New Jtm45 hums

[James_Wildart]

I just finished building a Jtm45 clone, I used a TR-PW-05 power transformer. When I flip the Standby switch all I get is a loud hum and nothing from the guitar. Seems like I have all my wiring correct but I must have something wrong. What do you suggest I look at first?

Thanks
James 

[tubenit]

If it was wired correctly, it would likely be working.


1) Can you show us a schematic of exactly what you have made.

2) Have you checked voltages of tube plates and cathodes?  Can you post that?

3) Can you post detailed pictures of the amp build.

4) Have you tried another guitar, guitar cord to amp, and speaker?

5) Have you tried different tubes known to be good?   

It is easier to help you IF you give us this information that we normally will ask for.


With respect, Tubenit

[PRR]

> Seems like I have all my wiring correct but I must have something wrong.

That is very popular. So popular that Doug posted about it.
How to double check your amp wiring and find things you missed
"Hoffman's law states the the amp would be working if everything was correct"
https://el34world.com/Forum/index.php?topic=17701.0

[Brownie]

Maybe double check the wiring at the input jacks. The tip or inner of your cable may be going to chassis ground if it's a shielded cable such as RG174. Sometimes the inner gets melted or soldered to the shielding

[James_Wildart]

What I am trying to do is combine two layouts since I have the TR-PW-05 transformer. A regular Ceritone jtm45 layout and a Jtm45_Plus layout I got on Tube Depot. This layout uses the TR-PW-05 Power transformer. I just want to wire it real simple without a Master Volume. I'll get the voltages of the Tube Plates and Cathodes tomorrow. 
The Tubes are brand new Mesa Boogie's and Mullards 12ax7's, Genalax remake KT-66 power tubes and a Mesa 5Y3GT rectifier tube.
I'll try and get more pics too, I know it's hard to see whats going on.

Thanks so much, I actually like trying to figure what's wrong with it more than building it in the first place.

[Esquirefreak]

I'd use ONE layout. And a GZ34 rather than a 5Y3.

/Max

[Latole]

Most of the time, hum is from a bad ground or a ground missing or a bad solder on a ground wire(s) ,

[James_Wildart]

Most of the time, hum is from a bad ground or a ground missing or a bad solder on a ground wire(s) ,

I just heard an amp tech say he's fixed a lot of amps by just tightening some ground lugs.

[Latole]

Most of the time, hum is from a bad ground or a ground missing or a bad solder on a ground wire(s) ,

I just heard an amp tech say he's fixed a lot of amps by just tightening some ground lugs.

Anything to do with the ground must be suspected.

But in the case of a new construction, who knows what assembly errors could cause this hum?

In the case of an amp that has already worked perfectly, trouble shouting is simpler and follows a certain logic.
Which is not the case here.

[James_Wildart]

So I went around and tightened all the lugs that went to ground and got the hum down to a low purr but still no sounds from the guitar and smoke started coming up from one of the power tubes. I flipped it over and the 1K 2watt resistor was burned.
I attached a pic

Another odd thing...I have the pilot light hooked up to the power switch and when I plug the amp in the light comes on before I swtich it on. When I switch the amp on the light goes off, how can that be?

[sluckey]

Another odd thing...I have the pilot light hooked up to the power switch and when I plug the amp in the light comes on before I swtich it on. When I switch the amp on the light goes off, how can that be?

Pilot ain't wired correctly. Probably same issue with no sound/smoke issue.

[Latole]

From the beginning we know there are many wiring mistake.

OP must check his work more carefully

[Ronquest]

Another odd thing...I have the pilot light hooked up to the power switch and when I plug the amp in the light comes on before I swtich it on. When I switch the amp on the light goes off, how can that be?

I'd like to add, this is can happen with an IEC socket that's miswired "AND" IEC chords that are wired with the hot and neutral reversed.  I have a pile of factory chords that are cross wired.  I started testing my chords after having my LED lamp light in the off position once when I switched chords.  A surprising amount are crossed.  Guess this isn't a problem for some devices, but in an amp, it's not good!  Especially considering if your working on it.   However my amp lamp now tells me if the outlet or chord are miswired.  This is also a good example of why double pole switches are a good idea.

[pdf64]

…
Another odd thing...I have the pilot light hooked up to the power switch and when I plug the amp in the light comes on before I swtich it on. When I switch the amp on the light goes off, how can that be?

Please provide clear photos showing where each wire from the pilot light is connected.
Please provide the specification of the pilot light, as both layouts show a 6.3V type, intended for connection to the 6.3V heater circuit.

[Ronquest]

Please provide clear photos showing where each wire from the pilot light is connected.
Please provide the specification of the pilot light, as both layouts show a 6.3V type, intended for connection to the 6.3V heater circuit.

Looks like the 120V pilot light is wired to both sides of the power switch!  That could be your light problem.  One lead to the switched side and the other to ground.

[sluckey]

Looks like the 120V pilot light is wired to both sides of the power switch!  That could be your light problem.  One lead to the switched side and the other to ground.

No! Never ground. That indicator lamp should be wired to the same place as the PT primary wires. IOW, parallel to the PT primary.

[Ronquest]

Looks like the 120V pilot light is wired to both sides of the power switch!  That could be your light problem.  One lead to the switched side and the other to ground.

No! Never ground. That indicator lamp should be wired to the same place as the PT primary wires. IOW, parallel to the PT primary.

Your right!, go to fix one issue and make another.

[Latole]

If you had revisited your circuit as suggested several times, you would have seen this problem and all the others.

[JPK]

In the two layouts you posted I see a pilot light wired to the 6.3V filament supply. I'm not seeing any pilot wired to a power switch. So yeah pilot light wired wrong sounds about right. 

[James_Wildart]

So are you also saying that I could have the IEC female plug upside down making the wiring backward and that's what's making the Pilot light go on?

Another odd thing...I have the pilot light hooked up to the power switch and when I plug the amp in the light comes on before I swtich it on. When I switch the amp on the light goes off, how can that be?

I'd like to add, this is can happen with an IEC socket that's miswired "AND" IEC chords that are wired with the hot and neutral reversed.  I have a pile of factory chords that are cross wired.  I started testing my chords after having my LED lamp light in the off position once when I switched chords.  A surprising amount are crossed.  Guess this isn't a problem for some devices, but in an amp, it's not good!  Especially considering if your working on it.   However my amp lamp now tells me if the outlet or chord are miswired.  This is also a good example of why double pole switches are a good idea.

[sluckey]

So are you also saying that I could have the IEC female plug upside down making the wiring backward and that's what's making the Pilot light go on?

That's not why the pilot is misbehaving. The pilot is wired incorrectly. The fix is very simple. Look at the attached pic to see what you have to do to make it work correctly...

[James_Wildart]

Thanks, I went ahead and attached it to the heaters like the layouts show. I had an amp tech for a somewhat famous guitarist tell me to attach it to the pilot light.
I also flipped the IEC plug around to see if that makes a difference.

[sluckey]

That pilot lamp will not work when connected to the filament circuit. It is intended to be connected to the 120VAC.

[James_Wildart]

Well I have great news, whatever I did fixed it! I now have sound from the guitar! But I also have some little pops and crackles I need to clean up.
And you are right Sluckey that didn't fix the pilot light wiring it to the heaters so I'm taking your advice and wiring per your instructions.

[James_Wildart]

The pilot light works perfectly now! Thanks

That pilot lamp will not work when connected to the filament circuit. It is intended to be connected to the 120VAC.

[James_Wildart]

The amp is amazingly quiet except when I turn it to 10 a very low hum ...now I'm off to Youtube figuring out how to bias it.