fender princeton 65 problem

[matty]

Hey everybody heres a little something for ya,
So my princeton 65 dsp has been acting up quite a bit lately. what happens is the amp will work normal but then after a little while there is a tiny bit of static. this static gets louder and louder and usually within 5 - 10 seconds its all static with assorted pops and crackles. The level of static is always the same regardless of what the actual volume is at. If I catch the amp when it is first starting to make the noise and just tap it ( ok ok more like hit) on the top it sometimes dies down. but usually I just seem to make it worse.

so anyways what would a likely problem be thats causing the static? bad solder joint? input jack problem? something grounding out something?

I have had this amp looked at twice already for this exact problem and do not want to spend any more money on it as the repair costs will soon cost more than what i originally paid for it (I am ok with soldering and don't really care one way or the other if the amp stops working as it is not really function per se now) . I assume since two techs have looked at it that they would have caught any bad solder joints but I could be wrong.

any help will be appreciated
Matt

[matty]

oh and its definetely not a guitar or patch cord problem as i have tried several of each out on it with the same end result ( Static noise!)

[gitpiddler]

Matt-I have a Fender UltraChorus (first yr. Ultimate chorus) 212 with exactly the same deal. Took it to dealer, who sent it off to be repaired, with not much improvement. Dealer now retired, and I've noticed that several front panel jacks are loose on the board and/or broken. I haven't gotten around to taking it to GC to let their Fender tech have at it, vehicle troubles and gas eating up resources at the moment.

[sumgai]

matty (and gitpiddler),

It's a solder joint, I guarantee it. The problem is, which one?

In cases like this, the trouble area of the circuit board can often be located by setting up the amp to work with the chassis outside of the case. Remove the chassis, position it safely, plug everything in, and play. Sometimes you don't even need to play, what you do is use a piece of wood (officially, we call it an "orange stick", but the point is, you're using an insulator, not a conductor) to prod various parts and pieces into misbehaving. If it's a bad solder joint like I suspect, merely flexing the board will cause the static to start up, you probably won't even need to play anything.

USE EXTREME CAUTION, and play it safe - always think about what you're about to do! This "over-cautious" method will save your butt, that's another thing I guarantee to be true.

Often times I can't be sure which solder joint is bad, so I employ the "shotgun" method - I reheat every joint in the area, they all get the treatment. Takes more time to do the manual portion of the job, but that's offset by spending less time troubleshooting. Not elegant at all, and you don't learn a thing, but the bottom line is, your amp is back in business, and that's why you bought the thing in the first place!

Use quality solder. If the amp is more than 2 years old, it's a sure bet that it is NOT "RoHS compliant". That means, use the old style solder (the one we've been using for nearly 90 years). RoHS compliant devices require that you use the newer lead-free solder. NEVER mix the two, it'll only end in tears.

HTH





sumgai

[gitpiddler]

I'm a little solder-gun shy any more, but I'm a little less so every time I look at my chassis sitting on top of the cabinet. However since a couple of my jacks, namely the footswitch and hi-input are in pieces, and the effect loop jacks are loose, I figure I'm better off letting a tech do it.
As for my beloved VW bus, two beautiful new cylinder heads arrived last week, correcting a mistake I made rebuilding 3 1/2 yrs. ago-ordering the wrong ones, and later finding out that the new ones have crappy hardware designed to fail. So for $1600 I believe I'll have it right (double the cost). I've already spent that much for four crappy ones since.
Off topic I know, but: if it's worth doing, it's worth doing it right the FIRST time. Good luck Matt. Thanks Sumgai, you rock.

[matty]

thanks gitpiddler and a big thanks to sumgai! this is going to be my project for the coming weekend.

[Teleblooz]

Matty,

I have exactly the same amp with exactly the same problem. While it was still under warranty, I took it to the local authorized Fender repair shop. They gave it a good once-over but didn't find anything obviously wrong. They did say that they re-seated the ribbon cable that goes from the main board to the DSP board, and the problem went away for about 3-4 months.

When it showed up again, I opened 'er up and unplugged & re-plugged that same cable, with the same result. No snap, crackle, pop for a couple of months, then it would start up again. Lather, rinse, repeat. Over time the interval between episodes seems to have gotten shorter. I've since moved on to a tube amp for my band work and keep the Princeton around for occasional use at home.

Personally, I'm thoroughly disgusted with this amp, and about ready to gut it and use the cab as an extension speaker.

[matty]

hey thanks teleblooz!
I have actually stopped using it for the most part soley because it aggravates me to no end sometimes. I checked it over numerous times but could not find any bad solder joints or the like. I even re soldered a bunch of suspicious looking joints but it still came back. looking back I think that what did fix it ( for shorts periods, maybe a couple of weeks) was the fact I did take off and re connect the ribbon cable.
for whatever reason it does seem to work. thanks all again for the help,
Matty

[Teleblooz]

UPDATE: I've decided to split the difference between keeping and $h!tcannning the beast.

When I opened it up I found that there's lots of free airspace behind the rear panel next to the power transformer, so I'm planning to wire the speaker leads to a 1/4" jack there that'll interrupt the amp/speaker connection when something is plugged in, like a headphone jack. This way I can use it as an extension speaker onstage while still having it available as an amp if I should get desperate enough to need one.