Celotine Posted March 30 Share Posted March 30 Ok I have 3 ICs that have less than 5v for VCC is that normal? It's the 3 40 pin ICs that are not the 6502. They have 3.8 or 2.5. All other ICs including the 6502 show right near 5v. Any help is appreciated Frank Quote Link to comment Share on other sites More sharing options...
+-^CrossBow^- Posted March 30 Share Posted March 30 Check the voltage output on both of your voltage regulators. They essentially provide power to half the console components each. Quote Link to comment Share on other sites More sharing options...
Celotine Posted March 30 Author Share Posted March 30 8 hours ago, -^CrossBow^- said: Check the voltage output on both of your voltage regulators. They essentially provide power to half the console components each. Ok those are all good. I assumed you meant the 2 attached to the big heat sink. Also I went a reseated and reflowed the 4 big ICs I found 3 bent pins but no change after I fixed them. Any other ideas? Quote Link to comment Share on other sites More sharing options...
+x=usr(1536) Posted March 31 Share Posted March 31 19 hours ago, Celotine said: Ok I have 3 ICs that have less than 5v for VCC is that normal? It's the 3 40 pin ICs that are not the 6502. They have 3.8 or 2.5. All ICs should be showing 5VDC. ±5% difference is within tolerance, but at ±10% (or greater) you're getting into find-the-problem territory. 19 hours ago, Celotine said: All other ICs including the 6502 show right near 5v. Is this a 2-port or 4-port system, and what is the power supply you're using a) rated for and b) outputting? I realise that the issue is upstream of the PSU, but there may be one or more things going on in which the PSU is a contributing factor. Also: 11 hours ago, -^CrossBow^- said: Check the voltage output on both of your voltage regulators. They essentially provide power to half the console components each. This is one of the golden rules of 5200 troubleshooting, and you may want to double-check them just to be safe. Related: 2 hours ago, Celotine said: Ok those are all good. I assumed you meant the 2 attached to the big heat sink. Yup, those are the only VRs on the board. Were they (and the ICs) checked with a cartridge inserted or not? If not, find a sacrificial Super Breakout or similar and try with it inserted. 2 hours ago, Celotine said: Also I went a reseated and reflowed the 4 big ICs I found 3 bent pins but no change after I fixed them. Any other ideas? Which IC had the bent pins? If this is a 4-port system, has the power mod to eliminate the switchbox been done? If not, has the switchbox been checked? It's sounding like you'll need to start checking passive components in the power path to each IC to figure out if there's something not working properly. Finally, what are the actual symptoms that you're seeing when trying to use the system? I realise that this may have been covered somewhere else, but would appreciate a recap. Quote Link to comment Share on other sites More sharing options...
Celotine Posted March 31 Author Share Posted March 31 6 minutes ago, x=usr(1536) said: s this a 2-port or 4-port system, and what is the power supply you're using a) rated for and b) outputting? 2 port, OEM PSU with 15v output but that's with no load on. Not sure if that's ok or not. Don't recall which ICs had bent pins, maybe the 2 closer to the front? And my only symptom is green screen. No sound or anything else. Quote Link to comment Share on other sites More sharing options...
+-^CrossBow^- Posted March 31 Share Posted March 31 2 hours ago, Celotine said: 2 port, OEM PSU with 15v output but that's with no load on. Not sure if that's ok or not. Don't recall which ICs had bent pins, maybe the 2 closer to the front? And my only symptom is green screen. No sound or anything else. Pins being bent out is normal on the 2 port unit. Won't hurt or affect if you pop them back into socket, but that was done at the factory. And yes getting about 15v without a load is pretty normal. What do you read on the voltage on the MJE210s? That might be more like 12v coming from the input side. But I would start with replacing out the 6502 given the green screen condition. Although it could be just about any of the ICs, but I tend to start with the CPU first. Quote Link to comment Share on other sites More sharing options...
Celotine Posted March 31 Author Share Posted March 31 21 minutes ago, -^CrossBow^- said: . What do you read on the voltage on the MJE210s? 12v on the outside legs except for one was reading 11v. I assume the center pin was ground. Can I just order a CPU? Don't have donors except a colecovision but that seems to be a Z80 not a 6502. Quote Link to comment Share on other sites More sharing options...
Bratwurst Posted March 31 Share Posted March 31 Pull all 4 ICs, get readings for 5v point on each socket. If the voltage is coming back normal while empty populate each socket one at a time and then check 5v for each one, you might be able to isolate which chip is bad. If you're still getting low reads when the sockets are empty then you have a fault somewhere in the board. Quote Link to comment Share on other sites More sharing options...
Celotine Posted March 31 Author Share Posted March 31 4 hours ago, Bratwurst said: Pull all 4 ICs, get readings for 5v point on each socket. Ok yeah that problem is elsewhere. I downloaded the schematic but I'm no good at reading these. Also I probed around and everything is 5v around these ICs, except, this transistor and the 3 resistors to the right of it. That transistor has 2.1v. what do you think? Quote Link to comment Share on other sites More sharing options...
Bratwurst Posted March 31 Share Posted March 31 Look up the transistor markings for a datasheet. If I'm reading the 2-port schematics right that is a 3904 for the video circuit which should be 5v. Would not hurt to check C11, C116, C19 and any other nearby capacitors mylar or tantalum for possible shorts to ground. Quote Link to comment Share on other sites More sharing options...
Celotine Posted March 31 Author Share Posted March 31 2 hours ago, Bratwurst said: Look up the transistor markings for a datasheet. If I'm reading the 2-port schematics right that is a 3904 for the video circuit which should be 5v. Yeah everything else looks good. Looks like I got a jacked up transistor. Good excuse for me to order a box of transistors from the 'zon Quote Link to comment Share on other sites More sharing options...
Celotine Posted April 1 Author Share Posted April 1 8 hours ago, Bratwurst said: 3904. Ok I found a 3904 on a scrap colecovision and swapped it. No change. But I found that the voltage drops off right at these 2 resistors they read 3.5k for the blue one and 1k for the one next to it. Also the voltage looks low on those 2 to the far right and the ohm reading on those is 14.5k and 14k respectively. Couldn't find shorts on any of those caps or around them. Thoughts? Quote Link to comment Share on other sites More sharing options...
Bratwurst Posted April 1 Share Posted April 1 I don't have a 5200 to reference but I think you're going to see voltage drop through a resistor because that's what they are about. A bad or failed resistor would be obvious also, either blown out open/charred black or out of spec (high) resistance for the color code. Quote Link to comment Share on other sites More sharing options...
+x=usr(1536) Posted April 1 Share Posted April 1 10 hours ago, Celotine said: Thoughts? Have you tried testing the following scenario yet: On 3/30/2024 at 8:41 PM, x=usr(1536) said: Were they (and the ICs) checked with a cartridge inserted or not? If not, find a sacrificial Super Breakout or similar and try with it inserted. The reason I asked about testing with a cartridge inserted is that there's essentially a power lockout on the cartridge port. Things may read differently depending on whether or not a cartridge is inserted with the power on. Also, it looks as though much (or all) of the testing you're doing is with the components in-circuit. That's not necessarily a bad thing in and of itself, but component readings can be significantly different in- and out-of-circuit. Quote Link to comment Share on other sites More sharing options...
+-^CrossBow^- Posted April 1 Share Posted April 1 The fact that he is getting a green screen, means the video subsystem is working at this point and it all points to being something in the main logic. So again, I would start with the CPU. It is 1 of the 4 large ICs and is the one in the upper left. It could also be a faulty RAM chip, but I've not actually seen that happen in a 5200 yet unlike its 8-bit related XL/XE cousins and their died at a moments notice MT RAM they tended to come equipped with. 1 Quote Link to comment Share on other sites More sharing options...
Celotine Posted April 1 Author Share Posted April 1 1 hour ago, x=usr(1536) said: Have you tried testing the following scenario yet:. Yeah pacman is in. I'm familiar with Ataris love of locking out without a game. Both my lynx and jaguar were sold to me as no power only to find out the seller just didn't own a game 🤣 1 Quote Link to comment Share on other sites More sharing options...
Celotine Posted April 1 Author Share Posted April 1 1 hour ago, -^CrossBow^- said: It could also be a faulty RAM chip Ram was all replaced. I googled the issue and it said that so I ordered 8 and swapped them. They could have sent me some bad ones I suppose. I'll give them a probe with the oscilloscope. I just got one and not super familiar yet. After I check those I'll order up new ICs and try those. Thanks for all your help. Quote Link to comment Share on other sites More sharing options...
Celotine Posted April 1 Author Share Posted April 1 3 hours ago, -^CrossBow^- said: It could also be a faulty RAM chip Could you tell me if this looks normal? The address lines all do this on the RAM. Quote Link to comment Share on other sites More sharing options...
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