Trying to repair snowy 5200

[jum]

I'm having another attempt at getting my 2-port 5200 working.

 

Symptoms: snowy screen at power on, maybe faint vertical bars behind snow.

 

Also the "channel switch" at the back of the 5200 is missing/removed (switch is "open").

 

Also I'm powering it thru a 220 to 110 VAC stepdown to the 5200 power brick. My TV is auto PAL/NTSC.

 

Also I replaced VR1 and VR2 (3905's) because they had been ripped off in transit.

 

After taking a look at the 5200 Field Service troubleshooting chart, it seems that the problem could be a faulty RF modulator. I check GND on pin 1 and +5V on pin3 and they seem OK (0V and 4.93 V).

 

If the problem is the RF modulator, then I'd be happy to make a composite video mod.

 

However, before I go to that trouble, I want to make sure that the video output is the only fault in this machine.

 

Is there an easy way to tell if there are other faults?

 

Will tapping into the audio output help me determine if the machine is actually running a game?

 

Any help appreciated.

 

Thanks - jum

[Rybags]

I was having similar problems today with my 800XL. With my machine, it appears that the inner contact on the RF output is worn and/or corroded.

 

Try rotating the plug or pulling it out a bit.

 

Of course, the composite video mod would be the go if not too much work is involved (I've never seen a real 5200 - don't think they ever sold here).

[+Mitch]

I'm having another attempt at getting my 2-port 5200 working.

 

Symptoms: snowy screen at power on, maybe faint vertical bars behind snow.

 

Also the "channel switch" at the back of the 5200 is missing/removed (switch is "open").

 

Also I'm powering it thru a 220 to 110 VAC stepdown to the 5200 power brick. My TV is auto PAL/NTSC.

 

Also I replaced VR1 and VR2 (3905's) because they had been ripped off in transit.

 

After taking a look at the 5200 Field Service troubleshooting chart, it seems that the problem could be a faulty RF modulator. I check GND on pin 1 and +5V on pin3 and they seem OK (0V and 4.93 V).

 

If the problem is the RF modulator, then I'd be happy to make a composite video mod.

 

However, before I go to that trouble, I want to make sure that the video output is the only fault in this machine.

 

Is there an easy way to tell if there are other faults?

 

Will tapping into the audio output help me determine if the machine is actually running a game?

 

Any help appreciated.

 

Thanks - jum

963148[/snapback]

 

Since I assume you are not in the US what channel are you trying it on?

 

Mitch

[jum]

No I'm not in the good ol' US, but my small LCD TV handles NTSC/PAL/whatever.

 

I've done a full "program scan" on my TV, and only found the 5200 "signal" at one place in the VHF and UHF bands.

 

What does the "channel switch" on the back of the 5200 do anyway (ie: which channels/frequencies does it select)?

[+Mitch]

The channel select switch is for VHF channels 2 and 3 in the US. I don't recall the exact frequencies but you can probably find them in a Google search. If the switch is gone it might default to one of the channels but I'm not sure. You might try to find a switch to put in there just to verify.

 

OK, I just a Google search myself and it looks like channel 2 is at 55.25MHz and channel 3 is at 61.25MHz. I hope that helps.

 

Mitch

[jum]

The channel select switch is for VHF channels 2 and 3 in the US. I don't recall the exact frequencies but you can probably find them in a Google search. If the switch is gone it might default to one of the channels but I'm not sure. You might try to find a switch to put in there just to verify.

 

OK, I just a Google search myself and it looks like channel 2 is at 55.25MHz and channel 3 is at 61.25MHz. I hope that helps.

 

Mitch

963618[/snapback]

 

Thanks Mitch

 

It looks like the open switch selects one of the channels. I'll try to retune.

 

- jum

[jum]

Finally some closure to this forum post

 

Fixed my 5200 after 14 years - turns out it was a faulty inductor L3, which is on the SELECT line for the 74LS245s that multiple the address going into the RAM.

 

 

[ave1]

Love these old topics getting a resolution! Congrats

[+DrVenkman]

8 hours ago, jum said:

Finally some closure to this forum post

 

Fixed my 5200 after 14 years - turns out it was a faulty inductor L3, which is on the SELECT line for the 74LS245s that multiple the address going into the RAM.

 

 

That's a heck of a weird thing to go wrong! Glad you finally got things figured out though!

[jum]

7 hours ago, DrVenkman said:

That's a heck of a weird thing to go wrong! Glad you finally got things figured out though!

Yeah, pretty unusual fault.

 

Lots of pondering over schematics and datasheets, and probing with an oscilloscope, was involved...

 

Have now discovered the GTIA may be faulty - the player to player collisions don't seem to work! (Also unusual).