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Quote:
Originally Posted by lollersk8s View Post
On your boombox you should separate the speakers internally. Check the Vas specification, should be on a page that comes with the speakers - as a bonus you can make each compartment close to "ideal" size if there is one, but usually for sealed configs bigger is better.

However since they are playing different material (ie stereo) they do need to be separated and should not share the same volume.

Hmmm. Good to know.

I'm probably going to be upgrading it down the line for my mother a few times. bigger power supply, newer headunit with aux in, stuff like that. I'll put that on the list too. Will have to do some moving around of things, to keep it ventilated and to get it to go back together snug to separate the speakers.
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Old 12-30-2012, 03:27 PM someone else is offline  
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lollersk8s
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Some people simply glue small plastic buckets behind each driver, when other drivers share the same cabinet. For instance when separating a mid range from the main woofer space.

So maybe a thick potato salad tub? nobody will ever see it. I'm betting those will have a pretty low Vas, maybe ~1.5 liters?
Old 12-30-2012, 04:24 PM lollersk8s is offline  
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Quote:
Originally Posted by lollersk8s View Post
Some people simply glue small plastic buckets behind each driver, when other drivers share the same cabinet. For instance when separating a mid range from the main woofer space.

So maybe a thick potato salad tub? nobody will ever see it. I'm betting those will have a pretty low Vas, maybe ~1.5 liters?

I'm not sure. I'll have to look em up. I'm not worried about how it looks, more about space. Its not the deepest cabinet ever. I'll figure something out. For now it sounds pretty good. I've got a list of things I was going over when I was messing with it that would make for a good upgrade, thats something I never thought of. I'll find some fix for it.
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Old 12-30-2012, 04:36 PM someone else is offline  
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So, last I left you, I had troubleshot the Zenith. The filter condenser (capacitors) was bad. I put together a short video showing you some of my methods for troubleshooting this issue.

+ YouTube Video
ERROR: If you can see this, then YouTube is down or you don't have Flash installed.


So we have diagnosed the issue. Lets get soldering.

This is the starting point. I haven't touched anything at this point.



And here is where we will be working. The blue finned object is the selenium rectifier. On the early radios, the rectifier was a tube. On later radios, the made them out of selenium. Nowadays they just use a small rectifier diode. I tested this one with a 3amp rectifier diode and got a big boost in voltage, bringing the B rail voltage up where its supposed to be, so that will get changed as well.

Directly to the left of the rectifier you can see the bottom of the filter capacitor. The Triangle you see indicates the 60uf (uf = microfarad) 150v capacitor lead. Above it is the 80uf cap and to the left is the 40uf cap. Each capacitor has one positive lead, marked, and share ground leads, which are soldered directly to the chassis.



This is the filter condenser as viewed from the top.



I desoldered everything that was soldered to the leads on the filter and then cut the filter leads. I left the grounds in place to re-use, and because I didn't want to take the filter out - this way the chassis remains stock looking from above.



Here I have soldered in the three replacement capacitors. The 40uf cap was axial, meaning one lead came out from each side, so I soldered the negative lead directly to the chassis off to the side. The other two caps were radial, meaning both leads come out the bottom, and those were soldered to the negative leads from the original filter that I left on the chassis.



Here is the 3amp rectifier diode I replaced the selenium rectifier with. I sleeved both sides with some heatshrink so with any shaking they wont short out to the chassis. Diodes only work one way, so I used different color heatshrink to remind myself the direction it needed to be hooked up in.



Here is a closeup of the diode in place. I cut the lead off of the selenium rectifier to get it out of the way. Again, i left it in place for appearances.

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Old 01-26-2013, 04:06 PM someone else is offline  
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Here is a short video of it running. You can still hear some scratching and hum, but that is due to the volume and tone potentiometers (pots) being dirty. Cleaned those with some Deoxit...5? I think. The one safe for plastics. Most of the old pots are metal, but I keep the safe for plastic stuff around because it works on the old stuff and the new stuff.

+ YouTube Video
ERROR: If you can see this, then YouTube is down or you don't have Flash installed.




lit up at night
by megalime, on Flickr

Then I went and cleaned up the case. I used some Old English wood stain and polish. It polishes, cleans and lays down a light stain all at the same time. This way, it fills in the little scratches. I also cleaned the knobs and the front panel up the best I could.















The final test was a "torture test". I turned the radio on, and let it run for 24 hours. Sounded just as good the first 10 minutes as it did the last 10 minutes it was on.

And that's all folks.



Restored Zenith K-731
by megalime, on Flickr
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Old 01-26-2013, 04:06 PM someone else is offline  
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Next up on the bench is the Magnovox FM040 AM/FM tube radio. I just pulled it apart to check the cord and started the slow powering up process, reforming the caps. I turn the radio on and hook it up to my variac power supply/isolation transformer running at 40v for about 3 hours. Then I'll turn it up to 70-80v for another hour or two, and finally I'll crank it up to 115-120v and see where we are at. This gives the old, dried out capacitors a chance to reform and makes troubleshooting easier.









This radio is very similar to the Zenith, and they are from about the same time period as well. Unfortunately, this one is going to need more work. We have some chipped veneer on both sides, a missing knob, and one knob is missing the inner golden liner. Finding some new knobs will take some doing. But we'll see how bad off this one is once I get it running at 120v.

Lastly, I dug up a new tool to use. Not the most used tool in the world, but a nifty one:



It is a BK Precision capacitance tester. I can test the values of capacitors, batteries, leds, resistors, and transistors to make sure they are up to snuff.
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Old 01-26-2013, 04:17 PM someone else is offline  
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Tex Arcana
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Old 01-26-2013, 05:09 PM Tex Arcana is offline  
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That stereo in a box reminds me of the shit I used to do back in high school.... good times too bad you don't see shit like this anymore. I had some old equipment for the longest time too but had to downsize a couple of years ago :tear: I don't have much cool stuff anymore . Maybe I'll post pics of some of my equipment later.
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Old 01-26-2013, 06:42 PM grjr is offline  
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Berleen0
 
Its really nice and informative community and good discussion which you discuss above i want to ask that i have a electric project in my study and i find some relevent informations for it its really nice and informative....
Old 02-20-2013, 12:09 AM Berleen0 is offline  
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#24  

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So I believe when I left you last, I was here:



I have since sold the Zenith. Kinda sad to see it go, being the first one I finished and all, but I made some goooood money on it, so on to the next one!



So once I got the Magnavox warmed up and started, I had NO output on the speakers. Ok. First step: test the tubes



I tested all of them, and two tubes were toast: the 12BA6 AM Detector and FM Driver, and the 12AL5 FM Ratio Detector. This would be why I would have ZERO output. Quick summary of a detector (From Wiki)

Quote:
A detector is a device that recovers information of interest contained in a modulated wave. The term dates from the early days of radio when all transmissions were in Morse code, and it was only necessary to detect the presence (or absence) of a radio wave using a device such as a coherer without necessarily making it audible. A more up-to-date term is demodulator, but "detector" has a history of many decades of use, even if it is a misnomer.
So I happened to have another BA6, but not an AL5, so I had to get one from ebay.

Flash forward a week, and voila!



SHE'S ALIVE! and while I waited for new tubes, I borrowed a Sam's Photofact from a buddy of my dad's. He's a vintage TV collector, so occasionally he'll toss me a neat radio he found in his travels. On top of that, he has pretty much a COMPLETE catalog of Sam's Photofacts dating from about 1980 back. My dad has a bunch as well, but his are mostly newer - he sold all his old ones when he sold his shop. Sam's Photofact was a subscription service that produced schematics, diagrams and parts lists for radios and televisions (and other stuff too) for repair techs. With the photofact in hand, I checked voltages and whatnot, and the radio is spot on. Which leads me to this...



The filter capacitor has been changed recently. (within, say, 20 years). If it was original, it would most certainly be metal on the outside, and most certainly would be bad. But voltages were spot on with what is expected in the diagrams. Sweet!



The replacement tubes were an RCA and a Philco. other than that, all the other tubes are original.



It still sits like this. I'm on the hunt for knobs. and these ones, 1/4" spline type push on knobs, are fucking hard as hell to find. Most shit was 1/4" half moons. I'm hoping to get over to the flea market tomorrow and see if I can locate some. Otherwise, I'm going to have to keep scouring Ebay.
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Old 03-02-2013, 03:22 PM someone else is offline  
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While I waited for the tube to come in from Ebay, I got into a small little project:



A vintage Honeybreeze fan. When plugged in, it worked, but it spun very slowly and the cord was rotting away.

So, I took it apart and cut the cord off.





As you can see, not safe to use.

Once you get into it, the fan is extremely simple:



The problem with these older fans is, the motor gets varnished on the inside. So once apart, I used some VCR head cleaner first to get the varnish off, then used some red lube to lubricate the SHAFT.



Put a new grounded plug on it and Presto chango, we have a working fan:



Theres some play in the output shaft, but thats to be expected for a 60 year old fan.


EDIT: Oh yeah, and here's whats on the bench right now:



The Hallicrafter. This one is COOL. Once done, I'll get you some pictures. This ones proving to be a bit tricky.
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Old 03-02-2013, 03:31 PM someone else is offline  
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bjgeeky
 
cool!!
Old 04-02-2013, 01:26 PM bjgeeky is offline  
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Tex Arcana
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The motor on the fan: drill out the rivets, pull the motor apart, then clean it carefully, get the clearances between the armature and the rotor more open or more clear, so more crap doesn't get in there and stick.

Next, clean the fuck out of the shafts and bushings. The bushings are sintered bronze, so they're porous: soak them in a solvent (something stronger than alcohol), let them dry thoroughly; then, toss em in an over or on a hot plate, let them get nice and hot (just over ouch temp), then drop them into a bowl full of a blend of Marvel Mystery Oil and 30w Mobil One.

The MMO will act as a penetrant and carrier, and migrate into the bushings pulling the M1 with it into the porous spaces. When the MMO evaporates, the M1 is left behind, and is a excellent lube. Then put a coat of moly or lithium grease (moly is better) on the shafts, and reassemble. Use bolts and nuts to replace the rivets.

Your little motor will run even longer than 60 years now.
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Old 04-02-2013, 10:01 PM Tex Arcana is offline  
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Hornswoggler1
 
Very cool!!!

I took two years of electronics via vocational school my junior/senior years of HS... worked some consumer electronics repair but shit started getting cheap enough to replace (circa 1994) so I jumped to printers and computers. Very cool stuff and these look like fun projects!
Old 04-08-2013, 08:15 PM Hornswoggler1 is offline  
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