10m FM Monitor. Quick Repair.

 My 10m FM monitor (modified old CB transceiver) lost its audio out a few days ago.

I waited starting the repair until I had some of the 23cm equipment better tested. As that has now happened I took the rig up to the lab and made a quick test.

Most of the receiver looked like it was working, as the S-meter acted normally, so the fault seemed to be in the audio output system.

Sure enough, when I had the rig open and rocked the output electrolytic capacitor the audio speaker went on and off. 

Looking at the bottom of the TRX it looked like there was a dry solder point. I re-soldered the capacitor and the wire going to the speaker/jack, and all sounds normal.

It is possible that the electrolytic capacitor has gone bad. If that turns out to be the case, the fault is a known one, and I may change all the electrolytic capacitors in the TRX.

The TRX is a nice addition to the 10m monitoring, as signals will sometimes come through when nothing else is heard by casual monitoring, or even systematic monitoring on fixed frequencies.

Filters for AR8600 and AR7030 Arrived.

Two new Collins Mechanical filters have arrived.

A 2.5kHz SSB filter for the AR8600. This will be mounted in the Mk 2 I have, and is intended for use as back-end for some microwave converters/transverters. Initially the main use will be for the QO100 reception system on 10.489GHz, down converted to 739MHz, and probably switchable to the 10.368GHz down converted to 618MHz.

The original SSB filter in the AR8600 is not very good, the main weakness is a poor selectivity, resulting on poor rejection of the unwanted sideband. The SSB filter should solve that problem.

A quick alignment of the AR8600, especially of the BFOs for SSB, and the D/A converter for the fine frequency steps.

Now I need to make space on the lab desk for doing this, so a bit of tidying is in order. 

The CW 500Hz filter will go into the AR7030 receiver for HF ... well, 15kHz - 32MHz. This is a very nice receiver, albeit with a relatively high current consumption.

The AR7030 also needs a replacement of the backup battery. Yes, with time the batteries go empty. I have a few other radios and other stuff that needs new backup batteries, but this one comes first.

This year, I suspect, will be a year for getting much more of the equipment I have up and running for my propagation monitoring system and some of the microwave activity. So maintenance, repair, and renewal is on my program, as well as some building projects.

Last year's challenge was operation, so I did not write so much about "working a QSO a day" or so. This year I will write more about my progress or completion of many projects, large and small.

Mini(?) Project #3. Ten-Tec PM2B.

After finishing the IC910 mod, here is the next mini project. This may be more than just a small one.

For a very low price I purchased two low pass filters (30MHz) and a non-tested Ten-Tec PM2B, so I do expect to have some activity before it is fully functional.

This is an old CW only QRP transceiver, officially with 1 or 2W out, and with a direct conversion receiver. The rig covers the 80, 40 and 20m bands

After cleaning the AF potentiometer and some slide switches I got it to draw about 30mA from a 14V power supply. The headphone output showed some noise, variable with the pot. It looks like the headphone output is high impedance. It does use banana plugs, not even a mini jack connector. Yes, this is very old.

With an external SSB receiver I found that the local oscillator is working and can be tuned correctly.

No external signal received yet.

No transmit output detected.

Also I have no documentation, not even a circuit diagram

It does indeed look like there is more work to do with this one

Looking into the casing I was not impressed with the build quality, with long flimsy wires running around, and it looks like it has been messed up somewhat.

This might end up being a larger project, essentially building a modernized version of a direct conversion CW transceiver with a digital VFO, and maybe with additional bands. We shall see what I do with this one.

If I do a total make-over I may add some shielding to the sides of the transceiver, as they are totally non-shielded.

Quick Update. Mini Project #2a. IC910

Messing around inside the IC910 did get me improvements, but it developed a fault.

When setting a frequency, after a short while the dial moves the frequency without any action.

Initially I suspected that the switches in the microphone had got faulty, but this happens even with the microphone disconnected.

Then there are two more obvious possibilities:

a) Dust has entered into the the rotary encoder, or

b) A flat cable has a poor connection.

So tomorrow the radio goes on the lab desk again, let us see if we can get rid of that annoying fault.

Yes, beware when you mess around inside an older radio.

Outdated Computers - Spare Parts?

Over time I have collected a bunch of old laptop computers, all too old to run just about anything remotely modern, even decent Linux distributions.

So what to do with this? 

One of the older laptops has 2GB memory and a Pentium 4 (2.4GHz), I could probably run a Windows XP with some "Windows only" programs that I still want to use, e.g. the control program for the 35 - 4400MHz signal generator, some spectrum analyzer software etc, possibly WSJT or QRSS software.

The processors of those old laptops simply don't run fast enough, and the RAM is too low to run any modern applications, so that is really useless. 

What else can be used of such old laptops? 

Batteries can always be disassembled, and the cells used for rechargeable battery packs, providing that the cells have not died. Some testing of their capacity will be needed.

Old hard disks should be checked for usable information on them, and backed up. Really old ones, i.e. used PATA disks should probably be discarded and disassembled for parts. (Stepper motors and magnets come to mind, maybe a few more items.)

From the main boards a few components could be of interest as spare parts. Switch transistors, possibly some capacitors or inductors for the switch mode circuits.

A few modules, such as WiFi modules could possibly be used elsewhere

I would save some small speakers from laptops.

One thing seems quite useful: The laptop screens. With an interface they should be useful for some Raspberry Pi projects. I have a few from old netbook PCs with only 1024x600, a 800x480, and one 1366x768 screen from a recently disassembled defective machine.

With all the propagation monitoring I want to do those screens should prove useful in the shack, and in the lab.

Right now I have two dead Asus machines (one with dual core i5 and one with quad core i7). absolutely nothing happens when the (19V) power supply is connected, and the PS is working. From the description of other faulty laptops etc I suspect one or two defective switch transistors, as I have have had some power cuts with possible transient voltages. Here the disassembled old laptop main boards might provide spare parts. If not I should try to get some replacements.

Fault finding and repair is something I have not done a lot of, but learning something new is always of interest, especially if I can get some useful equipment up and running again. Yes, I have had the tendency to just buy new (or good used) stuff, but the stock is quite high now, so I should get to use more of what I have.

Additionally, I have some very old - and very large/heavy - test equipment. I have got some new and smaller equipment, so the really old/heavy stuff, like an ancient 1.7 - 4GHz signal generator with a **klystron** is not too useful. Very heavy and bulky, and unstable. The new ADF4351 based generator is much better and takes up a fraction of the space. Any useful parts from the generator, like the attenuator(s), will, of course, be salvaged, as they are useful in the lab. 

So this is an effort combining tidying the lab, making space and improving my test equipment, all while I am building some ham radio projects. Absolutely no time to be bored (what is "bored?)

Especially the lab is in an attic with essentially no useful vertical walls, so space is at a premium. Also, while the newer/smaller test equipment is not of professional standard, it will work nicely for my amateur use.