used a Harley Benton PA-100 Power Attenuator now my mesa boogie lone star wont power back on. help please

[Englishhobbymaker]

I was using this new attenuator for a day or so... my mesa boogie lonestar special combo 1x12 8 ohm speaker through it. it was reducing volume ok but at the lower settings it was abit jumpy involume if you had the gain or master volumes cranked abit.

suddenly when on the drive channel the amp just powered off and the red light went off... there was no burning smell to my memory...

I changed the fuse, then changed the V1 pre amp valves with the other pre amp valves in the amp.

The power valves x4 were all changed a month ago and the rectifier too...

I am feeling pretty annoyed by this , as the sales rep said yes no issue it will be fine for my mesa boogie model amp.

I get the feeling that either something small has blown like a diode or maybe at worst the transformer ...

There is a amp tech living near me who has good experience and good rates but I understand a transformer is going to set me back atleast 100-250 even if its refurbished and salvaged.

Please advise me thanks

 

[Englishhobbymaker]

it power off and died when I had the amp on the drive channel and switched the settings between 5 and 30 watts and then put the master / output volume up on the mesa as well as gain and treble...

I feel some what foolish as the amp itself has the master volume and output volume and I should have been happy with that and just settle on using my champ clone for good bedroom practice and sound....

I really felt the attenuator would enable me to crank the amp and have low levels. ... even then the volume level when attenuating the volume to be way lower it jumped really suddenly up with unsmooth volume increase as I turn the attenuator knob a mm!

any best guesses or advice? I understand that it really needs a good tech to check it and diagnose but just wonder if any have knowledge on this

thanks

 

[Alex_C]

Does it have an internal fuse? I had a Laney GH50 that had an internal fuse, if I remember correctly it was there to protect the power amp section.

 

[Englishhobbymaker]

i will google it. thanks for that input

 

[2L man]

When attenuator make volume/decibels lower while producing more power there come increased stress for amplifier and amp can break.

Most likely one of four new power tubes did fail if they are used only one month.

Tubes follow "bathtub reliability" which simplifying mean that if they pass about ten hours normal use (or one hour full power playing) they have higher possibility to function few hundred hours of normal use in guitar amp. New tubes full power use can stress amp and tubes so that failure rate stay higher until tubes weaken after ten or so sessions.

High Voltage fuse is what often "burn" when tube fails and sometimes it is installed inside because failed tube can burn also Screen resistor which "amp tech" check. Basic checks are not difficult to DIY if you get a digital multimeter

 

[codamedia]

Does it have an internal fuse? I had a Laney GH50 that had an internal fuse, if I remember correctly it was there to protect the power amp section.

i will google it. thanks for that input

An HT fuse (different purpose than a main fuse) is often internal. The most common cause of that to blow (that I've encountered) is a failing/failed power tube but I'm sure a qualified tech could list a variety of possible problems.

If the amp has one and it's blown, replace it with the same spec of fuse. It is quite possible your amp has always had a weak spot... you just never had it cranked up enough to expose it. Attenuators are not to blame (unless is has design flaws or is faulty itself)... they just expose weakness as you make your amp work harder.

 

[Festofish]

I would toss that attenuator. Hopefully it’s an internal fuse. I’ve used the JHS amp top box as an attend it never gave me problems. I think it’s just a volume knob but it works. I hope your amp can be fixed simply and cheaply.

 

[jhundt]

I would toss that attenuator. Hopefully it’s an internal fuse. I’ve used the JHS amp top box as an attend it never gave me problems. I think it’s just a volume knob but it works. I hope your amp can be fixed simply and cheaply.

Sure, throw away a piece of equipment without even trying to find out whether it played any part in the failure of the other piece of equipment. Why not just throw away the piece that failed? Or just discard the both of them!

 

[johnb]

Check the rectifier tube. I had bad luck with a JJ 5AR4/GZ34.

 

[Festofish]

Sure, throw away a piece of equipment without even trying to find out whether it played any part in the failure of the other piece of equipment. Why not just throw away the piece that failed? Or just discard the both of them!

I would start at the start. Is it plugged in? Are all the plugs snug? This is what I do even after 30+. I was being a bit flippant about throwing it away.

 

[Englishhobbymaker]

When attenuator make volume/decibels lower while producing more power there come increased stress for amplifier and amp can break.

Most likely one of four new power tubes did fail if they are used only one month.

Tubes follow "bathtub reliability" which simplifying mean that if they pass about ten hours normal use (or one hour full power playing) they have higher possibility to function few hundred hours of normal use in guitar amp. New tubes full power use can stress amp and tubes so that failure rate stay higher until tubes weaken after ten or so sessions.

High Voltage fuse is what often "burn" when tube fails and sometimes it is installed inside because failed tube can burn also Screen resistor which "amp tech" check. Basic checks are not difficult to DIY if you get a digital multimeter

thanks for that. that rings a bell about the new tubes either failing early on or lasting for a long time . I will try my spare set of el84s... I am no expert but last time my power tube failed the fuse blew with it. ( the outside fuse showing ) I replaced it this 2nd time and no luck. I will try the power tubes any way. but I read that on some other forum some one said if the pilot light is not even lighting it is probably something different like transformer or something near the pilot light area. who knows. but thanks for your input and I will update once i test it as you said.

 

[Englishhobbymaker]

An HT fuse (different purpose than a main fuse) is often internal. The most common cause of that to blow (that I've encountered) is a failing/failed power tube but I'm sure a qualified tech could list a variety of possible problems.

If the amp has one and it's blown, replace it with the same spec of fuse. It is quite possible your amp has always had a weak spot... you just never had it cranked up enough to expose it. Attenuators are not to blame (unless is has design flaws or is faulty itself)... they just expose weakness as you make your amp work harder.

I am tempted to get a duffer stick and try look inside the amp. but my small bench at the moment is full of telecaster stuff im making slowly , I have a multimetre and other basic electrical tools, just i worried about the caps blasting me if i dont discharge them all well.

thats interesting about the weak spot. this amp is 17 nearly 20 years old and never had a service from new. maybe its needing it for a long time overdue,

 

[Englishhobbymaker]

I would toss that attenuator. Hopefully it’s an internal fuse. I’ve used the JHS amp top box as an attend it never gave me problems. I think it’s just a volume knob but it works. I hope your amp can be fixed simply and cheaply.

i was feeling like smashing the thing up haha , but I will likely return it and get my 58 pounds back along with a aby pedal i dont like.

 

[Englishhobbymaker]

Check the rectifier tube. I had bad luck with a JJ 5AR4/GZ34.

good point , i heard they fail alot in this mesa model. but would that mean the lights dont even power on at power on?

 

[Nicko_Lps]

I really felt the attenuator would enable me to crank the amp and have low levels. ... even then the volume level when attenuating the volume to be way lower it jumped really suddenly up with unsmooth volume increase as I turn the attenuator knob a mm!

any best guesses or advice? I understand that it really needs a good tech to check it and diagnose but just wonder if any have knowledge on this

A while ago people started writing in forums ATTENUATORS RUIN OUR AMPS, we finally came to the realistic conclusion that is not the attenuator to blame, its ourselves for cranking that thing up and expect it to last.

While it is infuriating, imagine running your car MAX speed/rpm all the time... Would break down for sure.

Tube amps get old and still work because we cant crank them

You can get an attenuator but not crank the amp all the way down, you will wear out the tubes really fast plus nowadays tubes are nothing like the old US/UK made ones.

but would that mean the lights dont even power on at power on?

If its only the rectifier tube that failed, the amp would power on, it would have LED lights and switching, it would have filament in your tubes but when you get off standby mode, nothing would work.

Your rectifier tube supplies only the high voltage, the rest low voltage power for relays/bulb/LED will still be there.

You said your amp is 17 years old and never serviced, that includes never changed tubes?

 

[gimmeatele]

i was feeling like smashing the thing up haha , but I will likely return it and get my 58 pounds back along with a aby pedal i dont like.

I have used this same attenuator for a few years with all three of my tube amps with no problems, don't dismiss this as the sole cause of the problem

 

[Englishhobbymaker]

A while ago people started writing in forums ATTENUATORS RUIN OUR AMPS, we finally came to the realistic conclusion that is not the attenuator to blame, its ourselves for cranking that thing up and expect it to last.

While it is infuriating, imagine running your car MAX speed/rpm all the time... Would break down for sure.

Tube amps get old and still work because we cant crank them

You can get an attenuator but not crank the amp all the way down, you will wear out the tubes really fast plus nowadays tubes are nothing like the old US/UK made ones.



If its only the rectifier tube that failed, the amp would power on, it would have LED lights and switching, it would have filament in your tubes but when you get off standby mode, nothing would work.

Your rectifier tube supplies only the high voltage, the rest low voltage power for relays/bulb/LED will still be there.

You said your amp is 17 years old and never serviced, that includes never changed tubes?

I changed one pair of power tube once in those 17 years and its had light use as an amp. I literally played it cranked with the rectifier for two days one hour or so each at most. The 2nd day I put it on the mesa boogie lone star drive channel and put the drive and gain up then the master and output volume too.... the tone was really good for 2 minutes then it just suddenly fizzed out and powered off over 2 seconds

 

[Englishhobbymaker]

I have used this same attenuator for a few years with all three of my tube amps with no problems, don't dismiss this as the sole cause of the problem

ok thanks , I think it was definately something a weak point on the drive channel when i cranked the drive and most of the knobs high for 2 minutes. then it just died aha..

 

[Englishhobbymaker]

would it be fair to ask for a refund for brand new tubes i purchased from a tube dealer if it does prove to be a tube failure? or is it just what comes with this territory of valves amps

 

[jhundt]

I would start at the start. Is it plugged in? Are all the plugs snug? This is what I do even after 30+. I was being a bit flippant about throwing it away.

It's cool, flippant is acceptable! I took you too seriously, my apologies.