New Rocket blowing fuses

[martin manning]

Yss, reconnect the filament circuit, correct the B+ connection to the rectifier tube (get it from pin 8, not pin 2), and check that you have the high voltage and the filament wired correctly from the PT.

Make sure that the caps are drained, which you can do by closing the standby so the bleeder resistor is connected to all of the filters. Check the voltage at the standby switch to confirm that it is zero. Then, measure resistance to ground from rectifier pin 8 with the standby switch closed, and then open, with no tubes installed. You should see tens of thousands of ohms either way, and it will not be stable since your meter will be charging the filter caps. If you get a small resistance value with it open, then you will know on which side of the standby switch to look (rectifier side).

If that checks out put just the rectifier tube in and power it up. Use the bulb limiter if you want to be extra careful. Carfefully measure the voltages on the pins, AC on 6 and 4, DC on 8 and 2, and see what you get.

[showsii]

Yss, reconnect the filament circuit, correct the B+ connection to the rectifier tube (get it from pin 8, not pin 2), and check that you have the high voltage and the filament wired correctly from the PT.

Make sure that the caps are drained, which you can do by closing the standby so the bleeder resistor is connected to all of the filters. Check the voltage at the standby switch to confirm that it is zero. Then, measure resistance to ground from rectifier pin 8 with the standby switch closed, and then open, with no tubes installed. You should see tens of thousands of ohms either way, and it will not be stable since your meter will be charging the filter caps. If you get a small resistance value with it open, then you will know on which side of the standby switch to look (rectifier side).

If that checks out put just the rectifier tube in and power it up. Use the bulb limiter if you want to be extra careful. Carfefully measure the voltages on the pins, AC on 6 and 4, DC on 8 and 2, and see what you get.

Ok Great I will do this. Just to be clear, closing the standby means "Not-play mode" and opening the standby would be "play mode"?


Thanks for your patience and help!

Ian

[martin manning]

Just to be clear, closing the standby means "Not-play mode" and opening the standby would be "play mode"?

No, just the opposite... a "closed" switch has the contacts connected together, "open" is open circuit.

[showsii]

Just to be clear, closing the standby means "Not-play mode" and opening the standby would be "play mode"?

No, just the opposite... a "closed" switch has the contacts connected together, "open" is open circuit.

Ok great.

QUESTION!

So on the tree that i connect my heaters too to the string of heaters going to the tube, they are a common solder joint!

This is not right correct? shouldn't the two separate heater lines should be isolated from each other?

Ian

[martin manning]

Look at the layout- all the filaments are in parallel (like rungs on a ladder). Pins 4 and 5 on the EL84's go to oposite sides, and pins 9 and 4/5 on the 12AX7's go to opposite sides. With one side of the PT filament winding disconnected you should measure infinite resistance from one side to the other with the tubes out. It's a good idea to use two different colors of wire for the filament wiring ;^)

[Structo]

I can't tell from looking at it but are the heater wires away from ground on this small terminal strip?

[img:388:447]https://lh5.googleusercontent.com/-RZ-1 ... 0Wreck.JPG[/img]

And to back track just a bit, when somebody says check the continuity, it means you are checking the conductivity of a circuit or wire from point A to point B.

So you would check all your grounds by clipping your black probe back near the AC power cable entrance (IEC)

Then probe with the red probe to various ground points. Some meters have a dedicated continuity checker that beeps when you complete the circuit.

With grounds you should use the ohmmeter because you want to make sure you don't have any resistance between ground points as this will cause ground loops and hum.

No offense to anybody and certainly not to Ken Fischer but that heater wiring has always bugged me.
The lazy twisting and loops just doesn't look like good lead dress to me.

Showsii, what gauge wire is that stuff on the heaters and the rest of the amp?

Do you live here in the states?

[showsii]

I can't tell from looking at it but are the heater wires away from ground on this small terminal strip?

[img:388:447]https://lh5.googleusercontent.com/-RZ-1 ... 0Wreck.JPG[/img]

And to back track just a bit, when somebody says check the continuity, it means you are checking the conductivity of a circuit or wire from point A to point B.

So you would check all your grounds by clipping your black probe back near the AC power cable entrance (IEC)

Then probe with the red probe to various ground points. Some meters have a dedicated continuity checker that beeps when you complete the circuit.

With grounds you should use the ohmmeter because you want to make sure you don't have any resistance between ground points as this will cause ground loops and hum.

No offense to anybody and certainly not to Ken Fischer but that heater wiring has always bugged me.
The lazy twisting and loops just doesn't look like good lead dress to me.

Showsii, what gauge wire is that stuff on the heaters and the rest of the amp?

Do you live here in the states?

Thanks for all of this! I will do this and check everything like you said.

I have to go get some more fuses before I can check my Rec voltages so I will report back tomorrow with that data.



I do live in the states!


I used 18 gauge on the heaters, and pretty much 20 gauge on everything else. I only used 18 and 20 gauge all over the amp.


Ian

[showsii]

Yss, reconnect the filament circuit, correct the B+ connection to the rectifier tube (get it from pin 8, not pin 2), and check that you have the high voltage and the filament wired correctly from the PT.

Make sure that the caps are drained, which you can do by closing the standby so the bleeder resistor is connected to all of the filters. Check the voltage at the standby switch to confirm that it is zero. Then, measure resistance to ground from rectifier pin 8 with the standby switch closed, and then open, with no tubes installed. You should see tens of thousands of ohms either way, and it will not be stable since your meter will be charging the filter caps. If you get a small resistance value with it open, then you will know on which side of the standby switch to look (rectifier side).




If that checks out put just the rectifier tube in and power it up. Use the bulb limiter if you want to be extra careful. Carfefully measure the voltages on the pins, AC on 6 and 4, DC on 8 and 2, and see what you get.

Ok, So I have my voltages for my rectifier

Pin
8-300v dc
2-300v dc

6- 213 Vac
4-213 Vac

I think I might have found the problem earlier. My heater wires were connected to the same terminal at the terminal strip before the string of heater wires. I am going to proceed now with regular voltage checks.

Any objections?


Ian

[martin manning]

I think I might have found the problem earlier. My heater wires were connected to the same terminal at the terminal strip before the string of heater wires. I am going to proceed now with regular voltage checks.

Any objections?

Ian

That would certainly explain the high current draw. I think you are good to move on- Have you closed the standby switch (play mode) with the rectifier tube in and power on? You should see essentially constant voltage on all the power supply nodes (B+ 2, 3, 4, 5). If so, I think you can install the rest of the tubes and try it.

[badtweed]

Ok, So I have my voltages for my rectifier

Pin
8-300v dc
2-300v dc

6- 213 Vac
4-213 Vac

I think I might have found the problem earlier. My heater wires were connected to the same terminal at the terminal strip before the string of heater wires. I am going to proceed now with regular voltage checks.

Any objections?


Ian

Congratulations on locating what is likely the source of your problem. Connecting the secondaries together in that fashion is what I would call a major oversight. I am scratching my head wondering how you had been lucky enough to build 2 of these amps prior to this one without a similar
unhappy event.

Not meaning to be unkind but this is a good illustration of how wrong a build can go when novices attempt to build using a paint by numbers approach. I strongly encourage anyone wanting to get into tube amplifier building to at least have a basic understanding of electronics in order to avoid similar and potentially lethal incidents.

Ok, nuff said, I will get off my whiny little soapbox.

You have got a lot of great help from Martin but there is only so much folks can do to guide you along. You can always rebuild an amp if you destroy components, but you cannot build another you so please be careful and double check your work.

[showsii]

Ok, So I have my voltages for my rectifier

Pin
8-300v dc
2-300v dc

6- 213 Vac
4-213 Vac

I think I might have found the problem earlier. My heater wires were connected to the same terminal at the terminal strip before the string of heater wires. I am going to proceed now with regular voltage checks.

Any objections?


Ian

Congratulations on locating what is likely the source of your problem. Connecting the secondaries together in that fashion is what I would call a major oversight. I am scratching my head wondering how you had been lucky enough to build 2 of these amps prior to this one without a similar
unhappy event.

Not meaning to be unkind but this is a good illustration of how wrong a build can go when novices attempt to build using a paint by numbers approach. I strongly encourage anyone wanting to get into tube amplifier building to at least have a basic understanding of electronics in order to avoid similar and potentially lethal incidents.

Ok, nuff said, I will get off my whiny little soapbox.

You have got a lot of great help from Martin but there is only so much folks can do to guide you along. You can always rebuild an amp if you destroy components, but you cannot build another you so please be careful and double check your work.

So the amp is running and sounds GREAT. That was definitely the problem with the heaters. It was my mistake to buy the terminal strip and not realize they were connected. I receive the criticism and understand your frustration with my lack of understanding of some basic concepts. I am beyond thankful for the willingness to help and be patient her on TAG.

I have definitely learned form this mistake and hopefully am better for it.


Thanks again

Ian

[martin manning]

Glad it's working. Do spend some time understanding some more of the concepts if you are going to keep at this. Maybe get a copy of something like Dave Hunter's Guitar Amp Handbook that explains things from a basic level. Troubleshooting is an art in itself, and a good understanding of how the circuit works is essential to being able to know what to measure, why, and what an expected vs. unexpected result is.

[showsii]

Glad it's working. Do spend some time understanding some more of the concepts if you are going to keep at this. Maybe get a copy of something like Dave Hunter's Guitar Amp Handbook that explains things from a basic level. Troubleshooting is an art in itself, and a good understanding of how the circuit works is essential to being able to know what to measure, why, and what an expected vs. unexpected result is.

Thanks Martin,

I will do that!

Ian

[ToneMerc]

I should have saved the author of this good quote I saved in my files.

Using a GZ34/5AR4? Take the B+ from pin 8, not pin 2. Pin 8 is the cathode. Pin 2 is only the filament. You are loading up the filament supply with the whole circuit and it is dying under the load.

Mark

It was contributed by Phil_S

TM

[Structo]

You are welcome.