Wurlitzer 200a speakers/headphones distorted AFTER recapping amp...UPDATE

[gbkd80]

I recapped my 200A amp and preamp last night and following the job, the speakers and headphone output are completely distorted.  I read that this could potentially be output transistors that had blown.  I'm aware I could have heat-damaged something during the re-cap but I won't make assumptions.  The main reason I recapped the amp was because the AUX output was not working at all and there was a lot of noise present lately behind the notes that got more and more noticeable especially through the headphone output. 

The good news out of this is it seemed to fix the AUX output and that works now, and it's clean.  (I also noticed that the 4.7uf axial cap under the AUX wire that is tied to the 680r resistor was reading out at 7uf, which could have been part of the problem?)  At any rate, that is working well.  The speakers and headphones on the other hand not so much.  I ordered the correct replacement transistors to give that a go later on.  However...

Being that I really want to run the piano from the AUX output, but the AUX output does NOT cancel out the speakers (not sure if it's supposed to or not), could I keep the speaker output disengaged from the amp and use the AUX without damaging anything?  I'm pretty sure there is a load resistor in there on the headphone jack but I'm not sure about AUX.  Or could I plug a dummy plug into the headphone jack and use the AUX out?  I just don't want to burn anything up any worse. 

Are the speakers supposed to output sound when the AUX is plugged in anyway?  Also, I do want to mention that my wiring doesn't follow the service guide drawing exact but it's close.  It's possible I goofed up a connection; would that cause my distortion issue possibly or is it more likely I screwed something during the recap..?

EDIT: I do notice at fuller volume the AUX still has noise, just like the noise I was hearing before.  Just not completely annihilated like the speakers and headphones...

[cinnanon]

Being that I really want to run the piano from the AUX output, but the AUX output does NOT cancel out the speakers (not sure if it's supposed to or not), could I keep the speaker output disengaged from the amp and use the AUX without damaging anything?

Yes, just put a dummy plug into the Headphone out jack.

Are the speakers supposed to output sound when the AUX is plugged in anyway?

Yep, you're good.

[beginnersluke]

First thing I would do in your case is double check the polarity of your electrolytic capacitors.

Do I understand correctly that this noise was not really a problem before (just the AUX thing)?
Is the noise always there or just when you play?

My other "first thing" suggestion was going to be to check all your ground connections, but the fact that it's better on the AUX doesn't point to that. Still worth double checking though, I'd think.

[pianotuner steveo]

I second that- if it was working fine before, you may have accidentally reversed the polarity on a cap or two...

[gbkd80]

First thing I would do in your case is double check the polarity of your electrolytic capacitors.

Do I understand correctly that this noise was not really a problem before (just the AUX thing)?
Is the noise always there or just when you play?

My other "first thing" suggestion was going to be to check all your ground connections, but the fact that it's better on the AUX doesn't point to that. Still worth double checking though, I'd think.

So I was beginning to hear more and more "hiss" or distortion behind the notes when playing lately (very subtle, just know it's sounded cleaner before).  I figured a re-cap was in order, also because the AUX output has never worked and after the re-cap it does.  Now, out of the speakers and headphones is just dirty nasty distortion.  I will pop it back open and have a look at my polarities; I was pretty careful when I did the job but who knows.  I'll report back. 

[pianotuner steveo]

It's easy to do by mistake, especially if the caps are small. I've done it a few times in the past when I worked on electronics every day.

[gbkd80]

Now do you think it's worthwhile to replace the transistors on the amp (if the problem is a cap) as well when I get them in?  Or save 'em for an emergency? 

[pianotuner steveo]

Except for caps, I generally don't believe in replacing components unless they are fried. I don't see any advantage unless yours are bad. Someone else may have a different opinion though.

Have you made sure your volume control doesn't need cleaning or replacing?

[cinnanon]

I'd replace the amp. They're old anyway. Will save you many headaches and you'll love the sound.

[sean]

I agree with PTSteveO. 

No need to replace any component unless you have specific evidence of malfunction.  You are unlikely to trace down and resolve issues by sequentially replacing components.  If a transistor has failed, maybe it died of old age, but more likely it died from some other circuit imbalance during a specific set of circumstances.  And just replacing the transisitors will not fix the other component problems, and eventually the transistor may burn out again.  Also, electronic problems that are intermittant may not like to cooperate on the test bench.

I am not saying it is impossible to get lucky.

You did try to get lucky in a very reasonable way.  Replacing 45-year-old electrolytic capacitors can bring many circuits back to life.

But in the situation where it doesn't work out and new problems crop up, you should get a well-qualified technician to look at the circuit.  If you have a good music-oriented electronics repair shop within driving distance, go there.

If you have a network of friends that can find someone with experience (and the tools) who will work for beer and pizza, think twice about this.  Working on the audio circuit is not that big a deal, but you do have the 120V power mains to work around, and also that notorious 170 VDC feed to the reed bar, and the transformer that feeds this.  I am curious to know how painful it would be to touch it, but I am just barely smart enough not to try.  (Does anyone have experience getting a jolt from their Wurly?)

If you really want to find an online electronics expert that loves fixing Wurlies, go join the WurliTzer group on Yahoo, and submit your issues with as much evidence and explanation as possible.  If you are lucky, Chris Clifton will answer.  (Make sure it is the WurliTzer Elec Piano group, not the WurliTzer Jukebox group.)

See https://groups.yahoo.com/neo/groups/Wurlitzer_Elec_Piano/info
The activity on this group is really intermittent, but it isn't dead yet. 


I also agree with Cinnanon.  A few hundred bucks for a redesigned amp will sound great and be much more reliable than the old amp could ever hope to be.  Maybe the amp costs more than you paid for the Wurly, but well, it depends on what you want to do with the piano.  If you hope to use it for years, the expense make more sense.


Golly, I just can't write a short answer.

Sean

[Jenzz]

Hi .-)

On a distorted but otherwise playing 200A, ALLWAYS check the 2 fuses on the amp board. Due to the fact that these are soldered into the PCB and their somewhat obscure design, the inner fusing wire gets stressed over the years (warm up and cool down every time you Play) and fails / breaks, even when there was no 'electrical' incident.

So, before doing anything further, check these 2 fuses.

Jenzz

[gbkd80]

Hi .-)

On a distorted but otherwise playing 200A, ALLWAYS check the 2 fuses on the amp board. Due to the fact that these are soldered into the PCB and their somewhat obscure design, the inner fusing wire gets stressed over the years (warm up and cool down every time you Play) and fails / breaks, even when there was no 'electrical' incident.

So, before doing anything further, check these 2 fuses.

Jenzz

First, this ^^ is something I didn't do because I didn't even realize those were fuses lol!  I will be sure to check this (when I once again get the time to bench it and figure out what happened - full-time with my kids...)

Don't get me wrong, I certainly don't like sounding incompetent with electronics, as I really like to repair and troubleshoot my own gear and have been lucky more than once getting something working again, but I am a novice with a scope and also in this particular case, I'm not too worried if I blow it up accidentally because well... I'll just get a new amp... if I can repair the basic stuff myself though, I'm satisfied. 

The piano was free.  I know no one likes hearing that!  Well, I won't say completely 'free' as it was more of a gift for some work I did, but it was one hell of a gift!  I've had it about 5 years now, finally wanted to get some of the annoyances taken care of.

[pianotuner steveo]

Wow- Free eps are harder and harder to find. I was fortunate enough to get a free 120, (waiting for trash pickup!!). a free 140B ( a barn unit that had mice in it) and I bartered a 2 piano tunings plus $35 for my first Rhodes... Those days are long gone.

I traded the 120 for 2 206's, and sold both of them...

[gbkd80]

So I got back in there and checked those fuses on the board; F2 was definitely blown so I replaced it with a makeshift 1A fuse + leads and heatshrink.  Didn't solve the problem, still fuzzy distortion.  Then I started checking my wiring and making sure things were in the correct places, and I accidentally plugged something onto the wrong post and cooked it (saw smoke)... my luck ain't happenin' this week....  It still works, still distorted, and can't figure out what I burned out but I'll find it eventually...

The other fuses tested out fine (out of circuit).  All my caps are oriented properly... 

[cinnanon]

I'd replace the amp. They're old anyway. Will save you many headaches and you'll love the sound.

[gbkd80]

I'd replace the amp. They're old anyway. Will save you many headaches and you'll love the sound.

I know, but I had most of the parts available as it was and replacing the entire amp is sort of cost-prohibitive at the moment... I'm more than comfortable pulling and replacing a handful of caps; done it a bunch of times.  And on the bright side, it did correct my AUX issue.  Had I known I was going to burn something up or damage the amp in any way, I would have waited to do anything until I had some cash in case.  But like anything else I just wanted it done with my limited time and so I went for it... at this point if I have to change out the entire amp I'll just put it all back together and dummy-plug the headphones / run the AUX line out.  That seems to be fine..

I 'traced' the burnt component smell to one of the 2200uf power caps (aka removing them and smelling 'em).  I ordered a couple of good quality caps this time as I should have done in the first place.  BUT, I did put the old cans back in for the moment and fired it up to the same issue, so it's not the cause of the problem. 

[cinnanon]

I wish I had more of an understanding of electronics, and I am jealous of those that do 

Sounds like you're on the right track though. If your aux out is fine, then your preamp must be fine. The power amp section must be bad. You can always wire up the Phono Input section of the amp to run a test signal through instead of always having to play notes. That may make tracing the problem easier with a probe/amp type tester.

[gbkd80]

So I have good news.

A full re-cap of everything minus ceramics, all transistors including power trannies, and both amp fuses somehow got the amp working again.  I say 'somehow' because I really would have liked to at least know what part was truly causing the problem.  But because of the work involved putting that amp back into the piano and wiring it up with those ridiculous crimped wires on the posts (had to re-attach and solder at least 4 of them) I wasn't going to keep testing it out.  I figured I'd put all these parts in, the piano wouldn't even fire up, and I'd just give up.  But it was the exact opposite.  I'm in happy camper territory now! 

I ran into a couple issues, one really simple but stupid one where I needed to find two super thin longer screws and washers in a pinch to secure the new, larger power transistors; but I got lucky and had something that worked.  The other was the fuses... I intended to order 3AG fuse holders but somehow got 2AG, so I just went ahead and rigged my own with pigtails and heatshrink.  It works fine, just in the future if I ever blow a fuse... amp's gotta come out...

I do have what sounds like a slight ground buzz at the moment, but the piano is apart, so I'm just hoping when it's all back together and grounded properly that will go away. 

[Tim Hodges]

The other was the fuses... I intended to order 3AG fuse holders but somehow got 2AG, so I just went ahead and rigged my own with pigtails and heatshrink.  It works fine, just in the future if I ever blow a fuse... amp's gotta come out...

What you need is an inline fuse holder. Then if it ever blows all you need to do is unscrew it and pop in a new fuse.

[gbkd80]

What you need is an inline fuse holder. Then if it ever blows all you need to do is unscrew it and pop in a new fuse.

Yea, I bought several of them but they turned out to be 2AG and I was impatient to get the amp back in  

[pianotuner steveo]

Using 2ag is safer if there s a problem. If a fuse blows, there is an issue, and you want it to blow sooner rather than later.