Need help with CT6810p-517

[mixedgas]

When I taught Sunking's staff to test the galvos, and made a fixture for them, I told them to ship with blown fuses. Your galvo was tested at 150 mA and 250 mA dc, for free motion. Nothing more.

[mixedgas]

One does not tear the rotor apart on these. You'll scrape the coil out and loose the upper bearing. It's that tight. I got somewhat burned organizing a group buy on these. Force Sunnking to replace it. It's easy to bypass their ebay "co-ordinatot" if she does not replace it.

[blaine1963]

I shorted the fuse and drove it with my SG (very low power). It still did not respond. So I opened the coil from the PCB, still 2.9 Ohms, but no motion.

I disagree on the spring (It is NOT a torsion rod).

Sunking just responded:
"Thank you for contacting us. We do test these. We had another customer send us a homemade tester he put together for us. I think this tester goes around that fuse. We have not had any problems with the 1000s of units we have tested this way so far. It was bound to happen. We are retesting 2 units and will get them sent right out for you. Please let me know if there is anything else we can do for you. We appreciate your business. Have a great day. "

Sounds like they are referring to you?

So, I am very pleased with Sunking.

[blaine1963]

I was wondering if the Class-D amp would go to DC, are you sure it will not?

[mixedgas]

The spring is not a torsion rod. It puts a mechanical preload on the rotor which can actually slide along the shaft axis a bit. It is there for a reason. When you push the shaft out of your dead one, you will see a thin spiral wound coil bonded to the inside of the galvo body with a specialized heat transfer material. Unlike a G120, you will not be able to rebuild it. When you push it out, the upper bearing will likely scar the coil.

Yes, I organized a group buy here on PL. When they arrived, a full 50% had bad bearings or frozen shafts. I got burned by a promise from the Ebay manager at Sunnking. She stalled me for a month, refused to return calls.

To recover the group buy, I made a tester and went way over her head within the company. I nearly had to drive to Rochester to straighten this out. I could not see a legal out as it was a verbal deal and I had already paid her by credit card. So being a schmart guy, I taught them to screen them and sent them a very nice test kit. She stalled even further. I went further up the food chain. Net result, they raised the price on Ebay and I personally ate a 250$ loss to one purchaser for administering the group buy. They did however send me enough tested pieces plus one spare to complete the deal.

The easiest way is to quickly test without a closed loop amplifier is to set it to one side and see how freely it flips with a constant current source. The other way is to see what the minimum current it "unsticks" at when at rest. They do not test the position sensor at SunnKing.

I was going to sell them a nice amp PCB in bulk, but after phase two of her stalling I decided I had other fish to fry.

They are a very nice Cambridge with a extra precise position sensor. The ones I have have two leds and four photodiodes. This compares to the usual one LED and two PDs on older Cambs.

You may have to carefully drill the mirror mount set screw to install a lower inertia mirror. The set screw is precision torqued into a hole with a ~85% thread, meaning it is so tight it will not come out. Many have Red high temp Loktite as well as the tight thread. Don't put a bend in the shaft or damage the bearings if you try to remove the mount. Clamp the mount, not the galvo.

If you have burned a coil, you may have just learned that Cambridges and clones need a lot of heat sinking.


Steve

[mixedgas]

I was wondering if the Class-D amp would go to DC, are you sure it will not?

Google "Class D Bus Pumping" , going down to DC means even a balanced class D can Bus Pump,

There are a few parts on the market that are DC coupled, but that does not mean they go down to below LF response. They are set up that way for avoiding "pop" in headphones. It is also a function of the symmetrical LC filter structure needed on the output of the class D. Most, ie 99% of stock class D chips will not go down to DC. I had to research that for a former employer.

Steve

[The_Doctor]

Google "Class D Bus Pumping" , going down to DC means even a balanced class D can Bus Pump,

There are a few parts on the market that are DC coupled, but that does not mean they go down to below LF response. They are set up that way for avoiding "pop" in headphones. It is also a function of the symmetrical LC filter structure needed on the output of the class D. Most, ie 99% of stock class D chips will not go down to DC. I had to research that for a former employer.

Steve

Good to see this. When Dream's thread about projector current consumption came up, my first thought was 'measure, then look at what eats the most'. And thought immediately turned to class D amps for efficiency, but I had no idea if any scanners used them. So this is a very well-timed and useful bit of discussion.

The only thing I can add to it is that there are tiny credit-card sized class D amps, modules, maybe these can do LF all the way to DC? Dedicated chips might not, but the modules might have been aimed at different purposes and may be adaptable (but perhaps not so neatly) into class D scan amps. Also, there may be projects at the Elliot Sound Products site that can be adapted for full designs. If laser diode powers keep rising, class D might help there too, but no doubt demand some fancy filtering.

[mixedgas]

Oh, It can be done. just not with stock chips of any serious power rating. I have a discrete solution.

If i published it, that former employer would try to have me shot, sued, imprisoned, and then hurt. He's that paranoid.

Fortunately for me, his customer keeps him on a short leash.

Steve

[mixedgas]

Oh, It can be done. just not with stock chips of any serious power rating. I have a discrete solution, but its expensive to implement.
Steve