Troubleshoot No Video - Magnavox Odyssey 2

[Wil_Bloodworth]

My wife has her original Magnavox Odyssey 2 (service manual:  https://www.digitpress.com/library/techdocs/o2-svc.pdf) from the late 70s and I've been trying to get it to work again... clearly for some points on the home front!

After purchasing an adapter to go from the RF Out (RCA coax) on the console... to a Coax to RCA (Red, White, Yellow) converter box... to a RCA to HDMI box... to a TV.

I've cleaned the console inside and out, fixed a few soldering points on the main board, tested all of the voltages and now everything "seems" fine.  The input voltage is good and the on-board voltage regulator seems to be working well too.

When I turn the console on, I get audio but no video.  The game is responsive and when I touch keys on the keyboard, the console is responding to my input.  So... everything appears to be loading and running fine. BUT... no video is making it to the TV.

How do I troubleshoot this video issue?  I'm going to assume that the converters I purchased work (let's just go with that assumption for now as they're brand new and I don't have any other 'old' devices in the house to test them with).

The Channel 3/4 module seems to be working fine and I'm getting voltage from the main board to that daughter board... but I don't know how to test the output.  Can I test this somehow with my scope (without a logic analyzer)?

I can post photos of anything you like upon request.

Thank you!

- Wil

[wasedadoc]

Do you really need those two converter boxes?  I haven't heard of a TV with HDMI input but not analogue RCA phono jacks,  yellow composite video, white left audio, red right audio.  And even though the US has now no analogue RF broadcast TV transmissions, modern TVs are essentially "worldwide" designs and tend to still have analogue tuners.

Put your scope on pin 5 of IC1 and you should see the video signal that goes into the RF modulator.

[Wil_Bloodworth]

Do you really need those two converter boxes?  I haven't heard of a TV with HDMI input but not analogue RCA phono jacks,  yellow composite video, white left audio, red right audio.  And even though the US has now no analogue RF broadcast TV transmissions, modern TVs are essentially "worldwide" designs and tend to still have analogue tuners.

Yes. None of our TVs have any inputs other than HDMI.

Put your scope on pin 5 of IC1 and you should see the video signal that goes into the RF modulator.

Ok. What am I looking for exactly?  What should I expect to see?  I recently purchased the scope and haven't used it for anything other than some voltage measurements.

Thank you,

- Wil

[wasedadoc]

You expect to see NTSC video.  Similar to the waveform at https://en.wikipedia.org/wiki/File:Analogue_Video_Signal_PS1.png.  Very approximately 1 volt peak to peak.  The pulses at the bottom will be constant.  The top parts between the pulses will depend on the picture content.  Frequency of the pulses is 15.75 kHz.  Period just under 64us.  Set scope to 10us or 20us per division.

If in doubt post a photo of what your scope does show.

I'd like to know the make and model numbers of your TVs.

[Wil_Bloodworth]

You expect to see NTSC video.  Similar to the waveform at https://en.wikipedia.org/wiki/File:Analogue_Video_Signal_PS1.png.  Very approximately 1 volt peak to peak.  The pulses at the bottom will be constant.  The top parts between the pulses will depend on the picture content.  Frequency of the pulses is 15.75 kHz.  Period just under 64us.  Set scope to 10us or 20us per division.

Awesome!  I will try that and report back.

These are our TVs:

• Samsung - 50” Class CU7000 Crystal UHD 4K Smart Tizen TV
  Samsung - 75" Class 8 Series LED 4K UHD Smart Tizen TV
  

- Wil

[oPossum]

• Samsung - 50” Class CU7000 Crystal UHD 4K Smart Tizen TV
• Samsung - 75" Class 8 Series LED 4K UHD Smart Tizen TV

Both of those have an antenna input that supports NTSC and ATSC.

[wasedadoc]

Hmm. The page https://www.samsung.com/sg/tvs/uhd-4k-tv/cu7000-50-inch-ua50cu7000kxxs/ for the UK model says it does have an analogue tuner but no composite video input, only HDMI.  (The UK switched off analogue TV transmitters years ago.)

Could be that the US model has the same hardware (with the tuner present) but the firmware doesn't show it in the user menus.  I still have and occasionally use gear with only analogue video output.  A TV that couldn't accept that would be a no-no for me.

Edit: Given the info from oPossum posted just seconds earlier, ignore the parts in this post about analogue tuner.

[Wil_Bloodworth]

Could be that the US model has the same hardware (with the tuner present) but the firmware doesn't show it in the user menus.  I still have and occasionally use gear with only analogue video output.  A TV that couldn't accept that would be a no-no for me.

I have no idea about anything outside of the US, but all of my TVs only have HDMI inputs.  There are physically no other input types.  Honestly, until I have had the need to deal with this legacy junk, we have never needed any other options since I do not own any analogue devices.

- Wil

[oPossum]

There clearly is an F connector for antenna/cable.



https://www.rtings.com/tv/reviews/samsung/cu7000-cu7000d

[Wil_Bloodworth]

Well, crap. I'm not sure how I missed that! LOL

- Wil

[Wil_Bloodworth]

There clearly is an F connector for antenna/cable.

Well, while it is clearly on the TV... there is nothing in the TV software that lets you switch to anything other than an HDMI input. I've reset the TV and gone through all of the advanced settings... there is no way to switch to that input.

- Wil

[wasedadoc]

There clearly is an F connector for antenna/cable.

Well, while it is clearly on the TV... there is nothing in the TV software that lets you switch to anything other than an HDMI input. I've reset the TV and gone through all of the advanced settings... there is no way to switch to that input.

- Wil

Of course there is a way.  That is the way the TV receives over the air transmissions.

Post a picture of the remote control.

[Wil_Bloodworth]

Of course there is a way.  That is the way the TV receives over the air transmissions.

LOL.  Who does that?  I haven't received an OTA broadcast since the 70s.

Regardless, it does not seem to be an option in the software even though there is clearly a piece of hardware there.

- Wil

[wasedadoc]

Post a picture of the remote control.

[Wil_Bloodworth]

Post a picture of the remote control.

It's just the standard Samsung remote control. Also, according to the manual "Live TV" is not an option in some countries. Live TV / Antenna / Broadcast options are not in the software.

This is the remote:  https://m.media-amazon.com/images/I/41wn37g8VYL._AC_SX679_.jpg

[wasedadoc]

Samsung USA web page for CU7000 50 inch.  https://www.samsung.com/us/televisions-home-theater/tvs/crystal-uhd-tvs/50-class-cu7000-crystal-uhd-4k-smart-tv-2023-un50cu7000fxza/

[wasedadoc]

e-manual https://downloadcenter.samsung.com/content/UM/202307/20230705133212135/BN81-24055A-410_EM_OSPATSCC_NA_ENG-US_230609.0.pdf

Page 116. Scanning for available channels. Auto Program

Connect the game console RF out to the TV antenna socket and use the Auto Program to tune the TV to the channel.

[Wil_Bloodworth]

Connect the game console RF out to the TV antenna socket and use the Auto Program to tune the TV to the channel.

That resulted in nothing positive.

[Wil_Bloodworth]

Here are the results of attaching the scope to pin 1 of IC5.  I'm not even sure how this helps.

[wasedadoc]

1.  So the TV does indeed have the software for analogue RF reception.  How exactly were you connecting the console output to the round F-type connector on the TV?

2.  That is not the place I told you to probe!

[Wil_Bloodworth]

1.  So the TV does indeed have the software for analogue RF reception.  How exactly were you connecting the console output to the round F-type connector on the TV?

I'm using a normal RCA cable with an RCA-to-Coax connector/adapter on the TV end.

2.  That is not the place I told you to probe!

My apologies... it's been a long day and I'm tired.  I will try again with less dyslexia in a few minutes.

- Wil

[Wil_Bloodworth]

Ok... IC1... pin 5.

[Wil_Bloodworth]

Maybe I should check pin 4 of IC6 too?

[wasedadoc]

Nothing wrong with that.  Probe the other end of R7 which connects to W2 on the modulator unit.  Audio is going into the modulator at W3.  Clearly at least part of the modulator is working or you would not have got the sound operational as you reported in the first post.

Signal at pin 4 of IC6 will be about 60 MHz.

It is after 1 am here so no more from me now.

[Wil_Bloodworth]

I was able to trace (electronically), the video pin backwards from the RF Modulator box to Pin 27 of IC5.  There does not seem to be any meaningful signal coming from that pin.

When I (try to) read the schematic, it looks like IC1 is passing all of the video data to IC5 but the audio is being sent directly from IC1-Pin 5 over to IC6.  We tested and confirmed we are getting signal out of IC1-Pin 5 and we know that is audio because... I'm getting audio but no video.

I traced the video signal from IC5 Pin 27 to the RF Modulator (IC6 Pin 6).  I could not find an details on this 612178-1 chip so I don't know what happens to the video signal when it gets there... but I do not think that is important right now because there does not appear to be any video signal coming from IC5 pin 27.

Amy I approaching this correctly?  If no video signal is coming from pin 27 of IC5, what should I try next?  Should I try to pull that IC and clean the pins / socket and try again?

Oh, and I know that pin 27 of IC5 is making contact with the board because there is continuity from the board traces directly to IC5 pin 27... so cleaning the socket is probably not going to solve anything.



- Wil

[wasedadoc]

Your reading of the schematic is incorrect.

IC5 pin 27 is sound coming out of the sound generator and into the RF modulator.  IC5 also generates the separate parts of the video signal namely red, green, blue, sync and blanking.  Those are fed into IC1 which forms the composite video signal and outputs it from pin 5 into the RF modulator IC6.

D2 and L4 determine the frequency of the 4.5 MHz oscillator.  D2 is a varicap diode.  The sound input via R49, R40 and C35  varies the capacitance of the diode and hence frequency modulates the sound carrier.  That is added to the composite video signal on pin 2 of IC6.  The combined sound and vision then amplitude modulates another oscillator within IC6.  Frequency of that one is around 60 MHz, determined by L6 and capacitors C17, C18 and C32.  The switch around C32 changes the frequency between CH3 and CH4.

The part of IC6 that does the 60 MHz oscillator and modulates it must be working otherwise you would never have got sound through your original chain of console plus two converter boxes to HDMI.  Check that the pin 2 of IC6 is getting more or less the same video signal that you got on pin 5 of IC1.

[Wil_Bloodworth]

So... video signal is coming out of IC1 pin 5 and is making it all the way to IC 6 pin 2.  I believe there is signal coming out of IC 6 pin 4 but it is not making it to the RF output.  I'm unable to test any of the capacitors between IC 6 pin 4 and the RF output unless I desolder them. 

Any tips on figuring out where to troubleshoot next or do I just need to start desoldering stuff?

Thank you,

- Wil

[wasedadoc]

So... video signal is coming out of IC1 pin 5 and is making it all the way to IC 6 pin 2.  I believe there is signal coming out of IC 6 pin 4 but it is not making it to the RF output.  I'm unable to test any of the capacitors between IC 6 pin 4 and the RF output unless I desolder them. 

Any tips on figuring out where to troubleshoot next or do I just need to start desoldering stuff?

Thank you,

- Wil

I'm not totally convinced there is anything wrong with the console itself.  The RF signal coming out of pin IC6 pin 4 will be very small and very difficult for your scope to trigger on.  Easy to appear as just noise.

If you really did get sound as stated in your first post then the output from IC6 is definitely getting to the output socket.  The audio FMed 4.5 MHz and the composite video are combined inside IC6 before that mix is applied as a single input to the 60 MHz amplitude modulator.

I'm wondering if your TVs just don't like the video signal that the console generates.  Those old consoles only generated an approximation to the pukka NTSC standard.  TVs of the era when that console was designed were much more tolerant of deviations from the strict standard.  For example, your console probably generates non- standard non-interlaced video which the upscaler in your Samsungs may not be able to deal with.

The only way to conclusively prove that the console is working OK is to see it working with at least one TV.  Do you have access to, even temporarily, an older TV?

Update:  I just realised you can test the console's output.  Hook it up to the coax to 3 phono output box that you have.  Look at the video output (yellow socket?) with your scope.  Do you see the same waveform shape as when you looked at pin 5 of IC1?

[Wil_Bloodworth]

Well, after resoldering a couple of connections and changing some cords... voila!

Thank you Wasedadoc!  The first thing she said after seeing it working was, "Drop your pants!".  LOL



- Wil