SWR Workingman 15 crackling problem, repair or replace?

[CompleteHack]

tl;dr: after it sat a while, my SWR Workingman 15 bass amp is crackling badly, much of the time. If it can't be economically repaired, what should I get to replace it?

I bought this SWR Workingman 15 forever ago, probably around 2003-2004. It was a great amp for years. I was happy with it, but it's got problems now.

More info: the input instrument is a 1995 Fender Precision bass. As far as I know, this BG is 100% fine. I put fresh flatwound strings on it very recently.

This is the only instrument I have. If I'm actually having an instrument problem vs. an amp problem, how would I tell?


I've done some troubleshooting of the amp. Observations:

--"Horn Off" vs. "Fullrange" switch setting makes no difference.

--Moving the preamp section "Gain" knob at all causes instant crackling, always. That seems like a big clue, but I don't know what to do with it.

--The crackling while playing is not consistent. It'll come and go. Does not seem to be only at particular notes or amp volume settings.

--The crackling does not seem dependent on volume or tone settings on the bass.

--the headphone output is totally useless. Every note is badly distorted, all the time, through headphones. That's true whether I'm using the "headphones only" output mode, or still have the speaker cab operating (both are possible on this model), true with various volume settings on both amp and headphones.

--for testing, I started with all amp EQ controls at 0, preamp gain in the middle, Aural Enhancer fully "min," Effects full "dry" (don't have any effects/pedals connected), Master volume slowly increased from 0.

Turning the various knobs up and down does not seem to affect the issue, aside from the Gain knob as mentioned.


Some limits to my testing ability at home:

--I only have 2 proper, 1/4" plug instrument cables. They are both in good shape and have good electrical continuity. They have been in a closet for years, so I don't have any reason to suspect they are physically worn out or have loose connections.

While I can't 100% rule cables out as the source of problems, the fact that the headphone output is affected, suggests to me that there is in fact a problem within the amplifier.


--Similar thought re: I only have the one, Fender P-bass as input. I've plugged the bass into my PC's mic input, and heard no crackling through headphones connected to the PC, so I'm fairly sure it's not a problem with the bass.


Any suggestions on further troubleshooting I could do?

I have an appointment with a local amp repair shop, but if I can fix it myself instead, that would be great.

That said, my testing gear is limited. I do not have an oscilloscope but I do have a multimeter. Not 100% sure I know how to open up the amp safely, what with there likely being some capacitors involved, possibly big-enough ones to hurt me.

If you've got opinions on a roughly-equivalent, currently-available combo amp I could replace the SWR WM 15 with, let's hear it.

I'd like to stick with something reasonably portable. I don't play shows. Budget is flexible, but I'm not necessarily looking to drop $2k on an amp.

Would you spend the money to get this amp fixed, or move on?


Further info: I searched and found some prior discussions of similar problems, though none seem to match my case exactly. This one is close-ish:

https://www.talkbass.com/threads/swr-workingman-15-distorting.1387439/

Then again, OP's problem is not quite like mine - I don't get clean sound through the headphone output. Thread was never updated with a resolution.


Thanks!

 

[agedhorse]

It may be a cracked of damaged gain pot, but it could be a lot of other things too.

I don't remember if that amp has an effects loop, but if it does, you might try jumping from the effects send to return jacks with a short patch cord.

Otherwise, they aren't difficult to repair for a qualified, experienced service tech. How much it will costs depends on the shop and their willingness to work.

 

[CompleteHack]

Thanks for the reply. It does have an effects loop. I've never used it.

I called/searched around. There are at least 2 shops in my area that do amp repair work. Both charge $30-$40 for a diagnosis, which then comes off the repair price. I can live with that, even if it turns out not economical to repair.

Something I haven't tried is, hooking up an external speaker cab vs. the built-in one. The only externals I have are some bookshelf speakers, but I'm not sure it's OK to connect them. Don't want to damage the speakers, or do more harm to the SWR.

 

[loukash]

Moving the preamp section "Gain" knob at all causes instant crackling, always. That seems like a big clue, but I don't know what to do with it.

Just a few days ago I have fixed my Workingman's 12 crackling pots: A contact cleaner spray was all I needed.
The 15" will be likely built similarly on the inside.
First you need to loose the screws on top to pull the amp out of its slot. Then you need to remove all knobs and unscrew the pots from the front plate to have access to the pot openings, to apply the spray. Be careful with the Clip and Limiter diodes, not to break them off.

Oddly enough, I also noticed that a capacitor at the headphone output had a broken leg. I haven't used headphones with this amp in many years, so I never noticed anything. Since there was still enough of the wire left, it was an easy fix to solder it back to its spot. But I haven't tested the output yet…

Here my SWR 12" seen in the background after the above fix (while I was testing a double bass I'd like to buy, using my Schertler Basik pickup):

Worked flawlessly.

 

[CompleteHack]

I wish it were only the Gain knob causing crackling, as that could be an easy fix.

That's merely the most reliable way to introduce crackling. The other crackling happens seemingly at random while I play, without touching any knobs.

 

[agedhorse]

If you want to clean the pot, be sure only to use DeOxit D5 and only the tiniest amount possible, being careful not to get any on the PCB. Spray through the slot that the terminals exit. The goal is to not create new, messier problems.

Do NOT use "contact cleaner", these substances do not have the necessary (and correct) lubricant and can ruin a pot in a hurry.

 

[loukash]

Do NOT use "contact cleaner", these substances do not have the necessary (and correct) lubricant and can ruin a pot in a hurry.

Hm… I've been using WD-40 on failing pots since decades without issues. (Unless a pot was faulty to begin with like the one in my Ibanez SR1200, but that one got replaced on warranty.)
Perhaps I'm just lucky.
But I'm no expert, so I'm always happy to learn something new.

The other crackling happens seemingly at random while I play, without touching any knobs.

Mine did that occasionally in certain pot positions, too. The whole amp vibrates while we're playing, so it could still be the faulty pot contact reacting to those vibrations. In any case, after my cleaning all issues are gone. For now, at least…

 

[agedhorse]

Hm… I've been using WD-40 on failing pots since decades without issues. (Unless a pot was faulty to begin with like the one in my Ibanez SR1200, but that one got replaced on warranty.)
Perhaps I'm just lucky.
But I'm no expert, so I'm always happy to learn something new.


Mine did that occasionally in certain pot positions, too. The whole amp vibrates while we're playing, so it could still be the faulty pot contact reacting to those vibrations. In any case, after my cleaning all issues are gone. For now, at least…

Actually WD-40 is about the worst of the worst, you got very lucky. If an amp comes in with WD-40 smell, all pots get automatically replaced. I can't have an amp coming back under warranty to replace pot after pot that are likely to fail, nor would I want a customer to have to deal with ongoing failures.

This is why i recommend that any used gear be inspected for hack repairs, so that they don't get stuck with an expensive repair down the road. I am starting to see some unbelievably shocking repair attempts as hobbiests try to fix their own amps after watching YouTube videos... many of which are horrifying. In fact, I am thinking about simply doubling my shop rates when dealing with attempted repair damage because it takes so much more time to resolve CORRECTLY. I won't send out an amp that's not repaired to the original factory standards, it's just not worth the hassle of potential returns and the shipping costs.

 

[CompleteHack]

It's in the hands of a local repair shop now. If all it takes is a cleaning, that'll be great.

 

[DWBass]

WD-40??

 

[agedhorse]

WD-40??

All the real techs threw up a little bit in their mouths with that one

 

[mmbongo]

WD-40??

Hank Hill Wd40 GIF - Hank Hill Wd40 King Of The Hill - Discover & Share GIFs

 

[loukash]

Actually WD-40 is about the worst of the worst, you got very lucky.

Well, that was all that my local electronic parts shop had in stock some 30 years ago and what they gave me when I asked for a contact cleaner. Remember, that was the dark age before Teh Interwebz.

I am starting to see some unbelievably shocking repair attempts as hobbiests try to fix their own amps

"No risk no fun" or so they say…?

Usually I'm having a good look first if I'm confident enough to fix something myself, like soldering obviously loose contacts and the like. Other times I go directly to my local repair expert. At the moment he's trying to fix my 24/8/2 Tascam board, unsuccessfully so far, and it's likely gonna be expensive. Ouch…

 

[CompleteHack]

WD-40: It's not just a dessert topping any more!

Unfortunately, the repair shop is backed up by 5-6 weeks so I'll be amp-less for that long.

Yeah that's not ideal, but I couldn't use the amp as it was anyway. Especially once I discovered the headphone output was totally useless.

I'm going to need my bass fix sooner than that, so now I'm shopping for an inexpensive practice amp. If anyone has suggestions, I'm listening.

I would like to spend a modest amount, let's say under US$100. Since I will have a fullsize amp again sooner or later, let's say I'm looking for an amp especially suitable for practicing with headphones.

I do not need all the fancy features of e.g. the Fender Mustang Micro. I don't care about effects. I'm coming back to bass after not playing for many years, so I'm trying to keep it simple.

 

[agedhorse]

Well, that was all that my local electronic parts shop had in stock some 30 years ago and what they gave me when I asked for a contact cleaner. Remember, that was the dark age before Teh Interwebz.


"No risk no fun" or so they say…?

Usually I'm having a good look first if I'm confident enough to fix something myself, like soldering obviously loose contacts and the like. Other times I go directly to my local repair expert. At the moment he's trying to fix my 24/8/2 Tascam board, unsuccessfully so far, and it's likely gonna be expensive. Ouch…

If a tech can’t repair that console in a reasonable amount of time and at a reasonable cost, there may very well be a challenge with their qualification level. They are about as straight forward as it gets, but we are losing the good techs at a rapid rate as the real pros retire or move into different careers or industries to escape the often unrealistic expectations of players. Especially when they have to spend a lot of time cleaning up after hack repairs done earlier on gear. It gets very, very old.

 

[eniac]

When I was just a little kid I had a pet hamster. It would wait until I was in bed for the night before running on that stupid exercise wheel. One night the wheel started squeaking like crazy and kept waking me up. So I got up in the middle of the night and took a Q-tip and put a little dab of WD-40 on each end of the wheel. I spun the wheel to make sure it was quiet. It was. I went back to sleep. No more wheel noise. I woke up the next morning and found out no more hamster, either, because it had died. So, WD-40 eliminated not only the squeaking, but also the root cause. It was an excellent early lesson in root-cause analysis that I remember to this day.

My parents did not buy me another hamster.

 

[loukash]

If a tech can’t repair that console in a reasonable amount of time and at a reasonable cost, there may very well be a challenge with their qualification level.

Don't worry, he is qualified and trustworthy. Actually I just brought the board home earlier today, after he had it test run over the weekend. It runs perfectly. But apparently it was a challenge to fix because he couldn't get the ordered components at first, receiving wrong ones, plus some other complications. The price was alright, less than expected as he gave me a generous discount.

Oh, and he also explained to me in detail what's wrong and what's not wrong with WD-40.

 

[5stringedfrenzy]

That was my first amp, repaired and upgraded so many times! I had version 1 with overheating problems so we cut a hole in the top and mounted an external fan over the transformer, never shut down again. It did need regular pot cleaning or would become unusable as you describe, especially after my ventilation upgrade .

 

[agedhorse]

Don't worry, he is qualified and trustworthy. Actually I just brought the board home earlier today, after he had it test run over the weekend. It runs perfectly. But apparently it was a challenge to fix because he couldn't get the ordered components at first, receiving wrong ones, plus some other complications. The price was alright, less than expected as he gave me a generous discount.

Oh, and he also explained to me in detail what's wrong and what's not wrong with WD-40.

Everything's wrong with WD-40, mentioned in the same sentence as electronics. There's nothing right about it.

 

[loukash]

be sure only to use DeOxit D5

So… I finally found a small Swiss online shop that has it in stock, and I just ordered one (free shipping, nice!). Let's see how it works out. Thanks for the tip.