Why is the fuse blew out?

[psychepool]

I'm making an Bogner XTC styled amplifier.

Making it with turret board.
The power amplifier including the PI is done, so I installed a jack in front of the PI input for testing and turned on the power.

Waited for a while and the tubes dosen't heated.
So I checked the amplifier, and I found the fuse was blown.
I got the same result with other new fuses.
The fuse that I used is 250V 2A. (Our country uses 220V.)
It was well used in an amplifier with similar specs. (12ax7 x 4, 5881 x 2, same output translator - Hammond 1760H)

The vacuum tube has 6L6 pair and four 12ax7.
Heater wiring was connected to the all sockets, but I installed only one 12ax7 for PI and 6L6 pair for test.
The rectifier is solid state type(UF4007 x 6).

Why is the fuse blew out even standby off?
I checked all the ground connections, including power transporters.
Can this happen if the power transformer's heater current is low?
Is it dangerous to try a higher current fuse?

[xtian]

This is a new build, so treat it like one. Remove ALL the tubes, use a light bulb limiter, and find out if the basics are working without drawing excessive current.

[psychepool]

This is a new build, so treat it like one. Remove ALL the tubes, use a light bulb limiter, and find out if the basics are working without drawing excessive current.

What exactly is the light bulb limiter used for?
I searched it with google but I didn't really understand the purpose and how to use.
Can you tell me briefly?

And I found that the two main lines of AC power in the home had their respective roles.(Hot, Neutral)
I turn it on and off with only one of the two lines at PT primary.
Can the direction of this also be a cause?

[Stevem]

I would remove the output tubes and see if a 1 amp fast blow type fuse holds, as it should do fine since your on 220 vac, if not you have something wired wrong before the first filter section in all likelihood, or a bad diode.

A amp that could run on 120 vac with its normal 2 amp slow blow fuse should be just fine with a 1.5 amp slow blow type.

Also you should not really need 6 UF4007 diodes as in a 60s Fender amp , two in series on each PT leg will be fine.

[psychepool]

I would remove the output tubes and see if a 1 amp fast blow type fuse holds, as it should do fine since your on 220 vac, if not you have something wired wrong before the first filter section in all likelihood, or a bad diode.

A amp that could run on 120 vac with its normal 2 amp slow blow fuse should be just fine with a 1.5 amp slow blow type.

Also you should not really need 6 UF4007 diodes as in a 60s Fender amp , two in series on each PT leg will be fine.

I removed all the tubes and turned on the power.
The results were the same.

Is the number of diodes too much a problem? I used six when I made a similar specification amplifier, but it did not matter.
First, I will reduce the number of diodes and tell you the results. Thank you for your reply.

[pdf64]

There's a big problem somewhere. Unrelated to the number of diodes
To avoid causing further damage to your amp, it would be best to build and use a light bulb limiter. It is the most valuable item of equipment for any amp repairer / builder.
Don't keep repeatedly 'drop testing' your amp, eg until it catches fire or something.

This is a new build, so treat it like one. Remove ALL the tubes, use a light bulb limiter, and find out if the basics are working without drawing excessive current.

What exactly is the light bulb limiter used for?
I searched it with google but I didn't really understand the purpose and how to use.
Can you tell me briefly?...

See the sticky thread in the section at the top of the forum in which you have just started this thread https://ampgarage.com/forum/viewtopic.php?f=6&t=20341
I suggest that you read through that and then raise any queries you might have.

[norburybrook]

I would suspect you have a faulty diode. I had this happen to me once and the effect was blown fuses. I agree about the light bulb limiter it's a simple,cheap thing to make and will tell you immediately if you have a short etc.


M

[psychepool]

There's a big problem somewhere. Unrelated to the number of diodes
To avoid causing further damage to your amp, it would be best to build and use a light bulb limiter. It is the most valuable item of equipment for any amp repairer / builder.
Don't keep repeatedly 'drop testing' your amp, eg until it catches fire or something.

This is a new build, so treat it like one. Remove ALL the tubes, use a light bulb limiter, and find out if the basics are working without drawing excessive current.

What exactly is the light bulb limiter used for?
I searched it with google but I didn't really understand the purpose and how to use.
Can you tell me briefly?...

See the sticky thread in the section at the top of the forum in which you have just started this thread https://ampgarage.com/forum/viewtopic.php?f=6&t=20341
I suggest that you read through that and then raise any queries you might have.

I will proceed with caution. Thank you for your reply.

[psychepool]

I would suspect you have a faulty diode. I had this happen to me once and the effect was blown fuses. I agree about the light bulb limiter it's a simple,cheap thing to make and will tell you immediately if you have a short etc.


M

I am also considering diode replacement.
The diode I bought this time was not bought at the place where I usually bought it, so it was a bit suspicious.
I will have to reduce the number to four while replacing with a new one.
Thanks!

[pompeiisneaks]

One of your questions was 'how does the light bulb limiter work?'

It effectively becomes a current limiting 'resistor' if you will on the same line as the amp. If you power on the amp and it has no issues, it will glow slightly bright for a second or two with inrush current then dim down or go off, depending.

The problem it helps resolve is that if the amp tries pulling too much current the bulb lights up very brightly and stays there, it's pulling a lot of current and the bulb is keeping it under control.

You don't want to 'run' an amp on the limiter, just use it long enough to test the circuit.

I found that out the hard way once when I left my working amp on one and it didn't behave well, because it couldn't get enough current to run hehe

~Phil

[psychepool]

One of your questions was 'how does the light bulb limiter work?'

It effectively becomes a current limiting 'resistor' if you will on the same line as the amp. If you power on the amp and it has no issues, it will glow slightly bright for a second or two with inrush current then dim down or go off, depending.

The problem it helps resolve is that if the amp tries pulling too much current the bulb lights up very brightly and stays there, it's pulling a lot of current and the bulb is keeping it under control.

You don't want to 'run' an amp on the limiter, just use it long enough to test the circuit.

I found that out the hard way once when I left my working amp on one and it didn't behave well, because it couldn't get enough current to run hehe

~Phil

Thanks for the answer! Now I understand the usage.
I need to find parts for make it. Which bulb specifications should I use? Anything that works at 220VAC is it okay?

[pompeiisneaks]

I think it depends on the wattage of the amplifier, you want it to be near or more than the amp, usually a 100W is good, for most cases, but that's what I got. It does need to be an incandescent bulb, not an LED one, as the filament acts as the current limiter. LED's don't do that.

~Phil

[Stevem]

Hey gang , my comment on the diodes was in regards to Fenders use of them and in specific the rating on those diodes which called for the usage of 3 on each leg.
I was not inferring that the OP using 3 diodes was or could be part of his blowing fuse issue thank you!

In regards to your blowing fuse issue , if you see your pilot lamp flash on for a second before the fuse blows then your issue is likely on D.C. Voltage side of the amp, not the AC voltage filament side of the amp.

[xtian]

I think it depends on the wattage of the amplifier, you want it to be near or more than the amp, usually a 100W is good, for most cases, but that's what I got. It does need to be an incandescent bulb, not an LED one, as the filament acts as the current limiter. LED's don't do that.

~Phil

If you use a bulb rated "at or near" the total power consumption of your amp, it will not do very much to help you avoid burning things up. I use a 40w bulb (120vAC). Will all tubes removed from a healthy amp, this bulb flashes briefly at power up as the reservoir caps fill, then glows just bright enough to see during operation.

[pompeiisneaks]

I think it depends on the wattage of the amplifier, you want it to be near or more than the amp, usually a 100W is good, for most cases, but that's what I got. It does need to be an incandescent bulb, not an LED one, as the filament acts as the current limiter. LED's don't do that.

~Phil

If you use a bulb rated "at or near" the total power consumption of your amp, it will not do very much to help you avoid burning things up. I use a 40w bulb (120vAC). Will all tubes removed from a healthy amp, this bulb flashes briefly at power up as the reservoir caps fill, then glows just bright enough to see during operation.

Odd this may just be my misunderstanding then, but from what I recall someone saying was that they used a 200W bulb to ensure none of the amps they worked on would be impacted. I.e. the wattage of the bulb should be at or over the wattage of the max power of the amp, no? Did I get my wires crossed?

~Phil