Not Happy New Amp Day

[Robert]

How bad does it look?

I just got this used Fender Pro Jr from UPS, so I installed the tubes, powered it up and smoke started coming out of them within seconds.

I opened it up and this is what I saw -

http://lh5.ggpht.com/_kmpRYJWvkw0/TBaOcJ6StmI/AAAAAAAACCo/oBiNRDqR1qk/s800/P6146876.JPG

[duhvoodooman]

E-w-w-w-w-w, that big filter cap and around it definitely isn't looking good! Actually, the cap may just be singed--looks like it was the resistor below it that went up in smoke.

Calling Tung, calling Tung.....come in, Tung!

[Katastrophe]

Ewwwwwww. Someone call that amph a doctah!

I hope it's a cheap fix, Robert.

[bcdon]

I'm not an amph doctor, but it's just a cap and a few resistors. The real issue is what caused the blow out.. perhaps you didn't seat the tubes properly.

[duhvoodooman]

Here's a photo off Bill Machrone's site that shows how that section of the board should look. Looks to me like R32, the resistor below the 22 uf filter cap, is what let go:

http://machrone.home.comcast.net/~machrone/bjr/fullboard.jpg


I'm not an amph doctor, but it's just a cap and a few resistors. The real issue is what caused the blow out.. perhaps you didn't seat the tubes properly.
Yeah, exactly. And pray that it didn't take out the power transformer with it....

[Eric]

Here's a photo off Bill Machrone's site that shows how that section of the board should look. Looks to me like R32, the resistor below the 22 uf filter cap, is what let go:

http://machrone.home.comcast.net/~machrone/bjr/fullboard.jpg
Is that picture a modded board? It looks like there are a couple of wires -- one yellow and one blue -- that aren't in Robert's photo. Maybe those had something to do with it?

Don't know, just my uneducated observation...

[duhvoodooman]

Is that picture a modded board? It looks like there are a couple of wires -- one yellow and one blue -- that aren't in Robert's photo. Maybe those had something to do with it?
Good point! Those wires are part of one of BillM's mods for his Pro Jr. I was just trying to show what the unsinged components in that area of the board were....

BTW, here's a link to a Pro Jr. schematic:

http://www.ampwares.com/schematics/pro_jr.pdf

Looks like R32 is a 2.7 Kohm 2W power resistor that steps the B+ voltage down from 319 VDC to 294 VDC.

[sumitomo]

Robert it's not the 4th of July yet! I heard those were some bad caps but WOW! I haven't seen 'em light up like that before.Good luck with that one.Sumi:D :(

[kerc]

That's ugly.

[otaypanky]

Do you think you may have any recourse with the seller?

[wingsdad]

No way 2 know in hindsight, I s'pose, Robert...but...assuming that you know how to put tubes in correctly, could that damage have been done by the previous owner, which is why they were selling it in cyberspace, not face-to-face?

Their extortionate (isthataword?) fees aside, as bad as UPS can be (to whit: "What can Brown Do for You?"), blaming that frito-boardito on them may be a tad over-the-top. Although it is possible a solder joint cracked or connection came loose in transit, that could happen with the amp in the trunk of anyone's car hitting a bump in the road.

I think the amp was fried b4 it was packed and sent to you.

[sumitomo]

Ah Kimosabe how can I help,I saw your smoke signal.Sumi:D

[Robert]

Who knows what happened to the amp. I can't say for sure. I think I know how to put in tubes correctly, but I should have looked at them as powered up the amp. Perhaps one of the tubes are busted.

The seller already offered to take it back, but I don't want to have spent all this UPS rip off fees for nothing. They charged me over $130 just to let me have this amp, so I would rather get it repaired than to put more money in their nasty little pocketses.

[Tig]

Grrrrrrr!
At least it is repairable.

http://hackedgadgets.com/wp-content/2/_pcb4.jpg
http://www.hydropole.ch/hydropole/hydrogen/imghistory/Hindenburg.gif

[Robert]

Thanks Vood for the schematics link! I dropped it off to a repair guy this morning and he said he needed the schematics before he could go anything. Now I am crossing my fingers that the amp can be fixed without costing me a fortune.

[otaypanky]

I think you and I are being punished for something ~

or maybe out neighbors don't like our loud playing and sabotaged our amps

[tunghaichuan]

I'm not an amph doctor, but it's just a cap and a few resistors. The real issue is what caused the blow out.. perhaps you didn't seat the tubes properly.

Correct. That node is the B+ supply for the EL84 screens. The one good thing is that the resistor blew on top of the board, i.e., not on the trace side. The carbon can cause problems later on if it gets on the PCB's traces.

It is a fairly simple circuit, so any good tech should be able to fix it.

My guess based on the photos is that either one or both of the EL84's screen grids were damaged in shipping; they are not the most robust of tubes. But it is hard to say for sure as I don't have the amp in front of me. Your tech should probably check all the tubes to make sure they are good.

You will want to have the tech check R24 and R25 to make sure they aren't toasted as well. Those could be increased in size. right now they are 100 ohm. Anywhere from 470 ohms to 1.5K ohms would provide more protection for the EL84 screens.

Finally, I've heard bad things about the Illinois caps (marked "ic"). Depending on the age of the amp, you may consider having those replaced when the amp is serviced.

Sorry about your misfortunes with the amp, but hopefully it should be relatively painless to have it fixed.

[Tone2TheBone]

Noooooooo!!! :what :nope :nope :nope

[Robert]

The Gods are punishing me... perhaps because I have too many amps now?

[Tone2TheBone]

The Gods are punishing me... perhaps because I have too many amps now?

Why did it have to be the Pro Jr. though! :thwap

[bcdon]

The Gods are punishing me... perhaps because I have too many amps now?
Allow me to take some of that bad karma, you got there buddy. Please ship all amphs marked "Marshall" to Vancouver and don't you dare use UPS!! :dance

[DeanEVO_Dude]

The Gods are punishing me... perhaps because I have too many amps now?

Is that even POSSIBLE!? ;)

Cheers!

[Robert]

All is good - I got the amp back today. It sounds great!

What was the problem? I am embarrassed to say - I put the power tubes into the preamp tube sockets, and vice versa... go ahead, slap me twice :thwap :spank :spank

Live and learn...

[Eric]

Haha. Well, live and learn. At least it works now!

[Tone2TheBone]

All is good - I got the amp back today. It sounds great!

What was the problem? I am embarrassed to say - I put the power tubes into the preamp tube sockets, and vice versa... go ahead, slap me twice :thwap :spank :spank

Live and learn...

Are you serious?

:spank :spank :spank

Doh! Ya newb! :dude

[gregsguitars]

Bummer....

[sumitomo]

Glad to hear it's all good now,and that is an easy mistake to make.Your a good man to fess up to it.Sumi:D

[sunvalleylaw]

How many swedes does it take to screw in a light bulb? ;)

Just kidding, not like I know anything about installing tubes. Glad it worked out!

[duhvoodooman]

....I think I know how to put in tubes correctly....NOT!! :poke :laughingatyou

As Bugs Bunny used to say, "What a maroon!"

Only joshin' with you, RR. To err is human as they say. Just glad that it turned out to be easily fixed and is running OK for you now.

Obligatory video demo forthcoming, we trust?!?

[Robert]

I deserve all the spank and humiliation!

Just finished recording a demo on the camera, wait a day or two before it's edited and uploaded.

[duhvoodooman]

How many swedes does it take to screw in a light bulb?
Just one, but don't count on it ending up in the right socket.... :rollover

Seriously, looking forward to hearing the demo.

[marnold]

Well, if he posts a video with his underwear on his head, we'll know why.

In all seriousness, I hope that that resistor is the only thing that went bye-bye.

[kiteman]

Finally, I've heard bad things about the Illinois caps (marked "ic"). Depending on the age of the amp, you may consider having those replaced when the amp is serviced.

Sorry about your misfortunes with the amp, but hopefully it should be relatively painless to have it fixed.

You heard right tung. I got a terrific book on tube amps and the author despises ICs as they're pure garbage (in his words) and says replace all of 'em and as a result the amp will sound 10x better.

I hope all the best for you Robert.

EDIT: now that the posts are updated I had thought that Robert switched the tubes.

[Tig]

Glad to hear it's all good now,and that is an easy mistake to make.Your a good man to fess up to it.Sumi:D

I agree with Sumi. You're a good sport, Robert, and you may have just insured that the rest of us never make the same mistake. So at least something positive may come of it.

I won't ask how much $$ this amp has run you.

Oh, I almost forgot to poke fun at you...

http://techbuddha.files.wordpress.com/2008/11/vader-fail.jpg

http://lukey.miauu.info/picsahz/fail/2043-fail-camera.jpg

[duhvoodooman]

I got a terrific book on tube amps and the author despises ICs as they're pure garbage (in his words) and says replace all of 'em and as a result the amp will sound 10x better.
While he doesn't badmouth them, it's interesting to see that Bill Machrone had replaced the IC filter cap in the first filter stage of his Pro Junior in that photo I posted earlier in this thread (repeated below). He states that the two Xicon caps he substituted "....have lower ESR (equivalent series resistance) and better ripple rejection." But he left the IC caps in the 2nd and 3rd filter stages, so he must not consider them "pure garbage".

BTW, his Pro Junior is a newer version (2006) and had a 47 uf IC cap in that first filter stage (Robert's has two 22 uf IC's there). Machrone replaced it with two Xicon 47 uf's to cut the voltage ripple in half.

http://machrone.home.comcast.net/~machrone/bjr/fullboard.jpg

[Robert]

Ahh well, I have an amp for life now! :) I can never sell it and expect to get back what I paid for it!

So no, don't ask how much it has cost me so far... :cry:

[tunghaichuan]

All is good - I got the amp back today. It sounds great!

What was the problem? I am embarrassed to say - I put the power tubes into the preamp tube sockets, and vice versa... go ahead, slap me twice :thwap :spank :spank

Live and learn...


Oops :thwap

I'm glad neither the OT or PT were taken out. Live and learn I guess. :dude

[M29]

:socool :D

[Robert]

Shhhh.... already... move on people.... nothing to see here.

:spank: :munch:

[kiteman]

Shhhh.... already... move on people.... nothing to see here.

:spank: :munch:

See what? :rockya

[marnold]

To quote Red Green: "If it ain't broke, you're not trying!"

[sunvalleylaw]

I can't see nuthin'. Some kinda exxplloosion blinded me!!!

[tunghaichuan]

I can't see nuthin'. Some kinda exxplloosion blinded me!!!

That's why I were prescription safety glasses when I work on amps. I haven't had anything blow up on me yet (knocks on wood.) I did flip molten solder up in my face and missed my eyeball (was not wearing safety glasses at the time) and it made a believer out of me. I never work in my shop without my safety glasses.

[sunvalleylaw]

I have never done any amph work, but good thoughts. I always wear eye protection, for mountain biking, (and road), skiing, mowing the lawn and string trimming, cutting with the chop/table/worm drive saw, etc.