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Ever see a Heathkit AS-103?


donquixote99

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to the OP: Yep, we all enjoy the thrill of an exciting "find", and there should never be any objection to spending cash at a charity thrift store.

And David's comment brings us right back to square one: just exactly how is a "good one" defined, when speaking of capacitors?

Meanwhile, it is interesting to reflect on this attached piece of dated price list. To those many of us who have opened up several old AR speakers or who have read many threads in this forum, we know that the type-manufacturer-style of capacitors showed a rather wide variety. Yet in 1977 AR was publishing a one-price-fits-all data sheet for replacement caps, which suggests to me that they never used any high-falutin' special breed or brand or bromide component in fulfilling these sales orders. They bought 'em cheap by the truckload, and then marked up the price just for you - - no different from Parts Express or other middlemen today. My guess is that with the possible exception of the very early oil-filled caps or the hearty blue Sprague Compulytics, all of these cap configurations we are discussing most probably exceed the performance of the factory originals.

post-112624-0-42952800-1433899455_thumb.

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to the OP: Yep, we all enjoy the thrill of an exciting "find", and there should never be any objection to spending cash at a charity thrift store.

And David's comment brings us right back to square one: just exactly how is a "good one" defined, when speaking of capacitors?

Meanwhile, it is interesting to reflect on this attached piece of dated price list. To those many of us who have opened up several old AR speakers or who have read many threads in this forum, we know that the type-manufacturer-style of capacitors showed a rather wide variety. Yet in 1977 AR was publishing a one-price-fits-all data sheet for replacement caps, which suggests to me that they never used any high-falutin' special breed or brand or bromide component in fulfilling these sales orders. They bought 'em cheap by the truckload, and then marked up the price just for you - - no different from Parts Express or other middlemen today. My guess is that with the possible exception of the very early oil-filled caps or the hearty blue Sprague Compulytics, all of these cap configurations we are discussing most probably exceed the performance of the factory originals.

attachicon.gif1977 price.jpg

Yep, actually their prices were decent, weren't they?

You need to look no further than the different permutations of AR crossovers within the same model. Would be nice to be able to do freq sweep graphs before and after changing caps though. Then you can actually see what is going on at the crossover points.

I'm still listening to a pair of AR-6's everyday. One was recapped and the other wasn't -- film vs old Royalitic electros. I thought I would run them in for awhile before doing more A/B/C'ing. At the moment they are paired with AR-5's sporting forty-year-old Sprague npe's. I haven't A/B'd the 5's yet since all three set are not functional at the moment.

I think there are some crossover redesigns out there for some of the Classic era speakers also using npe's. They are easy and inexpensive and small. Hard to resist using them.

Roger

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My guess is that with the possible exception of the very early oil-filled caps or the hearty blue Sprague Compulytics, all of these cap configurations we are discussing most probably exceed the performance of the factory originals.

They certainly exceed the price levels. Whether they do anything for actual audio performance is still a matter for conjecture. AR threw about a third of their drivers away because they weren't up to spec. A lot of those were probably good enough that we'd be thrilled to have them today. So they probably wouldn't have skimped on caps if they thought there was better performance to be gotten with more expensive ones.

The oil-filled can caps, btw, were common and cheap at the time. Military surplus. During the 50s and early 60s the electronics stores on Radio Row in NYC sold them out of open crates lined up on the sidewalks.

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They certainly exceed the price levels. Whether they do anything for actual performance is still a matter for conjecture. AR threw about a third of their drivers away because they weren't up to spec. A lot of those were probably good enough that we'd be thrilled to have them today. So they probably wouldn't have skimped on caps if they thought there was better performance to be gotten with more expensive ones.....

Yes, they upgraded the wire on the '74 AR-5's to 105 C rating and switched to Sprague Compulytics somewhere in that time frame. Not sure who filled Roy Allison's shoes but it took them a few years to come out with the AR-9. They were still players ...

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Roy mentioned to me the other day that if the blue stuff is there, you can pretty much assume they are beyond resurrecting. Mine looked like those and though I cleaned them up and get pretty much a full range of measurement on each, I can't imagine they will last very long. I just wasn't comfortable with them and went with the LPads. Easy peasy and cheap.

Edit: his comment was more like he doesn't try to fix them at that point.

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Those who advised replacing the pots were correct. Cleaned them up, and then looked at them with some good magnification. Ugh. Pitting. Chunks of edge of disk eaten away. Worst damage on edge of disk, right where the contact tracks. There would be noise, and spots of no contact.

So it's either new pots, or l-pads.

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I noticed something. There is a square hole on the front of the housing of my OEM pots, perfect for introducing deoxit and faderlube. Only problem is, when these are installed, that square hole is inaccessible, up against the back of the crossover plate. So I had the idea of drilling a hole in just the right place, so you can squirt treatment and lube into these whenever you want. A once-a-year clean and lube would probably keep clean pots in good shape indefinately. Obviously you'd need a good plug for the holes--put a short screw in them I figure.

Of course this idea is moot in the case of my pots, but if I had good pots I'd do it.

Pic showing hole: post-175813-0-06437900-1434636361_thumb.

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From what I can tell, the purpose of that punched square hole is to create the protruding metal tab on the outer surface of the assembled pot. This tab is intended to fit in the tiny indent on the interior side of the masonite crossover panel, thereby establishing the correct position of the pot so that the rheostat knob aligns properly from 'decrease' to 'increase'. I think the 3a restoration guide may explain this in greater detail.

To your point, though, even when fully assembled, it appears there is sufficient space between the metal and ceramic portions of the pot to be able to squirt your lube or cleaning solution thru the openings, even while the pot is fully installed in-place.

In the past, I have generally been an advocate of trying to restore the original pots, but much like yourself, I am growing less enthusiastic or less patient with the process and sometimes disappointed with the long-term results of these efforts. Nonetheless, I still think decisions on this matter should be evaluated on a case-by-case basis.

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From what I can tell, the purpose of that punched square hole is to create the protruding metal tab on the outer surface of the assembled pot. This tab is intended to fit in the tiny indent on the interior side of the masonite crossover panel, thereby establishing the correct position of the pot so that the rheostat knob aligns properly from 'decrease' to 'increase'. I think the 3a restoration guide may explain this in greater detail.

To your point, though, even when fully assembled, it appears there is sufficient space between the metal and ceramic portions of the pot to be able to squirt your lube or cleaning solution thru the openings, even while the pot is fully installed in-place.

In the past, I have generally been an advocate of trying to restore the original pots, but much like yourself, I am growing less enthusiastic or less patient with the process and sometimes disappointed with the long-term results of these efforts. Nonetheless, I still think decisions on this matter should be evaluated on a case-by-case basis.

Interesting. With the AS-103 the crossover panel is aluminum, there's only a little bit of a stub of a 'tab' at the hole location, and no indent for it to fit into.

You're quite right, there's plently of gap on the side of these pots when assembled. But getting at them that way, of course, requires pulling the woofer. My idea would allow one to accomplish this periodic maintenance with great ease.

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Still waiting for someone to produce a rebuild kit for the Aetna-Pollock pots. If my collection of these gets much larger I may consider it myself!

Roger

There WAS one, a few months back on ebay. It was from a seller in Korea and looked to be of good quality but rather expensive. Don't recall what was included--maybe just the wiper.

-Kent

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Oops, I'd totally forgotten about your earlier pics showing the metal plate at the crossover so of course, you are right, the Heathkit pots must've needed to have a minor modification. That tab was probably clipped or filed down in order to fit against the plate.

Clever thought you're having, though - - the idea sort of reminds me of the oil port of an old Sturmey Archer three-speed bicycle hub.

post-112624-0-52413100-1434652489_thumb.

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From what I can tell, the purpose of that punched square hole is to create the protruding metal tab on the outer surface of the assembled pot. This tab is intended to fit in the tiny indent on the interior side of the masonite crossover panel, thereby establishing the correct position of the pot so that the rheostat knob aligns properly from 'decrease' to 'increase'.

I suspect that the purpose of the tab was not so much to make an index mark (because the variation in resistance of these devices is pretty wide and you can't rely on the indent to be accurate if you're changing one out for another) as it was just to keep the thing from rotating in its hole while the retaining nut is being tightened. It's not as if they were being custom-made for AR at the time.

I always keep my eye out for the older version of this control, where the wiper was a thicker piece of formed brass pressed against the windings by a coil spring. I lucked upon a set of four that I used to in my 3a rebuild, and my 2ax's and 6's could use some level control fixing now.

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genek, your comment is certainly more accurate - - - instead of suggesting that the punch-tab was manufactured for this reason, it should have been stated that AR was able to use the tab for a utilitarian purpose, as you have described, when it becomes nested in the indent slot. And yes, the heavy duty version are rather rare - - I have never come across any.

Kent's recollection in post 41 is similar to mine - - someone in Asia was attempting to fabricate new stamped metal wipers, and I think they also replaced the center contact disc.

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This is my version of a "rebuild", though it would eliminate the worst cases.

Just flipping the center disk might be enough to save quite a few pots.

The disc on this one has lost some of its plating and has corroded around

part of the outside, but it's turned where the wiper doesn't travel.

post-102671-0-80580700-1434677039_thumb.

And, yes, I like the original iteration, though I've only seen them once (in

my tiny collection of 6 pairs of early ARs). Much stouter looking.

CIMG2709.JPG

CIMG2713.JPG

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This is my version of a "rebuild", though it would eliminate the worst cases.

Just flipping the center disk might be enough to save quite a few pots.

The disc on this one has lost some of its plating and has corroded around

part of the outside, but it's turned where the wiper doesn't travel.

How do you remove the rivet? New fastener includes a nut (and lock washer) on the other side?

I trust that pic shows the bad side of that disk....

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I just drilled the pressed side of the rivet out or off, I guess- the end that

faces the outside. Yes, I just used a(n apparently) stainless steel nut and

bolt. It's what I had on hand at that moment.

And that is the good side of the disc. It's what I described- lost some of its

plating and had some corrosion on one edge. It tested good, though, through

all its travel even with a half-eaten wiper, except at each extreme. Those

terminals holding the wire coil needed attention, but I didn't want to

disturb them (the pot in the upper picture).

Obviously this is more for personal use. I wouldn't want, if I was in the biz,

to send this out the door. But I'm a tinkerer, so I took the challenge.

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  • 7 months later...

OK, the AS-103 project is now on again! I'm off to buy laquer thinner and we'll see how the cabs clean up. Then sanding time. Plan is to hand sand, figure there's less chance of overdoing it. But if I get tired of that I may go buy an inexpensive orbital sander....

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