Many years ago (decades now) we found that we could buy 1% metal film resistors at a reasonable price. This was especially true with surplus parts in the mid 70's through the mid 80's.
Years before, 1% parts were very expensive and only usually used with precision attenuators in test equipment. 5% to 20% carbon resistors were used everywhere else. In the early 70's Mark Levinson started to use 1% resistors everywhere. They did become somewhat more affordable than previously, especially in quantity, and we knew that they potentially could be quieter than carbon resistors in many locations.
When we could buy 1% military grade resistors surplus from several outlets, we had the price reduced to a comparable carbon resistor, and we could easily get IRC, Corning, Dale, and many others. Unfortunately, these resistors had been sitting on a shelf, perhaps for years and the solder plated leads got oxidized. This made the resistors look bad and hard to solder reliably. We found that SCRAPING the leads of the resistors removed the tarnish best and actually removed a bit of the residual solder, that was probably not the best quality. This is VERY TEDIOUS, but worth it.
Even today, with more recent new purchases, we scrape each lead just before it is bent and soldered in. We also use solder holders to keep our hands off the solder, and pretreat the solder with Cramolin, before use. Each tiny detail makes a small difference, at least in our satisfaction that we have done our job as good as we can do it.
The listening results are the final proof.
Years before, 1% parts were very expensive and only usually used with precision attenuators in test equipment. 5% to 20% carbon resistors were used everywhere else. In the early 70's Mark Levinson started to use 1% resistors everywhere. They did become somewhat more affordable than previously, especially in quantity, and we knew that they potentially could be quieter than carbon resistors in many locations.
When we could buy 1% military grade resistors surplus from several outlets, we had the price reduced to a comparable carbon resistor, and we could easily get IRC, Corning, Dale, and many others. Unfortunately, these resistors had been sitting on a shelf, perhaps for years and the solder plated leads got oxidized. This made the resistors look bad and hard to solder reliably. We found that SCRAPING the leads of the resistors removed the tarnish best and actually removed a bit of the residual solder, that was probably not the best quality. This is VERY TEDIOUS, but worth it.
Even today, with more recent new purchases, we scrape each lead just before it is bent and soldered in. We also use solder holders to keep our hands off the solder, and pretreat the solder with Cramolin, before use. Each tiny detail makes a small difference, at least in our satisfaction that we have done our job as good as we can do it.
The listening results are the final proof.
I use 0000 steel wool to tidy up the leads to parts. It does an excellent job of cleaning things without removing too much of the plating. It also leaves the leads looking mirror-polished and generally spiffy--better than new, in fact.
Every time I post that I use steel wool, someone feels obliged to make an outraged post, pointing out the obvious: That steel wooling (and for that matter, John's scraping method, too) the leads will drop little bits of metal into the circuit. They then go on to rake me over the coals for doing something so dangerous and irresponsible.
Folks, it's only a hazard if you're stupid enough to do it over the circuit. Anyone with enough sense to pound sand should be able to figure out that if you do it off to one side--in my case, over the cardboard box I use for a trashcan--it won't cause problems. I've been using this method for years and never had a short yet. Well, except for the time a rather foolhardy spider happened to walk across the circuit board for my main tube amps...but that wasn't my fault. Scarred the board, too. Who'd a thunk a little-bitty critter less than the size of my pinkie fingernail could cause such grief? Body gone. Vaporized. For some reason his legs remained, which at least simplified forensics.
I believe I heard that Cramolin, per se, was removed from the market due to fluorocarbons. I still have a small stash of the original stuff.
Grey
Every time I post that I use steel wool, someone feels obliged to make an outraged post, pointing out the obvious: That steel wooling (and for that matter, John's scraping method, too) the leads will drop little bits of metal into the circuit. They then go on to rake me over the coals for doing something so dangerous and irresponsible.
Folks, it's only a hazard if you're stupid enough to do it over the circuit. Anyone with enough sense to pound sand should be able to figure out that if you do it off to one side--in my case, over the cardboard box I use for a trashcan--it won't cause problems. I've been using this method for years and never had a short yet. Well, except for the time a rather foolhardy spider happened to walk across the circuit board for my main tube amps...but that wasn't my fault. Scarred the board, too. Who'd a thunk a little-bitty critter less than the size of my pinkie fingernail could cause such grief? Body gone. Vaporized. For some reason his legs remained, which at least simplified forensics.
I believe I heard that Cramolin, per se, was removed from the market due to fluorocarbons. I still have a small stash of the original stuff.
Grey
John,
What is it that makes your boards sticky?
As I've mentioned, I make my own boards. I am in transition from that horrid laser print transfer method to optical. In either case, I end up with just bare FR-4 and copper traces and they're not sticky, whereas pictures I've seen of the Blowtorch lead me to believe that your CTC boards may be gold plated. Is it a residue left after the plating?
I clean my boards with either acetone or lacquer thinner after etching, then spray them with clear acetate lacquer to prevent surface oxidation. It also provides a modest amount of protection against shorts, should a bare wire touch the board. The boards aren't sticky, either as bare boards or after lacquering. My oldest lacquered board is on the order of fifteen, maybe eighteen years old and looks and functions just fine. No, I'm not suggesting that you use lacquer (if your boards are gold plated, you don't need it)...that's just something I hit on after trial-and-erroring my way through a number of other methods of surfacing my boards.
I was curious at first as to how FR-4 would respond to acetone or lacquer thinner, both of which are good at dissolving plastic resins. Neither seems to cause any noticeable degradation. I vaguely seem to recall seeing a post from you saying that you use something other than FR-4, but can't remember what. As a result, your mileage may vary, as they say, but acetone and lacquer thinner are both cheap and readily available. It would be a quick and easy experiment.
For what it's worth, I also burnish my boards to make sure that the copper has as fresh a surface as possible. That's right before I rub them down with solvent in preparation for lacquering, so there's no steel wool left on the board. The first wipe-down is a little messy, given that there's a small amount of steel wool and copper dust left on the board. By the second or third wipe, it's pristine and the rag comes away white. I also rub the edges of the board to remove anything that might be hiding in the rough stuff at the cut edges. And, yes, I even wipe the fiberglass side of single-sided boards. Why? I dunno. Anal, I guess. Just want the thing to look nice. (The glossy surface is not marred by either solvent, which was the thing that finally convinced me that using fairly active solvents was okay. I figure that if there was a problem, it would destroy the finish on the glossy side.)
Grey
What is it that makes your boards sticky?
As I've mentioned, I make my own boards. I am in transition from that horrid laser print transfer method to optical. In either case, I end up with just bare FR-4 and copper traces and they're not sticky, whereas pictures I've seen of the Blowtorch lead me to believe that your CTC boards may be gold plated. Is it a residue left after the plating?
I clean my boards with either acetone or lacquer thinner after etching, then spray them with clear acetate lacquer to prevent surface oxidation. It also provides a modest amount of protection against shorts, should a bare wire touch the board. The boards aren't sticky, either as bare boards or after lacquering. My oldest lacquered board is on the order of fifteen, maybe eighteen years old and looks and functions just fine. No, I'm not suggesting that you use lacquer (if your boards are gold plated, you don't need it)...that's just something I hit on after trial-and-erroring my way through a number of other methods of surfacing my boards.
I was curious at first as to how FR-4 would respond to acetone or lacquer thinner, both of which are good at dissolving plastic resins. Neither seems to cause any noticeable degradation. I vaguely seem to recall seeing a post from you saying that you use something other than FR-4, but can't remember what. As a result, your mileage may vary, as they say, but acetone and lacquer thinner are both cheap and readily available. It would be a quick and easy experiment.
For what it's worth, I also burnish my boards to make sure that the copper has as fresh a surface as possible. That's right before I rub them down with solvent in preparation for lacquering, so there's no steel wool left on the board. The first wipe-down is a little messy, given that there's a small amount of steel wool and copper dust left on the board. By the second or third wipe, it's pristine and the rag comes away white. I also rub the edges of the board to remove anything that might be hiding in the rough stuff at the cut edges. And, yes, I even wipe the fiberglass side of single-sided boards. Why? I dunno. Anal, I guess. Just want the thing to look nice. (The glossy surface is not marred by either solvent, which was the thing that finally convinced me that using fairly active solvents was okay. I figure that if there was a problem, it would destroy the finish on the glossy side.)
Grey
"ITW" Illinois Tool Works Inc.N-Channel said:
Chemical Products - Germany
http://www.itwcp.de/en/index.html
Some time ago I worked for a ITW company. After I left, a friend that still worked there called and asked me where he could get Cramolin. I told him that it was a product of his company. No one can keep track of all the small companies that ITW owns.
I use polystyrene caps, too. They're not exposed to the solvent. I don't use solvents after the board is populated--only when it's in preparation. The solvents and lacquer only touch the naked board. I then solder through the lacquer, which sounds like it would be a problem, but isn't. The lacquer withdraws exactly as much as the solder covers the copper, but no more; even after years I've not seen any halo of oxidation around the solder joints. When I'm done, the solder is exposed, but the rest of the board remains sealed.
I wandered a bit in my previous post, but I was curious as to what's on your boards that makes them sticky.
Grey
I wandered a bit in my previous post, but I was curious as to what's on your boards that makes them sticky.
Grey
- Status
- Not open for further replies.