Do I need to recap my intelvison 2 power supply?

[INTV123]

My intelvison 2 isn't outputting 12v when the rf modulator is connected. If I remove it the connection reads exactly 12v but as soon as its connected it drops to 11-6ish volts. Also was not getting any video from the rf out, and my composite mod is having problems keeping a stable signal. Wondering if the low voltage is the source of the problem. Also one of the ic's gets really hot and I'm not sure if that's related to the voltage or if that's normal. There is actually some yellowing inside the case in the area that its located.

[ChildOfCv]

The real cause of loss of voltage is that the power supply can't keep up with the demands of its load.  In a formerly working system, that typically means that something went wrong.  But the question is, is it due to something pulling too much power?  Or is the supply too weak?

 

Electrolytic capacitors can go bad and short out.  But typically when they do, it's because the electrolyte has leaked out.  When it does, it stains and corrodes the board.  So look closely at the board to see if solder joints or pins are corroded around it, or if there is an odd "spill" around any of them.  If so, remove the cap, clean off all of the electrolyte and corrosion, then add a new one.

 

But if a chip is getting hot, it likely pulling power and is the cause of the trouble.  Which one?

[INTV123]

2 hours ago, ChildOfCv said:

The real cause of loss of voltage is that the power supply can't keep up with the demands of its load.  In a formerly working system, that typically means that something went wrong.  But the question is, is it due to something pulling too much power?  Or is the supply too weak?

 

Electrolytic capacitors can go bad and short out.  But typically when they do, it's because the electrolyte has leaked out.  When it does, it stains and corrodes the board.  So look closely at the board to see if solder joints or pins are corroded around it, or if there is an odd "spill" around any of them.  If so, remove the cap, clean off all of the electrolyte and corrosion, then add a new one.

 

But if a chip is getting hot, it likely pulling power and is the cause of the trouble.  Which one?

Pretty sure its the video chip, but can't tell. It's labeled ay-3-8900-1s... i think. Its hard to read. 

[ChildOfCv]

Yeah that's the video chip.  It has some special power requirements, apparently.  Pin 40 should be -2.25V, pin 17 is ground, and pin 20 is 5.7V.  Neither of those should greatly affect the 12V power, but if it's pulling excessive power, it could be affecting all rails.

 

https://console5.com/techwiki/images/c/c3/Intellivision_II_Service_Manual%2C_Model_5872.pdf is the service manual.  The allowed voltage ranges on the power board for each output are:

 

TP1,TP2 - 16V-20V

TP3 - Ground

TP4 - -2.10V to -2.40V

TP5 - +5.45V to +5.95V

TP6 - +11.5V to +12.5V

TP7 - +4.86V to +5.15V

TP8 - +21V when off, +5V when on, and 0V while reset held

[INTV123]

5 hours ago, ChildOfCv said:

Yeah that's the video chip.  It has some special power requirements, apparently.  Pin 40 should be -2.25V, pin 17 is ground, and pin 20 is 5.7V.  Neither of those should greatly affect the 12V power, but if it's pulling excessive power, it could be affecting all rails.

 

https://console5.com/techwiki/images/c/c3/Intellivision_II_Service_Manual%2C_Model_5872.pdf is the service manual.  The allowed voltage ranges on the power board for each output are:

 

TP1,TP2 - 16V-20V

TP3 - Ground

TP4 - -2.10V to -2.40V

TP5 - +5.45V to +5.95V

TP6 - +11.5V to +12.5V

TP7 - +4.86V to +5.15V

TP8 - +21V when off, +5V when on, and 0V while reset held

voltages on the video chip seems OK, same with the power supply. i'm assuming tp1-tp2 means between the two pins, and i'm getting 16.9vac. 

[ChildOfCv]

Judging by the fact that your chip is getting hot in spite of getting correct voltages (I assume that's searing and not just a little warm?), it is possible that your STIC (AY-3-8900-1) is the problem.  The service manual also mentions that as a possible cause of video problems.  And wavy text with a vertical line definitely sounds like it's in that category.

[INTV123]

29 minutes ago, ChildOfCv said:

Judging by the fact that your chip is getting hot in spite of getting correct voltages (I assume that's searing and not just a little warm?), it is possible that your STIC (AY-3-8900-1) is the problem.  The service manual also mentions that as a possible cause of video problems.  And wavy text with a vertical line definitely sounds like it's in that category.

Yea the plastic was slightly yellowed above the chip when I got it and will burn you after a few minutes of running. Also I meant the lines are horizontal with the text.