[TechAssist] Re: [TechAssist]FIXED Re: RCA PTK195B, mostly dead.
- From: "Jerome Silverman" <greentron@xxxxxxx>
- To: <techassist@xxxxxxxxxxxxx>
- Date: Sat, 31 Jul 2004 13:53:47 -0400
Ethylene glycol does not evaporate and is in itself not conductive. The
coolant is usually a mixture of ethylene glycol, glycerine, water, and
proprietary secret ingredients, probably to suppress organic growths. Stuff
dissolves in the water. That and the secret ingredients are probably what
makes the coolant conductive when it gets on a circuit board. The reason the
coolant is a mixture is to adjust the index of refraction to maximize the
light transfer from crt to lense, as well as to provide adequate heat
transfer.
Jerry Silverman
Greentron Inc
4 Newland Ave Greenville SC 29609
Fax/Phone 864 232 3889
greentron@xxxxxxx
----- Original Message -----
From: "Kevin" <kevintv@xxxxxxx>
To: <techassist@xxxxxxxxxxxxx>
Sent: Saturday, July 31, 2004 1:46 AM
Subject: [TechAssist] Re: [TechAssist]FIXED Re: RCA PTK195B, mostly dead.
> I used 63/37 solder with flux in the core. So why this flux was
> conductive, I don't know. Maybe there was some of the glycol on the
> solder side that I didn't clean off. Would the combination of glycol
> and flux be conductive? I'm guessing that the glycol would just
> evaporate, but I don't know.
>
> Kevin Wilks
> Kevin's TV & Video Repair
> Penticton BC Canada
> kevintv@xxxxxxx
>
>
> -----Original Message-----
> From: techassist-bounce@xxxxxxxxxxxxx
> [mailto:techassist-bounce@xxxxxxxxxxxxx] On Behalf Of Jerome Silverman
> Sent: Friday, July 30, 2004 8:08 PM
> To: techassist@xxxxxxxxxxxxx
> Subject: [TechAssist] Re: [TechAssist]FIXED Re: RCA PTK195B, mostly
> dead.
>
> Pure rosin flux becomes an active acid when it is hot. The acid reduces
> oxides back to metal which is the condition that solder needs to wet the
> metal and alloy with it. When the rosin cools, it becomes inert again.
> The
> cleaning action of hot rosin flux is not enough if the surfaces were not
> pretty clean to start with, so usually the flux used in electronics work
> is
> an ACTIVATED rosin. The activator is a chemical that decomposes when hot
> to
> release lots of hydrochloric acid. That acid is a powerful reducing
> agent
> and usually does a good job of getting rid of the oxides. If the flux
> gets
> hot enough, all of the activator decomposes and the acid goes off in the
> vapors that rise from the soldering. The remaining residue is inert and
> does
> not have to be removed. If the flux is in the form of a core in the
> solder,
> the heat required to melt the solder also decomposes all of the flux
> activator. If the flux is applied seperately, some activator, partially
> decomposed activator, and some trapped acid may remain, so the residue
> can
> be corrosive and conductive. When liquid flux is used, it is
> conventional to
> clean the residues off. There are solvent soluble components and water
> soluble components to the residue, so the cleaning process must remove
> both
> components.
> Jerry Silverman
> Greentron Inc
> 4 Newland Ave Greenville SC 29609
> Fax/Phone 864 232 3889
> greentron@xxxxxxx
>
> ----- Original Message -----
> From: "Kevin" <kevintv@xxxxxxx>
> To: <techassist@xxxxxxxxxxxxx>
> Sent: Friday, July 30, 2004 5:03 PM
> Subject: [TechAssist] Re: [TechAssist]FIXED Re: RCA PTK195B, mostly
> dead.
>
>
> > I went back to the eeprom with the missing 5 volts on pin 6, and found
> > that it measured 860 ohms to ground. I had removed the eeprom 4
> months
> > ago to clean the coolant off the board and had soldered the eeprom
> back
> > in without cleaning the flux between each connection. I usually clean
> > them off, but for some reason, I didn't do it this one time.
> >
> > After cleaning the flux between pin 6 (clock) and pin 7 (ground), pin
> 6
> > now reads 15k ohms to ground. Of course the set is working fine now.
> > How could flux cause this bad connection to ground? What the flux? I
> > always thought that flux was nonconductive.
> >
> > Kevin Wilks
> > Kevin's TV & Video Repair
> > Penticton BC Canada
> > kevintv@xxxxxxx
> >
> >
> > -----Original Message-----
> > From: techassist-bounce@xxxxxxxxxxxxx
> > [mailto:techassist-bounce@xxxxxxxxxxxxx] On Behalf Of Kevin
> > Sent: Friday, July 30, 2004 1:30 PM
> > To: techassist@xxxxxxxxxxxxx
> > Subject: [TechAssist] Re: RCA PTK195B, mostly dead.
> >
> > I did have coolant leakage several months ago, but after cleaning the
> > board and changing R14110, the set worked fine for 4 months. There is
> > no coolant on the board now. Thanks.
> >
> > I just plugged the set in, the P/S tweaked like it was ready to come
> on
> > and found 5 volts on pin 19 of the micro, and 5 volts on pins 5, 6,
> and
> > 8 of the eeprom. Then of course as I as measuring these pins the
> > voltages disappeared and the set was dead again.
> >
> > Kevin Wilks
> > Kevin's TV & Video Repair
> > Penticton BC Canada
> > kevintv@xxxxxxx
> >
> >
> > -----Original Message-----
> > From: techassist-bounce@xxxxxxxxxxxxx
> > [mailto:techassist-bounce@xxxxxxxxxxxxx] On Behalf Of Ohio Consumer
> > Electronics
> > Sent: Friday, July 30, 2004 1:05 PM
> > To: techassist@xxxxxxxxxxxxx
> > Subject: [TechAssist] Re: RCA PTK195B, mostly dead.
> >
> > Look real close for coolant around the micro-eeprom area. Hard to see
> > but
> > only takes a couple drops to mess it up. I had one of these 195's
> that
> > was
> > intermittent and that fixed it. I had to remove the micro, eeprom and
> > the
> > keyboard and chipper-check sockets to clean under these components.
> > Then
> > the set came on and stayed on but it didn't have any menus because the
> > eeprom was corrupted. I replaced the eeprom and got the menu back but
> > had
> > to buy a chipper-checker to do the tuner alignment - what a nightmare
> > that
> > set was...
> > Joel Jacobs
> > Ohio Consumer Electronics
> > Pickerington Ohi'o
> >
> > ----- Original Message -----
> > From: "Kevin" <kevintv@xxxxxxx>
> > To: <techassist@xxxxxxxxxxxxx>
> > Sent: Friday, July 30, 2004 3:09 PM
> > Subject: [TechAssist] Re: RCA PTK195B, mostly dead.
> >
> >
> > > I already unplugged the keyboard and it is still dead most of the
> > time.
> > > I did some more testing this morning and found that the eeprom
> > (U13102)
> > > has only 3 volts on pins 8 (Vcc) and 5 (clock). Pin 6 (data) has 0
> > > volts on it, instead of the normal 5 volts. That certainly is not
> > > normal.
> > >
> > > Kevin Wilks
> > > Kevin's TV & Video Repair
> > > Penticton BC Canada
> > > kevintv@xxxxxxx
> > >
> > >
> > > -----Original Message-----
> > > From: techassist-bounce@xxxxxxxxxxxxx
> > > [mailto:techassist-bounce@xxxxxxxxxxxxx] On Behalf Of tvservice
> > > Sent: Friday, July 30, 2004 6:34 AM
> > > To: techassist@xxxxxxxxxxxxx
> > > Subject: [Tec'hAssist] Re: RCA PTK195B, mostly dead.
> > >
> > > Unplug the front panel keyboard see if operates OK with remote.
> > > lift the 1K ohm resistor off micro to U14701 then plug in AC power
> you
> > > should now always have +5 and +12 out of U14701
> > > Set will not be on until press power,
> > > I have seen this IC intermittent
> > > also remove bottom tuner cover and carefully resolder every ground
> > point
> > > and
> > > sm cap at ground points
> > > Remove glue from micro crystal and resolder
> > > If this set has dual tuners unplug cables to second tuner I have
> seen
> > > problems on the second tuner assembly cause intermittent dead set.
> > > hth
> > > Robert
> > > tvservice@xxxxxxxxxxxxx
> > > H & H Electronics Inc
> > >
> > > ----- Original Message -----
> > > From: "Kevin" <kevintv@xxxxxxx>
> > > To: "TECH-ASSIST" <techassist@xxxxxxxxxxxxx>
> > > Sent: Friday, July 30, 2004 4:08 AM
> > > Subject: [TechAssist] RCA PTK195B, mostly dead.
> > >
> > >
> > > > This set works sometimes, but most times not. When the set does
> > work,
> > > > it will wo'rk for a minute and then just shuts off by itself and
> > will
> > > not
> > > > come on. I have the SM on CD rom and I am following the trouble
> > > > shooting procedure. I found that when I monitor pin 19 of U13101
> > > > (microprocessor) and press the power button, pin 19 does not go
> high
> > > as
> > > > it is supposed to. The micro has 5 volts going to pins 16, 29, 32
> > and
> > > > 51. Pins 3 and 20 of U16201 are missing the required 7.5 volts.
> > > After
> > > > that the troubleshooting flowchart tells me to repair the
> defective
> > > P/S
> > > > source. So I traced the missing voltage back to U14701, a dual
> > > voltage
> > > > regulator. Pin 6 is missing 12 volts and pin 7 is missing 5
> volts.
> > > Pin
> > > > 1 and 2 both have 18-20 volts which is good. Pins 3 and 5 are
> > > supposed
> > > > to have the 5 volts from pin 19 of the micro when the set is on.
> > But
> > > of
> > > > course there is no 5 volts coming from the micro. The set must be
> > > going
> > > > into shutdown. What can I check next? Thanks.
> > > >
> > > > Kevin Wilks
> > > > Kevin's TV & Video Repair
> > > > Penticton BC Canada
> > > > kevintv@xxxxxxx
> > > >
> > > >
> > > >
> > > >
> > > >
> > >
> >
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