Electronics > Beginners

Power Supply Repair

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t1d:
Here's several more;-)

There are strong glues that are also intended, and designed, to be removable. Check into those. You need an industrial glue guy. Maybe call a manufacturer. Companies like to help folks. Maybe 3M?

As an example, but not necessarily for this particular use, is hot glue. It is easily defeated by isopropyl alcohol. It shocks (not electrically) the hot glue's chemistry, somehow, and the glue instantly becomes brittle. You just chip it away, in chunks. The effect only lasts, until the alcohol dries, but you just have to reapply it.

Another glue trick I use is "Shoo Glue." It is made for putting the sole back on a shoe. Tough stuff... But, it can be removed, by pulling it off. Stretching it causes it to relieve. It takes a lot of careful work, though.

Also, you need to find out what type of plastic the wheel is made out of. Some glues won't stick. Super glue, for instance, doesn't stick to some plastics. And, some types might hurt the plastic... Think about how model airplane glue sort of melts the plastic. You can't have that happen.

Oh, here's an easy idea... Use a hose clamp, over the base of the pulley. Get the kind of clamp that will unscrew the track, completely, to open it. Some won't open that far. Slide it over the hub and squeeze the hub down, onto the stem.

Here's another idea... Cut a keyway, into the stem of the pot and the hub of the pulley. Install a key, to mate the two.

Yet another... Cut the stem, of the pot, down the center. Drive a wedge, into the cut, to spread the stem.

Maybe try a Dremel rotary tool, with a cutting wheel. Because the pot is not in the best of shape, be careful, with vibration, and seal it with removable tape, to keep the dust out of it.

But, to be honest, I bet that pot is a common pot. Replace it, with one that has the right value, body size and pick a stem that will work to repair the slippage.

patrickoneal:

--- Quote from: t1d on November 15, 2018, 12:56:32 pm ---Here's several more;-)

There are strong glues that are also intended, and designed, to be removable. Check into those. You need an industrial glue guy. Maybe call a manufacturer. Companies like to help folks. Maybe 3M?

As an example, but not necessarily for this particular use, is hot glue. It is easily defeated by isopropyl alcohol. It shocks (not electrically) the hot glue's chemistry, somehow, and the glue instantly becomes brittle. You just chip it away, in chunks. The effect only lasts, until the alcohol dries, but you just have to reapply it.

Another glue trick I use is "Shoo Glue." It is made for putting the sole back on a shoe. Tough stuff... But, it can be removed, by pulling it off. Stretching it causes it to relieve. It takes a lot of careful work, though.

Also, you need to find out what type of plastic the wheel is made out of. Some glues won't stick. Super glue, for instance, doesn't stick to some plastics. And, some types might hurt the plastic... Think about how model airplane glue sort of melts the plastic. You can't have that happen.

Oh, here's an easy idea... Use a hose clamp, over the base of the pulley. Get the kind of clamp that will unscrew the track, completely, to open it. Some won't open that far. Slide it over the hub and squeeze the hub down, onto the stem.

Here's another idea... Cut a keyway, into the stem of the pot and the hub of the pulley. Install a key, to mate the two.

Yet another... Cut the stem, of the pot, down the center. Drive a wedge, into the cut, to spread the stem.

Maybe try a Dremel rotary tool, with a cutting wheel. Because the pot is not in the best of shape, be careful, with vibration, and seal it with removable tape, to keep the dust out of it.

But, to be honest, I bet that pot is a common pot. Replace it, with one that has the right value, body size and pick a stem that will work to repair the slippage.

--- End quote ---

I don't think I was completely clear on the issue. The pulley has a collet that locks down on the pot shaft. That pulley and collet is fine and grips as it should. The actual shaft of the pot can be completely pulled out of the pot itself, with the shaft still attached to the pulley. It's been working fine since I pushed the shaft back in, but I might pull the machine back apart, check for a part number on the pot and see if it's anything special, and glue the shaft back into it. I do appreciate the advice though.

tautech:

--- Quote from: patrickoneal on November 25, 2018, 04:38:01 am ---I don't think I was completely clear on the issue. The pulley has a collet that locks down on the pot shaft. That pulley and collet is fine and grips as it should. The actual shaft of the pot can be completely pulled out of the pot itself, with the shaft still attached to the pulley. It's been working fine since I pushed the shaft back in, but I might pull the machine back apart, check for a part number on the pot and see if it's anything special, and glue the shaft back into it. I do appreciate the advice though.

--- End quote ---
I'd guess the pot was a sealed preset type, in that the shaft is in the form of an X and just slides into the X in the pot center axis and the string tension on the pulley stops the pulley and shaft from disengaging....or it's supposed to.
If the pot's operation is OK and just the shaft keeps wandering out, why not just form a long metal finger to keep the pulley center held towards the pot. Bolt it onto the flat surface below the pulley or from the side of the box somewhere handy.

Finding a pot that can accommodate a sliding shaft, well not impossible but it might be easier to do a simple fix.
OTOH, was the shaft originally held into the pot with a circlip...well an E clip ?

6PTsocket:
I have not seen the pot so It is hard to make a suggestion but I can make a few points. Most types of Locktite EAT many types of plastic.I once rebuilt a fishtank diaphram pump. The nut on the diaphram had been locked with a dab of paint. I used a tiny drop of Loctite. The next time I looked, the whole side of the pump case was mush. I have used Goop for right duty plastic fastening and found no solvent damage. JB Weld works quite well on some plastics. I would look to see what was originally designed to hold the shaft and take it from there. A mechanical solution might work.

Sent from my SM-G900V using Tapatalk

patrickoneal:
I finally got my DER EE DE-5000 LCR Meter. I tested all the caps I replaced, but none of them look bad to me. I'm confused as to why the machine works now, unless there were cracked solder joints I repaired in the process. None of the caps would produce a readout at 100khz on the meter, which I found a bit odd. I guess it's some limitation of the meter. Here are the higher frequency readings I got:

Electrolytic Caps:
Cap 1: 1200µf 35V measured at 1kHz: 1100µf 0.03 ohms
Cap 2: 1200µf 35V measured at 1kHz: 1084uf 0.03 ohms
Cap 3: 560µf 35V measured at 1kHz: 486µf 0.04 ohms
Cap 4: 47µf 63V measured at 10kHz: 43.9µf 0.53 ohms
Cap 5: 33µf 63V measured at 10kHz: 27.7µf 0.80 ohms
Cap 6: 120µf 400V measured at 10 kHz: 91µf 0.24 ohms

X2 Safety Cap(metalized film?):
0.1µf 275V This one is weird. It measured 11 Megaohms at 100 Hz, 9 Megaohms at 120Hz, 7.6 Ohms at 1 Khz, 1.6 Ohms at 10 kHz, and 0.30 Ohms at 100 kHz. I'm not really sure what it should measure, or how to further test it.

I got the meter to satisfy my curiosity first, and secondly to understand which of the parts I replaced had actually failed so I can apply that knowledge to future repairs. The machine works now, I'd just like to know why :)

Does anything jump out at anyone? Any thoughts on why the DE-5000 would just read OL when trying to read ESR at higher frequencies?

Thanks.

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