Author Topic: Repairable (?) equipment  (Read 566 times)

TC Chris

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Repairable (?) equipment
« on: February 25, 2018, 06:47:56 PM »
Out in my shop I have a big old Sears shop vac, called a "dust collection system."  I inherited it from an old family friend when he was in his 90s. I got his drill press, radial arm saw, and  big old jig saw from a pattern shop.   He did a lot of wood turning and was allergic, as he got older, to many cool woods like walnut and apple. I think he was using this vac to keep turning without consequences.  It' a cool old device--a big 55-gallon cardboard drum with a fan system atop it.  A number of years ago after sucking abrasive bottom paint while sanding on the boat the bearings got noisy so I took it apart and used some old roller-blade bearings "temporarily."   Well, they've been noisy again so today was the someday-project day.  After disassembling and reassembling there was some little metallic thing loose in the fan.  It was pretty well sealed up--sheet metal formed over a pot metal motor body.  Couldn't get at it or even see it. Maybe it won't matter....  Plugged the vac in and yup, it did matter.  Little flakes of metal were coming out the exhaust and something sounded bad.  So I had to get the Dremel tool out, mount a cutting blade, and start cutting slits in the sheet metal part of the housing. Eventually I got a stray washer out.  Problem solved.  Now I've got to drill and tap for some screws to hold it back together.  But it's repaired.  And you know, the bearings felt OK.  One was a bit dry.  I squirted some grease in.  Sounds fine now.  And the brushes on that motor--geez, they'll be going strong when the next person inherits the device.

The big lesson, which most of you know, is that any project that you think will take X hours will usually take X times 3. 

Chris Campbell

ed from Baltimore

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Re: Repairable (?) equipment
« Reply #1 on: February 25, 2018, 10:49:09 PM »
        My mother's 40 year old Amana frig, which is coming 120 miles from Baltimore to Bethany in a rental truck,  accompanied by my aunt's '61 Magnavox next weekend, has a strangely built condenser fan motor and I wonder if you have ever "unsealed" one of these sealed for life motors.
       It has one full length motor shaft in a hollow armature and  the  shaft is grooved for part of its length. There is a huge felt wick maybe 1/2 inch  thick and the motor shaft has at least 1/2 inch of end play (!)   When the motor is running, the reaction force of air against the fan blades pushes the shaft to one end and it stays there.
         When the motor turns off the shaft oscillates end to end until it stops and presumably the spiral groove grabs some oil from the wick and distributes it up and down the bronze bearing. I had to pry off an aluminum cover to see the felt, which was bone dry after 40 years, so I drenched it with turbine oil and tapped the cover back in place. I sealed the cover seam with fingernail polish because something similar had to be chipped off the seam to get the cover off.
          The motor has been running silent and smooth the last 4 years so I guess the end play and felt wick and spiral groove is designed into it, but I am sure I have never seen a motor where the end play is intentional and part of a lubrication system. I'd love to hear about other motors that use the same principal. 
          I wish to heck that all vacuum tube equipment, especially with 5U4s, EL84s, and rows of 6V6s came equipped with a couple of carefully placed fans like this one. Even though it has "normal" blades, not squirrel cage, you can't hear it unless within a foot or two. Maybe it would drag in lots of dust, but at least a lot less recapping of these units would be needed, after fifty years, just a little re-oiling of the felt wick. Assuming also that everyone had Variacs and could talk owners into resisting the temptation to "try 'er out just to see" before selling their consoles!!   

TC Chris

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Re: Repairable (?) equipment
« Reply #2 on: February 26, 2018, 12:34:36 AM »
       
         When the motor turns off the shaft oscillates end to end until it stops and presumably the spiral groove grabs some oil from the wick and distributes it up and down the bronze bearing. I had to pry off an aluminum cover to see the felt, which was bone dry after 40 years, so I drenched it with turbine oil and tapped the cover back in place. I sealed the cover seam with fingernail polish because something similar had to be chipped off the seam to get the cover off.
         
          I wish to heck that all vacuum tube equipment, especially with 5U4s, EL84s, and rows of 6V6s came equipped with a couple of carefully placed fans like this one. Even though it has "normal" blades, not squirrel cage, you can't hear it unless within a foot or two. Maybe it would drag in lots of dust, but at least a lot less recapping of these units would be needed, after fifty years, just a little re-oiling of the felt wick. Assuming also that everyone had Variacs and could talk owners into resisting the temptation to "try 'er out just to see" before selling their consoles!!

Sounds like an interesting mechanical design.  I had a '49 GE fridge in my little cottage... a tenant reported that it wasn't cooling... the refrigeration guy said "compressor probably dead." I replaced it and was going to have it converted to modern refrigerant and donate it to the local national park for one of their old dwellings ( I had already given them a '49 electric range).  The shop doing the job called me to say they had bad news--the fridge was running and cooling just fine and they didn't think they should do the conversion if it was working. 

Now we've got all these little computer fans that are silent and effective.  Long ago I was making up a fan for my Dad's Heath AA-100 amp.  I had a limited budget and bought a cheapie that used an airplane-propeller type blade.  It wasn't  silent, but it did move air over the bank of output tubes (7591). 

Chris Campbell

ed from Baltimore

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Re: Repairable (?) equipment
« Reply #3 on: February 27, 2018, 01:33:05 AM »
    Those 7591As !!   They must've been designed to one physical dimension only with no diameter variations allowed, because some stereo "low silhouette" amplifiers lined them up 4 in a row with 1/16 " between them if you were lucky, sometimes with an aluminum heat reflector shield between them and the rest of the amp chassis, including some doomed electrolytic caps.  Add to that a 5AR4, a squashed down power transformer, maybe a matching tuner placed on top to cut off even more air flow, a solid wooden cabinet with shut doors, and you have a hot-cold environmental test chamber stuck in the hot position.
         Electro-Voice made the A-20 amp in the mid fifties with 2 5Y3s and 2 6V6s on a standard chassis with generous spacing between the tubes, caps, transformers all above chassis and all other components below. Later they made the A-20L (I had one) lowboy chassis with tubes and filter caps squeezed under a vented top lid all placed on their sides and nearly touching. It looked like a compact preamp but it was the exact circiuit part for part of the A-20. Google Electro-Voice vintage audio images A-20 and A-20L and take a look.
       HH Scott kept changing the 7591 tube layout on their LK-72 (had one of those too)and similar 299 models and I think Fisher did on their 500, 600, and 800 receivers, probably after seeing the ways creative owners squeezed them into unvented  bookshelves.
       Those fans, quiet or airplane propellor noisy, could have  prevented so many premature deaths. 
         That GE frig story happened to me too. After being stored for fifteen years unused in the basement I tried  out my mother's turquoise side-by-side Frigidaire. Just a hum, then the thermal cutoff shut it off. Tapped on the compressor thru a wooden block gently for hours at a time.  After 3 0r 4 days, the motor would spin but no cooling. A few more days of tapping and an occasional propane torch running up and down the metal pipe connections and suddenly one day, forgot to turn it off between tap sessions and when I came down next, opened the doors and icy air greeted me. Gave it to friends who had just bought a house and it was their kitchen frig for 20 more years before they got tired of the turquoise color.
      I used to have a GE from that era. Early models had a door with nothing on its inside but a temperature "safe" in the green zone indicator. Later models had a heated adjustable butter keeper in the door that was probably an RF interference generator.
       Saw one apart once. The compressor has a machined offset rotating solid cylinder with a radial slot cut in it. A phenolic blade fits in the slot and slides in and out of a elliptic machined cylinder bore past suction and pressure ports. No other reciprocating parts and only one rotating part. If it sits for years the phenolic blade freezes in position, but if the motor is run again, plus tapped, plus goes through a couple of heat and cool cycles, the blade frees up and it becoes a compressor again. Like an old tube console---if you're patient on how you power it up after a long winter's nap, it will rise again like a phoenix.
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TC Chris

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Re: Repairable (?) equipment
« Reply #4 on: February 27, 2018, 08:12:37 PM »
   
         
         
      I used to have a GE from that era. Early models had a door with nothing on its inside but a temperature "safe" in the green zone indicator. Later models had a heated adjustable butter keeper in the door that was probably an RF interference generator.
       Saw one apart once. The compressor has a machined offset rotating solid cylinder with a radial slot cut in it. A phenolic blade fits in the slot and slides in and out of a elliptic machined cylinder bore past suction and pressure ports. No other reciprocating parts and only one rotating part. If it sits for years the phenolic blade freezes in position, but if the motor is run again, plus tapped, plus goes through a couple of heat and cool cycles, the blade frees up and it becoes a compressor again. Like an old tube console---if you're patient on how you power it up after a long winter's nap, it will rise again like a phoenix.
                                                                   

Maybe mine just got stuck!  I miss it, because the new ones are much deeper and take up more space in a small kitchen. I saved mine after buying the new one.  It sat for a few months in a friend's garage, then got hauled on its side to the appliance shop, then down the freight elevator to the basement, where it was found to work.  Lots of jiggling to get the phenolic blade loose!  I counted it up--I had owned 4 of those GE fridges over the years, all basically the same mechanical configuration with a few sheet-metal variations on the doors and some changes in the innards like shelves and butter compartments.  One of them had been rolled end-for-end, kawhump-kawhump down a driveway for the trash pickup before I found it.  It ran just fine, and after a few years when I moved I gave it to a university work crew for their break room.  It may still be running there.  Those were not disposable devices.

Chris Campbell