Responsible Testing Before Sale

If a receiver, make sure FM can lock onto a stereo signal. This is a problem with a lot of analog and early digital tuners. In addition to the usual bias and offset, the suggestion to test over several hours is a good one. I usually play an amp or receiver for several days to make sure there are no hidden surprises.
 
Take off the shoe, and try putting it on the other foot.

As a potential buyer, I look to see if a unit functions - Period. That tells me how much work I would have to do.

Golden Rule #1 - "Refurbished" usually means someone waved a dust cloth at it, nothing more. It's more subjective than a witch hunt;

Golden Rule #2 - "Professionally serviced" only means someone was either unskilled or lazy enough to pay someone else to wave a dust cloth at the unit for them;

Golden Rule #3 - If a unit has been "aligned" or had "bias set" or "offset adjusted" or whatever, unless test specifications are available, I know I'll have to go back in and check the work, without question.

It sounds like the philosophy of a used car dealer trying to spin a product into better-than-new but without a new warranty.
 
I've read a service manual (don't remember the brand or model) that instructed the techs to let the amp running for 36 or 72 hs before returning it to the owner.

So that could be part of your list: let it run for XX hours (more than 2hs).

A "pro sound" guy I met last year (he does sound for large events, hundreds thousand of people) , told me they test the PA amps with dummy loads, max power, a fan on the loads, all night long. If the amp is OK the next morning, they use it.
 
A "pro sound" guy I met last year (he does sound for large events, hundreds thousand of people) , told me they test the PA amps with dummy loads, max power, a fan on the loads, all night long. If the amp is OK the next morning, they use it.
That seems to be valid test for pro gear. They make money with working gear so a pre-use burn up attempt is a good policy. In use they may well be subjected to a significant power demand and be cooled by a big fan facing the equipment rack kinda as tested.
 
I've read a service manual (don't remember the brand or model) that instructed the techs to let the amp running for 36 or 72 hs before returning it to the owner.

So that could be part of your list: let it run for XX hours (more than 2hs).

A "pro sound" guy I met last year (he does sound for large events, hundreds thousand of people) , told me they test the PA amps with dummy loads, max power, a fan on the loads, all night long. If the amp is OK the next morning, they use it.

Such testing important when we are entertaining 10's of thousands (or even 2,000) people. They may have spent good money to hear the band or see the show, It is their responsibility to take reasonable measures see to it their equipment does not fail during the performance. It's also their lively hood at stake, Not some spare time they wish to fill with music.

When selling or buying used audio equipment, The most we can reasonably expect is that we can operate the unit and test all functions we see fit by sound and appearance (lights etc.). Some might be willing to play it loud for 2 hrs. Even supply the coffee, or beer. If it works after that, and both are happy...sell/buy.
 
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I use the same criteria when selling as when buying. I want to know if it works and if it does not, the extent of repairs needed. Many times the price is so low (like, for salvage value) I don't care about hearing it or testing it. If it works, it just means I got a bigger score.

I sell what I have moved out of rotation and have no desire to keep. I know what works and what doesn't and I put that in the ad. If a person wants to hear it before buying, we meet at my office where I have a test system ready to play. They are buying used gear with no guarantees.
 
If you go to the trouble to check offset and bias, why not check the high and low voltage rails too?

For electrical safety, check the case/chassis for stray voltage/bad ground.

Of course this all assumes that someone can get the manuals that lists these specs.

If I buy/sell stuff, I try it out and if everything works and sounds good, that's as far as it goes and all that I expect.
 
One more pre-sale test: I run the amp for a couple of hours to make sure it does not over heat. If the amp stays well behaved, I have reasonable confidence in representing the amp as good.
 
I create a 'birth certificate' for everything I work on, it lists the board, component, what is spec, what was put in (in case I alter a cap, res or trans). any bias and offsets, solder joints, I always address lighting now, I wont use incandescent unless I am instructed to. then I run it in for about a day, then its stuck in the store so they can hear it.
 
+1, A leakage test could be added to your list. That's usually the 1st page in many service manuals, to connect a probe with a resistor and a by-pass cap, and measure the voltage from the metal parts to a good ground connection.

The MAX value seems to vary from manual to manual...Perhaps the measuring method is different.

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It depends on the skill of the guy selling it. I'd rather not have "testing and setting bias" something that becomes common for an amplifier sale because I don't own stock in SanKen just yet though if the trend does take off I surely will buy some.

Most people aren't mechanically inclined so for me to see that some schmo has had the lid off and was screwdrivering around in there means I click to the next ad.

Unless I'm selling a unit fully restored it gets blown out and the cloth waved though I do like to polish up the face plate and case mostly for my own OCD as I hate the way fingerprinted stereo gear photographs.
 
If you want a full test battery, that would be power, THD, IMD, frequency response, bias, offset, and of course verifying all functions work as designed. It also would get a detail cleaning, inside and out.


Frankly I'm more inclined to sell it as-is, where-is. If you come over to check it out, all I can swear is that its working the moment you look at it, and as soon as it crosses my threshold its yours. OTOH, considering I still own a stereo that was given to me when I was 16 (I'll be 37 this year), the chances of that happening are pretty slim. I'm listening to that thing right now, its been on my desk at work running daily for several years.
 
Later that night he called me, very drunk. Called me every name in the book, least of which was 'crook'. Everything about the TT sucked, down to the RCA plugs and stylus (new). I could imagine that bent platter wobbling up and down, with wow out the wazoo, and throwing the needle out of the groove with every rotation.

Wow that sucks - I havent had to deal with anything like that, thank god
 
... I don't own stock in SanKen just yet though if the trend does take off I surely will buy some.

...

Well, I don't know that I'd buy stock, per se, but you may want to stock up. Sanken recently announced end of life on quite a few transistors of the MT-200 style, I believe. Wouldn't be surprised if most have already been scooped up by "investors".
 
I’ve had someone call me back in two separate cases. Neither of them Audio related. And in both cases, they refused to test it out before paying and leaving. My response to them is that I won’t take it back. I said I had it ready for you to try out, but you didn’t want to take the time. Then I tell them what I think is the issue. I never heard back from either of them.

I call lengthy listening tests, my “getting to know the gear”. I will typically try the gear in multiple configurations to find out what it sounds best with. At the same time, I’m trying to find out if my theory about how to predict from specks how certain gear will sound together. Every time I think I have it, some happens to throw it all out. Anyway, by the end of these listening trials, I’m pretty sure nothing is marginal. I do tend to try a range of music and sound levels.
 
About the only thing I've tested lately is the mouse as I click the "buy" button ... Lucky I guess.

And yes, I fully expect to have to put some work into any 40 year old piece of equipment I get. Anyone expecting more should plan to hit the big box store for new gear - and be sure to get the extended warranty after verifying their return policy ...
 
Anything bought on Ebay is suspect IMO. I'd prefer a unit that has never been opened or touched to one that has been "serviced". The ones that say recapped are probably the biggest red flags.
 
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