Listener's Guide

How To Ruin Perfectly Good Radio Receivers

We remember a childhood spent spoiling the classics.

The Powerless Eddystone 940

As a new recruit to the Eddystone User Group recoiling from Bill Lowe's comments, my learned Chairman who went on the record saying;

Some receivers are like chocolate eclairs, delicious to look at but when you bite into them, there is little of substance

His remark was probably based on the little EC10, a radio I had a deal of fun with.

But the big Eddystone was a 940 all right but when you picked it up, it didn't seem to have the rib-snapping weight I expected and a Plessey plug where we hoped to find a power lead. It had no power supply.

We lovingly made up a PSU with a transformer from a Vortexion WVB tape machine, decoupled up to the eye-balls against mains and modulation hum. I remembered Eddystones are noted for their audio so lets make the most of it.

When we plugged in, nothing happened. Everything lit up but that was it. Bags of HT, a reassuring blue glow from the stabiliser valve - but silence.

It was nice to see that after all this time, not even the S Meter zero needed adjustment but it was still very quiet.

A good antenna had the meter dancing about but an end-stopping signal only gave the quietest and most distorted signal known to man.

My chocolate eclair Chairman remarked I was wasting my time as every resistor will have gone high and every condenser will have gone low. Not so.

Abandoning the Company's electronic fault analysis systems for my AVO 8, I started prodding. Everything was as close to the book as parallax error would allow - except for one.

Not a volt to be had on the audio stage anode. And, Mr. Chairman, the anode load resistor was fine.

In this special release, the HT input was split. A main supply to all stages and a decoupled supply just for the audio amplifier. All I had to do was fit a series 10k and a 32uF stage decoupler to turn this into one of the most driveable radios I've ever had.

All I did to it in four years was rub a little WD40 into the cursor support bar as the pointer carrier would squeak when you spun the tuning from one end of the scale to the other.

Then it happened. Very slowly, one by one, each BBC station became slightly distorted. A curious sort of distortion, some parts of the audio spectrum sounding more distorted than the rest.

The Chairman's Rising Resistor problem? No - some stations sounded odd, others did not. Bite the bullet. Write to the BBC.

Why were the Domestic Services now so tiring to listen too?

As something of a writer on radio issues, I had heard that audio processing was becoming big business in the States. I learned that all AM broadcasters are now using some form of audio processing to improve the signal-to-noise ratio.

There was a time when the quality of the sound from your radio was determined by how much you were prepared to pay for it. And that Eddystone had it - the unprocessed sound of Radio 1 back in the Seventies was magic on the 940.

But not any more. The 940 was good enough to spot the start of the use of OPTIMOD on the 14th September, 1980.

How To Ruin A Perfectly Good AR88

I have just clicked on what my PC chums call a Radio Button. This virtual version has none of the feel of a real button on a real radio but it has sent an e-mail bulletin to about thirty customers. While I wait for them to get back to me, here's a few notes on what atrocities a young man can rain down on a classic AR88D.

It was Clive's. Clive was the least anoraky of the Development Guys. I think it was marriage that meant he and it would never see each other again. Paid around 45 quid? Sounds about right.

The only place for it was on the radiogram cabinet, the best speaker for it was the one inside. Disconnecting it from the record-player, even then, declaring vinyl dead and hooking it into the back of the AR88 resulted in a mere 2.5 to 15 ohm mis-match. It seemed rather quiet, certainly for a rock-loving listener to Radio Northsea International.

On that first evening, the AR88 was slid out of its oak case, on the hunt for easy mods. The output was a 6K6G, a valve I'd never heard of. It was capable of about 2 watts. Quite healthy - but for me, never enough. A 6V6 was an easy solution. If it seemed OK, try a KT66.

This was the one that went into heavy anode current and cooked the output transformer. That caramelised smell of expense. A sorry lesson was well learned.

Was there a fault on my AR88? It seemed to work best with a 2uF capacitor from AVC to ground. This was available by a connector on the back of the thing. It motor-boated without it. Without understanding what I was doing, I must have extended the AVC time constant to about a week. I was happy because it seemed quieter now.

The DIODE OUTPUT was fed to a VORTEXION tape machine to record Kenny Everett from the new Radio 1 on 247 metres. As this was a feed direct from the detector, the recorder neatly shorted out the AVC. I was happy because it sounded louder now.

My AR88, like so many others, had no S Meter. The over-long long-wires so swamped the front-end, the ANT TRIM seemed to have no effect. Metering was needed. At first, this was a traditional bridge circuit sensing changes in the cathode voltage of an IF stage due to the AVC. Not AGC, you will note. The AR88 had no schematic or manual. Every signal-handling valve cathode was tried. Some moved the meter, others didn't. When the meter did move with signal level, it was affected by the RF GAIN setting.

With no documentation, how was I to know which stages were controlled and which, if any, weren't. With no knowledge, what was I doing inside it anyway?

Meter calibration was carried out by finding the strongest station, then inserting a series resistance chosen to just ease the pointer off the end-stop. None of this 50uV for S9 at 14.2 Mc/s stuff.

Although every set I ever saw had this phenomenon of the S Meter gracefully rising as the RF GAIN was reduced, for some reason this could not be tolerated in my AR88. The cure was to replace the double-diode detector (a 6H6?) with one that had a triode in it to drive a right-hand-zero milli-ammeter in the anode circuit. A rare 6SQ7 was chosen, on the engineering premise of having one in the junk room. Not a junk box, you'll note - a junk room. AVC was applied to the grid turning the valve off, causing the meter to rise.

Calibration? This was done by shorting the aerial to deck and padding the anode load with a resistor until FSD (full-scale deflection, sorry) was achieved. FSD on a right-hand-zero meter gives you a traditional left-hand zero. And you can't end-stop it. All the AVC in the world would only cut the triode off, reducing the anode current and the meter to zero - on the right-hand side of the scale. And turning down the RF GAIN had no effect on the reading. This was a valve-voltmeter reading the AVC directly, sort of.

The meter was from the Derby Radio rally. 20p got me one with an uncalibrated scale, the first two-thirds in white, the last third in bright red. In the centre was an authority-lending legend, AM. The military logo used to put the fear of God into visiting listeners. They really thought that prolonged operation in the red would cause some dramatic failure. The sort of blow-out that puts inpromptu serving hatches into bedroom walls.

Thirty years has gone by since then, along with a career in Instrumentation. I have to say this was the most elegant indicator I ever came up with - totally uncalibrated, of course, but really effective.

A victory like this gives you the confidence to really go to town. Front panels are drilled to take switches for product detectors. A cardinal sin. The rectifier valve is changed for silicon diodes with no current limiting. It seems to hum a bit now, so a weepy electrolytic capacitor is slapped across the HT. While I answered the phone, that capacitor failed. A direct short across the power supply burned out the mains transformer, writing off a classic radio.

Why didn't the fuse go? Ah, well, an easy upgrade you can do as a child is to fit higher-value fuses. This stupidity cost me a radio I dearly miss now. And the motto? If you don't understand it - leave it alone. Enjoy it for what it is - rather than what you were hoping for.

There were no radio buttons on an AR88. The one on this PC is clicked with a mouse. A curious second-hand experience. I am doing it now to see if anybody has responded to my last e-mail. Apparently, I have a Fatal System Error at Module E004765007-00014. Never got those on my dear departed AR88.

How To Ruin A Collins TCS 12

There he would be. The closet World Service listener. No sexism here - the listener would be male and sadly, he won't have been listening on short-wave. He will have come in off a shift, come in from the pub or stumbled back from a party only to find his beloved Radio 4 LW has closed, opting over to Play of the Week on the World Service.

For my generation there were still warehouses full of ex-military kit looking for homes and all of us were experts in its restoration. If you read what I did to my AR88 in these pages, you will know that an ex is something that was and a spurt is a drip under pressure. Blaster Bates definition of an expert is not far from the truth.

The first real wage packet, all £8 of it, was blown on this solid little set affectionately known as The Cube. The shop was a weird place on Curzon Street in Derby, hoping to make a living out of militaria. It's now a wine bar. Known better as a Collins TCS 12, mine had no power supply. As a child, my PSU's always doubled as room heaters. Looking at the circuit now, it was capable of 80mA of HT max. Running a 12A6 in the local oscillator - a power beam-tetrode - with something similar biased for Everything Forward And Trust In The Lord in the audio output stage, that 80mA was easily exceeded. The mains transformer gently fried. They say the sense of smell is the most evocative for memory. I think of the TCS every time they resurface the roads.

The Local Oscillator was meant to be a power-oscillator. It radiated a very clean heterodyne across two villages. Local it wasn't.

Replacing all the capacitors for The Liquorice Allsort Series, our name for polyester types borrowed on long-term lease from work, no doubt made it better. I know I would have jacked up the screen volts for each valve whilst changing all the resistors. Here I learned about preferred values. Well, I liked them.

Whether it needed this mod is moot point. The caps were paper-block and the resistors solid carbon. Collins never used a half-watt if you could get a 3-watt in. Restorers insist you change all these. So I did.

At least with the incredible LO injection, you could use the longest of long-wires and still get a clean mix. Inexperienced ears don't know what a 3rd-order product sounds like. Today, new listeners have every noise they don't like down to a design fault. Back then, the TCS radiated better than some not-so-QRP rigs. Of the three gangs in the tuning, the oscillator was the biggest. Why? Not sure, but could have something to do with linearity.

On the Military Wireless Net, the TCS was condemned as useless due to broad selectivity. At 12 kHz, it made solid-carrier broadcast listening a real pleasure. The Two Bobs on Swiss Radio International was a joy to listen to.

Up in my room, this was all the contact I had with Real Radio and I miss them. World Service was on 5975 during the day making The Cube a real favourite.

The TCS grew a Carrier Meter, a naff loudspeaker first in the top of the case then on the front panel using a classic chrome trim nicked off an AIRMEC signal generator. The case was sprayed the inevitable FARINA GREY 9095, cans of it. It grew product detectors, infinite-impedance detectors and current-hungry audio stages.

The 600-ohm output defeated me, so this was RC coupled to an EL95 on the panel that held my mains transformer mods. This, in turn, had replaced a rack of ceramic sockets for XTAL operation at the back of the case. Unable to think of another mod and suitably ruined, I gave the TCS away.

A Classic Car Radio Distroyed

While I sit waiting for the next mid-life crisis to show up, it occurs to me I have lived through about four sunspot cycles.

Each one had me going through hoops to get the best out of the kit I had at the time. Hence all those catastrophic mods listed in these pages. Anyway, it's good therapy writing about it.

Some history. About this time, thirty some years ago, a grey Rover with my initials on the plate pulled away from Derby School on our first run up to The Rose and Crown. As I write this, the Rover brand is heading to be as collectible as Eddystone and the custom plate was only a coincidence.

When you take a pub, most folk think you own the place. Not so. You rent them, then go into a thirty year war with the brewery over getting any repairs done. The Crown was an ex-coaching inn with stables at the back and lots of disused rooms.

Mine was Room 2 with an off-suite olive green bathroom and a view over the stable block and the incinerator. It got the sun for about half an hour on the morning of the solstice. It was the start of a long and happy time when everything seemed so simple - just like the bloke writing this.

Mr Barlow's car radio was powered from Dad's battery-charger, memorable for its INCREASE CHARGE rheostat and a haunting cherry-red POWER indicator. The radio was in a white wooden box, a desperate attempt to silence the steady droning hum, the reason Mr Barlow got rid of it. The vibrator PSU would wake my brother Bill when we shared a room before pub life set us up in opposite wings at The Crown. A close family.

It had the ECH Series of valves - the radio, not the pub, running from that noisy HT supply. Can't remember what I did for an antenna here but at the pub with extensive carparks and random trees, it would have been an over-the-top long-wire.

The extra stations I thought I heard were just cross-mod.

It was, after all, a car radio designed to work off a car aerial. Such was my knowledge of impedance matching, I thought bigger had to be better. Did I really try to run it off the huge mast antenna that came with the 52 Set?

Heard Athlone for the first time. Another country, another way of life. And, even then, learned from it. The tension that became The Troubles was not news to me when the story broke over here.

Radio One would have been a year away then but I can't think what the offshore scene was doing at that time. Reception must have been major stations only, the poor thing so mismatched it must have been quite deaf.

Spoiled by all this space, the engineering criterion was get as much wire in the air as possible. Antenna length was determined by the distance from the bedroom window to that tree over there.

The chaps on 80 AM spoke of these allegedly magical 66-footers but for me, size was everything. And you needed the height. The pub was three storeys high and had a valley roof. This meant you could climb out there with tremendous confidence until you looked over the edge. Then the vertigo would kick in and you'd quietly hum Nearer My God To Thee until it passed.

Ernie: Do you have vertigo?

Eric: No. I only live around the corner.

Hi-Fi Made Low

GW3COI's impression of the writer warming his hands over a pair of KT66s

The other great love at that time was Hi-Fi. Even then, it seemed ridiculously expensive and had a certain snobbery by being priced in guineas.

The PYE Concerto was the classic KT66/GZ32/ECC33/ECC35 line-up in an ultra-linear configuration. The pre-amp used ECC41s. Noisy, especially in the GRAM mode. It was profoundly microphonic, ringing out like church bells when you tapped the case.

The tuner was a QUAD, almost ignored as there was only LIGHT, THIRD and HOME on VHF. I knew if you were running KT Series valves in the output stages, you were up there with the Big Boys. My idea of housework was to remove the valves now and again to clean them. Made them sound better. This sounds daft but reading today's audio press where you can buy a CD cleaner spray for £35, a plinth for the player to sit on, a mere £450 and special cables - sorry, interconnects - for anything up to £1000. My stupidity came in a lot cheaper.

Disaster. Broke off the locating spigot on the GZ32 valve base. Putting back incorrectly, it linked the raw AC HT over to the reservoir caps resulting in an explosion that rocked the place. It did £25 worth of damage. You may have bought your Hi-Fi in safely up-market guineas but repairs are the work of an artisan so you are back to honest working-class pounds.

Back To Radio

After being laughed out of the Derby & District Amateur Radio Club Home-brew Competition, I thought I'd have a go at going commercial. A CODAR CR70A. This radio introduced me to The 1930 Net, the Top Band natter-net on 1930kHz at 1930GMT. With the closure of the Coastal Stations this June, it's good to hear 160m alive again.

It fitted well on my bedside table - you could almost read by the dial lamps. Was it RNI or a parallel interest in Hi-Fi that has embedded Lucky Man by Emerson Lake and Palmer in my memory? And to think ELP are now the theme to The Generation Game. Proof that nothing is sacred.

Did I modify the Codar? Er, the normal output stage was a Class A ECC81 but with the EZ80 rectifier usurped by silicon, it made way for a 6BW6. A wonderful radiogram quality due to hideous mis-matching. Minutes of happy listening until the mains transformer burnt out.

It was replaced by a PCR Receiver. I liked this little radio. Made by Philips Lamps, it was really a domestic set made up for NAAFI Service. It was chosen because the dial lamps shone as bright as the CODAR so I could carry on reading in bed. How I don't know.

Little? The PCR was about the size of a PC base unit. Small in the world of militaria.

New readers now know you are dealing with high-end engineering. It needed the best test equipment. The best you could get for £22. The HARTLEY ELECTROMOTIVES 13A OSCILLOSCOPE was the toy of toys. Dual beam with only 807-class valves for gain to a 5-inch tube with 3000 volts on the plate, it got as hot as hell. Spent most of its time monitoring audio, stuff like Walter Carlos' Switched On Bach, the nearest I ever got to drugs.

Use the scope as a TV Monitor. To do this, feed CRT cathode signal via Z MOD link to scope. Bond scope earth return across to a live TV chassis and take X and Y drive from the timebases. Watch Vision On in a 3 by 4 inch green/black display with a perfectly good 21 inch monochrome picture on the telly right next to it.