AwkwardPotato Posted September 17, 2017 Report Share Posted September 17, 2017 I have a 12" RGB pizza-box-topper monitor connected to a PowerMac 6100, which according to this and this, should be able to output at the monitors 512x384 resolution. However, when starting the computer from either the OS 8.5 install, or the System 7 Disk Tools, the monitor doesn't display a raster. When powered on and off, I can hear it crackling, and the LED comes on. I've attempted adjusting the sub-brightness and sub-contrast controls, but to no avail. What are some things I should check for to attempt to repair it? Thanks in advance! Quote Link to post Share on other sites
beachycove Posted September 17, 2017 Report Share Posted September 17, 2017 Is there a functional pram battery in the 6100? If not, quickly turn the computer on, then off, then on and allow it to boot. Quote Link to post Share on other sites
AwkwardPotato Posted September 17, 2017 Author Report Share Posted September 17, 2017 The 6100 has a charged PRAM battery and works with both VGA monitors and the Multiple Scan 14 Display. Quote Link to post Share on other sites
beachycove Posted September 18, 2017 Report Share Posted September 18, 2017 You could try zapping the pram, I suppose. Quote Link to post Share on other sites
AwkwardPotato Posted September 18, 2017 Author Report Share Posted September 18, 2017 It isn't an issue with the 6100, the monitor is faulty. I'm trying to repair it in order for it to be ready for use with my Macintosh LC, after it is recapped. Quote Link to post Share on other sites
Byrd Posted September 18, 2017 Report Share Posted September 18, 2017 I'd test it on your (repaired) LC first though, before ruling out the monitor as faulty. It's an odd resolution for a PPC Mac so don't take the documentation you've found as gospel. Quote Link to post Share on other sites
Cory5412 Posted September 25, 2017 Report Share Posted September 25, 2017 I haven't tested the 6100 in particular, but the 7300 and 6500 have no trouble with 512x384 on this particular display, so there's no good reason it shouldn't work. Quote Link to post Share on other sites
CelGen Posted September 26, 2017 Report Share Posted September 26, 2017 (edited) I'm going from older knowledge here but if you can't even force the brightness up with an internal pot to see a raster check so see if the end of the tube has the orange glow of the heater. From experience one of two things has happened. Either the video stage itself has suffered a rather large failure and no signal is reaching the tube but the high voltage is good, or the cathode heater in the tube has failed, possibly from the monitor being very roughly handled or old age. Edited September 26, 2017 by CelGen Quote Link to post Share on other sites
AwkwardPotato Posted October 9, 2017 Author Report Share Posted October 9, 2017 I've looked inside and the cathode heater does indeed work, there is an orange glow at the neck of the tube. Quote Link to post Share on other sites
CelGen Posted October 9, 2017 Report Share Posted October 9, 2017 Okay then, so if the high voltage comes up and the heater lights then something is funky on your analog board. Quote Link to post Share on other sites
Scott Baret Posted October 10, 2017 Report Share Posted October 10, 2017 Re-cap your monitor boards!!! The CRTs and flybacks on these monitors are usually pretty reliable. However, bad caps will cause all sorts of issues, from poor focus to distorted rasters to monitors doing next to nothing. Quote Link to post Share on other sites
techknight Posted October 13, 2017 Report Share Posted October 13, 2017 I like these little monitors. Kinda cute for a CRT. lol. Quote Link to post Share on other sites
CC_333 Posted October 30, 2017 Report Share Posted October 30, 2017 (edited) Me too. They're not big and clunky looking like many contemporary PC monitors tended to be. I don't care too much about that myself, but I can see why an average person would have liked to not have a giant CRT take up most of their desk space (this it one of the many reasons LCDs became so popular, starting in the mid-2000's I think). The slightly bigger HiRes 13" is nice too, albeit a bit heavy (I have two of them, so yeah. Heavy). the 12" RGB is nice and light, at least for a CRT. c Edited October 30, 2017 by CC_333 Quote Link to post Share on other sites
360alaska Posted October 30, 2017 Report Share Posted October 30, 2017 I had one giving me some issues and I'm happy to say a recap and a adjustment fixed all my issues. Quote Link to post Share on other sites
AwkwardPotato Posted August 1, 2018 Author Report Share Posted August 1, 2018 (edited) Thread necromancy, I know, but: I decided to investigate further with this monitor and found that the horizontal output transistor is shorted. I've watched techknight's videos on repairing his monitor and read up on similar instances of this happening and from what I can gather, there's likely something else causing the HOT to fail and whatever replacement I put in will end up failing as well. Where should I go from here? BTW, I do plan on recapping the monitor. Edited August 1, 2018 by AwkwardPotato Quote Link to post Share on other sites
360alaska Posted August 1, 2018 Report Share Posted August 1, 2018 Hi, not an expert in the repair field, but doesn't a shorted horizontal transistor indicate a bad flyback? Quote Link to post Share on other sites
techknight Posted August 2, 2018 Report Share Posted August 2, 2018 (edited) Not always. HOTs are real sensitive to their drive signals, as well as the spikes that appear on the Collector of the transistor. The drive signals could get skewed on the front end, as well as the driven portion. So if the oscillator circuits or driver circuits and its coupling caps drag ass, it can destroy the HOT. As well as any overcurrent conditions on the flyback from either the flyback itself, or any secondary circuitry hooked up to the flyback. the Vertical output stage is hooked up to the flyback as well as other sweep circuits. Also, the B+ voltages divided between the different stages have to be clean as well. if its not clean it can distort the waveform which can destroy the HOT. Edited August 2, 2018 by techknight Quote Link to post Share on other sites
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