XR600B fuse blown

[Enzo]

You're right, probably could do that. But I am a 1960s kinda guy, I believe in helping my fellow man, and in particular helping someone who wants to learn something. Not to mention helping those too timid to post. And this is the internet, so for sure we'd have someone grumbling, "He's just in it for the money." SO payment for me is seeing people cooperating and helping one another. If I've been kind to you, you can be kind to the people you encounter.. and so on it grows.

And now, from the Bellamy Brothers:

He turned (sixty)-five last Sunday
In his hair he found some gray
But he still ain't changed his lifestyle
He likes it better the old way
So he grows a little garden in the back yard by the fence
He's consuming what he's growing nowadays in self defense
He get's out there in the twilight zone
Sometimes when it just don't make no sense

He gets off on country music
Cause disco left him cold
He's got young friends into new wave
But he's just too friggin' old
And he dreams at night of Woodstock and the day John Lennon died
How the music made him happy and the silence made him cry
Yeah he thinks of John sometimes
And he has to wonder why

Chorus:
He's an old hippie and he don't know what to do
Should he hang on to the old
Should he grab on to the new
He's an old hippie...his new life is just a bust
He ain't trying to change nobody
He's just trying real hard to adjust

He was sure back in the sixties that everyone was hip
Then they sent him off to Vietnam on his senior trip
And they forced him to become a man while he was still a boy
And in each wave of tragedy he waited for the joy
Now this world may change around him
But he just can't change no more

Chorus

Well, he stays away a lot now from the parties and the clubs
And he's thinking while he's joggin' 'round
Sure is glad he quit the hard drugs
Cause him and his kind get more endangered everyday
And pretty soon the species will just up and fade away
Like the smoke from that torpedo...just up and fade away

Chorus

[SemperFiSound]

Copy all. My PayPal account isn't setup either - same reasoning.
Cheers,
Steve

[Lee Thistle]

XR600B update. I used this rig for the first time since replacing the 4 rectifier diodes. It worked perfectly all night. Re all the free advice coming down this Peavey forum. Since suceeding at my first amp fix project, I have done 5 or 6 similar projects (not all Peavey) and all forked fine. I know I'll never be a real tech guy. But just to let you know....all your free advice goes even further than your forum clients. Oh Yea, I havn't charged for any of my work either. So far it's been for just friends. I can't wait till something else breaks.....NO NO NO just kidding !

[SemperFiSound]

Excellent news Lee. Glad you found some partially hidden talent.
Send some my way, will ya? I have an old QSC acting up.

Cheers,
Steve

[Enzo]

Now THAT is funny.

I can fix Peaveys in my sleep. I fall asleep trying to fix the QSCs. Geez they are a pain in the butt.

[SemperFiSound]

Well, I haven't actually opened it up yet, but if I can't get to sleep some night, I'll know that's when it's time to start the project.

[Lee Thistle]

An old QSC ah Steve. First things first. You need to post more info so we can help you. What use does the amp get ? Church, rock band, DJ? What speaker array do you use ? What input devices and how many ? See fellas........I'm gettin' the hang of it ! LOL

ps No need to answer this Steve. I'm just having fun.

[SemperFiSound]

You forgot to mention "Welcome to the forums where if you are not careful, you just may learn something!"

Cheers!

[rmm]

Hello all,

I have the exact same head with the exact same problem. Used this head for years, on my last gig it just didn't turn on and blew a new fuse immediately.

I have narrowed it down past the transformer and tested all rectifier diodes, which tested fine. My next guess is the problem could be a bad output transistor. I am new to electronics, and though I do understand the way to check diodes I am a little unsure about testing the transistors (TO-3 style I believe). Any help would be greatly appreciated.

Thanks!
rmm

[Marty McCann]

A transistor can be tested similar to a diode; it simply has a second diode type junction, that should show a lower resistance in one direction and a higher resistance in the opposite. They can be tested for shorts in the circuit, but are best tested removed for more precise junction measurements.

You have an Emitter, a Collector, and a Base; measurements across any junction pairs should measure like a diode if good.

[rmm]

Thanks Marty, and please excuse my inexperience. In this type of transistor (SJ6357), the chassis is the collector, making the two pins base and emitter, right?

My meter, which has a diode setting, gives me a dead short between base and emitter in 6 of the 8 transistors while still in the circuit. Safe to assume these are shorted? The other two, which are at the beginning of each set, give a reading of about.52 in each direction.

Thanks!

[Marty McCann]

Thanks Marty, and please excuse my inexperience. In this type of transistor (SJ6357), the chassis is the collector, making the two pins base and emitter, right?

My meter, which has a diode setting, gives me a dead short between base and emitter in 6 of the 8 transistors while still in the circuit. Safe to assume these are shorted? The other two, which are at the beginning of each set, give a reading of about.52 in each direction.

Thanks!

That is correct the metal case is the collector. I do not have the schematic, so I do not know if there are 6 or 8 devices in the output section. The two that are not shorted may be the driver transistors, you can tell if they are because the drivers have a higher value Emitter biasing resistor, usually something like 22 Ohms versus 0.33 Ohms for the actual outputs.

If however the other two are output devices with 0.33 Ohm EBR's, then the best advice is to replace them all.

[rmm]

Thanks, yeah I do not have a schematic either but it does have 8 and they are all the same (SJ6357), which is probably a Peavey number? My local store does not have them but I'm sure I can find them somewhere online. I was just unsure in my testing abilities of these transistors, but I think you are confirming my suspicion and you do think these might be shorted and I should replace all 8.

Thanks again Marty, I appreciate the help. Any other advise or anything else you think I should try and/or check I'd appreciate that too. And again, please excuse my lack of knowledge and inexperience.

Ruben

[SemperFiSound]

Reuben,
Peavey will email you the schematics for free.
Just email [email protected] and politely request the schematics for your unit. Usually takes a day or two.

Best of luck,
Steve

[rmm]

Thanks Steve, emailing now.

Just pulled out two of the transistors and they test fine once out of the circuit, which means there is something there shorting the whole thing out? and not the transistors? I did find one resistor to show only .6 ohms where marked 1, that couldn't be it could it?

Marty is right about the different resistor on the emitter of the two at the start of each set.

Thanks
-Ruben