Ordyne said:
This is probably where i'd look at first for something blowing F1 constantly - at least one of those diodes would be a likely suspect and TR20 would also cause that kind of thing going short.
It is also very possible (and easily done) with the cramped design on the 9000's to accidentally twist legs together or touch two components together (resistor and transistor for example) that weren't supposed to be directly connected - do a thorough visual inspection in that area using the schematic as your guide.
Ordyne said:
Craig, we sincerely appreciate the vast wealth of knowledge members like yourself and Grant have accumulated over the years - without one of you on speed dial we have only the internet or experience to turn to and as a like-minded community we try to help each other. I don't think your intention was anything other than supportive either, flat text on a screen is easy to misinterpret but consideration at the input stage is well appreciated.
There are many of us who have gotten into these kind of repairs later in life and want to soak up the knowledge that is out there and want to learn. If you and/or Grant decided to run a weekend monitor repair bootcamp believe me, i'd be there for one.
We all appreciate that there are seriously lethal voltages just waiting to get you and most of us take the appropriate - or probably more precautions than necessary (levitating while one arm has been gaffer taped behind you etc).
If it was within your power to do a more comprehensive flow-chart than the nearly 30 year old ones that are being used we'd welcome it.
It would be really nice to see these all in fix-logs as there's always a number of problems with a blank screen on these hantarex chassis - is it the B+, is it TH1 or TH2 (the mini transformer before the HOT), is the HOT, is it the LOPT.
I love reading a good fix log "Monitor was dead, on investigation, B+ was 186 even with a load applied, checked all PSU section, all seemed good at first but finally the problem was traced down to R99 being way out of spec - replaced R99 and now have 130v but screen still won't start, HOT ok, no shorted windings on flyback. Lifted one leg of D10 - still nothing. Visual inspection underneath reveals a cracked trace leading to pin 3 on the scan coil connector - patched the trace and the screen came up, a few minor adjustment faults and a missing red colour which was a bad neck card transistor - replaced all 3 for insurance and did a recap after finding a number of quite bulged electrolytics. Ran over the poly's to test for spec, all ok now. Adjusted using an RGB test pattern and..... {insert picture of perfectly working monitor saved from the dead}"
You bet those get bookmarked and filed under the "try this next time" folder.
But its the working out that's important and with that I would implore anyone with a higher level of understanding to help us who are not there yet to go that one step closer - the experts aren't going to be around forever so its important that the knowledge is passed down to those with interest - lest all our cabs will get LCD's about 20 years before they need to!
if you don't want to look up the transistor to see if it's NPN or PNP then just make sure you have nothing or a junction drop in every possible combination, it's a dirty way of testing but quick and easy. This won't work with mosfets as they are a different animal.
