Toshiba TV29C90 problem; Image fades to black...

James Sweet wrote:
Meaning they need to warm up before the problem went away? I can't
remember when I've seen a weak cap work better when it was warm (not
saying it doesn't happen). Lots of times I've lucked out with some freeze
spray reviving caps. Guess the OP could wait until the set warmed up and
the pic was ok then use a little freeze rather than removing dozens of
caps and esr'n all of them.


That's how it always is with electrolytics, the ESR drops as the
temperature rises. You can try it with any marginal 'lytic and an ESR
meter, shoot the cap with freeze spray and the impedance will skyrocket.
Heat it with a hair dryer and it will drop.

Rule of thumb is that if something works better as it heats up, look at
the caps. If it works better cold, look at the semiconductors. If it's
erratic, look at solder joints.
Click to expand...
If the set will work ok when warmed up with the back off, I would let
it warm up, run ok for a few minutes, and then apply cooling to all the
caps to see if one or more respond with a bad picture. If not, then go
after cooling the other components. Alternatively, you could apply
heat to components when the set is first turned on and see if you can
speed up the process toward getting a good picture. Method 1 is
preferable.

H. R. (Bob) Hofmannn
 
Meat Plow wrote:
On Sat, 06 Jan 2007 11:11:15 -0800, macy Has Frothed:

Need a schematic for a Daytek 1731-D

Where to get one?

Old unit, manufacutred in 1987

- Robert -

http://www.eserviceinfo.com/download.php?fileid=3482
--
Pierre Salinger Memorial Hook, Line & Sinker, June 2004

COOSN-266-06-25794
Click to expand...
THANK YOU!

-Robert -
 
This 17" Dell monitor, model number CN-0M1609-4633-3AG-2DTL, will
power on when AC is first applied.
In the middle of the screen appears, "Dell Genesis
Display Perfection." Then it disappears after a second. When you
press the power button with no input signal, the Dell self test
feature check illuminates in the bottom left corner of the display.
You can see the red, green, blue, and white bars within the self test
box. Then, it starts to scroll diagonally up to the right for about a
second and then the display turns off. The power light remains on. If
you hook it up to a PC, you do
not
get any display.
Click to expand...

Judging from the described defects in operation there seems to be a problem
in the electronic circuitry. I advise a basic troubleshooting routine be
performed on this device to localize the defective circuitry.

----== Posted via Newsfeeds.Com - Unlimited-Unrestricted-Secure Usenet News==----
http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups
----= East and West-Coast Server Farms - Total Privacy via Encryption =----
 
I think there are some counterfeit versions on the market so beware,

mc.preist@gmail.com wrote:

It hisses with interruptions, like a beep.. and when I press against
the cable with my finger the hissing increases rate and then becomes
constant (no interruptions). The cable gets really hot, but there's no
smell or anything. The led does not come on anymore also. Can it be a
surge protection system?

On Jan 4, 11:57 pm, "b" <reverend_rog...@yahoo.com> wrote:


this fault sounds like bad electrolytic caps, especially if there is
hissing and heat. this may have been brought on by a short in the
cable. either way, given that you may well break the thing by getting
it open I'd start looking for another.
-B.
Click to expand...
--
Joe Leikhim K4SAT
"The RFI-EMI-GUY"Š

"Treason doth never prosper: what's the reason?
For if it prosper, none dare call it treason."

"Follow The Money" ;-P
 
Tim wrote:

Hi all,

I am hoping someone here may be able to help me with solving an intermittent
fault with our family TV
It is a Phillips 21PT2012 / 79R and has what I think is the serial number
of BZ000231 723707 on the back cover.
The fault manifests itself as sudden loss of all picture, and light from the
screen and loss of sound at the same time, anywhere from 5 seconds to a few
minutes from switch on.
This started a week or so ago, and a turn off seemed to fix it, and now it
will not run longer than a minute or so without dying. It seems like the HT
supply drops out suddenly,
but as I understand it the power supply rails for all the circuitry on this
type of appliance may very well all come from one switching supply, and a
fault there could wipe out everything?
I have a reasonable understanding of electronics, and a good Fluke
multimeter, but no cct. diagram, and no experience with TVs. Any
suggestions? I think that the set is about 4 years old, and I guess it must
be some component that is built to a commercial standard starting to break
down, but I was hoping that there may be hope rather than junking it?
Thanks for any assistance.
Click to expand...
Cross-posted to a more suitable group

Graham
 
grames Wrote:
The said charger has a couple of components that have failed to the
point of not being identifiable. A circuit diagram would be great.
Model: DE9107-XE
220/240v (Australia)
7.2 / 14.4v

Thanks, Grames
Click to expand...
Hi Grames,

Can you tell me what type of transistor is used which is attached to
the cooling fin?

Thanks in advance,

Jan Hamer
janfreak@xs4all.nl




--
janfreak
 
Found it. Measured the length and came up with 9.5mm.

Thanks to all.

Zack


"Zachary Burns" <zacharyburns@shotmail.com> wrote in message
news:45a289d6$0$509$815e3792@news.qwest.net...
How would I know if I need a 1/4 or 1/2 watt, etc. Just by looking at the
resistor?

Zack


"Meat Plow" <meat@meatplow.local> wrote in message
news:pan.2007.01.08.16.54.06.178000@nntp.sun-meatplow.local...
On Mon, 08 Jan 2007 11:31:21 -0500, Zachary Burns Has Frothed:

Ok. So I think I get the following:

3900000 * silver tollerance band = 39,000

39,000 Ohms (includes 10% tollerance) and 5% failure rate per 1,000
hours.

Am I correct?

Anybody know of a good supplier to get this resistor?

Zack

3 million 900 thousand ohms. 10% tolerance.
3-9-00000

Or 3.9 megohms

Find them most any place that sells resistors, caps, semiconducters.
Click to expand...
 
Hi David

I bought aDell E172fp off Ebay recently which was sold as faulty, the Power
Light would flash on/off with no display.

Basically, what i have found is that the output transistors go s/c, these
are the small 2sc5707 transistors that sit near the 4 yellow transformers. i
had 2 go s/c in one of the channels, the other channel was ok. I replaced
these and now the green light stays on , the display comes on for about 3
seconds like you's does and then goes off.

I put a scope on the o/p of the transformers and can see them switching ok
for 3 secs then the o/p goes off. What is happening is that the Pulse Width
Modulator chip that drives the lamps is shutting down after 3 seconds, this
is the 16 pin chip marked TL1451A. I have the datasheet on this chip and i
am currently trying to work out why it shuts down. I have found that whe
you first switch on the monitor, the supply to this chip is 18vdc, when the
display comes on for 3 seconds this drops to 14 volts (because this supply
is unregulated) and then goes back to 18vdc.

I would be interested to know if you can confirm the dc voltage you are
seeing on pin 9 the 16 pin TL1451A chip during this startup period and
see if it compares to my results.

Theres a common problem here with these monitors, it may be overcurrent due
to s/c transformers or another transistor s/c somewhere, i am sure we will
track it down shortly.

Graham



"David Farber" <farberbear.unspam@aol.com> wrote in message
news:enmdu4$e8m$1@aioe.org...
This 17" Dell monitor, model number CN-0M1609-4633-3AG-2DTL, will power
on
when AC is first applied. In the middle of the screen appears, "Dell
Genesis
Display Perfection." Then it disappears after a second. When you press the
power button with no input signal, the Dell self test feature check
illuminates in the bottom left corner of the display. You can see the red,
green, blue, and white bars within the self test box. Then, it starts to
scroll diagonally up to the right for about a second and then the display
turns off. The power light remains on. If you hook it up to a PC, you do
not
get any display. The boards are in good condition and I reflowed the
solder
over many of the components with no improvement. Any ideas what might be
going on here?

Thanks for your reply.
--
David Farber
David Farber's Service Center
L.A., CA
Click to expand...
 
Arfa Daily <arfa.daily@ntlworld.com> wrote in message
news:Uhwoh.47370$Qa6.7736@newsfe6-gui.ntli.net...
"N Cook" <diverse8@gazeta.pl> wrote in message
news:ento64$1p6$1@inews.gazeta.pl...
Ten years ago I would have considered it impractical or even immoral.
But having to replace yet another effectively all plastic 12 mm pot
because
the wiper is almost invisible in thickness, perhaps time for a rethink.
This type of pot has a metal covering but its only function is as a
shroud
for fixing to the board, not even earthed, it does not strengthen the
pot
body to restrain abuse at the other, user end. No longer are such pots
fixed
to the front pannel.
I'm thinking that with the next one to replace it will be with a
standard
small 12 mm or so enclosed preset that takes a standard plastic shaft in
the
adjustment slot, fudging the other end of the shaft to take the knob and
through pannel bearer. The internal mechanism is just a pro-rata scaled
down
conventional paxolin backed track with double wiper nibs.
If this replacement physically breaks in use then that seems more
justifiable than the modern flimsy wipers losing spring action or just
aging
of the lubricant inside to wedge under the wiper and loose contact or
whatever their problem is, the tracks are always perfect (so little
wiper
pressure presumably).
Are the resistive tracks of presets more frail/easier scoored than pot
tracks, so for that reason cannot be used say for volume control ?
Anyone any opinions?

--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/


I would have said that the description " preset " tells you all that you
need to know on that score. These components are designed to be set and
left, pretty much for the lifetime of the equipment, so I can't see them
standing up to the rigours of regular use for long. Add to this that as
they
are not designed to be rotated repeatedly as a user control, the wiper /
track interface has not been designed to be specifically quiet. I also
think
that the control will feel bad to a user, as it will not have that "
stirring treacle " feel that a proper user control has, courtesy of the
drag
grease that the manufacturers put in the spindle bush. Why not replace
controls with manufacturer's originals ? Most group amp builders supply
spare parts. Failing that, there are plenty of reasonable quality pots
available - even the range that Maplin keep are pretty fair quality - and
if
you really want to fit top quality pots, these are also available from
audiophile outlets.

Arfa
Click to expand...
I had not considered the feel, which agreed is very 'scratchy'.
Squirting silicone oil in one and turning back and forth a hundred times is
very much improved, and resistive track still ok.
What is the point of the feather-light touch of the flimsy pots if the
downside is they just don't last.
I don't see the point of replacing with an exact match when the original is
say one of 8 and has only lasted for use once a week for 2 years before
internally failing , ie not abuse. In fact they seem to be the pots that are
not used much if at all, that's why I suspect clumping or something in the
lubricant.
I'll try a 1000 times and re-measure to see if the track fails.

--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/
 
"David Farber" <farberbear.unspam@aol.com> wrote in message
news:enmdu4$e8m$1@aioe.org...
This 17" Dell monitor, model number CN-0M1609-4633-3AG-2DTL, will power
on
when AC is first applied. In the middle of the screen appears, "Dell
Genesis
Display Perfection." Then it disappears after a second. When you press
the
power button with no input signal, the Dell self test feature check
illuminates in the bottom left corner of the display. You can see the
red,
green, blue, and white bars within the self test box. Then, it starts to
scroll diagonally up to the right for about a second and then the
display
turns off. The power light remains on. If you hook it up to a PC, you do
not
get any display. The boards are in good condition and I reflowed the
solder
over many of the components with no improvement. Any ideas what might be
going on here?

Thanks for your reply.
--
David Farber
David Farber's Service Center
L.A., CA
Click to expand...
<grobinso@lycos.co.uk> wrote in message
news:I0xoh.22673$RL5.14448@newsfe2-gui.ntli.net...
Hi David

I bought aDell E172fp off Ebay recently which was sold as faulty, the
Power
Light would flash on/off with no display.

Basically, what i have found is that the output transistors go s/c, these
are the small 2sc5707 transistors that sit near the 4 yellow transformers.
i
had 2 go s/c in one of the channels, the other channel was ok. I replaced
these and now the green light stays on , the display comes on for about 3
seconds like you's does and then goes off.

I put a scope on the o/p of the transformers and can see them switching ok
for 3 secs then the o/p goes off. What is happening is that the Pulse
Width
Modulator chip that drives the lamps is shutting down after 3 seconds,
this
is the 16 pin chip marked TL1451A. I have the datasheet on this chip and i
am currently trying to work out why it shuts down. I have found that whe
you first switch on the monitor, the supply to this chip is 18vdc, when
the
display comes on for 3 seconds this drops to 14 volts (because this supply
is unregulated) and then goes back to 18vdc.

I would be interested to know if you can confirm the dc voltage you are
seeing on pin 9 the 16 pin TL1451A chip during this startup period and
see if it compares to my results.

Theres a common problem here with these monitors, it may be overcurrent
due
to s/c transformers or another transistor s/c somewhere, i am sure we will
track it down shortly.

Graham
Click to expand...
Hi Graham,

I checked those 2SC5707 transistors again. This time I found two of them,
Q759 and Q760, were shorted b-e. I'll order those parts, replace them, and
let you know what happens.

Thanks for your reply.

--
David Farber
David Farber's Service Center
L.A., CA
 
David, ok, i havent been able to get any of them over here but i have used
BD911 as test devices.

If you get a minute would be interested to know what voltage you have on
pin9 of the PWM chip as i mentioned in my last post.

Graham


"David Farber" <farberbear.unspam@aol.com> wrote in message
news:enua68$n9b$1@aioe.org...
"David Farber" <farberbear.unspam@aol.com> wrote in message
news:enmdu4$e8m$1@aioe.org...
This 17" Dell monitor, model number CN-0M1609-4633-3AG-2DTL, will
power
on
when AC is first applied. In the middle of the screen appears, "Dell
Genesis
Display Perfection." Then it disappears after a second. When you press
the
power button with no input signal, the Dell self test feature check
illuminates in the bottom left corner of the display. You can see the
red,
green, blue, and white bars within the self test box. Then, it starts
to
scroll diagonally up to the right for about a second and then the
display
turns off. The power light remains on. If you hook it up to a PC, you
do
not
get any display. The boards are in good condition and I reflowed the
solder
over many of the components with no improvement. Any ideas what might
be
going on here?

Thanks for your reply.
--
David Farber
David Farber's Service Center
L.A., CA




grobinso@lycos.co.uk> wrote in message
news:I0xoh.22673$RL5.14448@newsfe2-gui.ntli.net...

Hi David

I bought aDell E172fp off Ebay recently which was sold as faulty, the
Power
Light would flash on/off with no display.

Basically, what i have found is that the output transistors go s/c, these
are the small 2sc5707 transistors that sit near the 4 yellow
transformers.
i
had 2 go s/c in one of the channels, the other channel was ok. I replaced
these and now the green light stays on , the display comes on for about 3
seconds like you's does and then goes off.

I put a scope on the o/p of the transformers and can see them switching
ok
for 3 secs then the o/p goes off. What is happening is that the Pulse
Width
Modulator chip that drives the lamps is shutting down after 3 seconds,
this
is the 16 pin chip marked TL1451A. I have the datasheet on this chip and
i
am currently trying to work out why it shuts down. I have found that whe
you first switch on the monitor, the supply to this chip is 18vdc, when
the
display comes on for 3 seconds this drops to 14 volts (because this
supply
is unregulated) and then goes back to 18vdc.

I would be interested to know if you can confirm the dc voltage you are
seeing on pin 9 the 16 pin TL1451A chip during this startup period and
see if it compares to my results.

Theres a common problem here with these monitors, it may be overcurrent
due
to s/c transformers or another transistor s/c somewhere, i am sure we
will
track it down shortly.

Graham


Hi Graham,

I checked those 2SC5707 transistors again. This time I found two of them,
Q759 and Q760, were shorted b-e. I'll order those parts, replace them, and
let you know what happens.

Thanks for your reply.

--
David Farber
David Farber's Service Center
L.A., CA
Click to expand...
 
But none of the 6 caps of this type seem to be grounded on either side.
I guess I'll try to find non-polar caps small enough to fit (3mm x
5mm), unless I get other suggestions.
Click to expand...
Should not matter. Measure each lead, using ground as a reference. The
more positive lead is the positive side. Or, the more negative lead is
negative side. If one is pos. and one neg., then pos. is pos.

Hope that helps.
 
Arfa Daily wrote:
"Mark D. Zacharias" <spammenot@nonsense.net> wrote in message
news:OrPih.2018$x67.528@newssvr17.news.prodigy.net...
JR wrote:
Mark D. Zacharias wrote:
jrgreene1968@suddenlink.net wrote:
Hello, i have a problem with a 3801 denon receiver, ..I bought this
receiver from a guy on the internet, said to be in exellent shape,
when it arrived, i plugged it in and it will not do anything, no
display, no standby light, no click when you hit power switch
nothing. I have checked all 7 fuses on the receiver with an ohm
meter, they are all ok. checked voltage where power cord plugs into
board, shows 120 volts, if you unplug receiver and checked switched
outlet on back of receiver, the outles show open with ohm meter,
unplug yellow and white wire on transformer to board and now
switched outlets are no longer reading open....does this sound like
a power transformer, any way to test?

OK, tried to send you the manual - it bounced because it was too
big. I'l split it and send it in 2 parts.

Mark Z.

man i really appreciate it...it looks like i have a bad relay, im
gonna get on the phone and see if i can find parts

Actually had to split it into about 6 parts. What a pain.These PDF split
programs could be better designed. One has to experiment with page ranges,
etc to get an acceptable size. Could be done better with a graphical
interface.

I really doubt you have a bad relay, more likely a circuit board crack.

Mark Z.

Agreed

Arfa
Click to expand...

well i finally give up, couldnt find the problem, so i sent it off to
an authorized denon repair center, they called me today, said the micro
processor is out, and probably alot more but they would ave to replace
processor before doing any more troubleshooting...i said..how much? he
replied, 170.00 to replace processor and as much as 760.00 for other
problems, i told them to forget it and send it back to me, so i guess
im back to the drawing board
 
Get a can of circut freeze spray and start cooling parts in the
horizontal to find it .
 
"N Cook" <diverse8@gazeta.pl> wrote in message
news:enu9fm$jhr$1@inews.gazeta.pl...
Arfa Daily <arfa.daily@ntlworld.com> wrote in message
news:Uhwoh.47370$Qa6.7736@newsfe6-gui.ntli.net...

"N Cook" <diverse8@gazeta.pl> wrote in message
news:ento64$1p6$1@inews.gazeta.pl...
Ten years ago I would have considered it impractical or even immoral.
But having to replace yet another effectively all plastic 12 mm pot
because
the wiper is almost invisible in thickness, perhaps time for a rethink.
This type of pot has a metal covering but its only function is as a
shroud
for fixing to the board, not even earthed, it does not strengthen the
pot
body to restrain abuse at the other, user end. No longer are such pots
fixed
to the front pannel.
I'm thinking that with the next one to replace it will be with a
standard
small 12 mm or so enclosed preset that takes a standard plastic shaft
in
the
adjustment slot, fudging the other end of the shaft to take the knob
and
through pannel bearer. The internal mechanism is just a pro-rata scaled
down
conventional paxolin backed track with double wiper nibs.
If this replacement physically breaks in use then that seems more
justifiable than the modern flimsy wipers losing spring action or just
aging
of the lubricant inside to wedge under the wiper and loose contact or
whatever their problem is, the tracks are always perfect (so little
wiper
pressure presumably).
Are the resistive tracks of presets more frail/easier scoored than pot
tracks, so for that reason cannot be used say for volume control ?
Anyone any opinions?

--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/


I would have said that the description " preset " tells you all that you
need to know on that score. These components are designed to be set and
left, pretty much for the lifetime of the equipment, so I can't see them
standing up to the rigours of regular use for long. Add to this that as
they
are not designed to be rotated repeatedly as a user control, the wiper /
track interface has not been designed to be specifically quiet. I also
think
that the control will feel bad to a user, as it will not have that "
stirring treacle " feel that a proper user control has, courtesy of the
drag
grease that the manufacturers put in the spindle bush. Why not replace
controls with manufacturer's originals ? Most group amp builders supply
spare parts. Failing that, there are plenty of reasonable quality pots
available - even the range that Maplin keep are pretty fair quality - and
if
you really want to fit top quality pots, these are also available from
audiophile outlets.

Arfa



I had not considered the feel, which agreed is very 'scratchy'.
Squirting silicone oil in one and turning back and forth a hundred times
is
very much improved, and resistive track still ok.
What is the point of the feather-light touch of the flimsy pots if the
downside is they just don't last.
I don't see the point of replacing with an exact match when the original
is
say one of 8 and has only lasted for use once a week for 2 years before
internally failing , ie not abuse. In fact they seem to be the pots that
are
not used much if at all, that's why I suspect clumping or something in the
lubricant.
I'll try a 1000 times and re-measure to see if the track fails.

--
Click to expand...
I'm actually really surprised that you seem to come across so many bad pots
in group amps. I have been repairing these for many many years, and do lots
of all makes and models, for a local shop, and I really don't have to
replace many pots that aren't physically broken through taking knocks. I
have found in general, that most manufacturers appreciate that this gear is
going to last its owners for a lot of years, and tailor their design
criteria, and component spec-ing to suit. I would agree that the pots fitted
these days tend to be Japanese ( probably Chinese actually ) small-bodied
types, which are not as good quality as say the large body Wellyns or the
typical RS components pots that you used to find in them a few years back,
but still, I don't seem to have that much trouble with them. If you really
think that the problem is insufficient spring tension on the wiper fingers,
just pile a bit more on. It's easily done with a pair of long-nosed pointy
surgical tweezers.

Arfa
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/
Click to expand...
 
Zachary Burns wrote:

How would I know if I need a 1/4 or 1/2 watt, etc. Just by looking at the
resistor?
Click to expand...
AaaarrggghhhHHH !

P = V^2/R maybe ?

Graham
 
Arfa Daily <arfa.daily@ntlworld.com> wrote in message
news:8YBoh.23419$RL5.14506@newsfe2-gui.ntli.net...
"N Cook" <diverse8@gazeta.pl> wrote in message
news:enu9fm$jhr$1@inews.gazeta.pl...
Arfa Daily <arfa.daily@ntlworld.com> wrote in message
news:Uhwoh.47370$Qa6.7736@newsfe6-gui.ntli.net...

"N Cook" <diverse8@gazeta.pl> wrote in message
news:ento64$1p6$1@inews.gazeta.pl...
Ten years ago I would have considered it impractical or even immoral.
But having to replace yet another effectively all plastic 12 mm pot
because
the wiper is almost invisible in thickness, perhaps time for a
rethink.
This type of pot has a metal covering but its only function is as a
shroud
for fixing to the board, not even earthed, it does not strengthen the
pot
body to restrain abuse at the other, user end. No longer are such
pots
fixed
to the front pannel.
I'm thinking that with the next one to replace it will be with a
standard
small 12 mm or so enclosed preset that takes a standard plastic shaft
in
the
adjustment slot, fudging the other end of the shaft to take the knob
and
through pannel bearer. The internal mechanism is just a pro-rata
scaled
down
conventional paxolin backed track with double wiper nibs.
If this replacement physically breaks in use then that seems more
justifiable than the modern flimsy wipers losing spring action or
just
aging
of the lubricant inside to wedge under the wiper and loose contact or
whatever their problem is, the tracks are always perfect (so little
wiper
pressure presumably).
Are the resistive tracks of presets more frail/easier scoored than
pot
tracks, so for that reason cannot be used say for volume control ?
Anyone any opinions?

--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/


I would have said that the description " preset " tells you all that
you
need to know on that score. These components are designed to be set and
left, pretty much for the lifetime of the equipment, so I can't see
them
standing up to the rigours of regular use for long. Add to this that as
they
are not designed to be rotated repeatedly as a user control, the wiper
/
track interface has not been designed to be specifically quiet. I also
think
that the control will feel bad to a user, as it will not have that "
stirring treacle " feel that a proper user control has, courtesy of the
drag
grease that the manufacturers put in the spindle bush. Why not replace
controls with manufacturer's originals ? Most group amp builders supply
spare parts. Failing that, there are plenty of reasonable quality pots
available - even the range that Maplin keep are pretty fair quality -
and
if
you really want to fit top quality pots, these are also available from
audiophile outlets.

Arfa



I had not considered the feel, which agreed is very 'scratchy'.
Squirting silicone oil in one and turning back and forth a hundred times
is
very much improved, and resistive track still ok.
What is the point of the feather-light touch of the flimsy pots if the
downside is they just don't last.
I don't see the point of replacing with an exact match when the original
is
say one of 8 and has only lasted for use once a week for 2 years before
internally failing , ie not abuse. In fact they seem to be the pots that
are
not used much if at all, that's why I suspect clumping or something in
the
lubricant.
I'll try a 1000 times and re-measure to see if the track fails.

--

I'm actually really surprised that you seem to come across so many bad
pots
in group amps. I have been repairing these for many many years, and do
lots
of all makes and models, for a local shop, and I really don't have to
replace many pots that aren't physically broken through taking knocks. I
have found in general, that most manufacturers appreciate that this gear
is
going to last its owners for a lot of years, and tailor their design
criteria, and component spec-ing to suit. I would agree that the pots
fitted
these days tend to be Japanese ( probably Chinese actually ) small-bodied
types, which are not as good quality as say the large body Wellyns or the
typical RS components pots that you used to find in them a few years back,
but still, I don't seem to have that much trouble with them. If you really
think that the problem is insufficient spring tension on the wiper
fingers,
just pile a bit more on. It's easily done with a pair of long-nosed pointy
surgical tweezers.

Arfa
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/
Click to expand...
The present problematic is a Carvin Pro Bass 100, PB100 which will come
bouncing back next weekend.
The new fault , could well be due to another pot failed, symptoms over the
phone so far, the previous one I replaced is fine.
I still have the previous original one lying around .
No makers name , a logo like cross-section of a flying saucer, a thin elipse
laid over a circle, just the outermost lineforms.
The wiper is only 0.15 mm thick , 0.6mm wide and using a force gauge, it
starts deflecting at only 12 grams pressure.

Followup on my endurance test on a preset, I survived 1000 turns back and
forth , whole track, as did the pot. No wavering on mid-track resistance
readings. The rough feel has returned but I doubt that is due to the wiper
action. Cracking it open, one obvious shiny, but not broken through to
paxolin, track from one nib and vague partial thin trace from the other nib.
I would estimate it could have done more than 10,000 rotations before both
tracks were worn through.

--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/
 
JR wrote:
Arfa Daily wrote:
"Mark D. Zacharias" <spammenot@nonsense.net> wrote in message
news:OrPih.2018$x67.528@newssvr17.news.prodigy.net...
JR wrote:
Mark D. Zacharias wrote:
jrgreene1968@suddenlink.net wrote:
Hello, i have a problem with a 3801 denon receiver, ..I bought
this receiver from a guy on the internet, said to be in exellent
shape, when it arrived, i plugged it in and it will not do
anything, no display, no standby light, no click when you hit
power switch nothing. I have checked all 7 fuses on the receiver
with an ohm meter, they are all ok. checked voltage where power
cord plugs into board, shows 120 volts, if you unplug receiver
and checked switched outlet on back of receiver, the outles show
open with ohm meter, unplug yellow and white wire on transformer
to board and now switched outlets are no longer reading
open....does this sound like a power transformer, any way to
test?

OK, tried to send you the manual - it bounced because it was too
big. I'l split it and send it in 2 parts.

Mark Z.

man i really appreciate it...it looks like i have a bad relay, im
gonna get on the phone and see if i can find parts

Actually had to split it into about 6 parts. What a pain.These PDF
split programs could be better designed. One has to experiment with
page ranges, etc to get an acceptable size. Could be done better
with a graphical interface.

I really doubt you have a bad relay, more likely a circuit board
crack.

Mark Z.

Agreed

Arfa


well i finally give up, couldnt find the problem, so i sent it off to
an authorized denon repair center, they called me today, said the
micro processor is out, and probably alot more but they would ave to
replace processor before doing any more troubleshooting...i said..how
much? he replied, 170.00 to replace processor and as much as 760.00
for other problems, i told them to forget it and send it back to me,
so i guess im back to the drawing board
Click to expand...
OK, read the other post which didn't really express the "two-tiered"
estimate. I can understand the possibility that the shop, after not finding
any obvious cracks, etc gave the estimate to replace the micro as an initial
step. Done this myself sometimes, usually after a lightning strike. I'll
tell the insurance company it's so much to replace the micro, win, lose or
draw - then we'll see what doesn't work after that.

Mark Z.
 
You were closer the first time.

If fourth band is silver or gold, you have two significant digits and
the third band is the exponent, fourth band is the tolerance , 5 or 10
percent. Special case if the first band is double-wide of the third
band is silver or gold.


If the third band is NOT silver or gold, then you have a three
significant digits and the fourth band is the exponent, fifth is the
tolerance. Not that since you have three digits, the exponents are
"one higher" than with the older format.

See any of the on-line resistor color code charts for the details.
 
On Tue, 09 Jan 2007 15:29:42 +0000, jtaylor Has Frothed:

Broke the one in a gadget; need a source for a repair part.
Click to expand...
http://www.horizontechnology.com/lcd_search.php


--
Pierre Salinger Memorial Hook, Line & Sinker, June 2004

COOSN-266-06-25794
 
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