AERIALITE TYPE TCD Band Converter

[radiozero]

Hi. I've got a circuit diagram of a band converter - Aerialite Type T.C.D. Can anyone please supply a picture of this set? Thanks. Rich

[Dave Moll]

Here is the Aerialite Band III converter I have. If this is what you're looking for, I'll dig it out and try to get some shots of the insides.

Incidentally, is there any chance of uploading the circuit diagram?

[rambo1152]

I had one of those as a kid. I repurposed the case for a Q-multiplier I built for my R107 receiver.

[Heatercathodeshort]

Very good Band 3 converter supplied under many brand names including EMI and McMichael. The museum at Dulwich has some working examples. Often contains a short length of co-ax cable wired internally as a stub in an attempt to remove the BBC signal from the RF output lead. Baffling if you don't know what it is! J.

[winston_1]

Hi John.

I've got one of those, the circuit is in one of the TV & Radio Servicing books. I've had it for around 60 years and it was working last time I tried it a year or so ago.

Regarding that stub I didn't know what it was for and removed it (60 years ago). Can't believe it was for removing the BBC signal though as the converted ITV signal was the same frequency and would be removed as well. Also it was much too short. I understood it was to remove something though I can't remember what.

[Heatercathodeshort]

The problem was the strong BBC signal was picked up on the lead that connected to the TV when tuned to channel 9 in London around 194mc/s. It was very difficult to remove and the stub was only partially effective. The output lead had to be cut to an exact length. Even with the BBC aerial input shorted on ITA the problem close to a BBC transmitter was patterning.

The Spencer West type 55 pattern removal unit was very effective cancelling out the BBC signal and was used by the GPO. TRF receivers did not convert well hence the hundreds of them that turned up at jumble sales to my delight when I was a kid. John.

[Dave Moll]

Fortunately, when mine was originally in use by my grandfather, it was before Oxford's Beckley transmitter, so the Band I BBC signal from London was weak enough not to swamp the Band III signal. Whether there was any co-channel interference I wouldn't know as I have no recollection of watching ITV with this setup.

[radiozero]

Originally Posted by Dave Moll

Here is the Aerialite Band III converter I have. If this is what you're looking for, I'll dig it out and try to get some shots of the insides.

Incidentally, is there any chance of uploading the circuit diagram?

Yes, I can upload the circuit. Will do so today or tommorrow. Rich

[Heatercathodeshort]

To save you the bother Rich and as I had one of these on the back of the bench I have taken some pics. The stub can clearly be seen wrapped around the smoothing block. The 2 amp 3pin socket on the back supplied the TV with mains via the front three position switch. OFF/Band1/Band3. A simple clever idea but it saved a double adaptor for the TV
and converter. Very well made. ECC84 and PCF80 valves and a tiny contact cooled rectifier.
They work very well. We have one working in conjunction with a PYE D16T at the museum. Regards, John.

[winston_1]

Hi John,

I'll assume ECC84 is a typo. Mine has a PCC84. the 2 valve heaters are in series off a winding on the transformer.

[radiozero]

What I've got as to the circuit.

[G6Tanuki]

That brings back memories: I 'reworked' one back in the late-1960s so it functioned as a converter from the 2M amateur-band down to something around 18MHz to feed a SW receiver. You didn't bohr with the converter's tuning - it was broad-enough that you could tune the entire 2M band on the SW receiver.

[Heatercathodeshort]

Originally Posted by winston_1

Hi John,

I'll assume ECC84 is a typo. Mine has a PCC84. the 2 valve heaters are in series off a winding on the transformer.

Hello Winston,
Probably due to slight circuit alteration during manufacture. The circuit shows ECC84 and ECF80 [6.3V] with a valve rectifier. Mine has a metal contact cooled type. They were probably swamped with orders and had to modify slightly to keep production going. John.

[Heatercathodeshort]

Originally Posted by winston_1

I'll assume ECC84 is a typo. Mine has a PCC84. the 2 valve heaters are in series off a winding on the transformer.

Hello Winston, There were probably minor change particularly around the mains transformer and rectifier. My version has a metal rectifier, ECC84 and ECF80 6.3V in parallel. The circuit shows E valves with a valve rectifier. The demand for these must have been incredible in 1955 and I suspect they encountered component supply difficulties. Everyone who owned a television in 1955 wanted the ITA [except old Aunt Heatherington Smythe.]

Another example does use the P range of valves and a metal rectifier. It has the EMI logo on it supplied by EMIs Sales and Service dept. Oddly it has an EMI serial number code H/19 50295. I also have a version with the McMichael logo. Aerialite must have supplied personalized versions to the manufacturers. Regards, John.

[winston_1]

Originally Posted by Heatercathodeshort

Hello Winston, There were probably minor change particularly around the mains transformer and rectifier. My version has a metal rectifier, ECC84 and ECF80 6.3V in parallel. The circuit shows E valves with a valve rectifier. The demand for these must have been incredible in 1955 and I suspect they encountered component supply difficulties. Everyone who owned a television in 1955 wanted the ITA [except old Aunt Heatherington Smythe.]

Another example does use the P range of valves and a metal rectifier. It has the EMI logo on it supplied by EMIs Sales and Service dept. Oddly it has an EMI serial number code H/19 50295. I also have a version with the McMichael logo. Aerialite must have supplied personalized versions to the manufacturers. Regards, John.

Hi John, Makes sense that there were changes over the production run. My one is branded Aerialite and has P valves

[Heatercathodeshort]

Just for completeness The McMichael logo with P series valves and a metal rectifier. J.

[Vintage Engr]

Interesting thread. As it is more or less all about this particular converter, the following story might amuse.
Way back , in about 1962, I was doing an apprenticeship with Rediffusion. It was very good, not only did I get day-release for Tech College, but most of the people I worked with were very technical, some ex-RAF.

So it was one morning, I arrived at work to find that a Philips 1768U had been dumped on my bench, with the fault label stating "Tuner drift".

This was not uncommon on these sets, & I knew where to look. Having changed a few well-out- of tolerance resistors in the tuner unit, and feeling pleased with myself I left the set on, whilst I went to make a pot of tea (part of the job spec) for the workshop...

When I came back, I made a passing glance at the screen of the Philips on my way through to our 'tea-bench'. I could have sworn that I had left the set on BBC, as there was a test card on when I left, but now it was displaying a very shaky, but none the less viewable ITA programme.

I poured out the tea, went back round to my bench, to be confronted with a perfectly normal, BBC test card C. I called over our senior engineer, Terry - (the ex-RAF one) and told him what I thought I'd previously seen... (O.K. so your all ahead of me, but then you know what the thread is about).

Terry said to me, 'You're imagining it, I know it's got drift, but to drift from channel 1 to channel 9..? That's about 150 150Mc/s!' Even I realised that the channel 1 biscuit might have a problem working at that frequency!

I know, I said, but honestly it did do it. Terry went back to the other side of the workshop, meanwhile I sat at my bench, mug in hand drinking my tea, & waiting to see if the fault would re-occur.

It didn't so I thought, let's try cooling the innards of the tuner down.

Nowadays of course we would use very carefully, it being a valve set, a can of freezer. Back then we all had a small length of aluminium aerial tubing in our tool kits, to physically blow through to cool the offending component down. (Very dodgy around the line or field time-base, - ouch!).

I duly gave the screen & anode resistor area a long blast of cool-ish air. Nothing, no wait, "It's doing it" I shouted. Three engineers appeared immediately, with stupid grins on their faces. But before I could show them the problem, the set magically 'drifted' all the way back to channel 1...

'You have replaced the frequency-changer?" they said almost in unison, & then ran out of the workshop, to the yard, where I found them in fits of un-controlled laughter.

I went back into the workshop, & looked at the mains socket & aerial distribution panel at the back of my bench, which we all had, complete with safe-block & mains isolation transformer, - all very neat & tidy. I traced the aerial cable back, under the bench across to my friend Terry's bench...

All became crystal clear! My feed had been cut, & There was now an Aerialite Band III converter in circuit. All the engineers were in on it, & they would randomly switch the converter on & off.
Being somewhat of a technical prankster myself, the whole thing unfortunately escalated, with some pretty nasty tricks being carried out from both sides. Some were somewhat dangerous, & would have today's HSE operative closing the workshop down.

All good clean fun, so now you can all have a laugh at my expense.
It's amazing how the picture of the Aerialite converter brought back a long- forgotten memory.

David.

[Heatercathodeshort]

What a great story! Young lads with time on their hands. [6.8K ? oscillator anode load] J.

[Vintage Engr]

Originally Posted by Heatercathodeshort

What a great story! Young lads with time on their hands. [6.8K ? oscillator anode load] J.

Correct, I deliberately left that out to see if someone would mention it!

There are a lot more tales from the same source, including one about a smoking Plessey (Rediffusion TA/17/4B) and a Cossor radio that apparently continued producing audio after it was switched off...

But I digress, I don't want to go off thread!

David.

[simpsons]

It wasn't the Aerialite Band 111 converter that caught my attention when, as an 8 years old boy, living in Banstead Surrey, my friend showed off The Lone Ranger on TV. It was the 3 element yagi that sat on top of the Pye B16T!

Blimey, I thought, a word gained from Billy Bunter BBC TV series but not one my dad ever used, I night get my parents to get the box but no way would they agree to the aerial on top of the TV!

Chris