• The move to the new server is done. There are some software and database maintenance updates in process. This has us passing the hat around to help out. We appreciate any donations. Seriously, even a dollar helps. The payment page may be found here - https://www.audiokarma.org/support.html

Electronics Repair Liabilities

A

avantbored

Active Member
Hi all. Have a technical & etiquette situation I could use the forum's perspective on.

What happened: Wharfedale Linton 85's right tweeter was blown by my recently repaired power amp (Nakamichi PA-7A II for the curious). The amp was repaired for the exact problem that blew up my tweeter: Two months ago, right channel protection circuit switched on. My guy repaired it, and ran it hot for like three hours before he called me to pick it up. But then my speaker blew up from too much DC sent to the speakers. Same channel, same problem.



First question: I got these Lintons used. Wrote to Wharfedale about seeking a replacement tweeter. Should I get in touch with a local hifi store to see if they can source it? And how likely is it that the crossover is damaged too? (Sorry, that's two questions).



Second question: This is more of an etiquette/transactional thing. I've given a lot of business to my electronics guy. Never had an issue with his work before. He's pretty certain that he set the bias to 100% factory standard. To what extent is he liable for my blown tweeter? For sure I am going to ask him to look at my amp again. I want to give him the benefit of the doubt that he did a thorough check, but also understand he's human and maybe didn't consider some or another factor. I'm more than open to bring this to a different shop (I live in LA, and George Meyer A/V and Howard at Audio Specialist are about 30 and 1 hour away from me respectively), but if he is liable, I am wondering to what extent it's fair for him to fund the cost for the replacement tweeter, the crossover, and the labor for fixing the speakers.


Thanks all.



(Footnoted context: The Lintons aren't my mains. I got them on a trade, and have been trying to sell them to fund the purchase of NS1000s. Found the NS1000s. Wharfdale's blew up on day of the Linton sale, which means NS1000s out the window. I know the community can commiserate with me on how much a bummer this was for me!)
 
Register to hide this ad
How much time passed before your tweeter was blown? If it was within a day or two of pick up, I would say tech is responsible for releasing amp prematurely. There are other factors to consider. You have a long term relationship with your tech who presumably has done satisfactory work up until now. Vintage gear techs are getting hard to find so the relationship is IMO far more valuable than one botched job. I think you will find common ground here. Both of you have done well by each other and I think that understanding will go a long way towards negotiating a settlement you can both live with. As you know, Nak PA-7II is fiddly to set Bias correctly because of how long it runs in Class A. It requires significant restoration to be 100% trustworthy. Talk it through and don't be emotional or rash. You and your tech will be fine.
 
SoCal Sam said:
How much time passed before your tweeter was blown? If it was within a day or two of pick up, I would say tech is responsible for releasing amp prematurely. There are other factors to consider. You have a long term relationship with your tech who presumably has done satisfactory work up until now. Vintage gear techs are getting hard to find so the relationship is IMO far more valuable than one botched job. I think you will find common ground here. Both of you have done well by each other and I think that understanding will go a long way towards negotiating a settlement you can both live with. As you know, Nak PA-7II is fiddly to set Bias correctly because of how long it runs in Class A. It requires significant restoration to be 100% trustworthy. Talk it through and don't be emotional or rash. You and your tech will be fine.
Click to expand...

Time-of-release is an important detail. It's been about a month, but he guarantees the work for 45 days (IIRC). But your response leans me towards not advocating or pushing for him to take responsibility, just opening up a Convo.

He's away working on another job out of state, so I called him and texted him in a bit of panic -- this is about the extent of my rash emotions I had. Really bummed more about the amp than the speakers or missing out on some future gear. Not really at my tech. When he gets back I'll reach out again and see if he's free.

Those are all good points. Repair isn't his main income these days so in my conversations with him I'll feel out if he's got the time to not only look at it again but spend some more time with it -- he found the first instance of the problem as loose cold solder joints; at the same time, he reset the bias.
 
Oerets said:
Talk to your guy on what was done. Intermittent issues are a tough fix.

What leads you to a hi DC issue?
Click to expand...

Yeah, that's also what I'm thinking.

That was my techs explanation for what may have happened with the first instance of the protection circuit turning on. What other possibilities might there be?
 
Oerets said:
Some speaker makers install a lamp on one side of the tweeters to shunt excess voltage.

Thus protecting tweeters.

Fuses work too...
Click to expand...

When the problem first appeared, Nak was driving KEF 105.2's that have the "S-STOP" protection circuit for overload. All I heard that first time was a tiny blip, but no damage to the KEFs (they're being driven by a NAD 2200 right now, my backup unit).

I don't think the Lintons have any protection, obviously.
 
Tell your guy what happened, and ask him to fix it correctly. He should owe a fix on the amp, and labor on the speaker. You might be out the price of a tweeter, but he should make it up to you on future business deals.
 
Unless the cap in the crossover network in the speaker was blown, it is not possible for the tweeter to be blown by DC voltage on the output of the amp, because the cap in series with the tweeter blocks DC voltage. If there was excessive distortion or a very large pop it is possible that could have blown the tweeter.
 
dr*audio said:
Unless the cap in the crossover network in the speaker was blown, it is not possible for the tweeter to be blown by DC voltage on the output of the amp, because the cap in series with the tweeter blocks DC voltage. If there was excessive distortion or a very large pop it is possible that could have blown the tweeter.
Click to expand...

I see. Thanks for that clarification. So it's more likely a cap on the crossover is blown. Cheers.
 
Hopefully your tech is not on AK... ;) You might be needing to find a new one , if he is.
 
avantbored said:
I think it would be unfair to reveal that. Just seeking some guidance here with regard to my issue. Not mad at my tech as I trust him and don't believe he shortchanged me.
Click to expand...

Just talk to the guy honestly while staying cool; you already have a standing relationship, so just be straight with the guy and see if there's anything he's willing do. Vintage electronics repair is a tough one, the components are all old, lots of different problems can arise for a million different reasons, often coincidentally. It's really a crapshoot sometimes, I don't know if I would own vintage gear these days if I weren't able to fix most of it myself.
 
From the tech's point of view I'd say he's responsible for the amp repair but not the speaker. How is he to know that the OP didn't drive the amp into clipping and in turn take out the tweeter? There could have been an underlying issue with the speaker also, such as a bad crossover.

The deal was to fix the amp, not the amp and related stuff. Give the guy a chance to check his work and report back. Being a repair tech is not easy at times and issues like this will crop up.
 
Yeh, it sounds like the kind of problem that can appear to have been fixt, but actually is still hiding somewhere. I agree the guy has to get back at it to finish the job, but can't really be charged with the cost of the fallout. It's a tough break for you, but I recon you guy might also have to take a deep breath.

On a side note: especially with this sort of problems I never feel secure without extensive testing. Several occasions several hours in all the relevant modes.
 
Last edited:
He should look the amp over and check his work but as many of us know, tweeters die, sometimes for no apparent reason. Age doesn't help matters.
It's not uncommon to drop a new engine in a truck and have it spit out a u joint.
U joint would have lasted a long time with a dog of a worn out engine trying to make torque. New engine makes effortless torque all day long, and those weak old u joints (or tweeters) may show problems that never would have shown up before.
Getting vintage gear back into top shape is a process. Tweeters will get blown up, but we must carry on.
 
dr*audio said:
Unless the cap in the crossover network in the speaker was blown, it is not possible for the tweeter to be blown by DC voltage on the output of the amp, because the cap in series with the tweeter blocks DC voltage. If there was excessive distortion or a very large pop it is possible that could have blown the tweeter.
Click to expand...
I agree that DC voltage was probably not the cause of the blown tweeter. One possible cause could be a high frequency oscillation. If the amplifier was oscillating at a supersonic frequency you would not be able to hear it, but, the tweeter could be damaged.

Have you measured the DC offset of the amplifier? Have you tried measuring for AC voltage at the output of the amplifier?
 
Last edited:
Okke 70s said:
Yeh, it sounds like the kind of problem that can appear to have been fixt, but actually is still hiding somewhere. I agree the guy has to get back at it to finish the job, but can't really be charged with the cost of the fallout. It's a tough break for you, but I recon you guy might also have to take a deep breath.

On a side note: especially with this sort of problems I never feel secure without extensive testen. Several occasions several hours in all the relevant modes.
Click to expand...

I think this is the way. Thanks
 
You must log in or register to reply here.
Back
Top Bottom