HW-8 Audio Transformer

Posted: 28/05/2012 in Uncategorized

Well, long time no post. And I’m going to return my hiatus with possibly the simplest project I’ve ever actually written about.  At the W4MCT Swapfest this weekend, I purchased an old Heathkit HW-8 QRP rig. The first hurdle to overcome wass the audio output. The headphone output is high impedance while I only own low impedance headphones. Being impatient and not really wanting to wait on headphones to come in the mail, I rigged up an audio transformer to match the two together.

The schematic.

Like I said, simple as can be. And for the real world version,

Though, this is flipped from the schematic. That’s really it. I probably won’t use it too long, but if it works well, I may save my money. I still have to build an antenna for it. I’ll post that and an article on the radio its self before too long.



N8VEM: Minor issues

Posted: 25/01/2010 in Uncategorized

Hey everyone, I know it’s been awhile since I posted any news. Blame it on school starting back. Anyway, since December,  I’ve made little progress on the N8VEM. The board is finished, and all the chips are in save two. This is because of a few problems I’ve had.

A) I ordered the 2.5MHZ Z-80 but a 4.0 Oscillator

B) One of my chips is the wrong logic family.

As soon as I get some money to order from jameco, and some time, I’ll make an order and get some more picutres up.

In the mean time, I’ve started another Z80 project, Elvira. This one is lacking most of the bells and whistles of the N8VEM, but it has blinkenlights. More info soon.

N8VEM: Initial Soldering.

Posted: 21/12/2009 in N8VEM

After finals and some issues with snow and power loss I finally started soldering.  I’m going from lowest profile components and moving up to make soldering easier. I’m still missing a single socket and an EPROM burner, but other than that all my parts are in order.

The work area.

This is our work area, set up in my sisters old bedroom.

The board after soldering the resistors.

This is the board after I soldered the resistors on to the board.

The Board after adding the sockets. The board after adding all but one of the sockets. The mill-max sockets, such as the ones in the center of the board, are slightly lower than the cheaper sockets, so I had to solder them first and follow up with the other style.   While the mill-max sockets are nice looking and slightly sturdier, the cheaper sockets are much easier to solder and sturdy enough for the N8VEM in my opinion.

Finally, I added a few smaller componets and the S-100 bus connector.

The board after attaching the S-100 bus connector, some capacitors, the serial connector, and the power LED

Only 10 of the capacitors are installed so far. I’m planing on soldering the rest of the caps tonight, and the rest of the parts tomorrow. The only real difficulty so far has been holding some of the looser parts steady while soldering.

Still alive.

Posted: 30/11/2009 in Uncategorized

Just a quick apology for the lack of news. In theory the remaining parts are waiting for me at my house. I doubt I’ll get much done in the next few weeks due to finals. When Christmas hits, I’ll take a few days to solder the computer up and post lots of goodies. Hopefully I can get an actual VT-100 or a pocketterm before it’s ready.

N8VEM: PCB Unboxing

Posted: 04/11/2009 in N8VEM

My PCBs came in today.My first impression was that they were a bit smaller than expected, but that is a bit of a good thing. Size aside, the board is very well designed. The board is labeled well, and easy to read. Also, the parts are laid out to were soldering at least appears to be easy enough.

Empty PCB

After I finished looking at the board, I decided to pop some of the ICs in just to get a feel for what it should look like finished.  I’m still waiting for a few shipments of student samples to arrive before I order the remaining parts, but this gives a good impression. One note though, most IC legs come bent at a slight angle, but the board is designed for straight legs. I would recommend using one of the plug in sockets to straighten the legs before attempting to put them in the PCB. I mangled a few pins before I figured out this trick. PCB with a few ICs setting inside.


N8VEM: Pictures

Posted: 04/11/2009 in N8VEM

As promised, here are some pictures of my part testing.

First, is my generic testing set-up. The breadboard on the left is simply a byte created with LEDs (ignore the SRAM in the background). The breadboard has the IC I’m currently testing hooked up to an SX microcontroller. The microcontroller is very useful for controlling the values being input into the IC and for regulating the power. The output pins on the IC are jumped to the LEDs as well as the ground completing the circuit.

Generic SX Testing setup

Here is the same setup, while running. It’ s hard to tell which LEDs are on in the picture but when it looks much better in person.


All things considered this setup is very useful for showing how something works. I had trouble at times due to a lack of wires but other than that it worked as well as could be expected.

N8VEM: Parts

Posted: 02/11/2009 in N8VEM

While waiting for the remainder of my parts to get here, I’ve been going over the data sheets for the parts, the Texas Instruments parts in specific. So far everything has went as expected, sans me realizing the sram doesn’t quite have the juice to drive 8 LEDs, which was more of my stupidity than anything. I’m going to post some pictures as soon as possible, including my rather embarrassing collection of packaging materials (so far, TI wins in speed of delivery, Mil-Max gets the best box award, and Intersil for most insanely protective packaging and QMIrep gets the award for pretty much most helpful company ever).

Thats all for now, I’ll post pictures as soon as I get a camera better than my phone.