Toshiba TV29C90 problem; Image fades to black...

[bz]

"captainvideo462002@yahoo.com" <captainvideo462002@yahoo.com> wrote in
news:a0af529a-e358-4577-be1a-dd107caa9e25@a70g2000hsh.googlegroups.com:

I have a need for a power meter for general low band and VHF work. I
would like it to have at least two scales. One, a 0 - 10 W or so
scale and if possible another which would enable it to measure up to
around 125 W as well. The immediate need to satisfy the requirements
of a job we're doing is for an instrument that can measure 1.0 W at
72.0 MHZ. The signal is AM with a duration of .50 sec. and there is
some type of digital alarm transmission which modulates the carrier.
The only way I think that I can do this now is to measure the RMS
voltage accross a 52 ohm dummy load with my Boonton, and then
calculate the power. I feel though that this is clumsy and may be
potentially inaccurate. I'd love to have a Bird with all the bells and
whistles but I really can't afford one. Does anyone know of a home
brew project for doing this or even an inexpensive accurate kit?
Thanks, Lenny.

http://www.elecraft.com/mini_module_kits/mini_modules.htm



--
bz 73 de N5BZ k

please pardon my infinite ignorance, the set-of-things-I-do-not-know is an
infinite set.

bz+ser@ch100-5.chem.lsu.edu remove ch100-5 to avoid spam trap

 

[Kadaitcha Man]

<radiant_x@outgun.com> wrote in message
news:b4c7ef4d-c3bf-4643-876d-85404f889975@k37g2000hsf.googlegroups.com...

thanks a lot! any advice is appreciated!

After all that waffle and piffle, you never even once conidered removing
the
fucking DVD drive. Right?

Wow, you're quick to jump to conclusions.

Yes, very. You have a problem with that?

If you read the post, you'll
notice that:

"...I've tried replacing the power supply, and I've tried removing all
my hardware (other than
RAM), so I'm thinking it must be motherboard related."

So yes, of course I<BITCHSLAP

You need to be less overblown with the techno-bullshit. People like you do
that all the time in an effort to hide the fact that you don't know what the
fuck you're on about. The fact is, now that you offer that text in your
defence, the very first line in that mass of swollen verbiage you call a
post was a lie.

"I recently installed a DVD drive into my PC. (2 days ago.) Since then, I
get spontaneous power loss periodically..."

Had you been less of a fucking jaw-boner you would have said "I installed a
DVD drive into my PC then removed it. Since then, I get spontaneous power
loss periodically..."

The poor cunts who have to suffer your flowery, porcine posts wouldn't have
needed the ten extra pages of fucking bombastic waffle you added. The answer
would have been a straightforward, "You fucked something".

HTH

--
alt.usenet.kooks
"We are arrant knaves all, believe none of us."
Hamlet, Act 3, Scene 1 [129]

Hammer of Thor: February 2007. Pierre Salinger Memorial Hook,
Line & Sinker: September 2005, April 2006, January 2007.
Official Member: Cabal Obsidian Order COOSN-124-07-06660
Official Overseer of Kooks & Trolls in 24hoursupport.helpdesk

Member of:
Usenet Ruiner List
Top Assholes on the Net List
Most hated usenetizens of all time List
Cog in the AUK Hate Machine

Find me on Google Maps: 24°39'47.13"S, 134°4'20.18"E

 

[Kadaitcha Man]

"Butch Haynes" <butch@huntsville> wrote in message
news:zbmdnUfjYIjDTZXVnZ2dnUVZ_gWdnZ2d@comcast.com...

radiant_x@outgun.com> wrote in message
news:293e3140-e027-496c-89d8-27906e8991f7@t54g2000hsg.googlegroups.com...

I recently installed a DVD drive into my PC. (2 days ago.) Since then,
I get spontaneous power loss periodically - sometimes seconds after
booting, other times after hours of operation. I've tried replacing
the power supply, and I've tried removing all my hardware (other than
RAM), so I'm thinking it must be motherboard related.

Unplug/replug all power and data connections. That way, the errant loose
one will be fixed and your problem will be resolved.

BWAHAHAHAHAHAHAHAHAHAHAHAHA!

Tech support by feng shui.

--
alt.usenet.kooks
"We are arrant knaves all, believe none of us."
Hamlet, Act 3, Scene 1 [129]

Hammer of Thor: February 2007. Pierre Salinger Memorial Hook,
Line & Sinker: September 2005, April 2006, January 2007.
Official Member: Cabal Obsidian Order COOSN-124-07-06660
Official Overseer of Kooks & Trolls in 24hoursupport.helpdesk

Member of:
Usenet Ruiner List
Top Assholes on the Net List
Most hated usenetizens of all time List
Cog in the AUK Hate Machine

Find me on Google Maps: 24°39'47.13"S, 134°4'20.18"E

 

[Kadaitcha Man]

"Aratzio" <a6ahlyv02@sneakemail.com> wrote in message
news:9opi0456deigk7ihd4bq4mq3u9mar9tha3@4ax.com...

On Sat, 19 Apr 2008 13:26:03 +1000, in the land of alt.usenet.kooks,
"Kadaitcha Man" <nospam.nospam.nospam@gmail.com> got double secret
probation for writing:

"Butch Haynes" <butch@huntsville> wrote in message
news:zbmdnUfjYIjDTZXVnZ2dnUVZ_gWdnZ2d@comcast.com...
radiant_x@outgun.com> wrote in message
news:293e3140-e027-496c-89d8-27906e8991f7@t54g2000hsg.googlegroups.com...

I recently installed a DVD drive into my PC. (2 days ago.) Since then,
I get spontaneous power loss periodically - sometimes seconds after
booting, other times after hours of operation. I've tried replacing
the power supply, and I've tried removing all my hardware (other than
RAM), so I'm thinking it must be motherboard related.

Unplug/replug all power and data connections. That way, the errant loose
one will be fixed and your problem will be resolved.

BWAHAHAHAHAHAHAHAHAHAHAHAHA!

Tech support by feng shui.

"I've tried removing all my hardware(other than RAM)"

Do none of them understand what that entails?

None of them understand anything.

--
alt.usenet.kooks
"We are arrant knaves all, believe none of us."
Hamlet, Act 3, Scene 1 [129]

Hammer of Thor: February 2007. Pierre Salinger Memorial Hook,
Line & Sinker: September 2005, April 2006, January 2007.
Official Member: Cabal Obsidian Order COOSN-124-07-06660
Official Overseer of Kooks & Trolls in 24hoursupport.helpdesk

Member of:
Usenet Ruiner List
Top Assholes on the Net List
Most hated usenetizens of all time List
Cog in the AUK Hate Machine

Find me on Google Maps: 24°39'47.13"S, 134°4'20.18"E

 

[bz]

Graham <g0nbd@hotmail.com> wrote in news:329ab6b5-154c-4ee2-a6b7-77f841f27cf6
@f36g2000hsa.googlegroups.com:

On Apr 18, 11:26 pm, bz <bz+...@ch100-5.chem.lsu.edu> wrote:
"captainvideo462...@yahoo.com" <captainvideo462...@yahoo.com> wrote innews
:a0af529a-e358-4577-be1a-dd107caa9e25@a70g2000hsh.googlegroups.com:

I have a need for a power meter for general low band and VHF work. I
would like it to have at least two scales. One,  a 0 - 10 W or so
scale and if possible another which would enable it to measure up to
around 125 W as well. The immediate need to satisfy the requirements
of a job we're doing is for an instrument that can measure 1.0 W at
72.0 MHZ. The signal is AM with a duration of .50 sec. and there is
some type of digital alarm transmission which modulates the carrier.
The only way I think that I can do this now is to measure the RMS
voltage accross a 52 ohm dummy load with my Boonton, and then
calculate the power. I feel though that this is clumsy and may be
potentially inaccurate. I'd love to have a Bird with all the bells and
whistles but I really can't afford one. Does anyone know of a home
brew project for doing this or even an inexpensive accurate kit?
Thanks, Lenny.

http://www.elecraft.com/mini_module_kits/mini_modules.htm

The signal is AM with a duration of .50 sec. and there is
some type of digital alarm transmission which modulates the carrier

That sounds like a complex transmission , measuring the incident
voltage over the 50 ohm load may be the only way , may be hire
something expensive to get a calibration chart ?

One of the kits on the page I referenced could be the basis for his power
meter. There are others in _The Radio Amateur's Handbook_ that would work.

What he may need is probably to use a computer A/D card
(possibly the audio card) to capture the waveform. Then to numerically
integrate that over the time period of interest.

A simpler way would be to read the peak voltage across the load.
That can be done with a simple diode detector probe.
That would give the peak power with a simple calculation.

Nothing expensive is needed to get an accurate peak power reading.

A diode, a couple of small capacitors and a resistor will make a fairly
accurate peak voltage probe. Elecraft has a low price kit.

A couple of 100 Ohm surface mount resistors of the appropriate power
rating, soldered in parallel will give a very good, low reactance 50 ohm
dummy load that should cover the frequencies of interest.

Or 20 each, 1000 ohm resistors, 10 watt resistors (non inductive) in
parallel for a 200 watt 50 ohm dummy load.

P=V^2/R; V=sqrt(P*R);
easy enough to make a calibration chart:
v p
15.81 5
22.36 10
27.39 15
31.62 20
38.73 30
44.72 40
50.00 50
61.24 75
70.71 100
74.16 110
77.46 120





--
bz 73 de N5BZ k

please pardon my infinite ignorance, the set-of-things-I-do-not-know is an
infinite set.

bz+ser@ch100-5.chem.lsu.edu remove ch100-5 to avoid spam trap

 

[Erronous Monk]

For more information about batteries than you thought you might ever need go
to:

http://batteryuniversity.com

 

[Erronous Monk]

For more information about batteries than you thought you might ever need go
to:

http://batteryuniversity.com

 

[Dave Plowman (News)]

In article <363g04hkpo3a73a4ov8b2koh6vhp5t3dtv@4ax.com>,
Robert LaCasse <yamaha@here.info> wrote:

I tested some battery chargers last night , and found "as usual" that
the amps and voltages stated on the modules were not the same as what I
found on the Volt and Amp testers....

Some 12v charging modules, would say 1.5 amp, whereas the voltage
test was 12-->17v and/or 4-->6amps on the meters....

I'd be utterly amazed if any charger said to have a maximum output of 1.5
amps managed 4-6. The reverse I would believe...

All the "Walwart" max output 800ma (.8A) with 3 volts selected
showed 2amps on the amp meter, and almost 4amps at the 12v setting. The
inline charging modules were pretty much the same...

Just how are you measuring this? It needs to be done under actual
operating conditions.

I have a 12v 8Ah MF SLA battery to charge at .8amp and I can't get
anything to charge as low as .8 amp from the walwarts.......when I do,
nothing happens for days, as far volt checks are concerned...

Can you explain what you mean? An SLA battery needs a dedicated charger
designed for a constant voltage output. The charge current will then take
care of itself. A 12 volt power supply may well not charge a 12 volt
battery at all - the correct figure for that constant voltage is 13.8.

The charging volts are not higher than 12.4 volts on any of the
chargers....

Then they won't charge a 12 volt battery to anywhere near full capacity.

Some ppl discard this discrepancy with the volts compensate for the
current, expression, but does it really, if a low charging amp can't be
achieved? I don't want to buckle cells or dehydrate the $240 MF SLA
battery.

Sounds like you need to buy a proper charger for such an expensive battery.

--
*Red meat is not bad for you. Fuzzy green meat is bad for you.

Dave Plowman dave@davenoise.co.uk London SW
To e-mail, change noise into sound.

 

[Dave Plowman (News)]

In article
<293e3140-e027-496c-89d8-27906e8991f7@t54g2000hsg.googlegroups.com>,
<radiant_x@outgun.com> wrote:

I recently installed a DVD drive into my PC. (2 days ago.) Since then,
I get spontaneous power loss periodically - sometimes seconds after
booting, other times after hours of operation. I've tried replacing
the power supply, and I've tried removing all my hardware (other than
RAM), so I'm thinking it must be motherboard related.

I had a similar thing which drove me crazy. Happened just after fitting a
new graphics card. Which was just coincidence.
Turned out to be the main processor overheating and shutting down. Its
fan was working normally and no error messages generated. Removing the
heatsink, cleaning and applying new thermo conductive paste sorted it. Now
have a spare power supply...

--
*I'm really easy to get along with once people learn to worship me

Dave Plowman dave@davenoise.co.uk London SW
To e-mail, change noise into sound.

 

[Dave Plowman (News)]

In article <4ppOj.4843$iK6.2204@nlpi069.nbdc.sbc.com>,
Who Me? <hitchhiker@dont.panic> wrote:

I'd be utterly amazed if any charger said to have a maximum output of
1.5 amps managed 4-6. The reverse I would believe...


That IS somewhat of a stretch but not totally impossible. The max.
current output shown is at the rated voltage. So, for instance, a
device rated at 1.5A, 12V should supply 12V up to the rated current load
of 1.5A (or somewhere close). If you continue to increase the load,
the amperage may increase beyond 1.5A......as the supplied voltage
drops below 12V.

It would be a strange power supply that allowed that. Although it might be
possible with different tappings on a transformer.

--
*If at first you don't succeed, try management *

Dave Plowman dave@davenoise.co.uk London SW
To e-mail, change noise into sound.

 

[Dave Plowman (News)]

In article <OgOlGON20eCIFwpp@g3ohx.demon.co.uk>,
Ian Jackson <ianREMOVETHISjackson@g3ohx.demon.co.uk> wrote:

I had a similar thing which drove me crazy. Happened just after fitting
a new graphics card. Which was just coincidence. Turned out to be the
main processor overheating and shutting down. Its fan was working
normally and no error messages generated. Removing the heatsink,
cleaning and applying new thermo conductive paste sorted it. Now have a
spare power supply...


I had the same problem with the PC shutting down when the processor was
working hard. Its heatsink was full of dust. Soon afterwards, I again
had shutdowns. This time it was because the PSU fan had seized solid
(probably dry bearings). Freeing-off and re-lubrication with WD40 has
worked for the last 6 months (but I will fit a new fan one day).

Mine was relatively new and the heatsink clean. Plenty of fans, too, all
working. It's a home assembled one which worked fine for a year or so
before developing the symptoms. I used the paste which came with the
heatsink originally and that had gone hard - dunno why.

--
*Acupuncture is a jab well done*

Dave Plowman dave@davenoise.co.uk London SW
To e-mail, change noise into sound.

 

[Gareth Magennis]

"Bennett Price" <""bjpriceNOSPAM\"@NOSPAMcal berkeley.edu"> wrote in message
news:RFqOj.3153$h75.936@newssvr27.news.prodigy.net...

I've got a small 12V DC .9 Watt 'muffin' fan (1.75"x1.75"x3/8").
It was the cooler for a video card's processor chip and was
frozen up.

I put a drop of oil into its sleeve bearing and it now runs
reliably - almost. It will start every time as long as it is
not oriented with the open 'face' down. (The open face is the
side in which you can see the bearing). If the open bearing is
down, it sometimes starts and sometimes needs a slight nudge to
get it going.

What's going on? How come? TIA

Presumably because the bearings are worn out. Get another one.



Gareth.

 

[James Sweet]

"Bennett Price" <""bjpriceNOSPAM\"@NOSPAMcal berkeley.edu"> wrote in message
news:RFqOj.3153$h75.936@newssvr27.news.prodigy.net...

I've got a small 12V DC .9 Watt 'muffin' fan (1.75"x1.75"x3/8").
It was the cooler for a video card's processor chip and was
frozen up.

I put a drop of oil into its sleeve bearing and it now runs
reliably - almost. It will start every time as long as it is
not oriented with the open 'face' down. (The open face is the
side in which you can see the bearing). If the open bearing is
down, it sometimes starts and sometimes needs a slight nudge to
get it going.

What's going on? How come? TIA

The bearing may be a bit loose. I've had some success disassembling these
fans, cleaning out the dried up muck, and putting on fresh oil then
reassemble. It's better to replace it, but if you need to use the computer
and don't have one on hand, it works in a pinch.

 

[James Sweet]

"Dave Plowman (News)" <dave@davenoise.co.uk> wrote in message
news:4f929585a6dave@davenoise.co.uk...

In article <4ppOj.4843$iK6.2204@nlpi069.nbdc.sbc.com>,
Who Me? <hitchhiker@dont.panic> wrote:
I'd be utterly amazed if any charger said to have a maximum output of
1.5 amps managed 4-6. The reverse I would believe...


That IS somewhat of a stretch but not totally impossible. The max.
current output shown is at the rated voltage. So, for instance, a
device rated at 1.5A, 12V should supply 12V up to the rated current load
of 1.5A (or somewhere close). If you continue to increase the load,
the amperage may increase beyond 1.5A......as the supplied voltage
drops below 12V.

It would be a strange power supply that allowed that. Although it might be
possible with different tappings on a transformer.

If you put the ammeter straight across it, shorting the output of the
charger, it would not surprise me at all if it managed 4-6A, obviously this
is not a useful measurement and it wouldn't take long for it to overheat
though.

 

[Arny Krueger]

"EADGBE" <hwbosshoss@comcast.net> wrote in message
news:d8647727-1ae7-4fbd-96f7-1f9ffea3b0b9@e67g2000hsa.googlegroups.com

I am a home hobbyist who enjoys restoring vintage stereo
equipment. I have a good working knowledge of electronic
components and what they do. I have decent test
equipment and good soldering skills, and most of the time
I am able to track down and repair a particular problem.

However, I do feel that I need to know more about the
theory behind electronic circuits in order to improve my
troubleshooting skills.

Sometimes I find myself looking at a schematic and
thinking, "Boy, I wish I knew more about what is supposed
to be happening in this circuit!"

Can anyone point to any good books or online sources
where I can learn more about how to analyze schematics
and recognize what is supposed to be happening?

http://jacquesricher.com/NEETS/

24 PDFs that make up a pretty fair basic electronics course, fairly current
as of 2003.

US Navy Electricity and Electronics Training Series

Module 1 - Introduction to Matter, Energy, and Direct Current
Module 2 - Introduction to Alternating Current and Transformers
Module 3 - Introduction to Circuit Protection, Control, and Measurement
Module 4 - Introduction to Electrical Conductors, Wiring Techniques, and
Schematic Reading
Module 5 - Introduction to Generators and Motors
Module 6 - Introduction to Electronic Emission, Tubes, and Power Supplies
Module 7 - Introduction to Solid-State Devices and Power Supplies
Module 8 - Introduction to Amplifiers
Module 9 - Introduction to Wave-Generation and Wave-Shaping Circuits
Module 10 - Introduction to Wave Propagation, Transmission Lines, and
Antennas
Module 11 - Microwave Principles
Module 12 - Modulation Principles
Module 13 - Introduction to Number Systems and Logic Circuits
Module 14 - Introduction to Microelectronics
Module 15 - Principles of Synchros, Servos, and Gyros
Module 16 - Introduction to Test Equipment
Module 17 - Radio-Frequency Communications Principles
Module 18 - Radar Principles
Module 19 - The Technician's Handbook
Module 20 - Master Glossary
Module 21 - Test Methods and Practices
Module 22 - Introduction to Digital Computers
Module 23 - Magnetic Recording
Module 24 - Introduction to Fiber Optics

 

[Arny Krueger]

"EADGBE" <hwbosshoss@comcast.net> wrote in message
news:d8647727-1ae7-4fbd-96f7-1f9ffea3b0b9@e67g2000hsa.googlegroups.com

I am a home hobbyist who enjoys restoring vintage stereo
equipment. I have a good working knowledge of electronic
components and what they do. I have decent test
equipment and good soldering skills, and most of the time
I am able to track down and repair a particular problem.

However, I do feel that I need to know more about the
theory behind electronic circuits in order to improve my
troubleshooting skills.

Sometimes I find myself looking at a schematic and
thinking, "Boy, I wish I knew more about what is supposed
to be happening in this circuit!"

Can anyone point to any good books or online sources
where I can learn more about how to analyze schematics
and recognize what is supposed to be happening?

http://jacquesricher.com/NEETS/

24 PDFs that make up a pretty fair basic electronics course, fairly current
as of 2003.

US Navy Electricity and Electronics Training Series

Module 1 - Introduction to Matter, Energy, and Direct Current
Module 2 - Introduction to Alternating Current and Transformers
Module 3 - Introduction to Circuit Protection, Control, and Measurement
Module 4 - Introduction to Electrical Conductors, Wiring Techniques, and
Schematic Reading
Module 5 - Introduction to Generators and Motors
Module 6 - Introduction to Electronic Emission, Tubes, and Power Supplies
Module 7 - Introduction to Solid-State Devices and Power Supplies
Module 8 - Introduction to Amplifiers
Module 9 - Introduction to Wave-Generation and Wave-Shaping Circuits
Module 10 - Introduction to Wave Propagation, Transmission Lines, and
Antennas
Module 11 - Microwave Principles
Module 12 - Modulation Principles
Module 13 - Introduction to Number Systems and Logic Circuits
Module 14 - Introduction to Microelectronics
Module 15 - Principles of Synchros, Servos, and Gyros
Module 16 - Introduction to Test Equipment
Module 17 - Radio-Frequency Communications Principles
Module 18 - Radar Principles
Module 19 - The Technician's Handbook
Module 20 - Master Glossary
Module 21 - Test Methods and Practices
Module 22 - Introduction to Digital Computers
Module 23 - Magnetic Recording
Module 24 - Introduction to Fiber Optics

 

[DaveM]

Arny gave you a list of some teaching materials for electronics theory, however,
most of them seem to focus on more advanced systems theory. I don't know to
what level these texts assume the reader has progressed. It's been so long
since I looked at a basic theory text that I can't recommend any without a bit
of searching. Perhaps another reader can be of more assistance.

If your focus is on solid state equipment, then you'll need to focus your
studies on theories of transistor circuits. The most basic component that
you'll need to study hard and really understand is, of course, the transistor.

In reference to your tape deck problem, If you could think about how the various
voltages in the circuit are derived, then it might be a little clearer.
Remember that transistors are current operated devices, that is, a small current
through the base-emitter of the transistor modifies the current between the
collector and emitter. In normal linear circuits, a transistor's B-E junction
is forward biased, while the B-C junction is reverse biased.
Forward-biased: current flows; reverse-biased: no current flows.

Assuming silicon transistors, the B-E junction is forward-biased with a voltage
of approximately 0.5 to 0.7 volts between the base and emitter. Always use the
emitter as a reference point for voltage measurements around a transistor. For
an NPN device, the base is positive with reference to the emitter. For a PNP,
the base is negative to the emitter.

In your tape circuit, the big clue to the problem is lack of any voltage at the
collector of Q205. Q205 must be turned on, at least partially, in order for any
voltage to appear at its collector (which is showing no voltage). It is the
only path that can supply the current to Q203 is through the E-C circuit of
Q205. If Q205's B-E is properly forward biased, current should flow through the
C-E circuit.
Measure the B-E voltage of Q205. If it's in the vicinity of 0.5 - 0.7 volts,
then the transistor should be conducting current from its emitter to its
collector. If the voltage there is less than that, then the transistor can't
conduct, thereby shutting off the C-E circuit.

If the transistor's B-E junction is properly forward biased, then it should be
conducting. If it isn't conducting, then the transistor is either open or there
is another fault, and further troubleshooting is needed. My bet on your tape
deck's fault is on Q205. Let me know if that fixes it.

Hope this helps you get started,
--
Dave M
MasonDG44 at comcast dot net (Just substitute the appropriate characters in the
address)

Some people are like Slinkies. Not really good for anything, but they bring a
smile to your face when pushed down the stairs.
"EADGBE" <hwbosshoss@comcast.net> wrote in message
news:d8647727-1ae7-4fbd-96f7-1f9ffea3b0b9@e67g2000hsa.googlegroups.com...

I am a home hobbyist who enjoys restoring vintage stereo equipment. I
have a good working knowledge of electronic components and what they
do. I have decent test equipment and good soldering skills, and most
of the time I am able to track down and repair a particular problem.

However, I do feel that I need to know more about the theory behind
electronic circuits in order to improve my troubleshooting skills.

Sometimes I find myself looking at a schematic and thinking, "Boy, I
wish I knew more about what is supposed to be happening in this
circuit!"

Can anyone point to any good books or online sources where I can learn
more about how to analyze schematics and recognize what is supposed to
be happening?

CASE IN POINT: I am attempting to repair a tape deck. One channel
(the right channel) of the headphone amplifier doesn't work. The tape
deck has perfect output through the line out jacks.

Here is the schematic for one of the channels of the tape deck's
headphone amp:

http://i240.photobucket.com/albums/ff58/eadgbe123/amplifier.jpg

I have reproduced the schematic in my own handwriting because the
downloaded schematic was too fuzzy to scan. I *think* I have copied
everything correctly.

I cannot figure out why this particular circuit isn't working
correctly. I have checked each component--and even replaced a few
transistors even though all transistors tested fine--but nothing is
improving.

I have tested all of the electrolytics with my ESR meter and they all
check out OK.

I have checked all resistors and none of them have opened up or "gone
high".

Notice that there are some "typical" expected voltages indicated at
certain points. These "typical" voltages have come right out of the
service manual. All of the voltages marked "OK" are...well...OKAY.
But the three voltages marked with a star (*) are NOT okay...they are
all just a few millivolts each--around 20 to 30mV.

All capacitors are electrolytic with the exception of the 4.7pF
capacitor, which is ceramic.

All resistors are 1/4 watt. If there is no "K" after the number, then
that is the amount of actual ohms it has.

For the record, I replaced Q204, Q206, and Q208 but still got exactly
the same results.

What am I overlooking?

 

[DaveM]

Arny gave you a list of some teaching materials for electronics theory, however,
most of them seem to focus on more advanced systems theory. I don't know to
what level these texts assume the reader has progressed. It's been so long
since I looked at a basic theory text that I can't recommend any without a bit
of searching. Perhaps another reader can be of more assistance.

If your focus is on solid state equipment, then you'll need to focus your
studies on theories of transistor circuits. The most basic component that
you'll need to study hard and really understand is, of course, the transistor.

In reference to your tape deck problem, If you could think about how the various
voltages in the circuit are derived, then it might be a little clearer.
Remember that transistors are current operated devices, that is, a small current
through the base-emitter of the transistor modifies the current between the
collector and emitter. In normal linear circuits, a transistor's B-E junction
is forward biased, while the B-C junction is reverse biased.
Forward-biased: current flows; reverse-biased: no current flows.

Assuming silicon transistors, the B-E junction is forward-biased with a voltage
of approximately 0.5 to 0.7 volts between the base and emitter. Always use the
emitter as a reference point for voltage measurements around a transistor. For
an NPN device, the base is positive with reference to the emitter. For a PNP,
the base is negative to the emitter.

In your tape circuit, the big clue to the problem is lack of any voltage at the
collector of Q205. Q205 must be turned on, at least partially, in order for any
voltage to appear at its collector (which is showing no voltage). It is the
only path that can supply the current to Q203 is through the E-C circuit of
Q205. If Q205's B-E is properly forward biased, current should flow through the
C-E circuit.
Measure the B-E voltage of Q205. If it's in the vicinity of 0.5 - 0.7 volts,
then the transistor should be conducting current from its emitter to its
collector. If the voltage there is less than that, then the transistor can't
conduct, thereby shutting off the C-E circuit.

If the transistor's B-E junction is properly forward biased, then it should be
conducting. If it isn't conducting, then the transistor is either open or there
is another fault, and further troubleshooting is needed. My bet on your tape
deck's fault is on Q205. Let me know if that fixes it.

Hope this helps you get started,
--
Dave M
MasonDG44 at comcast dot net (Just substitute the appropriate characters in the
address)

Some people are like Slinkies. Not really good for anything, but they bring a
smile to your face when pushed down the stairs.
"EADGBE" <hwbosshoss@comcast.net> wrote in message
news:d8647727-1ae7-4fbd-96f7-1f9ffea3b0b9@e67g2000hsa.googlegroups.com...

I am a home hobbyist who enjoys restoring vintage stereo equipment. I
have a good working knowledge of electronic components and what they
do. I have decent test equipment and good soldering skills, and most
of the time I am able to track down and repair a particular problem.

However, I do feel that I need to know more about the theory behind
electronic circuits in order to improve my troubleshooting skills.

Sometimes I find myself looking at a schematic and thinking, "Boy, I
wish I knew more about what is supposed to be happening in this
circuit!"

Can anyone point to any good books or online sources where I can learn
more about how to analyze schematics and recognize what is supposed to
be happening?

CASE IN POINT: I am attempting to repair a tape deck. One channel
(the right channel) of the headphone amplifier doesn't work. The tape
deck has perfect output through the line out jacks.

Here is the schematic for one of the channels of the tape deck's
headphone amp:

http://i240.photobucket.com/albums/ff58/eadgbe123/amplifier.jpg

I have reproduced the schematic in my own handwriting because the
downloaded schematic was too fuzzy to scan. I *think* I have copied
everything correctly.

I cannot figure out why this particular circuit isn't working
correctly. I have checked each component--and even replaced a few
transistors even though all transistors tested fine--but nothing is
improving.

I have tested all of the electrolytics with my ESR meter and they all
check out OK.

I have checked all resistors and none of them have opened up or "gone
high".

Notice that there are some "typical" expected voltages indicated at
certain points. These "typical" voltages have come right out of the
service manual. All of the voltages marked "OK" are...well...OKAY.
But the three voltages marked with a star (*) are NOT okay...they are
all just a few millivolts each--around 20 to 30mV.

All capacitors are electrolytic with the exception of the 4.7pF
capacitor, which is ceramic.

All resistors are 1/4 watt. If there is no "K" after the number, then
that is the amount of actual ohms it has.

For the record, I replaced Q204, Q206, and Q208 but still got exactly
the same results.

What am I overlooking?

 

[§ńühw¤Łf]

Aratzio <a6ahlyv02@sneakemail.com> clouded the waters of pure thought with:

On Sat, 19 Apr 2008 09:01:56 -0700, in the land of alt.usenet.kooks,
§ńühw¤Łf <snuhwolf@netscape.net> got double secret probation for
writing:

On Sat, 19 Apr 2008 13:35:53 +1000
"Kadaitcha Man" <nospam.nospam.nospam@gmail.com> wrote:

"Aratzio" <a6ahlyv02@sneakemail.com> wrote in message
news:9opi0456deigk7ihd4bq4mq3u9mar9tha3@4ax.com...
On Sat, 19 Apr 2008 13:26:03 +1000, in the land of alt.usenet.kooks,
"Kadaitcha Man" <nospam.nospam.nospam@gmail.com> got double secret
probation for writing:

"Butch Haynes" <butch@huntsville> wrote in message
news:zbmdnUfjYIjDTZXVnZ2dnUVZ_gWdnZ2d@comcast.com...
radiant_x@outgun.com> wrote in message
news:293e3140-e027-496c-89d8-27906e8991f7@t54g2000hsg.googlegroups.com...

I recently installed a DVD drive into my PC. (2 days ago.) Since then,
I get spontaneous power loss periodically - sometimes seconds after
booting, other times after hours of operation. I've tried replacing
the power supply, and I've tried removing all my hardware (other than
RAM), so I'm thinking it must be motherboard related.

Unplug/replug all power and data connections. That way, the errant loose
one will be fixed and your problem will be resolved.

BWAHAHAHAHAHAHAHAHAHAHAHAHA!

Tech support by feng shui.

"I've tried removing all my hardware(other than RAM)"

Do none of them understand what that entails?


None of them understand anything.

I go toetally on into-ition.
Just do what feels good for a few hours...take out a few cables...fondle them...blow out the dust bunnies...listen to the Grateful Dead live at Winterland for inspiration.
Drink another beer...
Change a bunch of jumpers on the Mobo at random.
Leave shit scattered around on yer workbench and wander away.
Watch cartoons for another hour...
Come back and put it back together.
Holy Shit! Now it works.
Thats how I do it anyway.
FYI
HTH

Dunno why you geeks muck about with all that crap.

I take em out to the back 40, prop em against the side of the gully
and show them my Springfield 30-06.

BLINK

<BLINK>
OMG! I would never shoot a poor defenceless computer!

They always work after that.

I assume you miss...

Works good with the employees, wife and kids too.

Note to self: dont work for 'Ratz.

--
www.biologicaldiversity.org

 

[§ńühw¤Łf]

Aratzio <a6ahlyv02@sneakemail.com> clouded the waters of pure thought with:

On Sat, 19 Apr 2008 09:01:56 -0700, in the land of alt.usenet.kooks,
§ńühw¤Łf <snuhwolf@netscape.net> got double secret probation for
writing:

On Sat, 19 Apr 2008 13:35:53 +1000
"Kadaitcha Man" <nospam.nospam.nospam@gmail.com> wrote:

"Aratzio" <a6ahlyv02@sneakemail.com> wrote in message
news:9opi0456deigk7ihd4bq4mq3u9mar9tha3@4ax.com...
On Sat, 19 Apr 2008 13:26:03 +1000, in the land of alt.usenet.kooks,
"Kadaitcha Man" <nospam.nospam.nospam@gmail.com> got double secret
probation for writing:

"Butch Haynes" <butch@huntsville> wrote in message
news:zbmdnUfjYIjDTZXVnZ2dnUVZ_gWdnZ2d@comcast.com...
radiant_x@outgun.com> wrote in message
news:293e3140-e027-496c-89d8-27906e8991f7@t54g2000hsg.googlegroups.com...

I recently installed a DVD drive into my PC. (2 days ago.) Since then,
I get spontaneous power loss periodically - sometimes seconds after
booting, other times after hours of operation. I've tried replacing
the power supply, and I've tried removing all my hardware (other than
RAM), so I'm thinking it must be motherboard related.

Unplug/replug all power and data connections. That way, the errant loose
one will be fixed and your problem will be resolved.

BWAHAHAHAHAHAHAHAHAHAHAHAHA!

Tech support by feng shui.

"I've tried removing all my hardware(other than RAM)"

Do none of them understand what that entails?


None of them understand anything.

I go toetally on into-ition.
Just do what feels good for a few hours...take out a few cables...fondle them...blow out the dust bunnies...listen to the Grateful Dead live at Winterland for inspiration.
Drink another beer...
Change a bunch of jumpers on the Mobo at random.
Leave shit scattered around on yer workbench and wander away.
Watch cartoons for another hour...
Come back and put it back together.
Holy Shit! Now it works.
Thats how I do it anyway.
FYI
HTH

Dunno why you geeks muck about with all that crap.

I take em out to the back 40, prop em against the side of the gully
and show them my Springfield 30-06.

BLINK

<BLINK>
OMG! I would never shoot a poor defenceless computer!

They always work after that.

I assume you miss...

Works good with the employees, wife and kids too.

Note to self: dont work for 'Ratz.

--
www.biologicaldiversity.org