The RACAL RA1772, again!

Hi,

Apologies for my lack of postings. Many things have happened in my life since my last post. My younger brother Iain passed away aged 51 on the 8th of March.  I also retired from work at Reid Kerr College, Paisley, where I was an IT Support Engineer.   Retirement doesn’t seem too bad, but of course I could get bored. Who knows?

This time, I have some information for those who own a RACAL RA1772 that’s ‘thrown in the towel’, like mine.

The RA1772 is an excellent radio, but the overly compact   power supply lets it down a bit. The PSU is a linear type that’s crammed into a small space in the rear of he set. All linear PSU’s generate heat and this PSU is no exception. In a previous post, I described how the bridge rectifier D2 generates most of the heat and could be moved from the PSU area to the card cage where it can dissipate heat far more effectively.

This time, my RA1772 has failed again, for the third time since I bought it, quite a few years ago!

A quick ‘blip’ of the mains switch so I can flip through the various metered supply voltages shows only the -7V supply to be operational.

All of the positive voltages used in the set are regulated by 723 canned regulators and external pass transistors with the 723′s being fed from the +20V regulated line. If the +20V line fails, all the other positive supplies fall over like a stack of cards.

In this case, the electrolytic capacitor marked IC4 in the manual was found to be U/S.  This is the reservoir capacitor for the +20V supply and is mounted in a capacitor clip on the rear apron of the radio.

Rather than just replace the faulty capacitor, I decided to replace all of the electrolytics used in the PSU,  They have in all probability exceeded their ‘best before date‘ by a factor of 3 or 4!

In any radio of this age, it makes sense to replace the electrolytics in the PSU… and elsewhere too, if you have the patience.  It’s especially the case for the RA1772 because you KNOW they have been ‘baked’ for many years by that mad hot PSU board.

Here’s another hint for faultfinding the RA1772, ALL of the various transformer secondaries are protected by simple ‘fusible links’ connected across pins on the PSU board. IF a fault develops, these links protect the transformer from being burned out by short circuits. ERGO if you need to disable a PSU line, you can simply unsolder ONE END of the wire link for that particular supply.  The links are clearly marked on the PSU board… just pairs of PCB pins with ‘fuse wire’ soldered across them.

————————————————————————————————————-

The links are marked LK1 through LK6.  They protect the following trafo windings.

LK1  10V winding (for the -7V regulated line)

LK2  16.5V winding (for the +12V regulated line)

LK3 23V winding (for the +20V regulated line) … but see Note!

LK4  + LK5 (+ / – 60V line… used for the telegraph board if fitted… to drive a teletype)

LK6  10.5V winding … ( for the +5V (LOGIC) supply)

————————————————————————————————————-

NOTE!!   By simply unsoldering ONE END of a link, that supply line can be readily disabled for testing.  When you are finished, just re-solder the link in place, taking care not to get any solder build-up on the fusible link.  The fusible links are connected in series,  between the mains transformer secondaries and the rectifiers on the PSU board.

Remember too, if you DISABLE the +20V oline, the other positive supply lines will all quit because there will be no +20Volt supply to the +5V (logic) and +12V voltage regulators on pins 7&8 of each.  The -7V line is independent of these, so if the -7V line fails, then the rectifier, smoothing capacitor, regulator (ML1 on the PCB) or pass transistor may be faulty.

On the PSU board….

LK1 +  D1 & ML1 plus ITR1 (on heatsink) are supplying the -7V line

LK6+  D2 & ML2 supply the 5V line, along with pass transistors TR1 &  ITR2 (on heatsink)

LK2+   D3, ML3 TR2 and ITR3  (on heatsink) supply the +12V line.

LK3+ D4, ML4, and TR4 supply the +20V line.

LK5 & LK6 +   D5 and IC6 supply a +80-0V -80V DC supply to the teleprinter circuitry (optional board  )

ITR1, ITR2 and ITR3  are mounted on teh rear panel of the receiver (for heatsinking).

The ML1 through ML4 are metal canned regulators (Ua723).   Made of ‘unobtanium’.

Until next time,

73, AL  GM1SXX

Replacing the FT60 Keypad

Hi Again,

Today I’ll show you how to replace the rubber keypad on the FT60 radio.

My FT60 has been through a lot, but I like it a great deal and hope to use it for many years to come.  The FT60 in common with most modern handies uses a flexible rubber keypad in the form of a moulding.  Key legends are screen-printed onto one side  while the underside has pairs of conductive contacts that form the moving parts of the key switches, the other half being sets of interleaved conductive ‘fingers’ on the main PCB.  It works well but the lettering is prone to wear and tear, and is no doubt exacerbated by dog-drool when my dog carries my radio for me

Replacement  keypads can be ordered from Yaesu UK (or your own local Yaesu service organisation) and are fairly inexpensive.

To replace the keypad, you will need some tools. A set of jeweller’s screwdrivers will be needed.  If you need to buy some, you can usually find them in Pound Shops (in the UK),

Some of the parts are very small, so it helps to use a tea-tray as a ‘workbench’, so you don’t lose any!

Start by removing the battery and antenna. Next unscrew the belt clip (two crosspoint screws, reached through the holes in the clip. Place the belt clip and screws aside on your tray.

Remove the control knobs. They just pull straight off. Set the knobs aside on the tray.

You don’t have to do anything with the antenna socket. Just leave that ‘as-is’. It stays put.

Next turn the radio over and carefully remove the two silver coloured crosspoint screws and the two small black coloured crosspoint screws near the top of the battery housing.

Look down into the top of the radio where the controls are and you will see that there is a soft black rubber seal between the control spindles and the plastic radio body.  These keep moisture out of the radio and need to be picked out gently I used a very small plain bladed jeweler’s screwdriver to gently them out. Take care not to score or damage them.

You are now ready to pry the case halves apart.  Hold the radio over your tea-tray and gently pry the base of the plastic front of the radio away from the metal body of the radio.  The battery clip sits between them and should be carefully removed before you pry the front of the radio too far from the metal body.

The radio has a rubber sealing gasket that keeps moisture out of the gap between the metal body and the plastic cover of the radio, so the fit between the two halves is quite tight.  Easy the two halves apart from the base of the radio and pull the front of the radio gently upwards  to ease the front panel free of  the control knob spindles.

Once you have freed the front panel, carefully place the radio on your tea-tray, face up.

You can now ease the old keypad free and fit the new one. Try not to touch the black conductive dots on the underside of the keyboard. Oil from your skin wont do them any good. If you can use a clean pair of tweezers to remove and replace the keypad, that would be preferable to handling it with your fingers,

The reassembly process is just a simple reversal of the disassembly.  Just make sure the rubber seal/gasket that goes around the edge of the metal body of the radio is seated correctly when you reassemble the two halves.

So, why is my FT60 *NOT* sitting on a tea-tray in the photo?

Err, because I was a  total  idiot and while taking the radio apart, the battery locking clip ‘pinged off’ and I spent hours looking for it.  That’s why I recommend that YOU use a Tea-Tray!

If you need to replace the keypad on your Yaesu FT60, the part number is RA0613500.

All the best until next time.

AL

GM1SXX

Spare parts for Yaesu radios (UK)

Hi Again,

Today I went shopping for a new flexible rubber keypad for my trusty Yaesu FT-60 e.  I’ve had the radio a good number of years and it’s proved to be a very dependable performer.  I’d never deliberately mistreat it, but it has suffered some things that would trash a lesser radio.  These include falling off my belt onto rocks (several times), while out in the hills, falling down the concrete stairs at work (three times to date), being soaked (many times!) and being regularly carried by my dog and covered in dog drool (too many times to remember).  It’s also been used ‘bicycle mobile’ attached to the bars of my hybrid bike (by Gaffa tape) where it’s been violently shaken at the many potholes and speed bumps on my daily journey.

I imagine it’s the regular attack by dog drool thats done for the lettering on the keypad. The letters are barely visible now… acid etched by the doggy drool no doubt, so I went shopping for a new keypad.  I did find some on EBay, but from Taiwan, and the postage was as expensive as the actual item.  I then did the unthinkable and contacted Yaesu UK by email. They replied within an hour or so to confirm that they had the part in stock, along with the price. I emailed them back saying I’d like two of the keypads…. one to use and one for ‘future reference’.

Sam Ruddy, their UK service manager swiftly sent me a revised price quote which was very ‘competitive’ so I then phoned Yaesu who were very efficient and had my request details to hand. I paid for the keypads by VISA and they promised me swift delivery to my home.  If you do phone Yaesu, press 1 on your keypad for amateur radio and ask for Rebecca or Kelly.

Now be honest…. you don’t often get service like that nowadays, especially for low-cost items like rubber keypads.

So if you need spare parts for a Yaesu radio, it’s well worth phoning Yaesu to see if they can help. .. and it really helps to have that all important Yaesu Part Number and the model of your equipment to hand.

Their address and contact details are below.

YAESU U.K. LTD
Unit 12, Sun Valley Business Park
Winnall Close, Winchester
SO23 0LB
United Kingdom
Phone: +44-1962-866667

From the UK, thats… 01962 86667

Their service manager in the UK  is Sam Ruddy, IMHO the most helpful person I’ve dealt with in Yonks.

Before phoning through, you should do your absolute best to obtain the Yaesu Part Number for the item(s) you require.

These can often be found on the service manual for your particular radio.

73 Al.

GM1SXX

DON’T ever buy one of these! LED Driver LKF-20W-12V

Hi Again.

I hope you all had a nice Christmas and New Year holiday.    I’ve not been very active on the bands over the holidays, but when I switched on my trusty FT102 today, I found horrendously strong QRM over ALL the bands, with lots of noise peaks about 25Khz apart from Top-Band to 10M!

On 160-20M, the carriers were 20Db over S9, effectively rendering my radio useless.  Now when noise is *that* bad, it’s usually very local, and frequently to be found within your own walls, so I started searching for any new electronic toys or other stuff that could be to blame.

In the event, I didn’t have to look very far.  My fancy new LED lighting on my staircase was producing the broadband RF spikes from DC to at least 10 metres.  The lighting is powered by a dedicated LED Driver module, Model LKF-20W-12V.

This is a switch-mode type supply to drive strings of series-connected LEDs with a measured 12V DC.  Because I’ve had loads of problems before with switchmode PSU’s, I expected it to be electrically noisy, so I decided to treat it in advance  to some ferrite tubes placed over both the input and output leads.    Even with these in place, two on the input and two on the output.. the unit generates horrific QRM from Longwave to 10Metres.  I expect the QRM probably extends to VHF, but I didn’t bother checking for that.

Here’s a photo of the offending item.  made in China (but of course!) and stamped IP68 and ‘CE’, which I believe in this case to mean ‘China Export’ and NOT ‘CE approved!’

Don’t be fooled by the CE mark on stuff originating from China. From personal experience, stuff made in China  rarely has any RFI suppression components installed.  Often the PCB will be laid out for such components, but in practice, they are usually omitted.

In my work as an IT Engineer, I’ve seen dozens of different computer switch-mode PSU’s with absolutely no RFI suppression components. In fact they are now so commonplace in my profession, that it’s a pleasant surprise when you find a PSU that *is*  properly suppressed.   Good ones are now a rarity.  Shocking!

I actually purchased two of these LED Drivers to power my new LED lighting, but they are fit only for the garbage. They are sealed (potted) units and can’t be improved to the point where they’d be of use to me.  Instead I’ll build a simple linear regulated transformer type PSU with a monolithic fixed +12V regulator on a small heatsink.

I may send one or both to the RSGB’s EMC committee for their perusal, but take it from me… they are garbage. Please don’t ever buy one of these.  Buy a unit with a real transformer instead.

For now, my staircase lighting is OFF, and it’ll stay OFF until I build a 12V Regulated DC power supply for the LED lighting strips.

73 Al.

GM1SXX

My ‘other’ Blog

Hi,

 

I set up Hamradioal for my ham radio related stuff, but since I like to have a rant at the World in general, it now has a sister blog ‘GtumpyOldFartsBlog’ where I can rant and let off steam at the world. If you have a HUMAX PVR-9200T with dim video, you’ll find a fix for it there.  Ditto all the stupidity I’m seeing locally, and in the press, about banning things like Halloween and Christmas ‘because it could offend people’.  What bloody nonsense!

Anyway… have fun, and don’t go taking life too seriously

http://grumpyoldfartsblog.wordpress.com/

Regards  Al  (AKA the G.O.F!)

 

RF Analyser

Hi Again.

Since I like playing with radio aerials, I thought I’d get a new analyser.  My old MFJ 259B got fried in an accident.  This time, I bought a second-hand analyser, an AUTEK RF-1.  I’d read about AUTEK stuff before and a perusal of Eham Reviews showed that the RF-1 and other AUTEK products seemed to have a problem.  Lots of complaints about joints not being soldered.  I still went ahead and bought this RF-1 from EBay, because it’s small and covered the bands from Topband to 10 Metres.

The item arrived quickly and I’ve been experimenting with it over a couple of days. It’s small enough to fit in the palm of your hand and runs from a single PP3/6F22  nine-volt battery.  The analyser is quite flexible but lacks the dual meters present on some of the MFJ offerings. Don’t let that put you off.  It still does pretty much all you’d want to ask of it.

Intrigued with all the reports of garbage workmanship and unsoldered joints on the PCB. I opened the unit up to discover that although many joints were indeed not soldered, they didn’t NEED to be. The majority of the unsoldered joints were on the seven switches and these didn’t need to be soldered anyway. The switches all have 4 connections but only two on each switch are actually used. This could lead to the impression of shoddy workmanship, when of course if you know what to look for, you’d know there was no need to solder these connections!

The analyser is built on two PCB’s and the board that doesn’t carry the switches also has some unsoldered pads. Yet again, these pads serve no function so don’t require to be soldered either.

Autek RF-1

The photo above shows the PCB’s in some detail, including those unsoldered PCB pads. Well folks, IMO soldering them would be a waste of time, not to mention solder.

AUTEK RF-1 Analyser

The palm-sized AUTEK RF-1

The analyser starts up in Frequency mode, but can be switched to SWR, Impedance, Inductance or Capacitance at the push of a button.   The unit covers 160-10M in four bands, selected by the BAND button above the display.

Overall, I’m happy with my purchase. It does what I need and is extremely portable.

Until next time..

73 Al. GM1SXX

End Fed Dipole

Hi Again.

I’ve been asked on occasion by members of the local club if it’s possible to feed a dipole at one end. This can indeed be done, but since you are then feeding the dipole at a voltage node, rather than in the centre at a current node, a different feed arrangement is needed.  Of course then,  although it’s the length of a dipole, it’s really and end fed halfwave wire or an EFHWA… go Google it!

The aerial at resonance presents a very high impedance and so needs to be matched to the 50R co-ax. This is most easily done by connecting the aerial to the ‘hot’ end of a resonant parallel tuned circuit. A short counterpoise wire can be attached to the ‘cold’ end of the tuned circuit. This need only be a short ‘whisker’ rather than a conventional quarterwave radial.  You then have to find a way to match the 50R co-ax to the parallel tuned circuit.  There are two obvious ways to do this.  The simplest is to tap the coil at the 50R point,(as an autotransformer)  connecting the coax-centre to this point, and the braid to the ‘cold’ end of the coil.  The other way is to place a few turns of insulated wire on  top of the main winding, as an ‘overwind’ and connect your co-ax to that (as a conventional isolated transformer).

end fed matcher

The matching arrangement can be as above.

This arrangement is used to feed the end-fed dipole shown below.

End Fed Dipole

Those in the know will immediately recognise this as a Fuchs Antenna (aerial)

The Fuchs is an ideal field aerial.

Now I’ll describe another way to end feed a dipole.  Well actually, it’s cheating, because it’s really centre fed, but it LOOKS like it’s being fed from one end.

co-axial sleeve dipole

In this simple dipole, the outer skin of the  feed-line is used as half of the dipole radiator. A choke is placed at the appropriate point to choke off the outer of the co-ax, which effectively becomes half of the dipole  radiator.   It’s quite a simple and useful aerial to build and can be slung from a tree as a simple sloper.  If you use a ferrite ring type choke as in the top picture, it’s important that a single layer of coax is wound onto the core and locked in place with Ty-Wraps.   Put on as many turns as you can as a single winding, leaving a gap between the beginning and the end of the windings,  and make sure the co-ax on the radiating side is 95% of a quarterwave in length.  The centre conductor of the co-ax should be attached to a length of wire and the total length of this (including the exposed centre conductor) should also be 95% of a quarterwave in length.  The choke could also be made from Ferrite tubes placed over the co-ax. In this case, I use hot-melt glue to attach the tubes to the line with a gap of a few mm between them and once the glue is set, I wrap the ferrites in several layers of BLACK PVC electrical tape for protection from damage. This makes for a sturdy portable monoband aerial that can be rolled up when not in use.  I always place a large solder tag on the end of these aerials so I can thread some kevlar line through it to lift them into a handy tree. Remember that the tip of the ‘whip’ is at a voltage node, so you need some sort of insulation such as dry Kevlar line. In a permanent setup, it’s best to fit a decent insulator at the tip. With this dipole  there  will also be a high voltage on the aerial side of the choke, but the co-ax insulation provides protection from that.

RF on feedlines.     In normal use, the LAST thing you want is to have RF flowing along the outer skin of the braid of your co-ax, but in the aerial example above, the outer is used as a radiator in half of a dipole and the RF is being positively *encouraged* to flow on the outer skin of the woven braid for a quarter of a wavelength.  The choke placed on the outside of the co-ax, an electrical quarter-wave from the feed-point ensures that any unbalance doesn’t result in RF flowing back along the braid past the choke.  My preference is for using ferrite tubes wrapped in black tape rather than a toroidal core because it makes for a neater portable aerial.

So, to recap….you can end-feed a dipole at a voltage, rather than a current node, and you can also make something that LOOKS like an end-fed aerial, but is really centre fed.

You can click on the images for bigger versions.

So, until the next time, have fun and get some aerials built, not purchased.

Oh, and if you build a Fuchs aerial, note that with some thought, it can operate on several bands.

73 Al.