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Saturday 25 June 2022

Plans to sell refurbished and repaired CB radios

A money-making idea I've wanted to do for a while is repair and sell on older CB radio equipment, as I do have the know how to do this, and will ensure it's done properly, even undoing bad repair jobs done in the past by "rig doctors" and "screwdriver experts" as they are almost always people that claim to know what they are doing but in fact do not, like any transmitting radio a CB radio MUST be set up properly so as to be able to produce up to the legal power output and do it cleanly.

I have been putting together service diagrams to put my plan into action, as I need these, to do the job, I have a spectrum analyser however I cannot just connect a CB radio into it as I need to attenuate the output to avoid blowing it up, so a suitable attenuator is needed, the tinySA website links to one that should do the job, the spectrum analyser is needed to ensure very little of what the CB under test and repair transmits falls within 54-55MHz, as a lot of "rig doctors" will often tamper with the harmonic trap coil not realising why it is there, I need to order a frequency counter and signal generator and though the tinySA works as one it will not go low enough to set up a CB receive section properly.

I also need to order trimmer tools, another thing "rig doctors" and "screwdriver experts" tend to do is use screwdrivers in the variable inductor and transformer cores which breaks them making repairs for people with the right tools hard, most of the time these cores can be turned around and reinserted, which I had to do on my Uniden Uniace 100 (which I'm not planning to sell as it is a personal restoration project).

I have a Zetagi Model 203 power meter, a meter that reads power between 3-30MHz but it still is not the best instrument for the job, it will let me know IF I have peaked each stage of the transmitter correctly and also flag up if the transmitter final transistor is not working as it's been blown by high SWR in the past and the set basically scrapped for that reason alone.

I do have a Philips oscilloscope however it's an older CRT one and I am sensitive to the flicker it produces so do not often use it, so I'd have to get an LCD scope in its place, usually to help sort out the FM discriminator, the Maxon based CBs (Midland and Maxcom and a few others) are known for that going out of alignment.

I also need to get in a SINAD meter, these fetch ridiculous amounts of money on eBay and are often in America and don't stay on for long, so I have to build one, and found a circuit that should do the job and will get parts for that too, this is more to set up the receiver but the service details I found for the Uniden chassis suggests an AC voltmeter across the speaker terminals and the adjustments done for highest reading on the meter, not the best but it seems to work but I would prefer the SINAD meter route and the instrument does not have to be 100% spot on, just as long as it shows the receiver is properly set up.

Some radios are known for failing electrolytic capacitors (my own Uniden Uniace 100 is tarred with that brush) so I need to keep a stock of these, I have a stock of resistors so far but obviously need the other components, sadly some components such as the Sanyo LC7136/7137 and some kinds of transistors are long since discontinued so are close to unobtainable, crystals are also expensive and I'd only buy them IF I come across radios that are out of specification and cannot be pulled up to frequency properly.

On the sale side once the radios come out the other end and I sell them on car boot sales I need to be able to accept payment, many people don't carry cash now so I figured a card reader would be a good option, I can get one for about £30 and it would pair with my phone to connect it to the transaction system, I'm not planning to sell them via eBay, I may attend smaller radio rallies to sell them on too, however most hams by old CBs for conversion to 10-meters and I don't know many people from the CB side of things that will go to these events.

So time to put my knowledge of radio to making money, and promote wider use of CB, it still has a place in 2022 despite the mobile phone being common, and of course unlike mobile phones it is perfectly legal to use CB while driving.

73 de M0WNU/26CT730 (or just red squirrel on CB will suffice) 

Friday 10 June 2022

Update to the Uniden Uniace 100 repair

The project to repair the Uniden Uniace 100 I picked up for £20 from a radio rally is coming along nicely, with the radio receiving to some extent I turned my attention to the transmitter, and it now transmits fine.

One of the tuning stages within the transmitter had a broken core so I turned this over and adjusted it with an improvised trimmer tool from a piece of plastic I had lying about, this has brought the transmitter up to a suitable output and the 10dB switch does attenuate the signal as it is meant to do, though the default position on the Uniden Uniace 100 is in fact the low power mode, for high power it requires you push the switch in.

With the transmitter now operational my next job is to replace all of the usual suspect capacitors with new ones and any other capacitors that need to be replaced, these are normally electrolytic capacitors, and with the radio at least 41 years old it would be prudent to change them.

All repairs carried out so far have involved traditional 60/40 tin/lead solder for any soldering work as this is what would have been used by Uniden in 1981 as the powers that be hadn't outlawed lead solder in consumer electronics at that point.

Once the capacitors are done the radio will be subjected to a full retune of both transmitter and receiver as changing them may effect the tuning

I hope this set can give another 41 years of service, who knows, it may outlast me!

73 de M0WNU/26CT730

Thursday 2 June 2022

Uniden Uniace 100 repair project

After attending the 2022 Durham & District Amateur radio society rally I came away with 2 CBs, keeping up my long-standing tradition of buying radios at rallies, these were the Midland 77-095 and the Uniden Uniace 100, both type approved under the original CB 27/81 regime started in November 1981.

The Midland was all fine though if it did not work I'd have swiped the volume control from it for the Midland 38 as I suspect the part is identical, the Uniden was modified to 10-meters and this post is about me beginning to restore it to CB use.

So the first thing I found opening the radio was a board added by another ham long ago, this had a few components including 2 crystals and were tapped into the TX and RX stages of the radio, removing this and reinstating two resistors got it back on frequency but very little TX power, RX was fine bar channel 2, I next removed an errant resistor from the bottom of the board and replaced another resistor that was of an incorrect value, TX still very low output and still this fault on channel 2, I next spotted a link across one of the receive tuning cans and a capacitor across the unoccupied 10.695MHz filter position, removal of the link deafened the receive greatly, I then spotted a cut track leading from one of the tuning cans and the filter to another part of the circuit, this was reinstated and improved the receive by a tiny margin, so the radio is in need of a proper tune up once I get trimmer tools.

I suspect that the radio has been retuned to be optimum on 28MHz, so every stage of both the transmitter and the receiver will need to be gone over several times and the discriminator checked, deviation appears to be untouched as received on my handhelds, the meter has a working lamp but due to damage to the front panel it is held in by sticky pads, and fouled the latching mechanism on the PA switch.

This radio is the second Uniden I own so far as they made the President Grant II, and hopefully the third Uniden I'll have used as the first CB I used was an Audioline 341 that the owner mucked up with a screwdriver in front of me, the 341 using the same board as the Uniden Uniace 200, interestingly the Audioline equivalent of the Uniden Uniace 100 does not have a PA facility.

I'll update as progress on this 1980s classic is made

73 de M0WNU/26CT730