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Wells Gardner D9200 - Horizontal Collapse?
Rocketeer2001:
That's the impression I was getting looking at all the ones for sale. Thanks for clarifying!
The replacement transistor has arrived, and the MG Chemicals silicone compound has also arrived. Now I'm just waiting on the mica.
Rocketeer2001:
I'm back!
Got the replacement transistor for Q418, the MG silicone heat compound, and the mica sheets. I think the quality of mica sheets has severely declined since the early 2000's. I could only order them in a pack of 20, and out of all those only 1 looked somewhat better than what I already had.
Anyways, put all that stuff back on the board, put the board back in the cabinet, turned it on and....nothing. I get the *thump* sound when I flick on the power, and the neck tube is glowing, and I can hear a relay clicking 3 separate times, but the screen is black and it doesn't do that frightening electrostatic sizzle a tube typically makes when it energizes.
Seems like I have a power problem now. I don't think I hooked up any wires incorrectly, but I'll go double check. If not that, what else? The flyback? Q401, Q425, IC101, or IC403?
One step forward, two steps back... :banghead:
grantspain:
does the sheet fully cover the transistor metal body?
Rocketeer2001:
Yup! It's the same size as the old one.
lilshawn:
upstream from the transistor is a fet that can sometime get plotzed when the main transistors go. it'd be Q413. double check that D417 diode pack too if you haven't already. it's hard to tell what the problem is with these monitors since every single system is separate in these chassis, since it sounds like no HV is being produced now... but not sure since you can't actually tell if having the Q418 in there now is working and you have deflection... but can't see it cause of no HV.
if no hv sounds (and not just a horizontal line) you may have to go upstream from both those systems and look at the "h-outctrl" signal coming from the main IC driver chip (IC301 pin 21). if effs off in a tee and one direction goes to the horizontal Yoke drive circuit and the other goes to the drive circuit for the flyback. i'm dealing with a similar issue with a D9200 with "the jitters" and have been pouring over this area for a while trying to find the issue... so i've been getting very familiar with it.
anyway, sounds like maybe that signal has now stopped since you have no HV and previously you did. there is a bit of shared circuitry so it's possible for a failure in one to effect the other. could be worth looking into Q423 Q424... Q426 and Q427. they are pre-pre-drive transistors and pre-drive mosfets used to drive their respective transformers (T404 and T405) that fire off the h-deflection (2SC5144) and HOT transistors (2SC4770). this is the beginning of the "tee"
make sure you have a +32v power coming in to this part of the circuit at R470, this is the juice used to make the pulses in the transformers by grounding out the other transformers leg to ground through the pre-drive mosfets.
might be a problem with Q413 or D418, since the 170v drive that flows through the 2SC5144 flows through this fet and diode, and grounding that 170v out through an improperly attached 5144 can cause a huge amount of current to go through Q413 and D418. check and make sure you have 170v here as well. if not, you have an issue further up the chain in the power supply (possible blown out R854 or D814 or open L801).