84 Magnavox console TV

[liammc00]

I will go check the DC voltages on the IC but first i did what the Sam"s said to do and that is scope PIN 13 of the IC. i got a new oscilloscope but i never took it out of the box as was going to be moving soon but i finally broke down and took it out of the box and tried it out. The results are in the video link and i have never used an oscilloscope before so the results may not be usable.
The video is not of the best quality but its best me and my grandma could do and my phone camera is not very good. https://youtu.be/2Jepwuym8AQ

here is the datasheet for the NTE1416 https://www.nteinc.com/specs/1400to1499/pdf/nte1416.pdf was not able to find the one for the original NEC 303-1

[liammc00]

DC measurements on IC NTE1416 or NEC 303-1.

PINS 1-28 IN DC VOLTS
PIN 1 VCC 12V
PIN 2 Clamp Filter 8V
PIN 3 Brightness Control 8.7V
PIN 4 Resolution Control 6V
PIN 5 Luminance Input 2.5V
PIN 6 Peaking Filter 2V
PIN 7 Tint Control 6V
PIN 8 Auto Set Voltage 3V
PIN 9 Color Control 6V
PIN 10 Contrast Output 8V
PIN 11 Chroma Output 8.5V
PIN 12 Bypass 2V
PIN 13 Chroma Input 1.2V
PIN 14 GND
PIN 15 APC Filter 9V
PIN 16 APC Filter 9V
PIN 17 APC Filter 8.5V
PIN 18 Killer Filter 8V
PIN 19 APC/ACC Input 4V
PIN 20 Gate Pulse Input 300mv
PIN 21 OSC 8V
PIN 22 OSC 3.2V
PIN 23 OSC 3.2V
PIN 24 Blanking Input 1V
PIN 25 Demod Input 3V
PIN 26 R Output 2V
PIN 27 G Output 2V
PIN 28 B Output 2V
All voltages match the Sam's

[liammc00]

Update March 29. I did mark the AFT adjustment located on the main board and tryed to adjust it made no difference to the color but did improve the picture quality by a hair. Next I checked to make sure the color and tint control had a good connection between the main board and the user control board. Had no problems there. Next i checked the components on the input of pin 13 on the chroma luma processor chip could not find anything wrong with any of components. Not sure we're to go next but if someone would be willing tell me what troubleshooting they do for a tv that has color not working or can point me to were I can obtain the information. I have done a lot with this TV and I don't want to give up on it as feel it has some many good years left but I have worked on it for 8 months so I'm getting tried of working on it and I am kinda in rush to get fixed as I'm moving on May 9. If the TV is not fixed by then it will be a long while before I can get back to it.

[Alex KL-1]

Certainly is a hope... is alreaby woking before
The color vanished only after changing flyback, or when you changed components or resolder?
If only was after flyback change, maybe the pulses derived from flyback have different amplitude, upsetting circuits depentent form it, if flyback is a equivalent?
And, a very small invisible solder splotch/blob can maybe ocurred at some position (washing the PCB with isopropyl alcohol using a hard brush may solve it).

[liammc00]

Did some DC mesmurmnts on the video IF IC and I got some concerning results

Here they are
PIN 14 should be between 7.6-11.5 volts I'm reading 6.7volts IF AGC . PIN 14 splits between a 6.8kohm resistor and a .0027 cap which then goes to ground. After the 6.8kohm resistor it goes to a .047 cap and then to ground.
PIN 12 should be 5 volts I'm getting 3.7 with a full image on screen and 3.3 with no image this pin goes out and spilt between the sound IF and then goes to video buffer transistor Q153 on the collector is 6.6v, the base is 3.3v, and the collector is 2.6volts. the voltages should read base 4.8v and emitter 4.3v. after this transistor it goes to a .001 cap then to 1k ohm resistor then to splits between C175 which is a 39pf cap and L154 to ground. After C175 it spitls again between C176 82pf and L177 to ground. Finally it enters pin 13 chroma input of the chroma and luma processer IC. I don't know if this would case a B/W picture but I thought I would check.

[liammc00]

Originally Posted by Alex KL-1

Certainly is a hope... is alreaby woking before
The color vanished only after changing flyback, or when you changed components or resolder?
If only was after flyback change, maybe the pulses derived from flyback have different amplitude, upsetting circuits depentent form it, if flyback is a equivalent?
And, a very small invisible solder splotch/blob can maybe ocurred at some position (washing the PCB with isopropyl alcohol using a hard brush may solve it).

The new flyback is an HR diamond so it's not an original. On terms of the color loss it's not a solder bridge as I changed all the caps and resolder the entire board that was done a while ago and it didn't have any trouble until now. When I still thought it was the PSU I took a couple of transistors out test and put them back. I did breck one transotor it was Q457 cupler driver which as porbly guess to horizontal optic cupler IC 469 (PS2021). I did use the NTE replacement for that transistor.

[JohnCT]

Originally Posted by liammc00

The new flyback is an HR diamond so it's not an original. On terms of the color loss it's not a solder bridge as I changed all the caps and resolder the entire board that was done a while ago and it didn't have any trouble until now. When I still thought it was the PSU I took a couple of transistors out test and put them back. I did breck one transotor it was Q457 cupler driver which as porbly guess to horizontal optic cupler IC 469 (PS2021). I did use the NTE replacement for that transistor.

For what it's worth, the only aftermarket replacement flys that were any good IMO were the H.R. Diemens. They cost as much or more than OEM but I'd buy them when the OEMs stopped supplying flybacks and HV Splitters (RPTV). I never had an issue with any, and never had one fail.

Others (like Asti Magnetics) were hit and miss. Some worked fine, but others required modifying the circuit (Zenith) to get them to play nicely with the sweep and shutdown circuits.


John

[liammc00]

Originally Posted by JohnCT

For what it's worth, the only aftermarket replacement flys that were any good IMO were the H.R. Diemens. They cost as much or more than OEM but I'd buy them when the OEMs stopped supplying flybacks and HV Splitters (RPTV). I never had an issue with any, and never had one fail.

Others (like Asti Magnetics) were hit and miss. Some worked fine, but others required modifying the circuit (Zenith) to get them to play nicely with the sweep and shutdown circuits.


John

Well that's nice to know that HR diemens made good quality stuff as not all aftermarket parts are junk but unfortunately a lot are. Now if I can find the part that is giving me trouble.

[Alex KL-1]

Originally Posted by liammc00

Did some DC mesmurmnts on the video IF IC and I got some concerning results

Here they are
PIN 14 should be between 7.6-11.5 volts I'm reading 6.7volts IF AGC . PIN 14 splits between a 6.8kohm resistor and a .0027 cap which then goes to ground. After the 6.8kohm resistor it goes to a .047 cap and then to ground.
PIN 12 should be 5 volts I'm getting 3.7 with a full image on screen and 3.3 with no image this pin goes out and spilt between the sound IF and then goes to video buffer transistor Q153 on the collector is 6.6v, the base is 3.3v, and the collector is 2.6volts. the voltages should read base 4.8v and emitter 4.3v. after this transistor it goes to a .001 cap then to 1k ohm resistor then to splits between C175 which is a 39pf cap and L154 to ground. After C175 it spitls again between C176 82pf and L177 to ground. Finally it enters pin 13 chroma input of the chroma and luma processer IC. I don't know if this would case a B/W picture but I thought I would check.

Is not very common, but I see one time or another semiconductors damaged by the flyback sparks (especially IC), even at some distance (due to EMP). Last time it occured to me was with a Toshiba TV that made a lot of sparks due to bad HV connector plus a lot of dirt. A IF IC died.