Videokarma.org

Go Back   Videokarma.org TV - Video - Vintage Television & Radio Forums > Solid State CRT Televisions

We appreciate your help

in keeping this site going.
Reply
 
Thread Tools Display Modes
  #16  
Old 01-11-2017, 12:10 PM
mr_fixer's Avatar
mr_fixer mr_fixer is offline
VideoKarma Member
 
Join Date: Jul 2007
Location: Tennessee USA
Posts: 468
PM sent,
new transistor, no change in action. I have 30 volts on the hot which i think is the start up voltage, i have 320 in a different section, but don't know enough about this weird power supply.

Quote:
Originally Posted by Findm-Keepm View Post
I've got the service lit - most of it. I have the model specific data and the supplement with schematic, parts list, breakdown list and interchangeability data. I also have the Switchmode power Supply manual (theory, general operation, a must for the "bitch mode" supplies these have...) from NAP, all yours for postage. PM me your address, and I'll get it out to you.

In the meantime, do you have 130V across the diode (D404) on the yoke? Negative lead to the anode (hot ground...)That was always our starting point - D404 is a high-failure item in these chassis, and my earlier attachment provides a list of stuff to check as well - lots of bad solder jobs on the early runs of these chassis - the 25C55X series didn't seem to have the solder issues, just the earlier 25C53X and 25C54X stuff.

January 1986....when the Challenger tragedy struck.....
Reply With Quote
  #17  
Old 01-12-2017, 08:05 AM
Marco-nix's Avatar
Marco-nix Marco-nix is offline
VideoKarma Member
 
Join Date: Apr 2014
Location: somewhere on earth
Posts: 255
Quote:
Originally Posted by dieseljeep View Post
We had a considerable amount of snow, a lot of it melted in the unseasonable warm weather, but now we're paying for it. Zero or colder, with sub-zero wind chills. The snow is just an inconvienience, but that extreme cold.


Indeed! ... I would have let it take the temperature of the room at least 3 days before turning on the television. At least, I would have dried the circuits with a hair dryer for an hour or two by going gently so as not to soften some pieces.
Reply With Quote
  #18  
Old 01-12-2017, 08:06 AM
zeno zeno is offline
VideoKarma Member
 
Join Date: Mar 2013
Location: New Hampshire
Posts: 2,605
Watch for disc caps & box caps off the C of HOT. Common
for them to burn, melt or short. Also burned PCB that
may be hidden under frame plastic. Noise is probably from
SMPS running off freq to keep the overload from wrecking everything.
Assuming HOT is not shorted see if it gets hot in 30 sec.
If so probably bad FBT.

73 Zeno
LFOD !
Reply With Quote
  #19  
Old 01-12-2017, 08:52 AM
Electronic M's Avatar
Electronic M Electronic M is offline
M is for Memory+Moderator
 
Join Date: Jan 2011
Location: Pewaukee/Delafield Wi
Posts: 8,145
Quote:
Originally Posted by Marco-nix View Post
Indeed! ... I would have let it take the temperature of the room at least 3 days before turning on the television. At least, I would have dried the circuits with a hair dryer for an hour or two by going gently so as not to soften some pieces.
You sound like someone with a home humidification system! I wish I had one. Where I'm at this time of year there is just a small portable unit, and it can barely do anything...A cup of water with a napkin in it will dry in under a day.
__________________
Tom C.

What I want. --> http://www.videokarma.org/showpost.p...62&postcount=4

Reading between the scan lines since the mid 2000's.
Reply With Quote
  #20  
Old 01-12-2017, 09:27 AM
Marco-nix's Avatar
Marco-nix Marco-nix is offline
VideoKarma Member
 
Join Date: Apr 2014
Location: somewhere on earth
Posts: 255
Quote:
Originally Posted by Electronic M View Post
You sound like someone with a home humidification system! I wish I had one. Where I'm at this time of year there is just a small portable unit, and it can barely do anything...A cup of water with a napkin in it will dry in under a day.

Yes at home temperature and humidity are controlled. But what I wanted to say is that if I find a TV out in the winter I will never turn on the TV right away because of the difference in temperature (cold outside and the temperature inside my apartment) . Because the risk of components leaping, is high. That's why I said earlier that I would wait at least 2 to 3 days before turning on a TV found on the street in winter ..It's absolutely necessary to let the circuits dry completely. Even the CRT should not be wet. If not, .... BOUM! . It happened to me once because I was too eager to see if the TV was working. Now I'm careful.
Reply With Quote
Audiokarma
  #21  
Old 01-14-2017, 10:35 PM
mr_fixer's Avatar
mr_fixer mr_fixer is offline
VideoKarma Member
 
Join Date: Jul 2007
Location: Tennessee USA
Posts: 468
Hi all, I got the service manual from Findm keepm today and spent most of the day checking everything i can, to no avail. the 2 main symptoms are low voltage in the horizontal driver circuit, expected 33 volts got 6 and the 130 supply is around 21 volts. this is one of those switching power supplies that has 2 types of protection circuits over voltage shutdown and current limiting. I've taken a pic of the waveform on the switch mode regulator what i have vs what the book says it should look like, any hint on what i should try next?
Logan
Attached Images
File Type: jpg IMG_0317.jpg (99.4 KB, 25 views)
File Type: jpg IMG_0318.jpg (59.5 KB, 22 views)
Reply With Quote
  #22  
Old 01-15-2017, 11:18 AM
zeno zeno is offline
VideoKarma Member
 
Join Date: Mar 2013
Location: New Hampshire
Posts: 2,605
Unhook the C of the HOT & see if the voltage comes up. Also
do the heat test of the HOT.
Dont forget you are working with 3 grounds on this set.
Hot gnd for the primary of the PS
Cold ground the chassis ground / PS secondary.
I dont think this one does but some sets also had another ground for the
hoz osc/out.
CRT ground. Most NAPs do NOT ground the CRT dag as normal sets.
We used to just grab the CRT ground but that dont work on these.

73 Zeno
LFOD !
Reply With Quote
  #23  
Old 01-15-2017, 11:40 AM
zeno zeno is offline
VideoKarma Member
 
Join Date: Mar 2013
Location: New Hampshire
Posts: 2,605
OOPS !
Just pulled the training manual & the hoz output is
also on the hot ground side !
Reply With Quote
  #24  
Old 01-15-2017, 04:35 PM
mr_fixer's Avatar
mr_fixer mr_fixer is offline
VideoKarma Member
 
Join Date: Jul 2007
Location: Tennessee USA
Posts: 468
Ok, i disconnected the hot and flyback from the 130v supply, voltage went up to 138 v, I connected a small 40w lightbulb from 130v to ground for a load, volts dropped to 27v. Horizontal driver supply voltage is unchanged at 6-7 volts where 33 is expected.
hmmmm. resistors that drop the 33 supply from 312 volts are good and there is a diode that somehow is supposed to bridge the 2x20k resistors and 7 volts worth of zener diodes to ground. I'm not sure how a regular diode can act like a resistor, any thoughts?
Logan

Quote:
Originally Posted by zeno View Post
Unhook the C of the HOT & see if the voltage comes up. Also
do the heat test of the HOT.
Dont forget you are working with 3 grounds on this set.
Hot gnd for the primary of the PS
Cold ground the chassis ground / PS secondary.
I dont think this one does but some sets also had another ground for the
hoz osc/out.
CRT ground. Most NAPs do NOT ground the CRT dag as normal sets.
We used to just grab the CRT ground but that dont work on these.

73 Zeno
LFOD !
Attached Images
File Type: jpg IMG_0319.jpg (34.0 KB, 22 views)
Reply With Quote
  #25  
Old 01-16-2017, 06:53 AM
RCAZenith RCAZenith is offline
VideoKarma Member
 
Join Date: Apr 2016
Posts: 128
I-840 - Nashville is an interesting place to say the least. My father was in a country band in the late 90's about 2 steps from making it big and it didn't pan out for them. I was up there for training a couple of of years ago. I don't think I met anybody the whole time I was there that was local!

I've yet to see any tvs on I-285. I bet they would be smashed to bits long before any of us were to come along. That and I try and stay out of atlanta anyways...


Sent from my iPhone using Tapatalk
__________________
Game Room TV's:

1997 RCA Colortrak 27" Console
1987 Zenith 19" V3912W
Reply With Quote
Audiokarma
  #26  
Old 01-16-2017, 08:58 AM
zeno zeno is offline
VideoKarma Member
 
Join Date: Mar 2013
Location: New Hampshire
Posts: 2,605
What you need is horz drive from IC340 pin 11
That goes to the optic isolator IC469.
VCC for IC340 pin 10 comes from T453 / D461
Hoz drive is a must have to run the PS.

Since unloaded it seems to be doing what it should
I would suspect over voltage shutdown. Maybe test the small
transistors by lifting 2 leads for accuracy.
BTW one of our distributors made up kits for these to fix
them after lightning. Worked 100%. IIRC had an isolator,
4 small transistors & a diode.

The similar C3 chassis had a lot of bad FBT's Symptoms
were dead set, HOT gets too warm, R460/461 get warm.

73 Zeno
LFOD !
Reply With Quote
  #27  
Old 02-20-2017, 06:34 PM
davet753's Avatar
davet753 davet753 is offline
David Thomas
 
Join Date: Mar 2013
Location: Knoxville, TN
Posts: 304
Be sure to check for cracked solder joints on the horizontal driver transformer. C5 was about the time Philips started using the driver transformers that had a metal pin on each corner of the frame (the windings soldered onto the top of the pin and the bottom of the pin came through the board)....it's a good idea to re-solder all 8 points.

A bad connection on that transformer will most always zap the horiz. output or more.
Reply With Quote
Reply


Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT -5. The time now is 09:24 AM.



Powered by vBulletin® Version 3.8.4
Copyright ©2000 - 2017, Jelsoft Enterprises Ltd.
ęCopyright 2012 VideoKarma.org, All rights reserved.