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Title: EICO 720 filter & power replace Post by: w1vtp on March 17, 2012, 11:14:43 PM Tho't I'd share my experience with replacing a transformer in one of my 3 EICO 720s and my PS filter caps replacement
The transformer and 720 were two separate eBay purchases. I determined the different windings by apply 1 volt @ 60~ from a function oscillator to the two black wires of the primary. This was necessary because all the other windings (except for the green wire) had faded to a light brown. So with the 1 volt applied, the secondary was 12 volts (for the 1200 volt secondary), the center tap was 6 volts (for the 600 volts) and so on. A much safer approach than using a Variac or plugging directly into 110 volts. The filter caps need to be replaced without exception. I don't know what the source of caps were that EICO used but all three of my 720s needed to have them replaced. I tried to get away without doing this with one 720 and was completely fogged out in the workshop with some sort of vile white cloud. Fortunately, I have a good vent fan and was able to clear out the fog of unknown chemical substance but I learned my lesson. The first pic shows 720 #2 & #3 just after the transformer installation and before the cap replacement. The second pic shows #3 with more detail of my filter replacement, just before tie wrapping the transformer leads. I settled on a certain terminal strip that used an already present screw and epoxied the other end of the strip the the chassis -- no drilling and blasting. The above chassis pic shows the replacement power transformer in place Al Title: Re: EICO 720 filter & power replace Post by: WB4AQL on March 18, 2012, 02:44:54 PM Very nice! Al, how did you select that transformer for purchase in the first place? Wasn`t it an unknown quantity?
Mike WB4AQL Title: Re: EICO 720 filter & power replace Post by: w1vtp on March 18, 2012, 05:43:36 PM Very nice! Al, how did you select that transformer for purchase in the first place? Wasn`t it an unknown quantity? Mike WB4AQL Mike - it's an exact replacement for the 720. I have an ongoing saved search on eBay for the EICO 720 (and 730) so I got an automatic email alerting me to the transformer which gave me the opportunity to purchase it. That's how I "operate" - I buy stuff "just in case" and many times this has allowed me to do these sort of exercises. The downside of this approach is that I need lots of storage space and then I need to know where I squirreled the stuff away. ;D Al Title: Re: EICO 720 filter & power replace Post by: WB4AQL on March 18, 2012, 06:55:03 PM Smooth! Very smooth! AMfone - Dedicated to Amplitude Modulation on the Amateur Radio Bands
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