childhood inventions
 

On Sat, 12 Jan 2013 12:36:16 +0000, tony sayer
wrote:

In article , Brian Gaff
scribeth thus
I recall the problems actually attempting to make a radio transmitter from
early transistors. Of course you could just build an oscillator and modulate
its amplitude, but that was not very successful as no matter what you did,
it had some FM tendencies resulting in the middle of the carrier having an
almost dead spot.
The only successful one was three transistors, a buffer and an output stage
which was tuned and then it worked quite well.

Brian


Never bothered with transistors, much too flimsy. Once after I got a
ECC88 going there was no stopping thru 807's and 813's then QQV03-20A
VHF valves;)...


I was a topband enthusiast in the 70s and even at this low frequency
and 10W dc limit, transistor transmitters were a real novelty.

To paraphrase Tony Hancock "Give me a 6BW6 any day".



--
Graham.
%Profound_observation%

childhood inventions
 

tony sayer wrote:
Never bothered with transistors, much too flimsy. Once after I got a
ECC88 going there was no stopping thru 807's and 813's then QQV03-20A
VHF valves;)...

My father built an audio amplifier with a pair of 807s in push-pull in
the output stage (even though I think these are transmitter valves).
He was in the habit of testing amplifiers by putting his finger on the
grid cap of a valve and listening for a buzz in the loudspeaker. I tried
this one day with the 807s, not realizing that the cap on these valves
goes to the anode! The shock threw me back against the wall. Later when
I got a meter I found that the supply to the anodes was about 600 volts.

childhood inventions
 

"Graham." wrote in message
...
On Sat, 12 Jan 2013 10:11:14 -0000, "Brian Gaff"
wrote:

Actually, I think it was done to make testing them less prone to issues
when light fell on them.
Later of course they put their transistors inside metal cases, but many
of
these now suffer from a degeneration of the filler that shorts them out
so
they need to be replaced.

Brian

Yes, I have a classic Bush TR82C in the bedroom, and one of the AF117
started playing up. The fault practically put a short on the 9v rail.

Giving the transistor a sharp tap cleared the short temporarily. The
solution was just to snip the 4th screen wire, it really doesn't seem
to be necessary.



That was a common problem with those transistors almost from day one, AKA
ANLE (a nice little earner :-)

childhood inventions
 

Hmm a thousand fun things to do with a fix it badge, by penfold on Babani or
whatever it was called. I wonder if the collectors price will go up or down
on those. I think they were mostly plastic.
Brian

--
Brian Gaff....Note, this account does not accept Bcc: email.
graphics are great, but the blind can't hear them
Email:
__________________________________________________ __________________________________________________ __________


"Rick" wrote in message ...


wrote in message
...
secondary. Twelve or thirteen I suppose.

I don't know why this came to mind, but I just wondered if anyone else
had mad inventions when they were a kid...



Why didn't you write to Jim with your idea, maybe he could have fixed it
for you?

childhood inventions
 

wrote in message
...
I was brought up in a house that was a few hundred yards from the edge of a
vast estate of council and NCB houses. If anyone's interested it was on
Middlegate, Scawthorpe, Doncaster. We often used to walk up the hill to the
field at the side of the quarry, from where there was a view across the
estate and also across parts of Bentley. I used to fantasise about
broadcasting to the estate from there, by light. I would set up a powerful
lamp that would be modulated by audio. I knew a filament wouldn't respond
quickly enough, but I didn't know anything else that would, so I just hoped
that sopmething would turn up. Each receiver would have a large parabolic
mirror mounted somewhere high up enough to see my lantern, with a photocell
at the focal point. I remember talking to my science-inclined form master
about this, so that means I must have been first year secondary. Twelve or
thirteen I suppose.

I don't know why this came to mind, but I just wondered if anyone else had
mad inventions when they were a kid...

Bill

I spent countless hours in my youth inventing 'perpetual motion' - usually
involving magnets and bicycle wheels - until finally conceding that perhaps
the naysayers were right after all.

childhood inventions
 

On Fri, 11 Jan 2013 05:17:15 -0800 (PST),
wrote:

I was brought up in a house that was a few hundred yards from the edge of a vast estate of council and NCB houses. If anyone's interested it was on Middlegate, Scawthorpe, Doncaster. We often used to walk up the hill to the field at the side of the quarry, from where there was a view across the estate and also across parts of Bentley. I used to fantasise about broadcasting to the estate from there, by light. I would set up a powerful lamp that would be modulated by audio. I knew a filament wouldn't respond quickly enough, but I didn't know anything else that would, so I just hoped that sopmething would turn up. Each receiver would have a large parabolic mirror mounted somewhere high up enough to see my lantern, with a photocell at the focal point. I remember talking to my science-inclined form master about this, so that means I must have been first year secondary. Twelve or thirteen I suppose.

I don't know why this came to mind, but I just wondered if anyone else had mad inventions when they were a kid...

Bill


A contribution I made to a thread on another newsgroup has reminded me
of the hydrogen bomb I invented after learning about electrolysis at
school.


--
Graham.
%Profound_observation%

childhood inventions
 

In article ,
lid says...

On Sat, 12 Jan 2013 10:11:14 -0000, "Brian Gaff"
wrote:

Actually, I think it was done to make testing them less prone to issues
when light fell on them.
Later of course they put their transistors inside metal cases, but many of
these now suffer from a degeneration of the filler that shorts them out so
they need to be replaced.

Brian

Yes, I have a classic Bush TR82C in the bedroom, and one of the AF117
started playing up. The fault practically put a short on the 9v rail.

Giving the transistor a sharp tap cleared the short temporarily. The
solution was just to snip the 4th screen wire, it really doesn't seem
to be necessary.

That is not a permanent cure. The problem with the AF11x series is the
tin coating on the inside of the can which grows whiskers.

When one of these whiskers touches the transistor inside and causes a
short, it can indeed be cleared by cutting the screen wire.

The problem is that it doesn't actually clear the short so that, when
another whisker reaches another electrode there are now two shorts which
are connected via the can.

No less an authority than NASA has carried out a detailed investigation
into the problem - report he

http://nepp.nasa.gov/whisker/anecdote/af114-transistor/

Remember that the next time someone mentions unleaded solder ...

--

Terry

childhood inventions
 

Why didn't you write to Jim with your idea, maybe he could have fixed it for

you?

I did, enclosing a photograph. His agent wrote back and said that Jim only fixed it for good looking kids.

Bill

childhood inventions
 

On Sat, 12 Jan 2013 18:11:18 -0000, Terry Casey
wrote:

In article ,
says...

On Sat, 12 Jan 2013 10:11:14 -0000, "Brian Gaff"
wrote:

Actually, I think it was done to make testing them less prone to issues
when light fell on them.
Later of course they put their transistors inside metal cases, but many of
these now suffer from a degeneration of the filler that shorts them out so
they need to be replaced.

Brian

Yes, I have a classic Bush TR82C in the bedroom, and one of the AF117
started playing up. The fault practically put a short on the 9v rail.

Giving the transistor a sharp tap cleared the short temporarily. The
solution was just to snip the 4th screen wire, it really doesn't seem
to be necessary.

That is not a permanent cure. The problem with the AF11x series is the
tin coating on the inside of the can which grows whiskers.

When one of these whiskers touches the transistor inside and causes a
short, it can indeed be cleared by cutting the screen wire.

The problem is that it doesn't actually clear the short so that, when
another whisker reaches another electrode there are now two shorts which
are connected via the can.

No less an authority than NASA has carried out a detailed investigation
into the problem - report he

http://nepp.nasa.gov/whisker/anecdote/af114-transistor/

Remember that the next time someone mentions unleaded solder ...

Thanks Terry, I knew there was more to the problem as I was typing,
but I couldn't remember the details. Having seen the picture of the
inside of the can, I won't now forget.



--
Graham.
%Profound_observation%

childhood inventions
 

wrote in message
...
Why didn't you write to Jim with your idea, maybe he could have fixed it
for

you?

I did, enclosing a photograph. His agent wrote back and said that Jim only
fixed it for good looking kids.



With hindsight a blessing in disguise, as by recent accounts it probably
saved you from length of tongue...