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Somebody down my way...



 
 
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  #21  
Old October 30th 16, 09:42 PM posted to uk.tech.digital-tv
Terry Casey[_2_]
external usenet poster
 
Posts: 741
Default Somebody down my way...

In article ,
says...

"Terry Casey" wrote in message
...
In article ,
says...

"Terry Casey" wrote in message
...

You are comparing the dissipation of the BC148 with the
collector current of the BC108!

In practice, the specifications of both types are identical
(although I would back the BC108 as having a longer life as
it doesn't suffer from the problems caused by the plastic
encapsulation of the BC148).

The difference is the dissipation; 220mW for the 148 and 300mW for the
108.

I'm kinda wondering how you could miss 300mA was a
typo.............................................. ......


Sorry but you still got it wrong! The maximum collector
current for both types is 200mA whereas the maximum
dissipation of the BC148, at 350mW, is actually higher that
the 300mW specified for the BC108 ...

See:

https://dl.dropboxusercontent.com/u/24301298/BC108%20-%
20BC148.png

or http://tinyurl.com/bc108-bc148


The values I remember are from an early Mullard pocket databook maybe late
60s/early 70s - since then; dozens of companies have produced second source
devices, and a few had their own interpretation of the specifications.

However, the specifications I found are from a Mullard data
book - if you have any of these to hand you will see the
fonts and layout are distinctively Mullard.

--

Terry
  #22  
Old October 30th 16, 10:04 PM posted to uk.tech.digital-tv
Benderthe.evilrobot
external usenet poster
 
Posts: 148
Default Somebody down my way...


"Terry Casey" wrote in message
...
In article ,
says...

"Terry Casey" wrote in message
...
In article ,
says...

"Terry Casey" wrote in message
...

You are comparing the dissipation of the BC148 with the
collector current of the BC108!

In practice, the specifications of both types are identical
(although I would back the BC108 as having a longer life as
it doesn't suffer from the problems caused by the plastic
encapsulation of the BC148).

The difference is the dissipation; 220mW for the 148 and 300mW for the
108.

I'm kinda wondering how you could miss 300mA was a
typo.............................................. ......

Sorry but you still got it wrong! The maximum collector
current for both types is 200mA whereas the maximum
dissipation of the BC148, at 350mW, is actually higher that
the 300mW specified for the BC108 ...

See:

https://dl.dropboxusercontent.com/u/24301298/BC108%20-%
20BC148.png

or http://tinyurl.com/bc108-bc148


The values I remember are from an early Mullard pocket databook maybe
late
60s/early 70s - since then; dozens of companies have produced second
source
devices, and a few had their own interpretation of the specifications.

However, the specifications I found are from a Mullard data
book - if you have any of these to hand you will see the
fonts and layout are distinctively Mullard.


Its abundantly clear that you won't go away without an
argument.........................

  #23  
Old October 31st 16, 05:14 PM posted to uk.tech.digital-tv
Paul Ratcliffe
external usenet poster
 
Posts: 2,465
Default Somebody down my way...

On Sun, 30 Oct 2016 22:04:23 -0000, Benderthe.evilrobot
wrote:

The values I remember are from an early Mullard pocket databook maybe
late
60s/early 70s - since then; dozens of companies have produced second
source
devices, and a few had their own interpretation of the specifications.

However, the specifications I found are from a Mullard data
book - if you have any of these to hand you will see the
fonts and layout are distinctively Mullard.


Its abundantly clear that you won't go away without an
argument.........................


The same could be said of you (why couldn't you admit you
remebered wrongly?).
The only difference is that he is right and you are wrong.
So why don't YOU go away, eh?
  #24  
Old October 31st 16, 07:50 PM posted to uk.tech.digital-tv
Benderthe.evilrobot
external usenet poster
 
Posts: 148
Default Somebody down my way...


"Paul Ratcliffe" wrote in message
...
On Sun, 30 Oct 2016 22:04:23 -0000, Benderthe.evilrobot
wrote:

The values I remember are from an early Mullard pocket databook maybe
late
60s/early 70s - since then; dozens of companies have produced second
source
devices, and a few had their own interpretation of the specifications.

However, the specifications I found are from a Mullard data
book - if you have any of these to hand you will see the
fonts and layout are distinctively Mullard.


Its abundantly clear that you won't go away without an
argument.........................


The same could be said of you (why couldn't you admit you
remebered wrongly?).


I remembered correctly - I used to carry that Mullard Pocket Databook in my
back pocket constantly.

That family of transistors came out about 50 years ago and has been produced
by dozens of manufacturers.

Plenty of time/opportunity for published data to drift more than the actual
silicon.

BTW: I remember you from before - are you or he the other's sock puppet?

  #25  
Old October 31st 16, 11:51 PM posted to uk.tech.digital-tv
Bill Wright[_3_]
external usenet poster
 
Posts: 1,973
Default Somebody down my way...

On 31/10/2016 19:50, Benderthe.evilrobot wrote:

I remembered correctly - I used to carry that Mullard Pocket Databook in
my back pocket constantly.


With me it was the CAMRA real ale guide.

Bill
  #26  
Old November 1st 16, 08:13 PM posted to uk.tech.digital-tv
Benderthe.evilrobot
external usenet poster
 
Posts: 148
Default Somebody down my way...


"Bill Wright" wrote in message
...
On 31/10/2016 19:50, Benderthe.evilrobot wrote:

I remembered correctly - I used to carry that Mullard Pocket Databook in
my back pocket constantly.


With me it was the CAMRA real ale guide.


That explains plenty...............

  #27  
Old November 3rd 16, 07:33 PM posted to uk.tech.digital-tv
Graham.[_12_]
external usenet poster
 
Posts: 413
Default Somebody down my way...

On Fri, 28 Oct 2016 18:49:25 +0100, "Benderthe.evilrobot"
wrote:


"Graham." wrote in message
...
"Benderthe.evilrobot" Wrote
in message:

"Brian Gaff" wrote in message
...
Has one of those old analogue Video sender devices, as up in the 800Mhz
area I can often hear some sound from various sources, sometimes its
foreign sounding tv, sometimes one of the Sky channels or a movie.
I would assume whe this is illegal and may be interfered with by digital
transmissions at some time in the fuuture.
I wonder if they realise others can hear it. Not heard any video though
so
maybe that is too low a level.

With the old analogue TVs, it was possible for the sound IF to pick up SW
radio if it wasn't adequately shielded. Since there probably isn't much
FM
at 6MHz, it hinted at less than perfect AM rejection. The vision IF is
somewhere around 39.5MHz, breakthrough would indicate faulty
traps/filtering
at the final IF stage/detector.

You can also get heterodyning of perfectly legitimate transmissins that
shift a weak image of it into a band they shouldn't be.

TV sound is FM, usually its easier to demodulate FM with an AM detector
than
the other way round - the Bush/Rank A823 chassis early revisions used a
slope-tuned AM detector. OTOH: some band II radios will just about bring
in
the bottom edge of the VHF airband - it depends on the AM rejection (or
lack
of) of each individual receiver.



That RBM chassis was very badly designed and was the main culprit
for picking up Moscow and Piking on the 49meter-band.


When Television magazine was in its prime, I used to read about other
engineers complaining what a nasty piece of work the colour decoder was. The
were pretty much 2 versions - a 2 chip and the earlier 1 chip + many
discretes. It was more often than not one of the chips, and easy to diagnose
once you learned the ropes.

It was usually the vertical output that gave me the worse struggles.

One colour fault that could've been tricky was a SC emitter follower in the
signal path. The customer wanted to wait, so I rolled my sleeves up and got
stuck in. I noticed a heat stain rising from a BC148 near the edge of the
PCB. After a bit of searching, I couldn't find a culprit, so I replaced the
220mW BC148 with a 300mA BC108.

At least the early marks had the same stacked pair of horizontal output
transistors as the Philips G8. Setting up the balancing inductor was lots of
fun.


Unforgiving was the word I would have used.

And that over-volts limiter on the thyristor PSU


--

Graham.

%Profound_observation%
  #28  
Old November 3rd 16, 08:18 PM posted to uk.tech.digital-tv
Benderthe.evilrobot
external usenet poster
 
Posts: 148
Default Somebody down my way...


"Graham." wrote in message
...
On Fri, 28 Oct 2016 18:49:25 +0100, "Benderthe.evilrobot"
wrote:


"Graham." wrote in message
...
"Benderthe.evilrobot" Wrote
in message:

"Brian Gaff" wrote in message
...
Has one of those old analogue Video sender devices, as up in the
800Mhz
area I can often hear some sound from various sources, sometimes its
foreign sounding tv, sometimes one of the Sky channels or a movie.
I would assume whe this is illegal and may be interfered with by
digital
transmissions at some time in the fuuture.
I wonder if they realise others can hear it. Not heard any video
though
so
maybe that is too low a level.

With the old analogue TVs, it was possible for the sound IF to pick up
SW
radio if it wasn't adequately shielded. Since there probably isn't much
FM
at 6MHz, it hinted at less than perfect AM rejection. The vision IF is
somewhere around 39.5MHz, breakthrough would indicate faulty
traps/filtering
at the final IF stage/detector.

You can also get heterodyning of perfectly legitimate transmissins that
shift a weak image of it into a band they shouldn't be.

TV sound is FM, usually its easier to demodulate FM with an AM detector
than
the other way round - the Bush/Rank A823 chassis early revisions used a
slope-tuned AM detector. OTOH: some band II radios will just about
bring
in
the bottom edge of the VHF airband - it depends on the AM rejection (or
lack
of) of each individual receiver.



That RBM chassis was very badly designed and was the main culprit
for picking up Moscow and Piking on the 49meter-band.


When Television magazine was in its prime, I used to read about other
engineers complaining what a nasty piece of work the colour decoder was.
The
were pretty much 2 versions - a 2 chip and the earlier 1 chip + many
discretes. It was more often than not one of the chips, and easy to
diagnose
once you learned the ropes.

It was usually the vertical output that gave me the worse struggles.

One colour fault that could've been tricky was a SC emitter follower in
the
signal path. The customer wanted to wait, so I rolled my sleeves up and
got
stuck in. I noticed a heat stain rising from a BC148 near the edge of the
PCB. After a bit of searching, I couldn't find a culprit, so I replaced
the
220mW BC148 with a 300mA BC108.

At least the early marks had the same stacked pair of horizontal output
transistors as the Philips G8. Setting up the balancing inductor was lots
of
fun.


Unforgiving was the word I would have used.

And that over-volts limiter on the thyristor PSU


I vaguely remember a fluorescent starter tube - but I can't remember which
make used that (probably Philips).

Didn't the RBM just use a bog standard SCR crowbar circuit.

The SCS trigger device was very popular in those days (a PUT and SCR both on
the same die). AFAICR: one of those makes used one in both the vertical
timebase and the PSU.

  #29  
Old November 13th 16, 05:58 PM posted to uk.tech.digital-tv
tony sayer
external usenet poster
 
Posts: 4,985
Default Somebody down my way...

In article , Graham.
scribeth thus
On Fri, 28 Oct 2016 18:49:25 +0100, "Benderthe.evilrobot"
wrote:


"Graham." wrote in message
...
"Benderthe.evilrobot" Wrote
in message:

"Brian Gaff" wrote in message
...
Has one of those old analogue Video sender devices, as up in the 800Mhz
area I can often hear some sound from various sources, sometimes its
foreign sounding tv, sometimes one of the Sky channels or a movie.
I would assume whe this is illegal and may be interfered with by digital
transmissions at some time in the fuuture.
I wonder if they realise others can hear it. Not heard any video though
so
maybe that is too low a level.

With the old analogue TVs, it was possible for the sound IF to pick up SW
radio if it wasn't adequately shielded. Since there probably isn't much
FM
at 6MHz, it hinted at less than perfect AM rejection. The vision IF is
somewhere around 39.5MHz, breakthrough would indicate faulty
traps/filtering
at the final IF stage/detector.

You can also get heterodyning of perfectly legitimate transmissins that
shift a weak image of it into a band they shouldn't be.

TV sound is FM, usually its easier to demodulate FM with an AM detector
than
the other way round - the Bush/Rank A823 chassis early revisions used a
slope-tuned AM detector. OTOH: some band II radios will just about bring
in
the bottom edge of the VHF airband - it depends on the AM rejection (or
lack
of) of each individual receiver.



That RBM chassis was very badly designed and was the main culprit
for picking up Moscow and Piking on the 49meter-band.


When Television magazine was in its prime, I used to read about other
engineers complaining what a nasty piece of work the colour decoder was. The
were pretty much 2 versions - a 2 chip and the earlier 1 chip + many
discretes. It was more often than not one of the chips, and easy to diagnose
once you learned the ropes.

It was usually the vertical output that gave me the worse struggles.

One colour fault that could've been tricky was a SC emitter follower in the
signal path. The customer wanted to wait, so I rolled my sleeves up and got
stuck in. I noticed a heat stain rising from a BC148 near the edge of the
PCB. After a bit of searching, I couldn't find a culprit, so I replaced the
220mW BC148 with a 300mA BC108.

At least the early marks had the same stacked pair of horizontal output
transistors as the Philips G8. Setting up the balancing inductor was lots of
fun.


Unforgiving was the word I would have used.

And that over-volts limiter on the thyristor PSU


Anyone remember the 100 K resistor slow start mod?..



What balancing inductor used to work on them don't recall that?.

The BU 105's used to fallover quite regularly;(...


--
Tony Sayer

Bancom Communications U.K. Tel+44 1223 566577 Fax+44 1223 566588

4 Wingate close, Cambridge, England, CB2 9HW E-Mail


  #30  
Old November 13th 16, 06:43 PM posted to uk.tech.digital-tv
Benderthe.evilrobot
external usenet poster
 
Posts: 148
Default Somebody down my way...


"tony sayer" wrote in message
...
In article , Graham.
scribeth thus
On Fri, 28 Oct 2016 18:49:25 +0100, "Benderthe.evilrobot"
wrote:


"Graham." wrote in message
...
"Benderthe.evilrobot" Wrote
in message:

"Brian Gaff" wrote in message
...
Has one of those old analogue Video sender devices, as up in the
800Mhz
area I can often hear some sound from various sources, sometimes its
foreign sounding tv, sometimes one of the Sky channels or a movie.
I would assume whe this is illegal and may be interfered with by
digital
transmissions at some time in the fuuture.
I wonder if they realise others can hear it. Not heard any video
though
so
maybe that is too low a level.

With the old analogue TVs, it was possible for the sound IF to pick up
SW
radio if it wasn't adequately shielded. Since there probably isn't
much
FM
at 6MHz, it hinted at less than perfect AM rejection. The vision IF is
somewhere around 39.5MHz, breakthrough would indicate faulty
traps/filtering
at the final IF stage/detector.

You can also get heterodyning of perfectly legitimate transmissins
that
shift a weak image of it into a band they shouldn't be.

TV sound is FM, usually its easier to demodulate FM with an AM
detector
than
the other way round - the Bush/Rank A823 chassis early revisions used
a
slope-tuned AM detector. OTOH: some band II radios will just about
bring
in
the bottom edge of the VHF airband - it depends on the AM rejection
(or
lack
of) of each individual receiver.



That RBM chassis was very badly designed and was the main culprit
for picking up Moscow and Piking on the 49meter-band.

When Television magazine was in its prime, I used to read about other
engineers complaining what a nasty piece of work the colour decoder was.
The
were pretty much 2 versions - a 2 chip and the earlier 1 chip + many
discretes. It was more often than not one of the chips, and easy to
diagnose
once you learned the ropes.

It was usually the vertical output that gave me the worse struggles.

One colour fault that could've been tricky was a SC emitter follower in
the
signal path. The customer wanted to wait, so I rolled my sleeves up and
got
stuck in. I noticed a heat stain rising from a BC148 near the edge of the
PCB. After a bit of searching, I couldn't find a culprit, so I replaced
the
220mW BC148 with a 300mA BC108.

At least the early marks had the same stacked pair of horizontal output
transistors as the Philips G8. Setting up the balancing inductor was lots
of
fun.


Unforgiving was the word I would have used.

And that over-volts limiter on the thyristor PSU


Anyone remember the 100 K resistor slow start mod?..



What balancing inductor used to work on them don't recall that?.

The BU 105's used to fallover quite regularly;(...


Probably because you didn't balance them.

They were in series, so you had to balance the base drive. Whichever
transistor turned off too soon got all the flyback pulse to itself.

 




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