Warning: Creating default object from empty value in /homepages/11/d132647312/htdocs/Amfone/mkportal/include/SMF/smf_out.php on line 47
Recent Posts

The AM Forum
April 24, 2017, 03:28:15 AM *
Welcome, Guest. Please login or register.

Login with username, password and session length
   Home   Help Calendar Links Staff List Gallery Login Register  
Pages: [1] 2 ... 10
 on: Today at 02:00:38 AM 
Started by AG5CK - Last post by KA2DZT
Use an ohmmeter to try to figure out how the secondary terminals are connected.  Label shows only two voltage outputs 3000/1250.  Lot of terminals for only two.  See if all the secondary terminals are connected to only one set of windings (measure from each terminal to ever other terminal).  Remove the jumper to do this.  Xfmr may be wound with two separate secondary windings.  Terminals 5 and 12 may be the outer ends of each winding and jumping pairs of the other six terminals create the CT.

If this is the case, then it would seem that there are three different voltage level outputs not just two.

Take the ohmmeter readings with NO power on the xfmr.  


Thinking further,  having to jump terminals on the secondary of a plate xfmr would almost certainly indicate that there are two separate windings.

 on: Yesterday at 11:50:53 PM 
Started by w8khk - Last post by w8khk
I bought a power supply kit from the far east, which did not include any instructions.  Here is a link to the product:


I will attach a few pictures to clarify my question. 

The power supply uses a switcher to provide positive and negative voltages to a series of linear regulators: 78M05, 78M12, 1117-3.3, 79M12, and 79M05.  The switcher is an XLSEMI XL6008.  The regulators and switcher are all tab surface mount devices. 

The power supply works as designed, but I do not know the correct method to mount the heat sinks.  There are six finned aluminum sinks, which appear to have double-sided tape for mounting.  I would assume the sinks mount on the bottom side of the board, and heat is conducted from the solder tab through the board. 

But, is it possible I am wrong, and the sinks should be applied to the top of each device?  Someone reading this must know the correct method.  Thanks for your help!


 on: Yesterday at 10:48:23 PM 
Started by AG5CK - Last post by AG5CK
Is anyone familiar with the secondary taps on one of these old dinosaurs? The primary side seems simple enough but I'm not sure about the strand of wire someone used to bridge 8 & 9. I replaced it with something easier to see after wiping the dust off. The amplifier it came out of was not safe to power up and I removed the transformer to find the data tag.

As it is 15.5 vac into 1&4 gets 210vac out of 12 & 5. I don't know that this is correct but is how it was connected in the amplifier. The previous owner bought it as a project and suffered a stroke before working on it so he couldn't give me much information.

 on: Yesterday at 08:09:58 PM 
Started by Detroit47 - Last post by Detroit47
Thanks for the advice. No need to reinvent the wheel.

John N8QPC

 on: Yesterday at 07:14:18 PM 
Started by W2PHL - Last post by Steve - K4HX
The output network of your amp should kill any harmonics. The amp may be doing some "extra" work by amplifying the 2nd harmonic. It's probably not a big deal though. How many dB down is the 2nd harmonic coming out of your driver amp?

 on: Yesterday at 07:13:09 PM 
Started by Detroit47 - Last post by WD8KDG
Finial tips:

Need two clean work areas, close to each other. I used a shipping mat on the garage floor as the glue area. A table top where the over size material has been glued and now needs to be rolled from the center out to the edges, then trimmed is area #2.

Place new material good face down on shipping mat. (Dry Run) With two people practice setting desktop down on material. Use a marking pen to locate where to place desktop. That way the entire surface of the material does "not" need a coating of adhesive. I'll bet the two people will use the ribs on the under side of the desktop in order to move it to the table top/trim area. When I applied the adhesive to both the desktop & material, brother & I set it on the material. I then stood on top of the ribs for a brief moment or two. Then the lift.........flip.......and trip to the trim area.

Have a rolling pin, pizza dough roller or sumthin to work the material from the center out to the edges. If you got the desktop onto the material correctly, there shouldn't be any air bubbles. But work quickly before the adhesive really sets. As one would sit at the operating position of the Desk KW, the left & right edges are easy to trim. The carpet knife will use the metal edges of the desktop as a guide. This is a piece of cake. ""Big Hint""::::  Grin  The groves where the two trim pieces go, are your guide to cut/trim the front & back edges. ""Another Big Hint""::::: Grin    The Forbo material is the correct thickness needed for the two trim piece to clamp the material to the desktop!!!!! You ain't gonna slide it under those two trim pieces. This is the reason for the barbs!!!! After trimming the front & back edges, use a soft mallet to pound the trim back into place. This holds everything in place.

Gud Luck,


 on: Yesterday at 06:20:25 PM 
Started by Carl WA1KPD - Last post by Carl WA1KPD
Please check your junk box
Need at least the guts of one to finish a restoration. The winding in mine has gone south. Appearance is not important.
If you have a parts unit, I could also use one coil, but we can talk about that later......

 on: Yesterday at 03:11:09 PM 
Started by W1TAV - Last post by Opcom
Very nice room and setup!

 on: Yesterday at 03:03:19 PM 
Started by W1TAV - Last post by KB5MD
Nice setup!

 on: Yesterday at 01:08:29 PM 
Started by W2PHL - Last post by W2PHL
Thanks for the heads up Steve.
The spectrum view of the unfiltered driver amp is obviously full of harmonics but the spectrum view from the output of the AL-1500 looks the same whether using the unfiltered driver amp or a filtered one. It passes muster without a problem but I've only tried it on 75m. Perhaps the AL-1500 will complain at higher frequencies and/or the output will become dirty.

Pages: [1] 2 ... 10
AMfone - Dedicated to Amplitude Modulation on the Amateur Radio Bands
 AMfone 2001-2015
Powered by SMF 1.1.21 | SMF © 2015, Simple Machines
Page created in 0.06 seconds with 14 queries.