No Heater Glow

[ryanburton]

i've just finished a tweaked princeton build and i don't seem to be getting any reaction from the filaments from any of the tubes.

what is the proper way to check the voltage on the heaters?

[Phil_S]

Do you own a meter? I am sorry, to say, this is very basic and am afraid to tell you what to do. If you own a meter and you don't know how to use it, but you built an amp, you sound like you are in over your head.

Live amp circuits are very dangerous -- no kidding, they are kill you dead kind of dangerous -- and I don't feel well equipped to run through all the basic safety stuff you need to know and practice.

So, the only comments I'm going to make here are these:

1) Did you wire the tube sockets correctly? Normally there are small numbers next to the pins to tell you what's what. The typical layout diagram omits the heater circuit, as it is implied and makes for a lot of clutter. Maybe you didn't wire the filament (heater) supply?

2) If you think it is wired correctly, make sure your tubes are seated correctly in the sockets. They need to be all the way in.

If you will post something about your background, relevant education/training, level of experience, etc, this might give us some comfort level to guide you.

You should also consider posting one or more gut shots of the amp.

[ryanburton]

wiring is correct. tubes are installed correctly. power is going to heaters and rectifier, etc.

what i meant was:
1. dc or ac on the dmm?
2. am i measuring the voltage across the two different parts of the circuit as in pin 1 and pins 4/5 (on preamp tube)? or from ground to either pin 1 or pin 4/5?

i want to get my facts straight before reporting voltages for diagnosis.

[collinsamps]

Well just when I wanted to answer your questions you scared me to death wanting to measure from pin 1 to 4/5.

One is DC plate voltage and the other is AC filaments.

I think Phil is on to something. Take it somewhere please.

[C Moore]

Do you have a roach clip attachment for the negative test lead of your DMM? Can you verify that the rectifier has all of its proper voltages? Just clip on to ground, turn on the amp, and with one hand verify the numbers on the rec tube with your schematic. Have you verified that AC is getting into your amp? Those are some real basic numbers that you need to know. Be careful, use one hand in the amp, go slow, check your schematic.
Good Luck

[Tubetastic]

+1 with the other suggestions on taking the amp to someone to help you with this.

[Cygnus X1]

I would go with two roach clips and full body armor.

To be fair, the heater locations are kind of vague on the traditional Fender schematics.
On the 12AX7 it is pins 4 and 5 tied together for one leg, and pin 9 for the other. The schem shows "ground".
In reality it is 4 and 5 each side, pin 9 heater center tap.

For the 6V6 it is pins 2 and 7.
You should get 6.3VAC there.
If you clip your lead to ground and check then you get 1/2 of the heater readings.
If you attach the leads to each heater, you will get full reading.

Measured in AC volts.

[Tubetwang]

I would go with two roach clips and full body armor.

To be fair, the heater locations are kind of vague on the traditional Fender schematics.
On the 12AX7 it is pins 4 and 5 tied together for one leg, and pin 9 for the other. The schem shows "ground".
In reality it is 4 and 5 each side, pin 9 heater center tap.

For the 6V6 it is pins 2 and 7.
You should get 6.3VAC there.
If you clip your lead to ground and check then you get 1/2 of the heater readings.
If you attach the leads to each heater, you will get full reading.

Measured in AC volts.

Hey Ryan...

I just saw you post...

it took Cygnus X1 for an anwser...

The question was simple enough but...

This here lecturing about frying on a wire is a remnants of Jesus in Galilea...

While true that an electrical shock can kill you, you should know that i got zapped 6 times last week, and, after repenting 12 hours, i'm still here breaking rules....

I got a brand new Hammond 290CX drop in replacement last week for a 65 Tremolux. There was no voltage on the green wires. The tranny is open. Keep that in mind. The tranny could be defective.

P.S. it is too easy to bring the amp to the repair dude and not much fun...I say go ahead and fix that amp boy. You'll feel so good after.

One has to start somewhere...right?

Repent.

[Cygnus X1]

Thank you for the props, T.


And no I wasn't being cute about the two-clips method.
I'm never in a hurry, and meters are cheap.

So anytime I'm checking anything inside the amp, I power down, unplug, discharge, clip where I want, then power up again.
I think it's more accurate to do it this way, as the probe isn't sliding around on some small point while I'm looking at the meter(s).

[Phil_S]

One has to start somewhere...right?

Yes, one has got to start somewhere. Start with a book. Figure out what runs AC and what runs DC inside your amp. Learn what a rectifier does. The builder should know if the filament supply is rectified and then he knows if it is AC or DC. The builder of the amp shouldn't be asking this.

Tubetwang, you are asking him to flirt with stuff that is easily reasoned through, yet he asks if he's going to measure AC or DC.

You are right, I started somewhere and not all that long ago. I did a great deal of reading before I attempted to stick my fingers inside a chassis. I had a checklist of safety procedures posted at my bench. I solicited advice.

If he had said, "I haven't done this before. I want to be sure I'm doing the right thing. So, I set the meter for ACV, clip the black probe to the chassis and the use the red probe to touch pin 9, then pins 4&5 which are jumpered. Is this right?" If he had done that much, I think he'd have got a great deal of encouragement. This individual didn't know if he was to measure AC or DC (again, something that the builder should know, see above) and asked about a bad pin combination. It shows he's either not paying attention or can't understand some of the basic details in front of him.

I'm right there with "gotta start somewhere." I just don't think, in this particular case, the somewhere was the right somewhere. BTW, getting shocked 6 times last week isn't a badge of honor. I'd caution the original poster that taking advice from someone who gets himself shocked that many times in a week is cause for pause. We disagree in some measure about where to start.

Ryan: If you want to do this right, I suggest you take a few steps back. Read about safety procedures first. That will keep you safe and from getting shocked, an unpleasant experience and potentially life threatening. Here are some starters:
http://www.aikenamps.com/SafetyTips.html and lots of other good technical info on Aiken's site, some of which you may not be ready for just yet.
http://www.drifteramps.com/safety.html
http://aga.rru.com/ all sorts of good stuff, organization is a bit random

Read this book and get the video tape: How to Service Your Own Tube Amp by Tom Mitchell ... about halfway down this page: http://www.amptone.com/booksamps.htm#_Toc142020568 hint: don't get Mitchell's book from Amazon. They don't stock it and it will take 6-8 weeks. Sometimes it comes up on eBay for a discounted price.

You've got the makings of a good amp, but, from what you write, I do not think you are ready to safely move forward. Do some homework and you will get there. At the beginning, amp making takes a lot of patience and requires attention to details that are hard to see. Slow up a little. This is like the tortise and the hare. Slow and steady wins the race.

And, Ryan, for the time being, use 'gator clips with your meter and keep both hands outside the chassis when the power is on. Also, post your location. You might be closer to help than you imagine. Or find your local ham radio club, introduce yourself and ask nicely for help. The ham radio guys may not know jack about tone, but they know how to build and operate an amp.

[Tubetwang]

One has to start somewhere...right?

Yes, one has got to start somewhere. Start with a book. Figure out what runs AC and what runs DC inside your amp. Learn what a rectifier does. The builder should know if the filament supply is rectified and then he knows if it is AC or DC. The builder of the amp shouldn't be asking this.

Tubetwang, you are asking him to flirt with stuff that is easily reasoned through, yet he asks if he's going to measure AC or DC.

You are right, I started somewhere and not all that long ago. I did a great deal of reading before I attempted to stick my fingers inside a chassis. I had a checklist of safety procedures posted at my bench. I solicited advice.

If he had said, "I haven't done this before. I want to be sure I'm doing the right thing. So, I set the meter for ACV, clip the black probe to the chassis and the use the red probe to touch pin 9, then pins 4&5 which are jumpered. Is this right?" If he had done that much, I think he'd have got a great deal of encouragement. This individual didn't know if he was to measure AC or DC (again, something that the builder should know, see above) and asked about a bad pin combination. It shows he's either not paying attention or can't understand some of the basic details in front of him.

I'm right there with "gotta start somewhere." I just don't think, in this particular case, the somewhere was the right somewhere. BTW, getting shocked 6 times last week isn't a badge of honor. I'd caution the original poster that taking advice from someone who gets himself shocked that many times in a week is cause for pause. We disagree in some measure about where to start.

Ryan: If you want to do this right, I suggest you take a few steps back. Read about safety procedures first. That will keep you safe and from getting shocked, an unpleasant experience and potentially life threatening. Here are some starters:
http://www.aikenamps.com/SafetyTips.html and lots of other good technical info on Aiken's site, some of which you may not be ready for just yet.
http://www.drifteramps.com/safety.html
http://aga.rru.com/ all sorts of good stuff, organization is a bit random

Read this book and get the video tape: How to Service Your Own Tube Amp by Tom Mitchell ... about halfway down this page: http://www.amptone.com/booksamps.htm#_Toc142020568 hint: don't get Mitchell's book from Amazon. They don't stock it and it will take 6-8 weeks. Sometimes it comes up on eBay for a discounted price.

You've got the makings of a good amp, but, from what you write, I do not think you are ready to safely move forward. Do some homework and you will get there. At the beginning, amp making takes a lot of patience and requires attention to details that are hard to see. Slow up a little. This is like the tortise and the hare. Slow and steady wins the race.

And, Ryan, for the time being, use 'gator clips with your meter and keep both hands outside the chassis when the power is on. Also, post your location. You might be closer to help than you imagine. Or find your local ham radio club, introduce yourself and ask nicely for help. The ham radio guys may not know jack about tone, but they know how to build and operate an amp.

Well...

The guy asked a simple question and he should have got a simple answer to his problem...instead, he got a lecture.

Some guys just want to fix their amp and move on...or whatever...

Others, like me, have loads of books and video's but are either slow learners, don't have the math or whatever...

I don't like shocks, but i'm impatient and cut corners...i should do it properly...I will next time...i do feel that the menace is overblown...

I figure...if you know the answer...and are willing to help...just shoot it and let the poor guy move on with his repair...

Blabbing about the "danger" or "to bring it to the repair shop" is not going to help the poor guy much...right?

[Cygnus X1]

Good sources, Phil, thank you for that.
Many books go on the assumption that no one actually works on their amp, just "information for you to take to your technician, so you understand"...etc. Because no one wants the liability of telling a person to dive into such potentially lethal territory.

I found the "cap" answer to the radio interference problem that I'll try in there.

I have never gotten shocked from an amp while working on them.
I have gotten a couple zaps while playing though.

I took the approach that the filament circuit is frequently not even drawn in to many schematics, thus the confusion to the OP.

[Structo]

Tubetwang,
You think that the warning about hazards of getting shocked is overblown?

Did you know that if you get a shock from one hand to the other the current will pass through your heart?

Did you know it takes less than 300ma to stop your heart if you happen to get the right mix of voltage and current?

So no, the dangers are not exaggerated at all.

It would be very tragic if we helped somebody do something inside their amp without mentioning the hazards and dangers and that person electrocuted himself while probing inside the amp.

[M Fowler]

Just don't turn this forum in 18watt.com where I get my ass chewed out every time I post as the moderators are right on my heels snipping.

This site has been such a joy to me compared to the other sites, so take it easy on newbies and newbie questions is all I ask.

Mark

[Jana]

I stick my tongue on 9 volt batteries to test them.

Really, I do!