We know companies do not like unauthorized repairs and modifications of the products, mostly geared towards active product lines. Changes to design or unacceptable substitutes can change the intended function of a device, maybe makes a bad image, less than the device is supposed to be.
Maybe there should be an international symbol to mark it as modified from OEM design next to the manufacturer's ID and basic specification label on electrical products. The mark should be well known and honestly represents the product as altered from the OEM design.
Maybe next time a person buys a used stereo amp, they can look on the back and know it is not original equipment. They know it has been modified. And you will too.
Now watch the alligators laugh. LOL
At least, honest 3rd party (aftermarket) individuals and organizations will do that. It's the fair thing to do to help clear the OEM from legal battles over injury or loss claims.
Maybe there should be an international symbol to mark it as modified from OEM design next to the manufacturer's ID and basic specification label on electrical products. The mark should be well known and honestly represents the product as altered from the OEM design.
Maybe next time a person buys a used stereo amp, they can look on the back and know it is not original equipment. They know it has been modified. And you will too.
Now watch the alligators laugh. LOL
At least, honest 3rd party (aftermarket) individuals and organizations will do that. It's the fair thing to do to help clear the OEM from legal battles over injury or loss claims.
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I will never comply. 
It should be obvious if equipment has been modified anyway. If a unit contains parts that weren't manufactured at its time of assembly, then it's obviously been modified. Even replacement electrolytic capacitors are obvious, even if very neatly installed.
My mods have included extra features, extra boards, etc. I don't think you need an extra sticker to tell if it's been modded.
It should be obvious if equipment has been modified anyway. If a unit contains parts that weren't manufactured at its time of assembly, then it's obviously been modified. Even replacement electrolytic capacitors are obvious, even if very neatly installed.
My mods have included extra features, extra boards, etc. I don't think you need an extra sticker to tell if it's been modded.
It depends on the quality of the parts used in repair and whether or not OEM performance was restored.
It is true that performance can be degraded with substandard repairs. Many service schematics indicate when a special part is used (like a wider temp range). Failure to heed these notices may or may not affect the performance of the unit. I speak from experience as someone who once failed to heed this advice regarding a lowly voltage regulator chip. The unit wouldn't work properly below 35 degrees F ambient. It didn't help that I put in wimpy smoothing capacitors either. I thought it didn't matter since this part of the power supply only powered logic and relays. I was very foolish. I was just trying to use up parts I had. I didn't save anything and had to order the correct parts.
It is true that performance can be degraded with substandard repairs. Many service schematics indicate when a special part is used (like a wider temp range). Failure to heed these notices may or may not affect the performance of the unit. I speak from experience as someone who once failed to heed this advice regarding a lowly voltage regulator chip. The unit wouldn't work properly below 35 degrees F ambient. It didn't help that I put in wimpy smoothing capacitors either. I thought it didn't matter since this part of the power supply only powered logic and relays. I was very foolish. I was just trying to use up parts I had. I didn't save anything and had to order the correct parts.
Maybe not a requirement but an option to mark it. What if an unauthorized mod was made and some consequence came of it ? Wouldn't be fair to the OEM, but a person in the USA is no obligated by law to incriminate themselves.
Even a cop, the cop does not have to pull himself over and write himself a speeding ticket.
Even a cop, the cop does not have to pull himself over and write himself a speeding ticket.
Hi Wavewhipper,
Even repairs made under warranty contract may differ from the OEM parts that it left the factory with. It isn't unusual for engineering change orders / service bulletins and modifications under factory or distributor direction to make noteworthy changes to the device. We've even seen power transformer replacements required for safety approval (CSA vs UL). If you look in any owners or service manual, they all state that the design and/or specifications are subject to change without notice.
When modifying equipment to add features without the distributor/manufacturer approval, there are external indications (switches, jacks or other things). Other modifications may be made out of necessity due to parts not being available, or even defective design in the original product. This really does happen and not that infrequently.
Lastly there are those modifications that improve the performance of a device (real, measurable improvements). When rebuilding audio equipment I am often asked to improve performance. With today's parts and new component types, these improvements can be made, but there aren't any external indications. Some changes that are visible look so neat and "right" that they pass inspection as being the way the item was made.
If required and supplied with stickers, I would affix them to units that were modified without direction from the distributor/manufacturer. For factory changes, I wouldn't feel the need unless directed to by the distributor or manufacturer. But you can see the range and reach of circuit changes and why they were done. Some changes are unfortunately poorly conceived and executed, and those are the ones I think you are mostly concerned about. Those folks are unlikely to follow any directives from anyone. So it will always be, buyer beware.
-Chris
Even repairs made under warranty contract may differ from the OEM parts that it left the factory with. It isn't unusual for engineering change orders / service bulletins and modifications under factory or distributor direction to make noteworthy changes to the device. We've even seen power transformer replacements required for safety approval (CSA vs UL). If you look in any owners or service manual, they all state that the design and/or specifications are subject to change without notice.
When modifying equipment to add features without the distributor/manufacturer approval, there are external indications (switches, jacks or other things). Other modifications may be made out of necessity due to parts not being available, or even defective design in the original product. This really does happen and not that infrequently.
Lastly there are those modifications that improve the performance of a device (real, measurable improvements). When rebuilding audio equipment I am often asked to improve performance. With today's parts and new component types, these improvements can be made, but there aren't any external indications. Some changes that are visible look so neat and "right" that they pass inspection as being the way the item was made.
If required and supplied with stickers, I would affix them to units that were modified without direction from the distributor/manufacturer. For factory changes, I wouldn't feel the need unless directed to by the distributor or manufacturer. But you can see the range and reach of circuit changes and why they were done. Some changes are unfortunately poorly conceived and executed, and those are the ones I think you are mostly concerned about. Those folks are unlikely to follow any directives from anyone. So it will always be, buyer beware.
-Chris
This is of much more interest with classic automobiles than with hi-fi equipment. I was watching TV coverage of two high-end car auctions. For some cars there was added value if documentation could show that it was all original, but on the other hand there was added value to other cars that has modifications.
I don't think that there is a large market for all original hi-fi equipment.
I don't think that there is a large market for all original hi-fi equipment.
It depends on whether the modifications improve the sound but make the amp less stable.
Without lots of testing it isn't always possible to know the full extent of a modification.
I bought a 1980's Maplin 225WRMS amplifier which had no output transistors.
I bought in brand new genuine transistors and fitted them.
The amp oscillated badly. I had to increase VAS capacitor to tame it.
The oscillation was caused by new transistors never mind a mod !
I tested them on a semiconductor analyser and they had much higher gain than the original spec.
Without lots of testing it isn't always possible to know the full extent of a modification.
I bought a 1980's Maplin 225WRMS amplifier which had no output transistors.
I bought in brand new genuine transistors and fitted them.
The amp oscillated badly. I had to increase VAS capacitor to tame it.
The oscillation was caused by new transistors never mind a mod !
I tested them on a semiconductor analyser and they had much higher gain than the original spec.
Hi Nigel,
Yes! Replacing transistor types in output and/or driver locations can easily cause oscillation. That's why you need an oscilloscope if you work on almost anything. A distortion analyser is also required in case you are charging for your work. If not, working blind is frustrating, so you may as well get a half decent one.
What would have helped you was to look up the original transistor specifications and chose a transistor with similar high frequency characteristics. Even swapping the same STK module number can result in oscillation - never mind a newer version of the same chip.
-Chris
Yes! Replacing transistor types in output and/or driver locations can easily cause oscillation. That's why you need an oscilloscope if you work on almost anything. A distortion analyser is also required in case you are charging for your work. If not, working blind is frustrating, so you may as well get a half decent one.
What would have helped you was to look up the original transistor specifications and chose a transistor with similar high frequency characteristics. Even swapping the same STK module number can result in oscillation - never mind a newer version of the same chip.
-Chris
It got me out of a hole on one project.
I had a faulty amp and tested all the transistors on a DMM. The junctions all tested ok.
In the end the fault was one of the transistors had a Hfe of 1 !
The analyser picked that up straight away.
It was always a strict thing where I worked to only use exact BOM or ECO parts. Especialy aerospace. And someone along the line made that stern recommendation to not change anything except for official cross referenced substitutes. That way if someone's house caught fire etc., the fault can't be traced to me. Sometimes the subs aren't exact.
Maybe since it is not so easy to win a frivolous law suit, it is not so important any more.
Maybe since it is not so easy to win a frivolous law suit, it is not so important any more.
Hi Wavewhipper,
I guess in Canada we don't have as much of a problem with law suites as you do.
Under warranty, we always used the exact part required unless instructed otherwise by the distributor. That's part of the warranty contract for most of the good brands. After warranty periods had expired, we would use the same part or one with greater ratings. I wouldn't stock the lower rated transistors from a series, just the highest rated parts, so if a lower powered set came in, they would get a part that would function identically, but rated for higher voltage, current and / or power. It just wasn't worth keeping all the different skews on hand. We would order special parts from the distributor if we didn't have stock.
-Chris
I guess in Canada we don't have as much of a problem with law suites as you do.
Under warranty, we always used the exact part required unless instructed otherwise by the distributor. That's part of the warranty contract for most of the good brands. After warranty periods had expired, we would use the same part or one with greater ratings. I wouldn't stock the lower rated transistors from a series, just the highest rated parts, so if a lower powered set came in, they would get a part that would function identically, but rated for higher voltage, current and / or power. It just wasn't worth keeping all the different skews on hand. We would order special parts from the distributor if we didn't have stock.
-Chris
Frivolous law suits were previously easy but not since Bush made the no frivolous law suits law. It wasn't long ago, you make a faulty repair, someone gaged on some smoke, and they could sue for pain and suffering, that sort of thing.
I think the $1,000,000 McDonalds coffee burn law suit got that law going.
But he also enacted the three day contract cool down law, in which, supposedly, a citizen has three working days to back out from any contract they find faulty or inferior, or were tricked into.
I think the $1,000,000 McDonalds coffee burn law suit got that law going.
But he also enacted the three day contract cool down law, in which, supposedly, a citizen has three working days to back out from any contract they find faulty or inferior, or were tricked into.
This is the stuff that collectors in general, and particularly Japanese and Korean pay the big money for.
I'm not much into vintage or used gear (except for turntables, arms, and cartridges and/or speaker components), but I will not buy anything that has been modified or inexpertly serviced.
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