Wednesday, December 21, 2011

Ramsey Headphone amplifier project 12/21/2011

Ramsey Electronics - Stereo Headphone Amplifier Kit.   1 hr 30 minutes construction time

This evening I took a break in the construction of the Elecraft K2 to put together a Ramsey Electronic kit that is a Headphone Amplifier (Christmas Present for my Father).  The amplifier takes a line level audio signal and amplifies it using 2 lm389M IC amplifiers.



Ramsey Stereo Headphone Amplifier kit

Compared with the Elecraft K2 amateur radio transceiver that I am building, this project seems really simple.  The circuit board is single sided and doesn't appear to have many components on it.
Single Sided circuit board
All the parts for the kit are bagged.  There is a good manual that comes with the kit that explains how the amplifier works.
Amplifier parts

This is a shot during the construction of the kit.   The sequence of parts installed on the board are from the top to the bottom going left to right.  The Elecraft K2 transceiver kit components were installed (it seems) based on the hight of the component.  The smallest components being installed first.
Voltage regulator


LM389N amplifier ICs

Below is a shot of the finished circuit board.  Before mounting the circuit board into the case, it was tested.  After checking to see that there are no solder bridges and that the parts that have to be installed in a certain position (like the IC's and the Electrolytic capacitors), it was time to power up the amplifier.

It worked the first time!   Powering up a kit for the first time is always exciting.  You don't know if it is going to work or not.
Completed Circuit board
The Ramsey Headphone line amplifier kit also includes a case.  The case for the amplifier is included in the price of the kit.  In addition to the kit I also purchased a AC power adaptor.

Case for Amplifier

Hardware for the case

Circuit board mounted in the case

Well here are the photos of the finished product.  After the circuit board was mounted in the case, I hooked up the amplifier to my Directv receiver line out.  Next I hooked up some Bose earbuds to test it out.  It didn't take much to drive the earbuds.  I barely had the volume adjusted from off cause it was so loud.
Completed kit.  Front

Completed kit. Rear

I am pleased with the quality of the kit.  The assembly was straight forward ( After working on the Elecraft K2).  In the future I may consider building other Ramsey electronic kits.

Saturday, December 10, 2011

Elecraft K2 - Serial Number 007239 Build. Day 21

Hours 1:00:00    Total Build Time:   41:15:00     Dec 10, 2011


Well, I reached the section in the manual where it is time to wind the toroid chokes.  First the toroid  cores were separated into their groups.


Toroid cores

tinning the leads to the Toroid choke
The first RF Choke wound was RFC14.  It is shown installed in the photo below.  The manual had good instructions telling how to wind the choke.

RFC14 installation


Size of the RF Choke


 Here is another shot of RFC 16 which was also installed today.

RFC16

Thursday, December 8, 2011

Elecraft K2 - Serial Number 007239 Build. Day 20

Hours 0:33:00    Total Build Time:   40:15:00     Dec 8, 2011


Tonight I worked on steps 13 and 14 on page 55 of the manual.  On these steps, the crystals are grounded to the circuit board.  Crystals X5  & X6 use a single ground wire from the top of the crystal to the circuit board.  Crystals X7 - X11 use two ground wires from the sides of the crystal to the circuit board.


Crystals X7 - X11 use 2 ground wires from the sides to the circuit board

Crystals X7 - X11 use 2 ground wires from the sides to the circuit board

Crystals X5 & X6 use a single ground wire from the top of the Crystal to the circuit board

Wednesday, December 7, 2011

Elecraft K2 - Serial Number 007239 Build. Day 19

Hours 1:25:00    Total Build Time:   39:42:00     Dec 7, 2011


Today started making a circuit modifiaction connecting components to the MC145170 PLL Synthesizer chip. 


Additional modification near MC145170 (PLL Synthesizer w/Serial Interface) 

Next Crystals were installed.  So far 3 of the crystals have been grounded.  There will be a special grounding technique that will be used on X7 - X11 crystals as shown below:

Filter Crystals X7 - X11

Filter Crystals

BFO crystals

Tuesday, December 6, 2011

Elecraft K2 - Serial Number 007239 Build. Day 18

Hours 0:32:00    Total Build Time:   38:17:00     Dec 6, 2011


I am off to a slow start today working on the K2 RF board.  The past week I was on vacation to the Western Caribbean on a cruise.  Now that I am back I need to get back to work on the radio.


Today I started out installing some RF chokes and Electrolytic capacitors on the board.  The RF Mixer Z6 was also installed.


Z6 - RF Mixer

Monday, November 21, 2011

Elecraft K2 - Serial Number 007239 Build. Day 17

Hours 0:44:00    Total Build Time:   37:45:00     Nov 21, 2011



Spent the evening installing ICs on the RF board.  Ran into another set of NE602 ICs (Double balance Mixer/Oscillators) that were replaced by SA612AN chips.  The replacement chips were not mentioned in the manual or Errata sheet for the manual.  This was not a problem since the replacement could be confirmed by searching the internet.

One of the steps included mounting the MC1350 Surface Mount IF amplifier IC.  The Surface Mount IC came already soldered to the PC board as shown.  Connector pins were supplied to mount the Surface mount PC board to the main RF board.

Surface Mount MC1350 IF amplifier

Adding ICs to RF board

Saturday, November 19, 2011

Elecraft K2 - Serial Number 007239 Build. Day 16

Hours 2:12:00    Total Build Time:   37:01:00     Nov 19, 2011


Finally finished the step installing the capacitors.  67 Capacitors in just on step on the RF board.  Man thats a lot.....


Lots of capacitors to install on the RF board.  This is just one step!



RF Board

RF Board

RF Board

   

Tuesday, November 15, 2011

Elecraft K2 - Serial Number 007239 Build. Day 15

Hours 0:45:00    Total Build Time:   34:49:00     Nov 15, 2011


It is slow going installing the capacitors. I think it is progressing slow because first I have to sift through all the capacitors looking for the one I need.  Next the capacitor is stuffed into the board in the correct position, and finally it is soldered.  I was able to install 10 capacitors tonight.


Capacitors installed on the RF board

Sorted capacitors
There are 57 remaining capacitors to install before I can move on to the next step.... This could take a while.

Monday, November 14, 2011

Elecraft K2 - Serial Number 007239 Build. Day 14

Hours 2:24:00    Total Build Time:   34:04:00     Nov 14, 2011


Well, it had to be done some time....   I came to the step in the construction of the RF board where the capacitors are loaded on the board and soldered.  The first thing that I realized was  it was going to take forever sorting through the capacitors trying to find them.  I think I remember the step right before the installation of the first capacitor saying that all the capacitors should be sorted but who wants to do that..... :)  


The capacitors are not like the resistors.  The resistors come loaded on a tape in the order that they are used on the board.  Its a matter of verifying the color code, cutting the resistor off of the strip, and loading and soldering onto the board.


The capacitors came all mixed together.  The only capacitors that were not mixed together were the .01 uf and .001 uf .


Lots of really small capacitors!

Yes I spent 2 hours and 24 minutes tonight just sorting and taping the capacitors together.  First I was going to put the capacitors in zip loc bags.  After thinking about that I was going to use envelops.  Finally I decided that scotch tape would work and I would write the id number used in the manual on the tape.

Capacitors taped together


I am finally finished sorting them.  The biggest problem was with the small blue colored capacitors.  The ID number on them was in silver.   I had a hard time trying to identify them even under the lighted magnifying glass.  I would have to shade the capacitor just right to see the numbers on them.

Sunday, November 13, 2011

Elecraft K2 - Serial Number 007239 Build. Day 13

Hours 3:03:00    Total Build Time:   31:40:00     Nov 13, 2011


Started working on page 50 of the manual today.  The first item to build was the PLL (phased lock loop) upgrade.  The upgrade includes a thermistor that will keep the frequency more stable on the K2.

PLL Upgrade Kit


The PLL upgrade kit consisted of some wire, several resistors, a thermistor, and the circuit board.

Parts for the PLL Upgrade kit


Man these parts are small.  Most of the components of the PLL upgrade kit were 1/8 watt resistors.


View of the PLL upgrade kit


The PLL upgrade kit replaces on of the resistor packs RP3 on the RF board.  Wires were soldered onto the board so it could be soldered into place as RP3.

Completed PLL upgrade board


Once the PLL upgrade board was assembled, it was soldered into position at RP3.

PLL upgrade board soldered into position

PLL Upgrade board soldered into position


One of the many transistors soldered onto the RF board

View of the RF board

Varactor diodes added to RF board

Today I finished up on the second to the last step on page 51 of the manual.  Next time I start working on the project, I will be installing capacitors on the RF board.

Saturday, November 12, 2011

Elecraft K2 - Serial Number 007239 Build. Day 12

Hours 2:43:00    Total Build Time:   28:37:00     Nov 12, 2011


Work continued on the RF board.  All of the time was spent stuffing and soldering 1/4 watt resistors.


Soldering 1/4 watt resistors on the RF board

The lighted magnifying glass really helps when soldering the components onto the board.

Checking off components as they are installed on the RF board

I found the 'Annotate' mode in "Preview" when viewing a .pdf file.  I downloaded the K2 manual and errata sheet, made notes in the manual where there were changes from the errata sheet.  I check off each step in the manual after installing the part.   I like having the ability to also highlight, and add book marks.

Installing resistors on the RF board
Dang those parts are small.  The resistors in this case are not to hard to see.  There are some capacitors where the writing is so small that I even have a hard time identifying the part using the magnifying glass.


Installing resistors on the RF board


Resistor packs added to the RF board

Friday, November 11, 2011

Elecraft K2 - Serial Number 007239 Build. Day 11

Hours 3:15:00    Total Build Time:   25:54:00     Nov 11, 2011



Its been over 24 hours now on the build time and I have finally reached the step to turn on the K2 transceiver for the first initial power up test. This test will check the front panel, Control board, and the control chip and relays on the RF board. 



Well I was glad that the radio powered up with no problems the first time.  As I thought about it for a while, all it would take is one component in the wrong place or with the wrong polarity, or a cold solder joint or bridge somewhere....   Well, I just have to pay attention to each step and hope that the components are ok.


Its working!
After the initial power up, there where several other checks that needed to be completed.  First was the optical encoder test.  This test checked to see if the display was working correctly.  By pushing the rate button, I could verify that the display frequency changed correctly depending on the rate setting.

Next I tested to see if the 'band +' and 'band -' switches would cycle through all of the amateur radio bands.  As the band switches were pushed, the frequency display would change to the correct band and you could hear the relays clicking to accommodate the frequency.

I skipped over the section of the manual to construct an RF probe.  I decided that I would build that later when I needed it.

The next step was the construction of the 'Frequency Counter Probe'.  I found the parts and began construction.

Frequency Counter Probe
To test the probe, I had to enter the 'calibration' menu.  One of the menu items under the calibration section is the frequency counter.  With the Frequency counter activated, I tested the trimmer capacitor C22 which is just below U1.  It read 3999.98 hz which was within specs.

Next was the test of the CW keyed.  I connected my keyer to the radio and it worked correctly.  After that test the next test was setting the AGC threshold followed by the S-Meter alignment and 'Bargraph Current Test'.  No problems at all.  Each step was completed with no problems.  I ended the evening by dis-assembling the chassis back down to the bare RF board.   At that point, I started installing more resistors.  

Adding more components to the RF board


Currently I am on page 49 of the manual.  The next time that power is applied to the radio is on page 63 for the "Alignment and Test, Part II".  That will be at least another week worth of work.