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Fazio Electric
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mansaxel:

--- Quote from: rsjsouza on December 26, 2021, 04:57:13 pm ---
There are other minor things such as shotgun replacement of capacitors, etc. but these are more or less justified depending on the conditions.

--- End quote ---

I for one think -- while not being a confessed shotgunner myself -- that replacing caps is a refreshing down-to-earth attitude compared to the mythicism surrounding old leaky crapacitors; a bad offspring of the tube vulture vandalism.

It is the circuit that does the sound, not the age of the crapacitor. Any fool can swap in a NOS cap. Hardly any fool can design an amp. This borders on audiophoolery practices, which a lot of the time is "We can't change what's important (the acoustics of the room) so we place the speaker cables on small supports of special wenge and pockenholz construction and think that it's going to make our horrible room sound better."

There is one case of "worse is better", though, that bears mentioning:

Many years ago, I worked at a place where we were tasked with repairing theatrical dimmer packs, the kind where there's a 30A input, and 6 5A circuits controlled by a 0-10V signal per circuit. The triac would fail, and sometimes take the trig optocoupler and an adjacent resistor with it.  We looked up the values, got new parts, slapped it together, and out the door. Tested, working.

It came back, a bit too often, with the resistor fried. Ok, higher wattage resistor in, out the door, next!

And it came back again. Same fault.  It turns out that the original resistor was carbon comp. We'd fitted metal film. According to the manufacturer, the circuit was marginal enough that there were latent oscillations in it that only were tamed if the resistor was carbon comp. If a "better" metal film resistor got replaced, the oscillations went on a rampage.
nctnico:

--- Quote from: rsjsouza on December 26, 2021, 04:57:13 pm ---
--- Quote from: bsfeechannel on December 26, 2021, 04:27:55 pm ---
--- Quote from: rsjsouza on December 26, 2021, 12:59:24 pm ---Despite some procedural no-nos here and there,

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Example?

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Sure. In one of her last videos (or perhaps the last), she was repairing an amp sitting upright with all vaccuum tubes fitted. Easily disastrous scenario if the amp topples and breaks them.

Also, in the same video she was soldering/desoldering parts on the sockets with the vacuum tubes fitted - the thermal stress of rapidly heating/cooling the socket pins is also propagated to the tube pins, which can create small leaks in the metal/glass junction and reduce the lifespan of the tube. This was a common alert on all the vacuum tube manuals I ever read.

There are other minor things such as shotgun replacement of capacitors, etc. but these are more or less justified depending on the conditions.

--- End quote ---
I noted the can of Deoxit contact cleaner which was used to clean destroy the potmeters on a unit :scared:  A real repair would be to replace the potmeters with new high quality ones. Or just leave the potmeters as-is if they are fine. If it ain't broken don't ruin it.
rsjsouza:

--- Quote from: bsfeechannel on December 26, 2021, 06:24:46 pm ---
--- Quote ---There are other minor things such as shotgun replacement of capacitors, etc. but these are more or less justified depending on the conditions.

--- End quote ---

What is a "shotgun replacement of capacitors"? Did you perhaps mean the use of a heatgun to replace capacitors?

--- End quote ---
Ah, the term "shotgun" (espingarda) alludes to the very wide blast area of a shot that comes from a shotgun and is usually used when someone in repair goes and replaces all parts regardless of their current state. As you can imagine, this is very common with capacitors.

I, for one, always try to avoid doing this whenever faced with an equipment repair. Obviously that, depending on the complexity of the repair, importance of equipment or obvious recurring faults, this is the best approach.


--- Quote from: mansaxel on December 26, 2021, 06:39:36 pm ---I for one think -- while not being a confessed shotgunner myself -- that replacing caps is a refreshing down-to-earth attitude compared to the mythicism surrounding old leaky crapacitors; a bad offspring of the tube vulture vandalism.
--- End quote ---
I don't believe in the capacitor voodoo as well - I just hate replacing parts with no justification.

Throughout the years, however, I was faced with several scenarios where rows of capacitors were suspicious enough to warrant a shotgun replacement, such as my grandparents' 1946 Philips radio that had several paper-oil capacitors replaced in the early 1980s by my dad. This year I put it back on my table to do a renovation and all of them showed higher leakage than an original tar capacitor that he forgot to replace back then. I can't help but wonder if all these indeed needed replacement back then, but that is now history. Not to mention that, when a tar capacitor goes "kaboom", it makes quite a mess (just like the box Rifa capacitors).


--- Quote from: nctnico on December 26, 2021, 07:35:50 pm ---I noted the can of Deoxit contact cleaner which was used to clean destroy the potmeters on a unit :scared:  A real repair would be to replace the potmeters with new high quality ones. Or just leave the potmeters as-is if they are fine. If it ain't broken don't ruin it.

--- End quote ---
Although Deoxit is less crap than WD40 (commonly used by inexperienced people), some of these pots are unfortunately irreplaceable or their purchase is absurdly costly, making people take those desperate measures. Although Caig has some recommendations for potentiometer maintenance - I am not sure what product she used, though.
nctnico:

--- Quote from: rsjsouza on December 26, 2021, 08:53:19 pm ---
--- Quote from: nctnico on December 26, 2021, 07:35:50 pm ---I noted the can of Deoxit contact cleaner which was used to clean destroy the potmeters on a unit :scared:  A real repair would be to replace the potmeters with new high quality ones. Or just leave the potmeters as-is if they are fine. If it ain't broken don't ruin it.

--- End quote ---
Although Deoxit is less crap than WD40 (commonly used by inexperienced people), some of these pots are unfortunately irreplaceable or their purchase is absurdly costly, making people take those desperate measures.

--- End quote ---
According to my experience using 'contact cleaner' always makes the situation worse in the long run. The oil turns dust into a fine grinding paste and the acids will slowly corrode everything away. The worst part is that wires will wick it to other places causing havoc. My firm believe is that contact cleaner is great to make a piece of equipment work for another day before you throw it into the trash. Over the years I have seen enough examples of equipment which would be perfectly restorable if some idiot didn't use contact cleaner on it in the past.

If you really want to clean a contact or potmeter, take it apart and use alcohol to get rid of dust & oil and re-apply acid-free grease where necessary.
rsjsouza:

--- Quote from: nctnico on December 26, 2021, 09:00:41 pm ---If you really want to clean a contact or potmeter, take it apart and use alcohol to get rid of dust & oil and re-apply acid-free grease where necessary.

--- End quote ---
Indeed that is the best repair method.
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