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 Post subject: Re: coronado 550 cabinet repair
PostPosted: Jan Fri 10, 2020 1:20 am 
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HI Russie, yes the wood chips some how clean out the grooves as well as soak up the extra paint remover.
it works very well and does not harm any detail and is much less messy.
Rich


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 Post subject: Re: coronado 550 cabinet repair
PostPosted: Jan Fri 10, 2020 1:22 am 
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Rodney, sorry I some how missed your reply..
:oops:
Rich


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 Post subject: Re: coronado 550 cabinet repair
PostPosted: Jan Fri 10, 2020 4:03 pm 
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Location: Seattle, WA
Yes, thanks for explaining. Are you using a stripper that's formulated as a gel? What brand? I'm thinking it would have to sit on the surface and not immediately run off or dry off.

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Rodney -- KG7EPW
Measure it with a micrometer, mark it with chalk, cut it with a chainsaw.


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 Post subject: Re: coronado 550 cabinet repair
PostPosted: Jan Fri 10, 2020 5:07 pm 
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Hi Rod, I think it is Zip Strip. its like a jelly and it works better when applied in a cool place out of the sun. I let it sit (as long as it stays wet) for an hour or so then I sprinkle the wood chips on and start rubbing until most of the debris is off. I usually just take the used wood chips and reapply to the stubborn spots the scrub with some steel wool.
Rich


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 Post subject: Re: coronado 550 cabinet repair
PostPosted: Jan Fri 10, 2020 7:04 pm 
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Posts: 1382
Location: Pewaukee, WI
IIRC Alan Voorhees recently described a method using a gel stripper, covering it in plastic to keep it wet, and removing it with wood chips/hampster bedding.

The plastic sure helps me get more mileage out of the Citristrip I use.... not wanting wood chips mess I discovered Menards carries 3M stripping pads (porous, hard brush like sponges) and those seem to do well (provided there isn't too much small detail in the wood).... Before I used the pads I used a discarded toothbrush to scrub... that works okay but is slow and labor intensive on bigger cabinets...it ain't bad for details and the pad and brush make a good pair for stripping if you don't want to introduce woodchip mess to your work area...YMMV.


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 Post subject: Re: coronado 550 cabinet repair
PostPosted: Jan Fri 10, 2020 7:59 pm 
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Great job on the cabinet! It looks beautiful.
Years ago I worked in a custom wood shop and we refinished a lot of furniture there. I was taught to use wood chips to wipe off the stripper and burnish the wood. I've also used synthetic pads and they work really well as long as I keep the pads rinsed out. I think the wood chips leave a nicer finish to the touch. But I work the chips pretty aggressively. I've also used several different strippers. The ECO friendly strippers like Citristrip certainly have a much nicer aroma. And they work, but they take too long for my workflow. I've settled on Jasco. It is an extremely strong stripper and works fast. I always wear a respirator, safety googles and chemical resistant gloves and my work area is well ventilated when I use this stuff, but it works within a couple minutes. I work on small areas at a time. I use stiff synthetic brush and carefully clean out all the crevices with toothpicks before the gel hardens. I just finished stripped a Philco 18H lowboy with six heavy detailed fluted legs and a lot of detail on the cabinet. The whole cabinet took me about 4 hours, but it came out great.

Also.... on the warped wood issue. Here’s a trick I learned from a master luthier. Take a damp cloth and place it over the warped wood, then iron with cloth with the iron set on the hottest setting. Don’t let the cloth dry out. The steam from the cloth with eventually relax the wood. As soon the wood is relaxed, immediately clamp it flat. Word of caution, this can also undo some glues, so you have a bigger area to re-glue. I’ve bent a LOT of veneer and thin wood using this technique. I have a jig that is clamped onto my bench that holds a propane torch so the flame enters the end of an 10” long 3” steel pipe (capped on one end) that is held firm in the same jig. I place the wet rag over the pipe. As soon as the rag starts steaming, I place the wood on the rag and start working in around the bend. You can feel the wood start to relax, and the bending becomes quite easy.

I hope this helps somebody.
RT


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 Post subject: Re: coronado 550 cabinet repair
PostPosted: Jan Sat 11, 2020 12:33 am 
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Hi thanks for the great input, a tip from a professional is always helpful!!
for some reason some think that the wood chips are messy actually they are much easier to clean up.
no goo just sweep them up and in the trash!!
thanks again Rich


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 Post subject: Re: coronado 550 cabinet repair
PostPosted: Jan Sun 26, 2020 2:44 pm 
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Hi All, I'm in the middle of rewinding the IF transformers with Litz wire. I counted the turns on the bad primaries and had 120 turns on each coil of 7/41 wire. at the time I removed the 3 coils from the form I noticed that all were connected in series, I didn't give it much thought at the time. I checked the resistance of a good coil and it was 33 ohms at .33 mh and 25 feet of wire.? the print shows 13 ohms??? my new ones came up very close to that figure.
Does any one have an Idea what is up? both IF's were wired the same way, all I can guess is the print is wrong..
Rich


Attachments:
File comment: winding 1 of 3 coils with litz 10/41
winding a single if with litz 10.41.jpg
winding a single if with litz 10.41.jpg [ 264.47 KiB | Viewed 1063 times ]
File comment: untouched IF
new IF coils.jpg
new IF coils.jpg [ 147.78 KiB | Viewed 1063 times ]
origional IF.jpg
origional IF.jpg [ 268.78 KiB | Viewed 1063 times ]
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 Post subject: Re: coronado 550 cabinet repair
PostPosted: Jan Sun 26, 2020 4:51 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 3582
Location: Nr London, England, SS1 3PT
It looks to me as if the primaries and secondaries are very similar, say roughly 1:1 turns ratio.

I would say there are 3 coils in series to make a smaller diameter to fit the can, for the same inductance, and at the same time it reduces self capacity (always a worthwhile thing to do).

Well done you for being able to do wave winding, not cracked that one :)

Gary


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 Post subject: Re: coronado 550 cabinet repair
PostPosted: Jan Sun 26, 2020 6:07 pm 
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hi Gary, this is my first time also. The proof is in the pudding as they say. I have assembled one of the If"s and it works with my RF generator and a scope at the output. we will see how it does in the circuit.
Rich :roll:


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 Post subject: Re: coronado 550 cabinet repair
PostPosted: Jan Sun 26, 2020 7:31 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 3582
Location: Nr London, England, SS1 3PT
That looks a pretty nifty home made winder you have there. Mine is crude but OK for 'scramble' winding; field coils, transformers etc but has no wave traverse. A guru of mine says you can get close in performance to wave wound by fitting cheeks and waving it by hand but I haven't tried it. :D

Glad its going well Gary


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 Post subject: Re: coronado 550 cabinet repair
PostPosted: Feb Tue 04, 2020 5:17 pm 
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HI finally finished, the IF and antenna coils all worked fine. the set aligned well and is operating. the reception is very sensitive!!
the speaker rattles a bit but is ok at low levels, something is up with the cone. if pressed on the lower left the problem goes away??
Rich


Attachments:
File comment: chassis mounted
coronado back finished.jpg
coronado back finished.jpg [ 202.89 KiB | Viewed 1001 times ]
File comment: radio done sporting the knobs, one is made from some walnut the I had
coronado finish.jpg
coronado finish.jpg [ 168.52 KiB | Viewed 1001 times ]
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 Post subject: Re: coronado 550 cabinet repair
PostPosted: Feb Tue 04, 2020 5:47 pm 
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Joined: Nov Thu 11, 2010 6:03 pm
Posts: 1382
Location: Pewaukee, WI
Sometimes years of humidity and gravity sag the cone till the voice coil rubs. The way to fix this is to lay the speaker cone front facing upwards and level and wet the cone paper then let it bone dry facing up...it should no longer rub when reinstalled after that.


Last edited by Electronic Memory on Feb Tue 04, 2020 6:52 pm, edited 1 time in total.

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 Post subject: Re: coronado 550 cabinet repair
PostPosted: Feb Tue 04, 2020 5:52 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 3582
Location: Nr London, England, SS1 3PT
Impressive job there Rich.

What a tiny chassis for the cabinet.

Another speaker trick is to mount it up the other way. Gravity on the cone maybe enough and it might get better. In your case though with the magnet at the top it would make it too top heavy.

Gary


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 Post subject: Re: coronado 550 cabinet repair
PostPosted: Feb Tue 04, 2020 6:47 pm 
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Hi its an oddball speaker I've never seen one like it. it has the voice coil in the magnet assembly below and arms that go up vertically to the speaker cone. the noise seems to be coming from that connection..
Rich


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 Post subject: Re: coronado 550 cabinet repair
PostPosted: Feb Tue 04, 2020 6:56 pm 
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Joined: Nov Thu 11, 2010 6:03 pm
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Location: Pewaukee, WI
It uses the 1920s speaker motor design. That design lingered in some battery sets for a while...heck one of GEs earlier transistor sets used a miniature version.


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 Post subject: Re: coronado 550 cabinet repair
PostPosted: Feb Tue 04, 2020 7:15 pm 
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I thought about taking it apart until I had the aluminum bottom off then I was concerned that I may make it worse. Ill give it a think. this radio was truly a challenge
:roll:
Rich


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