Thanks! I was trying to grok that.

+James skippinhopper Yes, all you need is a signal generator (or a low voltage mains transformer) and a multimeter. With an analog meter you can check for inductance by measuring resistance and watching to check that the pointer hesitates before it accelerates to the resistance value.

What kind of BS is that?

@@garybrown8767 It's the kind of BS that you learn from to techs who have been designing, building and repairing tube amps for over sixty years.

@@silasfatchett7380 And that is a load of BS to.

Thank you. I will do my best to maintain good content

Carl Rudd Yep, need to sell a few D-lab units to keep the videos running. I made 4 of these units. Have 1 left. They are pretty handy on the bench

You did a good job. Nice video too.

i agree ...i would be glad to pay for a set of plans ,,since you do not plan to build any more of them...it would be a good income source for d-lab...just include statement of build at your own risk....

PeterPug007 Hi Peter, usually the transformer will open on 1 side disabling the high voltage from reaching one output tube.This will make the amp very distorted and yes loose power. You can buzz out the output tranny. Make sure the power is off and HV discharged. Check form the power supply HV to each tube plate. You should see equal resistance. Then check each leg to chassis. Make sure the tranny does not have an internal short. Hope this helps

Hello, nope, sorry, I made 4. Material cost was too high to continue the project. Glad you like the vids, more coming soon. TD

@@d-labelectronics All you have to do is use a variac and a DVM. I use 2 DVMs to make it a little quicker but it works just fine.

Hello, sounds like an open output transformer winding. Have you tried taking an Ohm check between the 2 pin 3's? Should be around 300 ohms.

@@d-labelectronics That's what I was afraid of. I haven't checked ohms yet. It got late and I had to get in the bed. I'll be able to check more when I get off work. Anything else to look for to confirm? Is it possible to get it fixed since its original to the amp?

Hey man, The originals can pop up on ebay or Reverb.com. I'd sub in a Classic Tone, Chicago, Great iron

@@d-labelectronics Would my amp continue working fine with zero noise if one of the OT wires wasn't putting out voltage to one tube? Everything is working fine, both tubes glowing fine but I just don't have voltage on pin 3 of that one tube. Also I get no ohm reading between the 2 pin 3s. I did order an Allen OT today anyway. Thanks for helping me.

Yes, Re-purposed the enclosure for the project

Sounds like your output tranny is fine. Check the high voltage and screen resistors. TD

Thanks for the feedback! I decided to test one the Transformers on one of my other amps to compare the results, and noticed that when I touched the inputs on the Tranny with the Multimeter that I heard noise from the speaker, which scared me at first, thinking perhaps I had left the power cable stuck in, wasn't so, but then I thought "A Ha", I didn't hear that from the "Broken" amp, so I traded the Speakers in the Amps, and my "Broken" Amp works!, It was the Speaker. Thanks for sharing your knowledge , I am enjoying learning how my Amps work and troubleshooting on my own. Robert Jefferies Berlin

Excellent, good to hear. Its a great hobby

I got my new Speaker, an Eminence Legend GB 128. Amp works, Sounds super. I hangedmy Multimeter onto the Speaker connections, and when I play at the Amps full volume, the Multimeter reads 23V. VxV/Ohms = Watts, right? So 23x23/8=66 , 66 Watts is too much to be coming out of my 40 Watt Amplifier. Der GB 128 is a 50 W Speaker, should be correct for a 40W Amplifier, but when it's giving out 66 Watts. Is this why I had to buy a new Speaker in the first place? or am I mistaken on my measuring of the Speaker connections?

It's important to know what the waveform looks like before you calculate power. It would be best to connect an oscilloscope across your speaker leads, inject a clean sinewave into the input of your amp, and then adjust the output of your sinewave generator and volume control until the output just starts to saturate. Note the peak-to-peak voltage on the scope screen, divide by 2.828, square that number, and then divide by your speaker's impedance (probably 8 ohms). That will give you your clean power output. Pushing your amp's gain up until the amp saturates will give you even more power, but with the complicated waveform, you would need a rue power meter to accurately measure the power.

Hello, That issue could be many things. The first thing I would check would be the bias thru each output tube. Also, a bad inverter tube can cause all kinds of issues. Where are you located? I would be glad to go over the amp for you.

+neutrodyne Hello, Yes a load is applied to the secondary. The turns ratio is simply based on dialing in the primary side until you see 1 vac on the secondary, then read the primary. The frequency is 60HZ. The ac voltage is current limited to prevent damage/shock. TD

So you are basily do a turns ratio test?

+neutrodyne Yes Sir, thats it

No.

Apologies are in order. I was assuming that you were testing a transformer which was not installed in an amp, in which case there should be no continuity. If the transformer is installed in an amp, then one side of the secondary will be connected to ground.

+BitterrootRambler Hello, Yes, I would agree. Sounds like the primary is shorted. Did you check one of the primary wires to the case of the transformer? Usually when they fail, you will find low resistance to the case also. TD

I did that but didnt notice anything. ill try again and cycle the meter. any recommendations on where to pickup a new transformer. Mercury Magnetics wants almost 200 bucks for one!

+BitterrootRambler You could install a Classic tone type, made in Chicago. Check Triode.com

+BitterrootRambler If you haven't order a transformer yet. I would not order one. There are a lot of other things that could cause a no sound condition on your amp. Spend the money by taking the amp to a amp tech and have it checked out. You would be wise to also replace all electrolytic caps in the amp while you are at it.

Hello, the transformer should be fine. If the amp still plays OK, your good to go. TD

A tube amp will happily idle with no speaker load. The damage occurs when it attempts to amplify a signal.

Yes. The voltage across the primary divided by the voltage across the secondary is the turns ratio. By applying 1V to the secondary, Terry didn't have to punch a division sum into his calculator.

Andrew Shropshire Joe Jackson. King Pleasure.

Thanks Flux.

Ah, I should have known. I just asked who this was in another post. Do you know the name of the album?

@@tiki_trash yup, that’s from the album Rain. Great stuff.

The Song is Called "King Pleasure Time". You are welcome.

+John Cunningham Hello John, Yes Sir, I have 1 more like the Heathkit style in this video

What is your asking price?

+John Cunningham Hi John, The best price is 200 shipped. My parts cost was high due to AC isolation. TD

Hello, Yes, I built 4 of them. Sold 3

D-lab Electronics how much did they go for?

I believe around 250. The parts are hard to come by, especially the meters

D-lab Electronics well it's a great tool. any plans to make more?

Not now, too many projects on the bench

+ian “valve doctor” forster Hello, take a look at a Fender Princeton phase inverter diagram. One half of the 12ax7 is for tremolo, the other half is the inverter. The 6AV6 tube uses that half of the diagram. A very simple but great performing inverter. TD

ok got you are just using the triode part of the 6av6

+ian “valve doctor” forster Yes Sir. The 6AV6 is a great tube for that application

Impedance is a function of voltage and current. If an 8Ω speaker has an 8V signal across it, there is 8V / 8Ω = 1A flowing in it. If it is connected to the secondary of a transformer with a 40:1 turns ratio, at the primary, voltage is stepped up by 40:1, 8V x 40 = 320V. Current is stepped down by 40:1, 1A / 40 = 0.025A. The impedance of the primary is 320V / 0.025A = 12,800Ω. 8Ω x 40 x 40 = 12,800Ω.

I was asking that myself. I worked it out using ohm's law and saw that this was a short cut. One of the 30s is the voltage on the left side of Terry's device. The other 30 is the number of windings as Terry's device reveals (30v/1v= 30 windings ratio). Primary ohms = 30 volts * 30 (winding ratio) * secondary ohms. The full equations is this: the current on the speaker side is 1 volt / 8 ohms or .125A. As Silas points out the current is multiplied going the other way through the transformer by the windings ratio which is 30 so it's .125A * 30 on the primary side. To to find the ohms on the primary side (ohms = volts/resistance) is 30v (as on the left or primary side of Terry's device) divided by .125A. * 30(windings ratio) or 30v/.125A * 30. You can take the reciprocal of .125A which is 8 and turn the division into a multiplication so Terry's short cut is ohms = 30 * 30 * 8.