Got a brand new Toy!

Lmao well...the Powerbrake is awesome! But uh, The SLX had an issue! Impedance was matched completely ( 16ohm input to 16 ohm output) , brand new speaker cables too. Had the amp volume on 10, pushing the power tubes, powerbrake at 50%, clicked it one step higher and POOF! Blew the Mains fuse and the left power tube kinda smells sizzled, looking at the top it certainly looks blown and milky on the inside. I had biased and changed these tubes last February but that means absolutely nothing, easily couldve been bad20210206_114631.jpg
20210206_113907.jpg
 
Mitch Pearrow SJMP said:
Congrats @steveb63 is a truly amazing friend I have been gifted by my brother a couple of times now as well!!
Enjoy that baby and let the Marshall roar be tamed a smidge
Cheers
Click to expand...
He is absolutely awesome! Helped me out tremendously on this deal!

Ok looks like we gotta culprit here. Heard the POOF! and this guy is clearly blown. Luckily i gotta brand new set right here lol20210206_115448.jpg
 
Clockworkmike said:
He is absolutely awesome! Helped me out tremendously on this deal!

Ok looks like we gotta culprit here. Heard the POOF! and this guy is clearly blown. Luckily i gotta brand new set right here lolView attachment 58197
Click to expand...
Before you replace it, you should determine exactly why it blew. It may not be just a spent tube, but an underlying issue that caused this to fry, and will make the next tube blow also. Maybe @ivan H , @67plexi @syscokid @Amp Mad Scientist @CabanaBoy and some others can tell you where to look
 
Clockworkmike said:
He is absolutely awesome! Helped me out tremendously on this deal!
Ok looks like we gotta culprit here. Heard the POOF! and this guy is clearly blown. Luckily i gotta brand new set right here lolView attachment 58197
Click to expand...

Blowing fuses is frequently speaker related...or bias related.
Inspect the tube sockets for burn marks, very closely.
Test screen resistors, cathode path, test bias resistors, test bias voltage.
Before the tubes are installed.
This will be tested with the standby set to "warm-up."
Test PI coupling caps, this is done with standby turned to "operate."
Before the tubes are installed.

Test speaker wiring, speaker jacks, speaker cables, measure speaker cab resistance.

Make all the tests before installing the tubes.
Correct any problems first. Install the tubes last.

Test Procedure:
If you need test procedures we will write them for you.
 
Amp Mad Scientist said:
Inspect the tube sockets for burn marks, very closely.
Test screen resistors, cathode path, test bias resistors, test bias voltage.
Before the tubes are installed.
This will be tested with the standby set to "warm-up."
Test PI coupling caps, this is done with standby turned to "operate."
Before the tubes are installed.

Test speaker wiring, speaker jacks, speaker cables, measure speaker cab resistance.

Make all the tests before installing the tubes.
Correct any problems first. Install the tubes last.

Test Procedure:
If you need test procedures we will write them for you.
Click to expand...
I appreciate that sir, ill start checking immediately. Unfortunately i gotta order the T3 mains fuses, no one anywhere remotely close by has any and itll be until at least the 13th before i can get them. Problems of rural living
 
Amp Mad Scientist said:
Blowing fuses is frequently speaker related...or bias related.
Inspect the tube sockets for burn marks, very closely.
Test screen resistors, cathode path, test bias resistors, test bias voltage.
Before the tubes are installed.
This will be tested with the standby set to "warm-up."
Test PI coupling caps, this is done with standby turned to "operate."
Before the tubes are installed.

Test speaker wiring, speaker jacks, speaker cables, measure speaker cab resistance.

Make all the tests before installing the tubes.
Correct any problems first. Install the tubes last.

Test Procedure:
If you need test procedures we will write them for you.
Click to expand...
The left tube socket has some slight burn marks
 
Oh man

I swear the attenuator ran o.k. on my JTM45, tested it before shipping.

If you think it's the attenuator, be happy to take it back. Just bums me out you had problems the first day.

Bummer, I'll look through my parts, if I have one of those fuses I will post it to you today, should get it Mon or Tues.

Get back to you in a couple, be right back.
 
Clockworkmike said:
The left tube socket has some slight burn marks
Click to expand...
The socket must be replaced.
Once a socket is burned, it cannot be cleaned.
The screen resistor may be also suspect.

Arcing on tube sockets is caused by one thing: impedance mismatch.

A mismatch can be a bad connection in a speaker cable, a bad jack that loses good contact, or the speakers possibly wired wrong.
Like example
4 ohm cabinet hooked up to 16 ohm amp. That will make the sockets arc and burn.

The socket must be replaced yes, but the source of impedance mismatch must be identified before playing the rig again.
If the mismatch is not corrected, the same thing will happen again.
 
Amp Mad Scientist said:
The socket must be replaced.
Once a socket is burned, it cannot be cleaned.
The screen resistor may be also suspect.

Arcing on tube sockets is caused by one thing: impedance mismatch.

A mismatch can be a bad connection in a speaker cable, a bad jack that loses good contact, or the speakers possibly wired wrong.
Like example
4 ohm cabinet hooked up to 16 ohm amp. That will make the sockets arc and burn.

The socket must be replaced yes, but the source of impedance mismatch must be identified before playing the rig again.
If the mismatch is not corrected, the same thing will happen again.
Click to expand...
AMS, I'm hoping that attenuator isn't the culprit?

Was working fine the night before I shipped it out.

@Clockworkmike is a sharp guy, I'm sure he had the connections and ohmage correct.

Man, I'm sorry Mike.
 
steveb63 said:
AMS, I'm hoping that attenuator isn't the culprit?

Was working fine the night before I shipped it out.

@Clockworkmike is a sharp guy, I'm sure he had the connections and ohmage correct.

Man, I'm sorry Mike.
Click to expand...

We could measure the attenuator just like everything else.
But when you measure you're probably going to find something that's causing it.

It can be a bad speaker cable or anything in the chain.

If all the parts are working right, the attenuator would normally not hurt anything.
 
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