Fender Pro Junior: Problem or Normal? Help!

[jgharding]

I just bought a Pro Junior from ebay. it has been fitted into a TAD 5E3 style lacquered pine case, and has a celestion vintage century in it. Now i know these amps are supposed to be noisy, but this is just odd! There are seemingly random puffs of white noise. With the volume at zero there is constant white noise and what sounds like a very loud power cycle hum. Surely this isnt normal? You have to turn the volume up quite high before you drown it out.

Also, i havnt been playing above 3, but the power tubes are incredibly hot, i mean burn your skin hot, and there is a subtle wood heat smell coming from the amp. Could this be just because the tubes are near the wood (it does smell deliciously pine like anyway!). I heard that class A runs em hot anyway is that true?

Basically this is my first tube amp, so i dont know how hot EL84s are supposed to be. They are TAD ones. The white noise is wierd though, fluctuates strangely. Basically i just wanna know if i need to start the elongated process of returning it or if it sounds ok. if it needs a ton of repairs, then i'll just get rid. Do i need to replace those EL84s?

Thanks for you help,

[PRNDL]

With the volume at zero there is constant white noise and what sounds like a very loud power cycle hum.

It sounds like your amp is in need of basic service, which includes replacing electrolytic capacitors and tubes that have gone bad over time. One bad EL84 will cause both to run at high current, which puts out excessive heat. Although prices can vary widely, a cap job and tubes will be $150 or more.

The Pro Jr is a really cool amp with a very simple circuit. The downside is the circuit board, which makes repairs more difficult and expensive (or impossible). Given that, it's usually best to purchase these amps new.

Although I haven't seen them, it may be possible to purchase a loaded replacement board, which would include new electrolytics.
They have them for the Valve Junior: http://www.turretboards.com/

[jgharding]

In my eagerness to be advised i forgot my manners! Hello all!

This guts of the amp are about three years old, is that long enough for the caps and the like to go? I really like the tone as is so it' probably worth me getting it serviced to make it run quieter and

I assume three years is easily enough for tubes to go, though these have been replaced at some point, probably when the chassis was moved into the new cab as theyre both TAD, though i have no idea how soon after the amp was bought that it was moved! I replaced the Fender branded GT 12ax7's that were in it with some EHX ones i had in one of their valve pedals (sounds a little cleaner and brighter now) so it cant be them.

Yeah the main annoyance is just that the hissing is so loud, its best described as a soft irregular crackle. I've read a few posts and this seems to usually be related to power tubes if i've gathered correctly? They're in there pretty tight, but i think one is a bit rattly too. Confused as to what to do....

[PRNDL]

This guts of the amp are about three years old

The output tubes are your first suspect. Although tubes do generate heat, they don't get hot enough to burn the cabinet, unless they are running a ton of current.

It is possible to simply swap in a new set of tubes (or old good ones) and see if it fixes the problem. It's best to have the output tubes biased, which involves measuring the cathode voltage and current. The repair cost is a bit less expensive - about $100 or so, depending on tube costs, etc.

I'd suspect that the seller was confronted by the repair costs and may have decided to sell this one and buy a replacement (or something else) instead of getting it fixed.

Confused as to what to do....

Since you purchased this on eBay, begin by reading the original ad very carefully to see if the seller described the amp as working fine. If so, contact him and ask what the options are and what he's willing to do to correct the situation.

If you used PayPal (a great idea), check to see how much time is left to file a dispute. I believe it's two weeks after the auction ends. You don't want to miss that date.

Find an amp tech in your area to find out what's wrong and get an estimate on repair costs. Most techs have a diagnostic fee (usually about $50) that is refunded when you get the amp repaired.

The general idea is to gather information so that you can make a good decision. The options are to keep the amp or return it for a refund. Everything is negotiable. Some sellers agree to pay for full repair costs, while others offer 50%.

[jgharding]

Yeah seems like that may be the case. Just to clarify, the crackling doesnt change in volume when i turn the amp up. its there when volume is off, but doesnt rise when the volume rises, just stays constant, so when you play louder you dont notice it, it just gets anoying at bedroom volumes. Is this behaviour constant with power tube rubbishness?

Perhaps my first attempt should be to buy a pair of JJ Tesla EL84s, and slap em in to see if that fixes it. £20 for a new matched pair new online, though i assumethey wouldnt be biased in any particular manner, unless thats what 'carefully matched pair means!'. if that sorts it then there'll be no expensive bill!

thanks for all the advice so far PRNDL,

[PRNDL]

Is this behaviour constant with power tube rubbishness?

That sounds more like a power supply problem (electrolytics), although it's hard to tell.

Perhaps my first attempt should be to buy a pair of JJ Tesla EL84s, and slap em in to see if that fixes it

You may want to open and inspect the amp carefully, especially the output section. Often a bad tube will take out resistors.

Even if it does fix it, it's best to get the tubes biased. 3 years is way too short, unless they were biased hot, which is extremely common these days.

Do check with the seller to see what your options are ... many will refuse to do anything after a week or two has passed, which is plenty of time to test it.

[jgharding]

if i were to open it up what would i be looking for? to be honest i don't know if i should! i have no electronics equipment, and no real knowledge! i couldnt test component etc. myself, and im scared of touching something full of current and doing myself some damage! i think beyond changing tubes its either hassle the seller or go to repair shop...

[PRNDL]

I just wanted you to know that sticking in new tubes could work, but need to be biased. Also, sometimes bad output tubes burn a resistor or two when they go, which could cause a new tube to go bad very quickly.

I recommend notifying the seller right away and sending it to a tech for a diagnosis and estimate.

You could also try new tubes, which is somewhat risky.

[52 Bill]

As PRNDL said, replacing the output tubes may solve your problem, but it may not as well. That type of crackling noise can be caused by many things.

If you have access to another set of output tubes, try them and see if the noise stops. They don't have to be new tubes, as long as you know they are working in another amp. You just want to eliminate them from the troubleshooting process.

The Pro Junior has a non user adjustable bias circuit, that would require you to change a resistor in order to alter the bias voltage to the output tubes. So for now, don't worry about output bias.

To try and isolate the noise, try pulling the pre-amp tubes one at a time to see what section the noise is being generated in. Pull out the first 12AX7 and turn on the amp. Is the noise still there? If it is, turn off the amp and replace the tube and this time remove the driver tube. Is the noise still there?

Hope this helps.

[allmodcons]

Well,the first thing I would do with your amp is to have a fistfull of 12ax7 and el84 tubes,and try every possible combination.These amps are really picky about tubes and I have found most of the noise usually can be reduced by having the right tubes installed.And not neccesarily expensive NOS tubes either.I currently have 2 tweed Pro Jr.'s and have messed around with them a fair bit. IF you are comfortable with high voltages/soldering/multimeter use-- I would just upgrade some caps etc..Its fairly quick and easy and will not only improve the tone greatly,it'll possibly solve some troubleshooting angst. Yes,these amps run hot--all mine have been cookin' hot.

[jgharding]

There's an amp tech not too far away, so i'll get him to have a look and see what he reckons could be up. Hopefully it's not a worst case, and can be repaired just by replacing something cheap and simple. The tone is spot on with my setup, so id rather get it sorted, but i'll definately request that the seller refunds me the cost of repair, since the amp is obviously faulty and has been sold as working fine.

It seems so odd, though i know little about amp insides, i wouldve thought that the tone would be adversely affected by such an issue, but it sounds great. Just that there's an exaggeratedly loud power hum and crackle which stays constant at all volumes. I spose it's probably something to do with the power then from what's been said, as it doesnt change when the volume is off or up.

[jgharding]

I currently have 2 tweed Pro Jr.'s and have messed around with them a fair bit. IF you are comfortable with high voltages/soldering/multimeter use-- I would just upgrade some caps etc..

I'm definately not skilled with solder! i've made some incredibly bad electronics in my time, i've practically banned myself from touching an iron!

Just out of interest, how is the power hum on yours? Is it something noticabl at low volumes? at the moment its too loud for me to use as a recording amp (combined with the fluffy noise) as the hum would be too prominent in parts with quiet playing, even at 2 or so on the volume.

[allmodcons]

The hum on my Pro Jr.s is noticeable at low volumes,although not much worse than other tube amps I have had.I do know what you mean however,since I have had that hum with some Pro Jr.'s at levels that just are too loud for "bedroom" playing,or for recording.Do you get a loud hiss as well as that hum? If you can get compensated for some of the repair cost,I would definately get an amp tech to work on it.When you get the hum/hiss/rattles to acceptable levels,this amp produces a good"Marshall-esque" overdrive that is quite addictive. I can help you identify which components to upgrade if you like.Until you get good at soldering and safety,I would just get someone to do it for you.The pc board especially doesnt tolerate excessive solder temps etc,.

[jgharding]

Update

Hi all,

I went to my tech and after a couple of hours he brought me in and seemed to have solved the problem. It was crap 12AX7's. When i first got the amp it had those Fender GT's in it, been there since it was first bought i assume, and they were really microphonic so i swapped them for some EHX's from my 2ube pedal. I forgot that i've had the pedal for an age.

We tried putting a nicer NOS Edicron (Mullard) in there. First we put it in the pre amp only: the volume and tone knob went mad (with the EHX still in the phase inverter) , the tone did nothing until the top where it went super brittle, and the volume went loud at 1, quiet and distorted at 3, and loud again above it! But there was next to no noise at all. The hum and fluttering were totally gone.

Next we swapped them. With the NOS in the inverter, the tonality was amazingly different, and the knobs responded perfectly normally. With the EHX in the pre-amp the hum was back to very loud at low volumes but the flutter noise was completely gone. Both EHX were quite microphonic too (though not as bad as the old Fender GT's!), which i hadn't noticed till my tech tested them with me.

I can only conclude it was a combination of two terrible, what worked out to be 6 year old (with moderate use), cheap tubes that had made the amp become such a heap of ****. The noisy pre amp and crazy fluttering must've been a stacking up of various interferences and microphonic episodes(!) with both those nasty old tubes, which for some reason i never even considered to be the issue. Also, one of the EHX tubes also rattled horribly whatever slot it was in. To top it all off the man gave me the NOS, no charge, and only charged me for 2 hours of time, which is beyond nice, it's actually pretty unbelievable.

If there's one thing i've learned from all this it's that in tube amps, tubes really matter!

I'll still get it overhauled soon, as the pots feel a little inconsistant as they rotate, and im sure some bits inside could do with an upgrade, but for right now i'm happy. I still have a little cabinet rattle on 6th string E-G notes specifically (both octaves, it must be some kind of resonant frequency for the 5E3 cab) but i'm gonna try a fix for that soon. I've heard owners of Victoria 20112's complain of this so i'm not too disgruntled.

I may try a Jan 5751 in the V1 Preamp, as i've heard this drops the noise significantly in pro juniors, and drops the gain about 30%. That'd be good since it's got too much volume for me at the mo, and i wouldn't mind pushing the power tubes a bit more.

Also i'll probably get some new EL84's fitted and biased just for piece of mind, but it's one step at a time!

Thanks for all the help guys, and here's my music link:

www.myspace.com/jgharding

Say hi if you're on myspace!

PS ALLMODCNS: Thanks, If you could point me towards which components are good to upgrade to improve noise etc. that'd be great. I have the schematic to take to the tech fella, so i can let him know what mods i want done!

[musicman2879]

tubes

hey there, i just bought a pro junior that was a demo at a music place. It was only 3 months old and the guy kinda cut me a deal. I just didn't see buying the Blues junior with there being a $170 difference in the two and and only 2 more knobs!! I just took the pro junior!! I got it home and within two days it just got muddy and it just sounded horrible. I started looking at the Tubes and sure enough it had 1 fender groove tube pre amp and a 1 regular fender pre amp tube, both are sovtek. I realized at least one had been changed already!!! I did alot of researching came across alot of info and i hate to tell all of the people out there that the best budget tube on the market is the Tung-Sol 12ax7. I bought a set and man it changed my amp drastically.. It so sweet now. I waited a few days and changed the Sovtek EL84's with JJ tesla el84's and wow an even bigger change in sound and man i didnt think it was possible. It sounds perfect. I have less rattling and vibration, no hiss, no crackle , no nothing. I still have some hum but i am scared to do a bias and i dont want to pay someone for something i can do!! My friend also bout a pro junior yesterday and we played them both for 30 minutes his started to sound crappy so we changed tube's he went with tung sol 12ax7 pre amp and mullard el84's but his had alot of noise so he bought a set of JJ's and man his sounds just as sweet as mine now!! The metal spring bracket that holds the el84's still makes alot of noise . Any one know how to fix this???? The best bet in helping decide what tubes is thetubestore.com check out the reviews they will help someone!!