Dead Blues Jr, let the resurrection begin

[Hfan]

ok, some of you have heard the story. This amp was powered up for about an hour with no load. Was surprised that it actually worked ok when the speaker was finally plugged in. Too good to be true, the little bugger put on a brave front but has given up the ghost. After about 4 hours of use, I started to get an audible snap crackle pop upon power up, then it worked ok for an hour or so of use. Next power up, snap crackle pop and zilch..tubes are lit but no sound.

 

From what I have heard, typical suspects are output xformer and or power tubes.

 

I know we have a few amp tinkerers here as well as our resident guru. I will tinker if I have to and with some advise I believe I'll get this done. Thought it prudent to ask for advise prior to ripping in to it.

 

My initial instinct is to power it up as is and take some preliminary test measurements for baseline comparisons unless someone tells me this could cause further damage. Maybe I can determine the root of the problem.

 

Option two is for me to just install a new pair of power tubes and re bias. I have a pair of Mullard reissues around. Not my favs but will do for troubleshooting swapping til I get good ones. Will I damage the new tubes if the culprit is the output xformer?

 

I also have an original Blues Jr output transformer on hand for troubleshooting if the upgraded Hyboer xformer is toast (hopefully not, they ain't cheap and this mod probably yeilded the biggest result of any of the other Bill M mods to my I need to learn how to troubleshoot the output transformer.

 

I may be able to get a look at the chassis this afternoon. Any advise welcome, well, good advise is preferred. I have a schematic and layout, will work on getting ones I can attach, when the kids give up my good pc, using a clunker right now.

[Hfan]

sorry for typos above, unable to use the editer on this old clunker pc

[kbp810]

Most likely just the power tubes that have failed - though it is worth taking a quick peek on the board to make sure there are no toasted looking resistors just above the power tube sockets (just in case the screen resistors might have gotten cooked)

 

I would take a quick visual inspection inside, and if all looks well try the new power tubes in there.

[Guest HRB853370]

ok, some of you have heard the story. This amp was powered up for about an hour with no load. Was surprised that it actually worked ok when the speaker was finally plugged in. Too good to be true, the little bugger put on a brave front but has given up the ghost. After about 4 hours of use, I started to get an audible snap crackle pop upon power up, then it worked ok for an hour or so of use. Next power up, snap crackle pop and zilch..tubes are lit but no sound.

 

From what I have heard, typical suspects are output xformer and or power tubes.

 

I know we have a few amp tinkerers here as well as our resident guru. I will tinker if I have to and with some advise I believe I'll get this done. Thought it prudent to ask for advise prior to ripping in to it.

 

My initial instinct is to power it up as is and take some preliminary test measurements for baseline comparisons unless someone tells me this could cause further damage. Maybe I can determine the root of the problem.

 

Option two is for me to just install a new pair of power tubes and re bias. I have a pair of Mullard reissues around. Not my favs but will do for troubleshooting swapping til I get good ones. Will I damage the new tubes if the culprit is the output xformer?

 

I also have an original Blues Jr output transformer on hand for troubleshooting if the upgraded Hyboer xformer is toast (hopefully not, they ain't cheap and this mod probably yeilded the biggest result of any of the other Bill M mods to my I need to learn how to troubleshoot the output transformer.

 

I may be able to get a look at the chassis this afternoon. Any advise welcome, well, good advise is preferred. I have a schematic and layout, will work on getting ones I can attach, when the kids give up my good pc, using a clunker right now.

 

Pete Pete Pete, you should know better than to operate an amp (any amp, solid state included) without a speaker load!!!! Shame on you but hope you get it fixed.

[DetroitBlues]

 

Pete Pete Pete, you should know better than to operate an amp (any amp, solid state included) without a speaker load!!!! Shame on you but hope you get it fixed.

 

It wasn't his fault... It was from someone messing with his amp after he left the barn...

[Kuz]

 

Pete Pete Pete, you should know better than to operate an amp (any amp, solid state included) without a speaker load!!!! Shame on you but hope you get it fixed.

 

Dude, he didn't do this on purpose. Didn't you read the previous thread he wrote on this about someone inadvertently unplugging the speaker and putting it into the reverb input jack???

 

Let's not accuse until we have the facts.

[Guest HRB853370]

 

Dude, he didn't do this on purpose. Didn't you read the previous thread he wrote on this about someone inadvertently unplugging the speaker and putting it into the reverb input jack???

 

Let's not accuse until we have the facts.

 

DUDE-I wasn't accusing him, I think Pete knew I was busting his chops, I guess I forgot the smiley face emoticon to go with it. So was the culprit identified?

[212Mavguy]

I can't add anything to what KBP said, but do keep us in the loop as things progress. i'm embarssed to say that most of my amp repair issures with components gone bad is initially diagnosed with my eyes, burnt resistor, I have two more amp rescue projects in my basement, so that is about to change in a very big way. I think that in some instances it's easier to assemble something new from scratch than to trouble shoot.

 

And on the idea of whether you ought to power up again to test, by all means do so. When I know something is starting to die in my amp I make sure it dies a hot, smoky death, again, easy to find and fix. If it's already on the way out, best to finish the job. Amps don't feel pain. If you cooked a screen resistor and it has a partial or intermittent open circuit because of it, go ahead and make sure and watch for the source of the death smoke.

 

The next words could be interpreted as hurtful, but they are not meant to be, they are only an opinion based on many, many observations...

 

I can see buying a used Blues Jr. and paying someone doing the mods, but compared with what is out now, in the best buyer's amp market the world has ever seen, there are far better ways to get tone and repairability for the buck than that road. period.

[Hfan]

 

DUDE-I wasn't accusing him, I think Pete knew I was busting his chops, I guess I forgot the smiley face emoticon to go with it. So was the culprit identified?

I suspect you actually...suspicious looking character..doesen't like baseball..proof enough..

[Hfan]

I can't add anything to what KBP said, but do keep us in the loop as things progress. i'm embarssed to say that most of my amp repair issures with components gone bad is initially diagnosed with my eyes, burnt resistor, I have two more amp rescue projects in my basement, so that is about to change in a very big way. I think that in some instances it's easier to assemble something new from scratch than to trouble shoot.

 

And on the idea of whether you ought to power up again to test, by all means do so. When I know something is starting to die in my amp I make sure it dies a hot, smoky death, again, easy to find and fix. If it's already on the way out, best to finish the job. Amps don't feel pain. If you cooked a screen resistor and it has a partial or intermittent open circuit because of it, go ahead and make sure and watch for the source of the death smoke.

 

The next words could be interpreted as hurtful, but they are not meant to be, they are only an opinion based on many, many observations...

 

I can see buying a used Blues Jr. and paying someone doing the mods, but compared with what is out now, in the best buyer's amp market the world has ever seen, there are far better ways to get tone and repairability for the buck than that road. period.

Did the mods myself and I like the amp but whatever..

[Hfan]

Ok heres the schematic, unable to get the pdf to photobucket to direct link the image. Going to havce a look now, there where no visible signs of burnt components etc last time I looked. Will poke around a little and try the power tubes..

 

http://support.fender.com/schematics/guitar_amplifiers/Blues_Junior_schematic.pdf

[DetroitBlues]

I suspect you actually...suspicious looking character..doesen't like baseball..proof enough..

 

I would of guessed just being GAS free would be suspicious enough...

[Guest HRB853370]

I suspect you actually...suspicious looking character..doesen't like baseball..proof enough..

 

Me don't like baseball? Oh come now!

[Hfan]

 

I would of guessed just being GAS free would be suspicious enough...

I even have documented proof that his state of GAS freeness is not genuine.

 

Anyway...wife and kiddies gone, crazy puppy in the yard, got the amp to my "bench". Problem is still occuring steady state which is a good thing. With original stuff still installed, tested various test points on the schematic (love the new Fender Schematics with test points). All expected Voltages low and high appeared to be present. I have high (320vdc or so) voltage at P1, P2 and P3 which is the output xformers circuit board connections and low and variable ac voltages at the xformer's conections to the speaker which I assume is normal. No obvious crispy critters evident on the PCB. Even tested the guitar and cable again in a known good amp.

 

Went to Brian's recommendation, swapped the power tubes, no help argghhh. Looked up how to test an output transformer..need a variac (aint got one) or one of those homemade light bulb socket variacs..got one of them, glazed over reading the test instructions. Figured screw it, will be easier to just swap in the original stock transformer. was about to start then thought what about the pre amp tubes? Swapped V1 (1st gain stage) and found it to be defective, problem gone. Reinstalled original V1, problem returned. Put original JJ power tubes back with the new V1, all seems ok, for how long, who knows?

 

I have more questions then answers. Would running with no load affect a pre amp tube? I had assumed from what I had learned it would not, would have cost me some time swapping the transformers in and out and then reinstalling the heyboer, can anyone say keep it simple stupid?. V1's failure just a coincidence? I honestly find it surprising that the thing works at all after all the time it had no speaker connected. It's working and I'll take that for now with fingers crossed.

[DetroitBlues]

It very well could of just been the preamp tubes time...

[Hfan]

It very well could of just been the preamp tubes time...

Possibly, I've been sitting around waiting for the power tubes or the output tranny to fail so when I finally had a failure I was like, "good, now lets get this thing back to normal one way or the other".

[kbp810]

Sounds like just a coincidence - the blunt of that strain would have been directly on the power tubes and the OT; so seems rather unlikely that they would have gone unharmed while a preamp tube (let alone V1) was sacrifriced.

 

Though from moving the tubes in and out and/or getting bumbed from taking the chassis in and out of the cab could have potentially/inadvertantly damaged the tube; all it takes is to wiggle a pin just right to create a small hairline fracture along side it running up into the tube that lets in just enough air/oxygen in to burn the tube out. Not saying that's what happened, just a potentially plausible scenario. (that and preamps have a habit of going bad just at the right time when you would least suspect them to be the culprit, those damned pesky tubes!)

 

Was the tube white at all around the top?

[Hfan]

Sounds like just a coincidence - the blunt of that strain would have been directly on the power tubes and the OT; so seems rather unlikely that they would have gone unharmed while a preamp tube (let alone V1) was sacrifriced.

 

Though from moving the tubes in and out and/or getting bumbed from taking the chassis in and out of the cab could have potentially/inadvertantly damaged the tube; all it takes is to wiggle a pin just right to create a small hairline fracture along side it running up into the tube that lets in just enough air/oxygen in to burn the tube out. Not saying that's what happened, just a potentially plausible scenario. (that and preamps have a habit of going bad just at the right time when you would least suspect them to be the culprit, those damned pesky tubes!)

 

Was the tube white at all around the top?

No Brian it looks like new and no white to be seen. I haven't had the chassis out in quite a while, maye a few years and when I did I always removed the tubes first. One nice thing about the Blues Jr is the main PWA and the tube PWA are right there when you remove the back panel no need to remove the chassis unless you need to get to the soldered / circuit traced side. I did swap out the pre amp tubes at one point before I noticed the speaker plug being in the wrong jack a week or two back.

 

Thanks for the help Brian. Care to speculate if the output tranny should be ok if it has not failed yet? I'm assuming the output tubes will need to be replaced at some point..there I go assuming again.

[Gitfiddler]

There's some wierd science going on with your Blues Jr.

 

Maybe you should rename your amp...Kenny's Dead Blues Jr.

 

[kbp810]

Sounds more and more like just a poorly timed coincidence to me

 

If the OT hasn't failed yet, it's likely good to go - the OT failure would be caused by overheating, which causes the internal windings to short out (or burn up and read open). There's usually not an in between for that condition. You also would likely be able to smell it if it had or was going bad - the smell of melted/burned resin from a toasted transformer is hard to mistake!

 

I would wager that the power tubes life may have been shortened considerably though

 

One quick after thought that should have dawned on me before... I wonder if they might have a safety/dummy load wired on the output jack (shorts to a saftey resistor when no cable is plugged in)? If so, there may have been no damage done at all.

[Hfan]

There's some wierd science going on with your Blues Jr.

 

Maybe you should rename your amp...Kenny's Dead Blues Jr.

 

Well the tough little bugger ain't dead yet, probably should be. Weird science indeed.

Sounds more and more like just a poorly timed coincidence to me

 

If the OT hasn't failed yet, it's likely good to go - the OT failure would be caused by overheating, which causes the internal windings to short out (or burn up and read open). There's usually not an in between for that condition. You also would likely be able to smell it if it had or was going bad - the smell of melted/burned resin from a toasted transformer is hard to mistake!

 

I would wager that the power tubes life may have been shortened considerably though

 

One quick after thought that should have dawned on me before... I wonder if they might have a safety/dummy load wired on the output jack (shorts to a saftey resistor when no cable is plugged in)? If so, there may have been no damage done at all.

 

From looking at the schematic doesen't appear to be any dummy resister, seems like a great idea for any amp though. Good to hear about the xformer. Maybe the Heyboer is more robust than the original? I can live with replacing the tubes if I have to but to order anything from Bill M takes a while and I am sure those x formers have gotten more expensive than when I installed it.

[212Mavguy]

Did the mods myself and I like the amp but whatever..

 

Absolutely, whatever is right for you. And the fact that you did those mods sucessfully yourself means you already know more than most guitar players as far as where your tone comes from, that deserves respect.

 

I tried to edit my post immediately after posting but for some reason got the "you don't have permission to edit" message when I got through and wanted to resubmit. What I meant to restate is the idea of buying a new BJ and doing the Bill M mods is not cost effective. But if someone got one used for a screaming deal, then that's different.

 

Not that you'd want to, but am thinking that you might enjoy a scratch or kit build. For quality and value, the Allen and Ceriatone stuff is hard to beat. And when it comes to mods, IMHO nothing beats a pure PTP, turret or eyelet board(s.) And am glad you got your amp to work just as you want, what a satisfying feeling!

[Hfan]

 

Absolutely, whatever is right for you. And the fact that you did those mods sucessfully yourself means you already know more than most guitar players as far as where your tone comes from, that deserves respect.

 

I tried to edit my post immediately after posting but for some reason got the "you don't have permission to edit" message when I got through and wanted to resubmit. What I meant to restate is the idea of buying a new BJ and doing the Bill M mods is not cost effective. But if someone got one used for a screaming deal, then that's different.

 

Not that you'd want to, but am thinking that you might enjoy a scratch or kit build. For quality and value, the Allen and Ceriatone stuff is hard to beat. And when it comes to mods, IMHO nothing beats a pure PTP, turret or eyelet board(s.) And am glad you got your amp to work just as you want, what a satisfying feeling!

No worries. I do have a KBP Reverb Delluxe and and old blackfaced Twin Reverb. I agree about the point to point designs being best for many reasons. And I agree that to buy a new amp to mod it would be a little nuts. This was a used amp E Bay buy that needed some work. I stumbled on Bill McChrome's site and every mod I did I liked it a little more and the fact that I did so much work on it makes me attached to it as well. Went so far as to remove 3 of the 5 ribbon cables and replaced them with straight wire. If time ever permits I might like to do a kit one day, nothing too hard.

[DetroitBlues]

No worries. I do have a KBP Reverb Delluxe and and old blackfaced Twin Reverb. I agree about the point to point designs being best for many reasons. And I agree that to buy a new amp to mod it would be a little nuts. This was a used amp E Bay buy that needed some work. I stumbled on Bill McChrome's site and every mod I did I liked it a little more and the fact that I did so much work on it makes me attached to it as well. Went so far as to remove 3 of the 5 ribbon cables and replaced them with straight wire. If time ever permits I might like to do a kit one day, nothing too hard.

 

You've got a real deal Fender amp and a KBP RD, but you're sweating over this sorry excuse of amp amp... I could only be so lucky...

[Guest HRB853370]

No worries. I do have a KBP Reverb Delluxe and and old blackfaced Twin Reverb. I agree about the point to point designs being best for many reasons. And I agree that to buy a new amp to mod it would be a little nuts. This was a used amp E Bay buy that needed some work. I stumbled on Bill McChrome's site and every mod I did I liked it a little more and the fact that I did so much work on it makes me attached to it as well. Went so far as to remove 3 of the 5 ribbon cables and replaced them with straight wire. If time ever permits I might like to do a kit one day, nothing too hard.

 

I need a KPB Reverb Deluxe so I can sell my sorry reissue Fender!