Silly Question: Can an 8 Ohm Speaker on a 16 Ohm Output of a TubeAmp, Blow out the Main Fuse?

This is on an Ampeg VT-60 amp. Here is the schematic:


https://ampeg.com/support/files/Sche...SCHEMATICS.pdf


It was the main AC fuse F1, a 2.5 Amp Slow-Blow fuse, that was blown open.

Then I noticed the single 12" 8 Ohm speaker, was incorrectly hooked
up to the 16 Ohm output. Was this possibly the cause of the blown
fuse?

Some people on the internet, feel that with tube guitar amps, the
impedance of the speaker is not as critical as it is with solid-state
amps, and that the main danger is to have a no-load condition (an open).

Paul wrote:
==========
> This is on an Ampeg VT-60 amp. Here is the schematic:
>
> https://ampeg.com/support/files/Sche...SCHEMATICS.pdf
>
> It was the main AC fuse F1, a 2.5 Amp Slow-Blow fuse, that was blown open.
>
> Then I noticed the single 12" 8 Ohm speaker, was incorrectly hooked
> up to the 16 Ohm output. Was this possibly the cause of the blown
> fuse?
>
** Wot an idiotic question.

Do some investigations FFS.


...... Phil

On 1/15/2021 12:29 AM, wrote:
> Paul wrote:
> ==========
>> This is on an Ampeg VT-60 amp. Here is the schematic:
>>
>> https://ampeg.com/support/files/Sche...SCHEMATICS.pdf
>>
>> It was the main AC fuse F1, a 2.5 Amp Slow-Blow fuse, that was blown open.
>>
>> Then I noticed the single 12" 8 Ohm speaker, was incorrectly hooked
>> up to the 16 Ohm output. Was this possibly the cause of the blown
>> fuse?
>>
> ** Wot an idiotic question.

Wot an idiotic answer!

>
> Do some investigations FFS.
>
>

Go change your diapers, FFS!

On Friday, January 15, 2021 at 1:06:13 AM UTC-5, Paul wrote:
> This is on an Ampeg VT-60 amp. Here is the schematic:
>
>
> https://ampeg.com/support/files/Sche...SCHEMATICS.pdf
>
>
> It was the main AC fuse F1, a 2.5 Amp Slow-Blow fuse, that was blown open..
>
> Then I noticed the single 12" 8 Ohm speaker, was incorrectly hooked
> up to the 16 Ohm output. Was this possibly the cause of the blown
> fuse?
>
> Some people on the internet, feel that with tube guitar amps, the
> impedance of the speaker is not as critical as it is with solid-state
> amps, and that the main danger is to have a no-load condition (an open).
_______

According to some of the 'experts' on here, those back side labels for impedance are "meaningless". So you can suppposedly mix and match if you like. I suppose those guys also put 50psi air in their tires - even if their vehicle placard calls for 33-35.

I choose to follow what the label says. I prefer higher impedance speakers anyway, even if 2-4ohm is the trend now for home speakers.

On 1/15/2021 6:43 AM, Chris K-Man wrote:
> It was the main AC fuse F1, a 2.5 Amp Slow-Blow fuse, that was blown open.
>
> Then I noticed the single 12" 8 Ohm speaker, was incorrectly hooked
> up to the 16 Ohm output. Was this possibly the cause of the blown
> fuse?

Highly unlikely, but you should connect the speaker to the 8 Ohm output
and then figure out why the fuse blew.

Did you replace the fuse and the replacement blew either instantly or in
a short time? If so, figure out what's causing it. It could be a shorted
diode in the power supply, a short in the power transformer, or
something in the amplifier circuitry drawing too much current.

If this was a one-off blown fuse, you replaced it, and it hasn't blown
yet, then just play on.

--
For a good time, call http://mikeriversaudio.wordpress.com

Theckmah pinched off message
...

> According to some of the 'experts' on here,

According the the village idiot "on here", Theckmah is still retarded. He
comes "on here" to remind everyone that he's still a retarded dumb****, and
proud of it! (And when he gets banned from moderated forums for being a
retarded dumb****).

> I choose to follow what the label says. I prefer higher impedance speakers
> anyway ...

Despite that fact that you don't even know what that means.

On 15/01/2021 15:40, Mike Rivers wrote:

> Highly unlikely, but you should connect the speaker to the 8 Ohm output
> and then figure out why the fuse blew.
>
> Did you replace the fuse and the replacement blew either instantly or in
> a short time? If so, figure out what's causing it. It could be a shorted
> diode in the power supply, a short in the power transformer, or
> something in the amplifier circuitry drawing too much current.
>
> If this was a one-off blown fuse, you replaced it, and it hasn't blown
> yet, then just play on.
>
I have had a problem in the past when excessive bass managed to overheat
the output transformer and/ or the mains input transformer , which blew
the main fuse.

--
Tciao for Now!

John.

On 1/15/2021 1:06 AM, Paul Dorman wrote:
> This is on an Ampeg VT-60 amp.Â* Here is the schematic:
>
>
> https://ampeg.com/support/files/Sche...SCHEMATICS.pdf
>
>
>
> It was the main AC fuse F1, a 2.5 Amp Slow-Blow fuse, that was blown open.
>
> Then I noticed the single 12" 8 Ohm speaker, was incorrectly hooked
> up to the 16 Ohm output.Â* Was this possibly the cause of the blown
> fuse?
>
That seems unlikely to me. The main power fuse is a protection for the
power supply portion of the amplifier. The output transformer isolates
the speaker from direct connection to the rest of the circuit, so it is
unlikely that an impedance mis-match would have any effect on the amp's
power supply. But, there would be an audible difference in the speaker's
sound.

> Some people on the internet, feel that with tube guitar amps, the
> impedance of the speaker is not as critical as it is with solid-state
> amps, and that the main danger is to have a no-load condition (an open).
>
This is way to generic to have much value. Whats can happen with
solid-state amps all depends on the design of their output stage. Cheap,
poorly designed amps can have many reasons to blow, just as
well-designed SS amps can have protections built in, including output
transformers.

--
best regards,

Neil

On 1/15/2021 8:40 AM, Mike Rivers wrote:
> On 1/15/2021 6:43 AM, Chris K-Man wrote:
>> It was the main AC fuse F1, a 2.5 Amp Slow-Blow fuse, that was blown
>> open.
>>
>> Then I noticed the single 12" 8 Ohm speaker, was incorrectly hooked
>> up to the 16 Ohm output. Was this possibly the cause of the blown
>> fuse?
>
> Highly unlikely, but you should connect the speaker to the 8 Ohm output
> and then figure out why the fuse blew.
>
> Did you replace the fuse and the replacement blew either instantly or in
> a short time? If so, figure out what's causing it. It could be a shorted
> diode in the power supply, a short in the power transformer, or
> something in the amplifier circuitry drawing too much current.
>
> If this was a one-off blown fuse, you replaced it, and it hasn't blown
> yet, then just play on.
>

Ok, I replaced the fuse, with no tubes installed, and
no speaker load, and I am reading a good +518 VDC, on at least
one pin, for all the tubes. And I also found a +274 VDC pad,
which I believe is connected to the +290 Volt "D" line.

The fuse is holding. My guess is perhaps there was a bad
tube, which blew out the fuse initially, and then tubes were
taken from this amp, because no one bothered to replace the fuse.

Chris K-Man wrote:
===============
>
> According to some of the 'experts' on here, those back side labels for impedance are "meaningless".

** Who the heck are they ?????

> I choose to follow what the label says.

** OK - but meaningless it ain't .

It will indicate, within a small margin of error the load impedance that gives the most clean watts.
Usually having double the number is harmless, but less powerful.
Going to half will shorten tube life or find any weak tube and make it fail.

Fact:

Many Fender *combo* amps, made in the 60 and 70s, have two speaker jacks on the back, wired in parallel.
Fender Twins Reverb and the like.

One customer of mine ( who played regularly in a local band) thought this meant there was additional power available to add an extension speaker. He was wrong and suffered very short tube life.

I only found out by seeing him playing at a gig.


....... Phil