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rasch_C

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Posts posted by rasch_C

  6. Posted

    Looks like Strictly Limited just announced release date of April 28 for PS4 and Nintendo Switch. I was hoping the collectors edition (or some variant) would've had the game on Genesis cart, but it only looks like the game on modern console, poster, soundtrack CDs.

     

    I am really baffled as to why it is not being released physical for the console it was originally designed.

     

    -Allen

    • Like 3

  7. Posted

    Well from what I gather and IIRC from reading this thread, all of the code came from the patent office so really anyone could do the same thing Waggie did if they really wanted to.

    I thought Waggie reached out to the original author and got his consent/permission as well.

     

    -Allen

     

    Sent from my Pixel 2 using Tapatalk

  8. Posted

    Do you mean you saw a single trace and then a blank screen? That typically means it didn't see anything to trigger on. The trigger switch can be set to "NORMAL" or "AUTO". On "NORMAL" it typically waits for a trigger before doing the next sweep. On "AUTO", it is free-running if no trigger is present, but will stabilize on the signal when it finds a trigger.

     

    I had my timescale backwards in my head. At .1 sec (all the way counter-clockwise) is when it shows just the sweeping dot and then 10 Msec is when I see the sweeping signal (the complete trace does not stay lit). It goes dimmer as I continue to go clockwise making it really hard to see.

     

    I did just play around some more with it tonight - getting a better feel for the scope. I set to Multiplier 1, 10uS timebase, DC, Negative trigger. Put my Volts/Div at 1 and reading pin 3 of U3 while power is on the trace went up 3 reticles and was a flat line for the complete width - I believe this would be indicating 3 volts?

     

    -Allen

  9. Posted

    Rigol? Okay Mr Big Spender :) Oh well, that would probably be about a gillion times better than recapping an old scope.

     

    Anyway, to show a full horizontal sweep you should be set on about 10us with a multiplier of 1. That will spread the sweep across a little more than 6 divisions on the screen, assuming I got my calculations straight...

     

    Also, try scoping U3 pin 3 directly (careful not to short pins). That is where the raw timing sync pulses are generated and before they are mixed into the composite signal. It should look mostly high with a low dip 15.7K times per second. With the above settings, once every (just above) 6 divisions.

     

    I don't know about big spender, but I suppose it is more than the $10 I have into this old Heathkit :-D The Rigol seems like the best value entry-level scope. I could get a used Tek scope or something for less, but I determined that I want to have a modern scope for the kids in the Makerspace and it is more compact. The space is very limited.

     

    I tried going to 10us, but the trace was not persistent. You would just start to see the trace go from the left to the right of the screen. At the lower setting you would just see the dot moving from the left to the right. I believe the last pic is at the 1 multiplier. Am I seeing the color-burst at the start of that signal? We are definitely beginners using a scope.

     

    I'll see about firing everything up tonight and testing on U3.

     

     

    Thanks again,

    -Allen

  10. Posted

    So, now that we're finally out of the -30°F temps .... brrr, that cold caused a lot of issues including taking my internet out for multiple days!

     

    After locating all the caps for my old scope and realizing that it would be ~$90, I decided it is not worth it to recap it. I did only spend $10 for it at a hamfest and thought it would be an easy way to get my feet wet. I am planning on buying a Rigol DS1054Z shortly.

     

    I decided to breadboard the easy composite mod and temporarily test that to see if I get picture. Still not getting a picture :(

     

    I have attached pics of the signal reading on my scope - it works roughly, but I don't know how well or accurate.

     

    -Allen

     

    5075985bff612a9b82ca7e7f45592783.jpg8cb3310501ca8ae27fc3048550ead995.jpgce94afa4480e0f2d3fd3e75d3dedb83e.jpg

     

    Sent from my Pixel 2 using Tapatalk

  12. Posted

    Looks like at this point I'll get my scope up and/or just do the A/V mod. I've been having a heck of a time locating some of the precision caps in the correct specs. I'll spend my night tonight hopefully tracking them down and ordering them now that my laptop is back up, and maybe order an A/V mod.

     

    Give some time for parts to come in and I'll report back with either results from a working oscilloscope, or a working console after A/V mod.

     

    Thanks again for all your help! It's been a great learning experience.

     

    -Allen

     

    Sent from my Pixel 2 using Tapatalk

  14. Posted

    Well, horizontal frequency should be closer to 15.7KHz, but a generic meter may not get a perfect reading on a signal either--after all it's not exactly a sine wave. But since we're in the ball park, it sounds more and more like the RF modulator really is the culprit. I guess it was too much to hope for, that the composite signal be directly compatible with a TV. Actually that makes sense after thinking about it because there is such an impedance mismatch between the signal mixer and the TV. That's why the various AV mods include an impedance matching amplifier.

    I was going to ask about the French of that. I was reading up today on the constriction of an NTSC composite signal and then though about my reading and wondered about the mismatch. So, what I should be reading at this location is in-fact the horizontal frequency?

     

    My plan is to composite mod this. So, if the RF modulator is bad, I don't really care. I'm just hoping to verify a working console before modding.

     

    -Allen

     

    Sent from my Pixel 2 using Tapatalk

  15. Posted

    Yes, I have still been working on this, but it's been cold here and the lab is in the garage which is a pain to get up to acceptable working temp w/ my kerosene heater. Also, I have been rebuilding stuck my laptop.

     

    I would have to remove the RF box to gain access to it (cover is on the PCB side). I did try pin 3 of the RF-PCB connection to the composite video input of my PVM directly and only had brief interference show up from actual touching of the signal pin. PVM does not indicate lock of signal of any type. This is w/ and w/o cart. I also measured freq. of pin 3 and it varied between ~12.5kHz - ~13.5kHz.

     

    I'll have to take pics of the reworked components and post. I do believe you guys are correct about Q4 and even the resistor on the RAM chip (didn't look like a rework to me, I was just curious on that one). There are a few components that have been reworked, however.

     

    Thank you,

    -Allen

  17. Posted

    Last year went OK, but still didn't get my next console as intended. If you remember, I was planning on finding a Jaguar, Vectrex, or 3DO for my next console. This hasn't materialized yet. So, that goal carries over this year (thinking about TurboGrafix 16 as another possibility).

     

    Other than that, the bullet points for this year:

    • Learn / go through more hardware - currently fixing my 7800 as posted in another thread, I also have my Sega CD model 1 to finish, and a PS4. As well as learning more on the electronics side more.
    • Commodore - continue expanding this collection and playing around with it (hardware and software) and get my 12yo son his own C64.
    • Programming - really delve into 6502 assembly and 2600 programming.
    • And, above all Family Time with hobby - Having my 12yo son go through the hardware things with me and expanding his own interest in C64 stuff. My 15yo daughter wants to start her own collection. We have had that talk and discussed on what she wants to collect, what her interests are, and determined her start would be best collection GBA (GB, GBC, GBA). Play more games with my 6yo son (as soon as we find where Bendy on the Switch has been lost to).

    Also, we may finally make an appearance again at MGC this year.

     

    -Allen

  18. Posted

    Fresh set of testing eyes today. Thank you ChildOfCv for turning me on to the freq. feature of my meter! Pin 3 of MARIA measures at 14.13Mhz -don't know how accurate/valid that is as that is outside the range of my meter. Pin 6 is 1.192Mhz. Pin 7 is 3.578Mhz. Pin 8 is 1.789Mhz.

     

    Pin 3 of the RF modulator connector to the board measures ~3.308V. Grounding for RF modulator is good. Pin 3 to output (center) measures 7.52 kOhm, pin 2 to output measures 0.618 kOhm, and pin 4 to output measures 52.5 Ohm.

     

    -Allen

     

    Sent from my Pixel 2 using Tapatalk

  19. Posted

    Well, the pins I'm asking about on U1 are timing signals, so you need to be in AC mode to read them. And that's assuming that your VOM is happy with reading voltages at that frequency. It's typically meant for reading wall power (60Hz), not MHz.

     

    If you don't have an oscilloscope and don't plan to use one for more than reviving a 7800, you could buy a cheaper one that has at least 20MHz bandwidth. You could also buy something called a "logic probe" for pretty cheap. Something like this: https://www.amazon.com/Precision-DP21-Digital-Logic-Probe/dp/B009D6O4X6/ref=sr_1_5?s=industrial&ie=UTF8&qid=1547344674&sr=1-5&keywords=logic+probe It will give you colored lights for high/low and also an indication of oscillation. Handy to have for basic "yes or no" troubleshooting, and would tell you if the clock is indeed clocking.

     

    As for the missing transistor, Q4 is just an amplifier for the clock generator. Even though the Rev A schematics they have show it there, it's possible that they decided that MARIA can work without the boost. In fact, R25 and R7 are missing too, and I'm guessing that C18 is the other missing component above that 74LS08 chip.

     

    As for pin numbers on the RF box, it appears that the one on the left in your first picture is pin 1. It has a wide trace that runs to the RF shielding outline, as well as running under the row of resistors. That is a pretty strong indicator of ground connection.

     

    It appears that J2 is just that double-row of connections there, with no pins soldered in to connect to. You could still use that as probe points. In fact, there is a composite video output that you could connect directly to your TV or VCR to see if you get anything before the RF. Most of those are obscured by J3 in the picture, but a VOM should easily let you figure out which one connects to RF pin 3.

     

    Just saw your latest post. Are you sure those components are after the fact? In other words, can you tell that there has been rework done (ie residual flux or something?)

    That's good to know about the clock being A/C. I can try to retest those knowing that.

     

    I have an Extech 430 meter. I do have an old scope that I've been meaning to recap and use to learn. I currently have it on my other bench in order to go through with the thought I could use it for this project. I thought I already bought the caps for it, but it appears not.

     

    Yes, the components I am talking about are obvious reworks including the Q4 position. I'm going to start with the absolutely known reworks and go from there. There is also a resistor soldered directly to pin 21 on one of the RAM chips. I'm not sure where that goes or what it's for.

     

    Thanks for your help,

    -Allena43bf656fdf626d5a5f78e3d982630c4.jpg

     

    Sent from my Pixel 2 using Tapatalk

  20. Posted

    I currently have the board in my Panavise now. Reason? Upon further inspection, it looks like 10 components have been replaced. I believe spots on the board are a mixture of resistors and capacitors, but they have all been replaced w/ resistors. This includes the aforementioned Q4 location.

     

    I will start desoldering these components and then I'll be able to read the locations (why didn't they mark the board next to the component instead of underneath?) I do have a 2N3904 transistor so I should be good there.

     

    Probably will stop for the night and doubtful I'll get to it tomorrow. Idk if maybe it was somebody's attempt at a mod that went wrong or what, but the best immediate course is to get it correct first.

     

    -Allen

     

    Sent from my Pixel 2 using Tapatalk

  22. Posted

    After looking more closely at my pic that I just uploaded in my last post, I noticed something strange. Some weird resistor is in place of the Q4 2N3904 transistor.

     

    Board is CA025234- Does anyone know why someone would replace Q4 with a resistor? I have gone over the board and nothing else looks out of place. I will see if I have an equivalent transistor in my lab to replace.

     

    Thanks,

    -Allencf50ddc225c7f58e5ed4fc0f3ab253d0.jpg

     

    Sent from my Pixel 2 using Tapatalk

  23. Posted

    How's the signal at U1 pins 3, 6, 7, and 8?

    Pins 3 & 8 of MARIA are steady at 1.246V & 4.92V respectively (0V w/ power button off). Pin 6 starts at ~1.939V and decays at rate of about 1mV every 3-4 seconds. This is also 0V w/ power button off. Pin 7 starts at ~0.745V and also decays at rate of about 1mV every 3-4 seconds. This is ~0.7V w/ power button off and shows similar decay rate.

     

    W/ 2600 cart in, I checked LUM and Color lines from TIA and MARIA. TIA was showing ~21mV on most these lines (I believe LUM was lower if memory serves) and MARIA was showing ~15mV.

     

    I think I'm going to check U3 next. I do not currently have a scope up.

     

    Also, can anyone inform me of the pin numbers for the RF connector (J3) as I am not seeing labels for that on the board?

     

     

    Thanks again,

    -Allen902dda37c5aa36fb92bacaeee47734a6.jpg

     

    Sent from my Pixel 2 using Tapatalk

  25. Posted

    Just a quick update. I did test Vcc, Vdd, etc. On the major ICs (TIA, RIOT, Sally, Maria). I thought I might have narrowed it down to being held in reset because the reset pin on Sally is always high when power switch is on, but going through the schematics and my understanding of how U10 works this is normal (pin 13 on U10 goes high and then goes through an OR gate and then to the reset pin on Sally).

     

    All power at major ICs seems to be appropriate via the testing done so far. I'm still going through the schematics and am starting to understand better the layout. I will do some more probing yet, test the logic chips, etc.

     

    Is there a better (high-res) schematic for this somewhere? I have the one(s) off AtariAge printed out, but it is still fuzzy.

     

    Thanks,

    -Allen

     

    Sent from my Pixel 2 using Tapatalk

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