed the volume pot (which the bright switch bypasses), no sound made it to the known working amp. I found the long wire within a minute after that realization.
People either love or hate Gerald. All I know is that I have learned a lot form his books and DVD's. This cheap little do-it-yourself tool worked as advertised and saved me lots of frustration.
Good luck.
I recently fired up a build that I had checked and rechecked, and there was no sound. I finally had a chance to try out the simple little audio probe that I had read about in Gerald Weber's books.
Axial lead cap (.047, but its value is not critical) attached to a wire attached to the tip of a 1/4" jack.
A second wire attached to the ground of the 1/4" jack, and an alligator clip on the other end. Electrical tapethe cap to a chop stick leaving 1/4 - 1/2" of the cap lead sticking out.
Plug the 1/4" jack into a known working amp, a micro amp, or a stereo, or whatever. Plug a sound source into the amp you want to test.
Now, touch the cap lead to various points in the amp circuit, starting at the input jack, and wokring your way through the signal chain. If the part of the circuit you probe is working, the swound will come out of the other amp. Move on to the next point in the signal chain. When the sound stops, you know that you have moved past the problem.
In my case, it was a "too long" wire attached to a bright switch that was grounding out. I got sound coming out of my "known" working amp when I probed the input jack, the plate of V1-a, etc, but once I probed the volume pot (which the bright switch bypasses), no sound made it to the known working amp. I found the long wire within a minute after that realization.
People either love or hate Gerald. All I know is that I have learned a lot form his books and DVD's. This cheap little do-it-yourself tool worked as advertised and saved me lots of frustration.
Good luck.
Re: New build--zip, zero, zilch, nada sound
If you get crackle through the speaker, then you know that the output section is capable of generating or passing signal. I'd start at the power tubes, and pull on every wire and component connection to make sure they are soldered solidly in place. I've had bad solder joints that had the end of the wire sitting beside a blob of solder, but not fused to it. If everything is solid, look at any resistors going to ground, like the grid to ground resistors. Make sure an expected 220K resistor isn't actually 22K - a low value resistor to ground will dump your signal like a volume pot turned down. Also, a 100 ohm resistor in place of a 100K plate resistor will kill your signal.
Before I did any of that, I'd have a voltage chart for the entire amp, with every tube lug and power supply node accounted for. Correct voltages will rule out a lot of problems. I also do a ground check of the entire circuit to make sure all ground points are actually connected to ground.
Before I did any of that, I'd have a voltage chart for the entire amp, with every tube lug and power supply node accounted for. Correct voltages will rule out a lot of problems. I also do a ground check of the entire circuit to make sure all ground points are actually connected to ground.
Re: New build--zip, zero, zilch, nada sound
Not much information to go on here. I'd start by posting what schematic and layout you used, pics of the build and voltages at the various key tube pins, I.E. plate grid cathode.
Re: New build--zip, zero, zilch, nada sound
On Sunday I puzzed and I puzzed till my puzzler was sosre, so I decided to take a few days away from the amp. I went in there a few minutes ago with fresh eyes, and......gee, no grid supply wire to the v2b side of the cathode follower. My, my, my, what a difference one wire makes!!
So the amp is alive, and my hunches on values = tone were right, and it is a profoundly cool jazz amp.
I'll try to post some pics this weekend. Then I'll start on the cab making.
Thanks for all your ideas, I'll store them away for future screw ups.
So the amp is alive, and my hunches on values = tone were right, and it is a profoundly cool jazz amp.
I'll try to post some pics this weekend. Then I'll start on the cab making.
Thanks for all your ideas, I'll store them away for future screw ups.
Rich Gordon
www.myspace.com/bigboyamplifiers
"The takers get the honey, the givers get the blues." --Robin Trower
www.myspace.com/bigboyamplifiers
"The takers get the honey, the givers get the blues." --Robin Trower
Re: New build--zip, zero, zilch, nada sound
Glad to hear you found it. Looking forward to pics and clips.