Toshiba TV29C90 problem; Image fades to black...

That may be true for today's hard drives (used in new laptops and
desktop systems), but I was referring to the hard drive in my IBM
Aptiva 595 system which was new eight years ago. Were the read/write
heads on HDs of that vintage designed to retract on power down as
well? If so, I'm sure I was worrying for nothing every time the disk
crashed on that system and my first Windows computer circa 1997 (AST
Adventure! model 200).

The last time I saw a hard drive that needed to be parked was in the mid
1980s, and the largest of that nature I came across was 20MB, yes,
megabytes. I had a PC with a 40MB drive which used a stepper motor head
actuator, but even that had a clever system where the inertia of the
platters generated enough power to step the heads into the park position. In
short, any PC old enough for this to be an issue probably ought to be in a
museum rather than daily use.
 
That may be true for today's hard drives (used in new laptops and
desktop systems), but I was referring to the hard drive in my IBM
Aptiva 595 system which was new eight years ago. Were the read/write
heads on HDs of that vintage designed to retract on power down as
well? If so, I'm sure I was worrying for nothing every time the disk
crashed on that system and my first Windows computer circa 1997 (AST
Adventure! model 200).

The last time I saw a hard drive that needed to be parked was in the mid
1980s, and the largest of that nature I came across was 20MB, yes,
megabytes. I had a PC with a 40MB drive which used a stepper motor head
actuator, but even that had a clever system where the inertia of the
platters generated enough power to step the heads into the park position. In
short, any PC old enough for this to be an issue probably ought to be in a
museum rather than daily use.
 
§ńühw¤Łf wrote:
On Sun, 20 Apr 2008 22:15:06 +0100
"Dr.Hal0nf1rŁ$" <femail@nospam.kustomkomputa.co.uk.invalid> wrote:

§ńühw¤Łf wrote:
On Sat, 19 Apr 2008 15:34:16 -0700
Aratzio <a6ahlyv02@sneakemail.com> wrote:

On Sat, 19 Apr 2008 16:09:53 -0500, in the land of
alt.usenet.kooks, snuhwolf@netscape.net (§ńühw¤Łf) got double
secret probation for writing:

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.

Never had need to actually fire the damn thing.

Interesting. So you say that pc's respond to threats of
annihilation? I've got a sledge hammer laying about...
Will it solve my booting problems?

Try steel toe caps.

That didnt help at all.
You didn't kick it hard enough.

--
http://www.kustomkomputa.co.uk
- Personalised Desktop Computers
 
§ńühw¤Łf wrote:
On Sun, 20 Apr 2008 22:15:06 +0100
"Dr.Hal0nf1rŁ$" <femail@nospam.kustomkomputa.co.uk.invalid> wrote:

§ńühw¤Łf wrote:
On Sat, 19 Apr 2008 15:34:16 -0700
Aratzio <a6ahlyv02@sneakemail.com> wrote:

On Sat, 19 Apr 2008 16:09:53 -0500, in the land of
alt.usenet.kooks, snuhwolf@netscape.net (§ńühw¤Łf) got double
secret probation for writing:

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.

Never had need to actually fire the damn thing.

Interesting. So you say that pc's respond to threats of
annihilation? I've got a sledge hammer laying about...
Will it solve my booting problems?

Try steel toe caps.

That didnt help at all.
You didn't kick it hard enough.

--
http://www.kustomkomputa.co.uk
- Personalised Desktop Computers
 
EADGBE wrote:
On Apr 21, 6:41 pm, Eeyore <rabbitsfriendsandrelati...@hotmail.com
wrote:

And yet you continue to refuse to *directly* measure it's Vbe which
is what's important.

According to the datasheet for Q205, the Vbe is:

MINIMUM: -0.58
TYPICAL: -0.62
MAXIMUM: -0.68

These figures were arrived at using the following test conditions:

Vce = -6.0V
Ic = -1.0mA

As I have said, I am a hobbyist. Not sure how to do "real world"
testing for Vbe or why it's important. I do know how to test NPN and
PNP transistors using the diode function of a multimeter, that's it.
That's a good starting point, and will likely identify 95% of any problems
in an amp. Transistors and diodes, that is.

Other things to look for are blown emitter resistors, other burned
resistors, and bulging capacitors. Problms relalting to drifting component
values are pretty rare.

geoff
 
I have no cell service in my basement but I'd like to be able
to take a call without running up the stairs. Could I splice a
50ft extension cord into my headset?
How will you be able to "pick up" the call (ie, lift the cover or press the
button)?

----- The Lady from Philadelphia
 
Jerry Peters <jerry@example.invalid> wrote in news:_18Pj.117388$D_3.86716
@bgtnsc05-news.ops.worldnet.att.net:

When I worked for a large aluminum company, I had a 14" platter from a
crashed drive, the aluminum substrate had been gouged by the heads in
at least a 1/2" wide circle.
I have one of the 14" platters here, now.

In the late 70's, early 80's I actually replaced platters and heads and
aligned drives.

Again at the large Al company we had some IBM 3380 drives where the
head actuators retracted against a rubber bumper. Over time the rubber
degraded and became sticky, the IBM CE's actually replaced or covered
the rubber bumpers with new ones, while the disk were spinning! Turns
out that the disk assemblies while having a clear plastic surround,
were not really sealed.
One crash was caused by the rubber bumpers in the top of the removable disk
pack shrinking and dropping onto the hub of the spinning disk.
The friction caused the rubber tow abrade and the dust crashed the heads.

4 heads, two platters, one fixed, one removable got trashed by the dust.

Another crash was due to the velocity transducer coming loose.
The head loading current kept increasing because there was no indication of
the heads moving.
The carriage made a max velocity seek toward the hub.
Sounded like a shotgun going off.
Broke off the head travel stop.


.....
Not in my experience. Given the number of times W9x locked up with no
alternative but to do a hard reset,
If the system is locked up, the hard reset is necessary. No choice.

It is less likely to cause damage than just killing power to the computer
in the middle of normal boot up, running or shutdown.

I have had few problems. Never had
to do a reinstall because of this.
Depending on how and what NTFS journals, XP should be good in that
regard also.
Well as the department's 'fix it' person, I see the results of bad luck.
Often they tell me 'the power was shut off accidentally' or some such.

And I have managed to crash a few, on my own, by ignoring the 'proper
shutdown' rules.

--
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
 
time for some new convergence amps and resistors

"eganders" <eganders@yahoo.com> wrote in message
news:494602f5-bf32-490b-86e2-f4449960009b@a70g2000hsh.googlegroups.com...
On Apr 21, 7:37 pm, eganders <egand...@yahoo.com> wrote:
My RCA rear projection TV has worked well after help from you TV
service people in January, 2005. It has
a chassis number of PTK195AC and is model P60812BL

At that time I found that the surface of the PC boards had some of the
coolent and other debris which I cleaned and that fixed the problem.

Coming home from vacation today, the main fuse from the AC input
failed. Upon replacing it, the convergence is all messed up. I went
into the service mode using the front panel as the service manual
describes, I can't seem to get the grid pattern that I got back in
2005. Can anyone tell me

1. What typically goes wrong when the main fuse blows and the picture
goes out of adjustment

2. How do you get into the built-in geometric alignment grid pattern?

I am into the service mode, but it does not seem to have any pattern
except the P:(for parameter) and V (for parameter value): on the
screen.

I would like to nurse this TV along for a while. It has given good
service and I have no reason to replace it other than the present
problem. I really don't want to get into it deeply. For example, I
would prefer NOT to get a chipper checker or have to hook an
oscilloscope to it.

sci.electronics.repair
Here is a photo of the problem

http://img.photobucket.com/albums/v384/eganders/60inchConvergence100_1203.jpg
 
"EADGBE" <hwbosshoss@comcast.net> wrote in message
news:785f8ff8-a4a8-4389-8337-023b58d8060e@26g2000hsk.googlegroups.com...
On Apr 21, 6:41 pm, Eeyore <rabbitsfriendsandrelati...@hotmail.com
wrote:
There is only 131.1mV on the collector of Q205, despite +11.09V on its
base and +11.59V on its emitter.

And yet you continue to refuse to *directly* measure it's Vbe which is
what's important.

According to the datasheet for Q205, the Vbe is:

MINIMUM: -0.58
TYPICAL: -0.62
MAXIMUM: -0.68

These figures were arrived at using the following test conditions:

Vce = -6.0V
Ic = -1.0mA

And from your own measurements there is only 0.50V Base-emitter, so the
transistor is not correctly biased.
Possibly a fault in a preceding stage, or even an O/C resistor or possibly a
dry joint.
Keep looking and measuring other voltages.

MrT.
 
"bz" <bz+ser@ch100-5.chem.lsu.edu> wrote in message
news:Xns9A87DE7F5C25DWQAHBGMXSZHVspammote@130.39.198.139...
Jerry Peters <jerry@example.invalid> wrote in news:_18Pj.117388$D_3.86716
@bgtnsc05-news.ops.worldnet.att.net:

When I worked for a large aluminum company, I had a 14" platter from a
crashed drive, the aluminum substrate had been gouged by the heads in
at least a 1/2" wide circle.

I have one of the 14" platters here, now.

In the late 70's, early 80's I actually replaced platters and heads and
aligned drives.

Again at the large Al company we had some IBM 3380 drives where the
head actuators retracted against a rubber bumper. Over time the rubber
degraded and became sticky, the IBM CE's actually replaced or covered
the rubber bumpers with new ones, while the disk were spinning! Turns
out that the disk assemblies while having a clear plastic surround,
were not really sealed.

One crash was caused by the rubber bumpers in the top of the removable
disk
pack shrinking and dropping onto the hub of the spinning disk.
The friction caused the rubber tow abrade and the dust crashed the heads.

4 heads, two platters, one fixed, one removable got trashed by the dust.

Another crash was due to the velocity transducer coming loose.
The head loading current kept increasing because there was no indication
of
the heads moving.
The carriage made a max velocity seek toward the hub.
Sounded like a shotgun going off.
Broke off the head travel stop.


....
Not in my experience. Given the number of times W9x locked up with no
alternative but to do a hard reset,

If the system is locked up, the hard reset is necessary. No choice.

It is less likely to cause damage than just killing power to the computer
in the middle of normal boot up, running or shutdown.

I have had few problems. Never had
to do a reinstall because of this.
Depending on how and what NTFS journals, XP should be good in that
regard also.

Well as the department's 'fix it' person, I see the results of bad luck.
Often they tell me 'the power was shut off accidentally' or some such.

And I have managed to crash a few, on my own, by ignoring the 'proper
shutdown' rules.

Depends on when it happens. If write caching is enabled and the machine
loses power before the cache is flushed to the disk, whatever file it was
writing will often be corrupted. These little errors tend to accumulate
until you have all sorts of weird unreliable behavior. Even proper shutdowns
don't seem to prevent Windows from eventually deteriorating.
 
EADGBE <hwbosshoss@comcast.net> wrote in news:7a5f62ce-00ec-4fac-84f3-
838743faa613@e67g2000hsa.googlegroups.com:

In the interest of clarification, I have added some information to the
schematic of the tape deck headphone amp that I'm having problems
with.

Some circuit paths are now labeled:

http://i240.photobucket.com/albums/ff58/eadgbe123/amplifier-1.jpg

As always, the points at which voltage readings are marked with a star
are NOT producing the voltage indicated. The +7V location is
measuring 131mV instead. The other two points where a star is
indicated are measuring between 20mV and 30mV (fluctuating slightly).

I am starting to think that a circuit OUTSIDE of this circuit might be
at fault, because NOTHING inside of this circuit seems to be
faulty...but the darn thing still WILL NOT work.
You do NOT indicate the voltage on Q205's base, also Q204's collector.

If it is 11.9, then Q204 is not conducting and Q205 has no forward bias,
will not conduct, and all other bad values follow from there.

Since the OTHER voltages around Q204 are correct, the collector of Q204
should be LOWER than the 11.9 rail by half a volt or so.
It should thus be 11.4 on Q204 collector and Q205 base.

If it isn't, then Q204 is probably bad, open on the base/collector
junction.




--
bz

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

bz+spr@ch100-5.chem.lsu.edu remove ch100-5 to avoid spam trap
 
EADGBE <hwbosshoss@comcast.net> wrote in news:7a5f62ce-00ec-4fac-84f3-
838743faa613@e67g2000hsa.googlegroups.com:

In the interest of clarification, I have added some information to the
schematic of the tape deck headphone amp that I'm having problems
with.

Some circuit paths are now labeled:

http://i240.photobucket.com/albums/ff58/eadgbe123/amplifier-1.jpg

As always, the points at which voltage readings are marked with a star
are NOT producing the voltage indicated. The +7V location is
measuring 131mV instead. The other two points where a star is
indicated are measuring between 20mV and 30mV (fluctuating slightly).

I am starting to think that a circuit OUTSIDE of this circuit might be
at fault, because NOTHING inside of this circuit seems to be
faulty...but the darn thing still WILL NOT work.
You do NOT indicate the voltage on Q205's base, also Q204's collector.

If it is 11.9, then Q204 is not conducting and Q205 has no forward bias,
will not conduct, and all other bad values follow from there.

Since the OTHER voltages around Q204 are correct, the collector of Q204
should be LOWER than the 11.9 rail by half a volt or so.
It should thus be 11.4 on Q204 collector and Q205 base.

If it isn't, then Q204 is probably bad, open on the base/collector
junction.




--
bz

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

bz+spr@ch100-5.chem.lsu.edu remove ch100-5 to avoid spam trap
 
bz <bz+spr@ch100-5.chem.lsu.edu> wrote in
news:Xns9A881ACC87A34WQAHBGMXSZHVspammote@130.39.198.139:

Since the OTHER voltages around Q204 are correct, the collector of Q204
should be LOWER than the 11.9 rail by half a volt or so.
It should thus be 11.4 on Q204 collector and Q205 base.

If it isn't, then Q204 is probably bad, open on the base/collector
junction.
OR, the Q204 collector is not connected to to the 12 k resistor and the
base of Q205.

You said you replaced Q204. You could have a bad transistor(new parts can
be bad), a part soldered poorly, or a transistor soldered in wrong.
Check for broken traces and make sure that the orientation is correct on
Q204's replacement.




--
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
 
bz <bz+spr@ch100-5.chem.lsu.edu> wrote in
news:Xns9A881ACC87A34WQAHBGMXSZHVspammote@130.39.198.139:

Since the OTHER voltages around Q204 are correct, the collector of Q204
should be LOWER than the 11.9 rail by half a volt or so.
It should thus be 11.4 on Q204 collector and Q205 base.

If it isn't, then Q204 is probably bad, open on the base/collector
junction.
OR, the Q204 collector is not connected to to the 12 k resistor and the
base of Q205.

You said you replaced Q204. You could have a bad transistor(new parts can
be bad), a part soldered poorly, or a transistor soldered in wrong.
Check for broken traces and make sure that the orientation is correct on
Q204's replacement.




--
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
 
"EADGBE" <hwbosshoss@comcast.net> wrote in message
news:7a5f62ce-00ec-4fac-84f3-838743faa613@e67g2000hsa.googlegroups.com...
In the interest of clarification, I have added some information to the
schematic of the tape deck headphone amp that I'm having problems
with.

Some circuit paths are now labeled:

http://i240.photobucket.com/albums/ff58/eadgbe123/amplifier-1.jpg

As always, the points at which voltage readings are marked with a star
are NOT producing the voltage indicated. The +7V location is
measuring 131mV instead. The other two points where a star is
indicated are measuring between 20mV and 30mV (fluctuating slightly).

I am starting to think that a circuit OUTSIDE of this circuit might be
at fault, because NOTHING inside of this circuit seems to be
faulty...but the darn thing still WILL NOT work.



Make sure your transistors are oriented the right way round, i.e. B,C & E
really are where you think they are. I remember once being stuck with a
repair where the lead out of a replacement transistor was not the same as
the original. Couldn't work out what the hell was going on for quite a
while, but C and E were reversed. (don't just use a diode check for this)

Gareth.
 
"EADGBE" <hwbosshoss@comcast.net> wrote in message
news:7a5f62ce-00ec-4fac-84f3-838743faa613@e67g2000hsa.googlegroups.com...
In the interest of clarification, I have added some information to the
schematic of the tape deck headphone amp that I'm having problems
with.

Some circuit paths are now labeled:

http://i240.photobucket.com/albums/ff58/eadgbe123/amplifier-1.jpg

As always, the points at which voltage readings are marked with a star
are NOT producing the voltage indicated. The +7V location is
measuring 131mV instead. The other two points where a star is
indicated are measuring between 20mV and 30mV (fluctuating slightly).

I am starting to think that a circuit OUTSIDE of this circuit might be
at fault, because NOTHING inside of this circuit seems to be
faulty...but the darn thing still WILL NOT work.



Make sure your transistors are oriented the right way round, i.e. B,C & E
really are where you think they are. I remember once being stuck with a
repair where the lead out of a replacement transistor was not the same as
the original. Couldn't work out what the hell was going on for quite a
while, but C and E were reversed. (don't just use a diode check for this)

Gareth.
 
"Gareth Magennis" <sound.service@btconnect.com> wrote in message
news:lyhPj.444$244.4@newsfe1-win.ntli.net...
"EADGBE" <hwbosshoss@comcast.net> wrote in message
news:7a5f62ce-00ec-4fac-84f3-838743faa613@e67g2000hsa.googlegroups.com...
In the interest of clarification, I have added some information to the
schematic of the tape deck headphone amp that I'm having problems
with.

Some circuit paths are now labeled:

http://i240.photobucket.com/albums/ff58/eadgbe123/amplifier-1.jpg

As always, the points at which voltage readings are marked with a star
are NOT producing the voltage indicated. The +7V location is
measuring 131mV instead. The other two points where a star is
indicated are measuring between 20mV and 30mV (fluctuating slightly).

I am starting to think that a circuit OUTSIDE of this circuit might be
at fault, because NOTHING inside of this circuit seems to be
faulty...but the darn thing still WILL NOT work.




Make sure your transistors are oriented the right way round, i.e. B,C & E
really are where you think they are. I remember once being stuck with a
repair where the lead out of a replacement transistor was not the same as
the original. Couldn't work out what the hell was going on for quite a
while, but C and E were reversed. (don't just use a diode check for this)

Gareth.

As an example: BC184 and BC184L have different pinouts.



Gareth.
 
You need to get a scope or at least a signal tracer and see where the signal
stops on the bad side. It's a stereo amp so it should be a no brainer to
compare signals as you move through both sides. If all you have is a meter
then you just don't have enough equipment to do repair work.

"EADGBE" <hwbosshoss@comcast.net> wrote in message
news:7a5f62ce-00ec-4fac-84f3-838743faa613@e67g2000hsa.googlegroups.com...
In the interest of clarification, I have added some information to the
schematic of the tape deck headphone amp that I'm having problems
with.

Some circuit paths are now labeled:

http://i240.photobucket.com/albums/ff58/eadgbe123/amplifier-1.jpg

As always, the points at which voltage readings are marked with a star
are NOT producing the voltage indicated. The +7V location is
measuring 131mV instead. The other two points where a star is
indicated are measuring between 20mV and 30mV (fluctuating slightly).

I am starting to think that a circuit OUTSIDE of this circuit might be
at fault, because NOTHING inside of this circuit seems to be
faulty...but the darn thing still WILL NOT work.
 
One of the basic principles of troubleshooting -- which I think other
posters have been trying to get across -- is to look at the DC voltages on a
device to see what they tell you about the device's operation.

For example, in "normal" operation, a tube's plate voltage should be at
least 100V higher than the cathode *, while the grid should be several volts
lower. If this isn't so, something is wrong and you need to find out why.

I was recently troubleshooting an electronic crossover with about 10 volts
DC output. The output stage used an op amp driving a current-boost device. I
had no schematic. The parts were difficult to remove, as there was no easy
way to remove and flip over the PC board. I didn't want to go through the
hassle of removed a 14-pin op amp from the top of the board, if it wasn't
defective.

A friend (a well-known audio designer -- yes, I'm name dropping) said "Look,
the current-boost thingy has a gain of 1 for both AC and DC. The input and
output should be the same, regardless of circuit design. What are you
getting?"

"There's 1V on the input, -3V on the output."

"Then it _must_ be defective. Right?"

Right. I clipped the leads and sucked out the stubs. Then I shoved in the
replacement and carefully applied solder.

It worked.

Voltage checks provide really good troubleshooting clues -- if you know how
to interpret them.


* Obviously, the exact nominal voltages vary with the tube, the circuit,
etc.
 
You might want to look at pc scopes. Or ebay. If all you are doing is
audio and possibly lower rf frequencies there are lots of decent used scopes
on ebay.

"EADGBE" <hwbosshoss@comcast.net> wrote in message
news:e79927cb-9552-41f4-81e9-0c380ce099b0@f36g2000hsa.googlegroups.com...
I have revised the schematic further by adding the voltages at the
base of Q205 and collector of Q204....

http://i240.photobucket.com/albums/ff58/eadgbe123/amplifier-2.jpg

I guess I don't have enough equipment to fix this problem. I can't
afford a 'scope right now. This will have to go on a shelf until I
can deal with it.
 

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