Macross_VF1

Here's a bit of an oddball technical question. I've recently managed to acquire a 5200 at a pretty good price that was listed as powering up but no signal. I thought it was worth looking into and I'm glad I did as it actually works, though the picture over RF is pretty poor so I will mod it with S-Video and/or composite. I like to future proof my consoles and computers so they at least can output composite. However, it also lacked controllers and while this is not much of a concern to me, this particular unit is mostly just going to sit in my collection, I do want to see at least one game going past the start/title screen. If this were a 2600 or similar machine I could easily just short the appropriate controller input pins to produce the necessary 'button' press but the 5200 is of course different in this regard. So basically, which input pins needs to be 'connected' to produce the start and indeed any button press? I'm not terribly familiar with the grid layout of the buttons on the 5200 but if I'm reading the schematic correctly I think the start button should be activated with pin 7 and 4?

So I've managed to snag myself a rather unusual old computer (at least over here in Sweden), a PAL TRS-80 Coco model 1. Now I'm wondering if there is any big differences between the PAL model and the far more common US version? Because if at all possible I want to give it a composite mod, something that seems to be rather easy to do just based on a simple google search, though I can't tell if the mods available will work without modification on a PAL computer.

No matter, it's dead now. I tried reseating the socketed chips and I must have damaged at least one because it only shows a black screen. FML

So I have an issue with my Philips Videopac G7400. It outputs a piss poor RF signal, no matter how much I try to tune the TV. When I started digging around the net I saw that it was easy to convert to RGB, just a matter of installing a number of components. https://www.the-nextlevel.com/odyssey2/articles/g7400guide/rgbmod.php Unfortunately, nothing improved. As can be seen in the attached image (the image was taken while using RGB), the signal is still distorted and it does not matter if it is RF, composite or RGB. Anyone have any idea what the problem might be? I have tested the internal AC adapter and it outputs pretty much the correct voltage, 4.95V on one line and 11.43V (should be 5 and 12V respectively) on another.

Just managed to acquire a really old console; A Philips Odyssey 200. Unfortunately, it behaves strangely. The picture is warped and it does not seem to start as intended. As the first picture below shows, I get some strange results. I can manipulate the two darker icons with the controls but the game doesn't seem to start, the "ball" is missing and nothing really happens. And before anyone asks if it's the TV coulnd't tune into the right channel, what is shown is actually composite since I have connected an external composite circuit. When using RF the picture remain the same though obviously blurrier. What I primarily wonder about is whether this can be due to low voltage. The original battery holder is missing (second picture) but it's supposed to accommodate 6 C batteries for a total of 9V. Instead, a previous owner has soldered an external AC adaptor that can only handle 4.5V (is tested and gives 5V so well within tolerances) .

The extra/external ground wire you are referring to is present on the 1531 but it has been fully integrated into the cable. It's called 'shelled wire' in the schematic.

I'm hoping the hivemind might help me with this. I have a 1531 datasette that lacks a plug, just bare wires at the end of the cable. I also have a dead 1530 from which I can scavenge a plug from. Of course I first have to figure out which wire goes where. First of all, a 1531 have an extra wire, yellow, compared to a 1530. From what I can see of the 1531 mini-DIN pinout, the extra wire should be an extra GND not found in a standard C64/128 cassette plug. I've also managed to figure out that the PCB on my 1531 is a #017-5001-01 by studying the service manual but the order of the colours in the schematic does not match my 1531 as I've noted in the attached image. Curiously, the dead 1530 does not have a corresponding PCB revision in the service manual. By carefully tracing where each wire enters the PCB, what it connects to and comparing to the schematic I think I have the proper order but I need confirmation, particularly on the +5V line so I don't fry the entire thing. White - + 5V Black - Motor Green - Sense Yellow - Read or Write Blue - Read or Write Red - GND Brown + shell - GND I'm almost 100% sure about the black, green, red and brown wire. The same cannot entirely be said about the white, yellow and blue.

Considering the game was brand new and sealed in the box when I got it, it shouldn't be possible that the cartridge connectors are dirty. Of course that does leave the console connector. Still, I'm inclined to believe that it is the game that's defective. When I put it it into the console and power on, it takes about three seconds to get a red screen. If I instead deliberately insert the game improperly, for instance at an angle or not fully pressed down, I get the red screen immediately. To me it would seem that, when fully inserted, the game tries to load but fails. Anyway, thanks, you guys have at least helped me with how to identify EU and US games. Turns out that my Raiden game and one other in my collection are indeed the US version.

So the game should work, regardless of the machine being PAL or NTSC?

So I've had a Raiden cartridge for my Jaguar since I bought the machine back in 2005 or so. However I've never gotten it to work so I always thought it was broken or something. However, I recently found out that this particular game, while not specifically being region locked, was optimized for the region it was supposed to be sold in, ie the US or Europe. Could this be the reason that I've never gotten it to work? That I might have a US version when I have a PAL Jaguar? Also, is there any way to actually tell if a game is the EU or US version?

Tested again while connected to the main board and a game running. TP-4 is still a bit high, though perhaps not overly so at 19V, and TP-6 outputs a far more reasonable 5.85V. So probably just a false alarm then. Oh well, better to be safe than sorry with electronics that are this old.

So I'm currently doing some maintenance and cleaning of my Intellivision console and while doing some research on the machines schematic I came across the chart below and figured I might as well give it a try. And I'm pretty happy that I did for I got some readings that I hope you guys might be able to help me with. So, using the above chart I mapped out the suggested test points. TP-1,2,3 and 5 are all good but TP-4 gives +25.6V and TP-6 outputs +13.8V. Since TP-4 is directly connected to C3 I figured I might as well replace it as I have a decent number of 2200uF/50V capacitors lying around, however the TP-4 and 6 voltage levels remain the same. Unfortunately I don't have any to replace C1 with (10000uF/16V). Normally, voltage that high above their suggested levels are not good for a console though I wonder, could this be due to me having a Pal console, a different revision or any other possible reason? Also, I suppose I should add that I tested it while unconnected to the console.

I forgot to add that I've also replaced the RAM chips and the OS chip as well. I kinda wonder what could cause this much damage. I suppose it is likely the original PSU might have died and damaged the system with it, or it might have been connected to a PSU with the wrong specs. Anyway, thanks everyone who helped bring it back to life. I couldn't have done it without you. Extra kudos to ChildOfCV who just didn't quit even after the colour problem was found.

Ok, here's the good news. With C53 replaced I get a rather different set of readings at Q6: Q6 C 1.6V Q6 B 0.5V Q6 E 0V I've also replaced 74LS74 and now I finally get colour! Just for shits and giggles, here's all the repair timeline. Bought it several years ago and it didn't function at all. Started tinkering some months ago with the capacitors and finally got it to power on, though only to a black screen. Replaced all the electrolytic capacitors. Still black screen. Replaced all the transistors. Still black screen. Started removing the major chips except Pokey to test them in a 600XL. All major chips worked fine. Removed Freddie to test in a 130XE. Finally found something faulty. Borrowed the working Freddie from the 130XE to the XEGS. Got a picture but lacked colour. Ordered a new Freddie while asking you guys for help. One resistor connected to the colour trimpot found to be of the wrong value. Replaced though still no colour. 4050 chip tested in 130XE, worked as intended. Colour issue finally traced to faulty 74LS74. Ceramic capacitor C53 closely connected to transistor Q6 found to be faulty. 74LS74 and C53 replaced and the machine works as intended! Here's some pictures to celebrate:

No problems mate. Replacement parts have been ordered and will arrive in a few days. I'll post again when they have been installed and I (hopefully) have the good news.

No need, it's already been tested and found to be working though it's a good suggestion none the less.

My particular crystal is mostly covered in some kind of shrinkwrap so it severely limits the possibility of a leg touching the case. Still, I checked just to be sure and the legs do not appear to touch the case. Anyway, yeah I got 36 ohm when testing the actual capacitor when it is pulled from the circuit. When testing R72/Y2 junction with C53 pulled I get 4.6-4.7k ohm.

I've disconnected the crystal and taken another resistance reading between R72 and where Y2 would connect. At first I got 4.6k ohm but then I remembered that I had not resoldered C53 and with that returned to its rightful place I got 37 ohm again. Conduction between a leg and the case? Do you mean the metal shield? If so, that's impossible, all this time I've tested the machine without the shield.

I've checked it ut of circuit but with almost no difference, 36 ohm compared to 37 previously. Replace I suppose? However I don't know what to replace it with. It's marked with A5E 104 ZTX 738.

Resistance to ground between R72 and Y2 is 37 ohm. Would that qualify as close to zero? I have checked C53 just to be on the safe side and I got 11 nF capacitance on it. I've also checked and double checked for debris and other stuff that don't belong but I just can't find anything.

Ok, so this turned out to be a lot more difficult than I had first anticipated. It seems that my XEGS is vastly different around Q6 than compared to the schematics. I've tried to do my own diagram, though I fully admit that I might have missed something. *Edit* Just saw that I missed marking which leg is the emitter on Q6. It's the leg connected to ground.

Paydirt indeed! Since you guys suggested that U10 (LS7474) might be a possible culprit I promptly desoldered it and tested it in my 600XL as every chip is socketed in that machine. And sure enough, no colour when using my 600XL with the XEGS LS7474! Finally! Unfortunately I don't have a 14 pin socket to put in my XEGS though considering I have to order a new LS7474 anyway, that's not much of a problem. While I feel it's unlikely that this particular unit will have more challenges to present to us as just about every part of it has been scrutinized under a magnifying glass and/or been replaced, I will hold my breath until I have the new parts. Still, it has been a pleasure to work with you, and I've learned more about troubleshooting and reading schematics than all of my previous 37 years of life combined. I'll be sure to return if I have any other problems.

In most cases I certainly agree with you on the resistors. The only one I would find any major fault with is R80 and even then, I don't think it's serious. I just figured it would be better to include the values, instead of leaving them out. Speaking of resistors. I've changed the 680k resistor to a 1k and the voltage across the trimpot now go from 0-8.7V. Sadly no colour despite that bit of improvement. Resistance from +5C to Q5 base is indeed 6.6k Ohm. Spot on. Oh yes, this is most certainly a PAL machine. Pin 16 gives 4.5V DC and the same low 0.01V AC. I saw that Q6 is also closely connected to pin 16 so I figured I should take those readings as well. Q6 C 4.5V Q6 B 0.2V Q6 E 0V Also part of this particular corner of board is Y2 which I suppose is the oscillator you mention. Any tips on how I should measure it?

I have at least one bit of good news, I've received my new Freddie chip so I no longer need to borrow one from my 130XE. All the chips I've desoldered (GTIA, PIA, Sally, ANTIC, Freddie and 4050) have been tested successfully in other computers. The only major chip I haven't desoldered is Pokey but that chip really shouldn't be an issue here. It turns out that Jerzy's schematic of the XEGS is pretty darned accurate when it comes to the video output from GTIA so I've used it to visualize my findings. Red are resistors with a faulty value, though I haven't checked yet if the rings on the resistors match the value I'm getting from my multimeter. Yellow is just a typo, the resistor is named R78 instead of R53. Blue are the voltage readings I get from all the transistors Green are other voltage readings, DC if nothing else is written. I also used red to show the resistance across L5.

I've done some further measurements based on your suggestions though I admit that I'm not well versed with AC voltage. I pretty much only get 0.01V AC no matter where I take my readings though it just might be that I don't know how to do it properly. Pin 3 of Sally gives 1.5V DC Q5 Collector - 5V DC Base - 0.73V DC Emitter - 0.23V DC