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LOL LOOK AT THE SCOPE. Especially when he says it looks good
- Thread starter Low_Boy
- Start date
These would be a bad choice because it has only 20ga. stranded center conductor.
I think the conductor will go to plasma state when hit with 800 watts dead key. Even if it says in the specifications 8 Kilo watts.
I hope you polished these with 1500 grit before the install. The gouges left by the diamond knife sharpener will do heat transfer a disservice.
I won't even start to wonder what ESD methods were used.
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Apples and oranges. Those Teflon cables from DX Engineering are true Mil-spec and are good to 12 Gigahertz. They are not RG-58 or RG-8x made up in the back room of a CB shop either. There are applications where that level of isolation is required such as VHF/UHF/SHF EME installations.
You beat me too it. A properly lapped surface should be almost mirror finish and certainly have no scratches on it.
This is the second one I've done. The first one is still kicking 10 years later. No mirror finish necessary.
So does that mean checking the transistor for flatness is a complete waste of time? There are amps out there that have been running for years without this ever being done. The logic youre using here is that if it hasn't blown up yet it has to be the right way.
I have several amplifiers that were put together without lapping the transistors. Some of them are 10 years old or more with the original transistors. That must mean it's not necessary to lap them at all.
The question of properly lapped surfaces of both the heatsink and the solid-state device bolted to the heatsink isn't even up for discussion it goes without saying that perfectly flat device tab bolted to a perfectly flat heatsink surface would not even need heatsink compound. The real question is do you have the proper airflow over the heatsink and in the case of a system that uses the case for a heat sink that air flow is none existent. In the case of amplifiers that have heatsinks the heatsink is of little help once it reaches a critical state of heat saturation if there is no airflow to remove the heat from the fins.
So after nearly 50 years of doing this, I still have old 455 amps that are 30 years old and have run fine without the help of any fan and most certainly don't have perfectly matted surfaces I also have some old Galaxy 88 chassis that have been beaten to He-dbl L and back and have never had the finals or regulators changed because of failure. I think it speaks more to how durable these devices are than how perfect/imperfect the mating surface may be. After having repaired literally many thousands of devices over the last 45 years I can tell you it sometimes amazes me how some of these items can take a licking and keep on ticking and in other cases how quickly some bite the dust, and yes I know that many of the failed devices are the result of problems with hacking and improper installation but on the same note it's amazing how some seem to keep working in spite of how they have been hacked. It reminds me of my doctor after finding out I had a 200+ over 130 blood pressure he simply looked at me and said "YOU SHOULD BE DEAD" while he was giving me nitro to knock it down and this could be the result of how I hacked my body?.
So after nearly 50 years of doing this, I still have old 455 amps that are 30 years old and have run fine without the help of any fan and most certainly don't have perfectly matted surfaces I also have some old Galaxy 88 chassis that have been beaten to He-dbl L and back and have never had the finals or regulators changed because of failure. I think it speaks more to how durable these devices are than how perfect/imperfect the mating surface may be. After having repaired literally many thousands of devices over the last 45 years I can tell you it sometimes amazes me how some of these items can take a licking and keep on ticking and in other cases how quickly some bite the dust, and yes I know that many of the failed devices are the result of problems with hacking and improper installation but on the same note it's amazing how some seem to keep working in spite of how they have been hacked. It reminds me of my doctor after finding out I had a 200+ over 130 blood pressure he simply looked at me and said "YOU SHOULD BE DEAD" while he was giving me nitro to knock it down and this could be the result of how I hacked my body?.
I started a company that built Solid State Refrigeration units. The outsides of the Peltier effect devices are a fragile beryllium ceramic. Heat sinks required drilling and tapping on the same side the and the machining would deform the metal. The heat sinks had to be lapped to get it as flat as possible, otherwise when you tightened the heat sinks together you would hear a high pitched snap and then the heat sink would ring. That was the sound of the thermo-electric module cracking and around Thirty Dollars worth of parts going out the window.
You also had to use heat transfer compound sparingly. Too much and it would not work as well as it should. Too little and the part would fail early which was bad since they were supposed to last at least 25 years.
I used a piece of perforated prototyping board like a notched trowel. I have units that have been in continuous operation since 1996.
You also had to use heat transfer compound sparingly. Too much and it would not work as well as it should. Too little and the part would fail early which was bad since they were supposed to last at least 25 years.
I used a piece of perforated prototyping board like a notched trowel. I have units that have been in continuous operation since 1996.
Sorry if I came off as saying that lapping the transistors and heatsink was useless. I believe it is good practice.
It was a failed attempt to make another point. Plenty of jacked up amplifiers have been in service for many years. Whether you lap, don't lap or make a poor attempt is not the only factor in how long something lasts.
It was a failed attempt to make another point. Plenty of jacked up amplifiers have been in service for many years. Whether you lap, don't lap or make a poor attempt is not the only factor in how long something lasts.