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Wells Gardner D9200 - Horizontal Collapse?
grantspain:
yes diode test is what i use, in general a bad fet or transistor will read a dead short if bad. I have had a transistor fail and not read dead short but will have an odd reading
lilshawn:
i suspect a cap has gone out of spec in the horizontal tuning (search 400 area)... or a FET has gone bad (one of the ones the chassis uses to switch to tune the Hfreq)
also suspect anything attached to CS1/CS2/CS3... find your Hf logic in the table for your frequency you are running and check for shorts in the caps/opens in the resistors/transistors/fets attached to them (IRF640's etc) C455 C456 etc. so on.
Rocketeer2001:
Sorry for the tardiness, it's been a busy week. Finally got some time to work on this today.
Before I put the board back in the cabinet and turn it on without an input signal, I wanted to check over a few more components since the board is already on the workbench.
I read that the deflection yoke could cause horizontal collapse if it's busted, so I tested the resistance of the coils and got 0.2 ohms for the horizontal and 2.3 ohms for the vertical. These numbers seem low, right? Then again, I don't know what the resistance should be on a D9200. If it's noted on the schematics, I couldn't find it. Anyone have a D9200 they could measure to give me a ballpark? I attached a pic so you can see the stellar condition it's in.
I then removed transistor Q418 to check it again. I use my LCR tester to check all sorts of parts, and normally it will identify what the part is and give you a little diagram with the resulting values (see pic of Q428 and Q430 to see what I mean). Q418 was identified as a "resistor", which seems odd to me (see pic). I did a diode test afterwards with my multimeter and I got 0.262V between center and one leg, and 0.334V between center and the other leg, which is what I think are normal, so Idunno.
Following lilshawn's advice, I checked a few other transistors and didn't see any issues. Then checked the big C456 polypropylene capacitor and got 0.304uf as a result (see pic). Schematics say it should be 0.24uf, so that seems close enough. Decided to check the other 4 big polypropylene capacitors but they were all stuck together with some kind of glue, so they had to be removed as a clump (see pic). The results I got are below [figures in these brackets are what the schematics say the values are]:
C430 [1.2uf, 440V] = 1.18uf, ESR 0.23 ohms
C438 [0.39uf, 440V] = 0.303uf, ESR 0.09 ohms
C455 [0.15uf, 250V] = 0.319uf, ESR 0.10 ohms This one looks to be double the value it should be. Too far out of spec?
C475 [394pf, 440V] = 390.4nf, ESR 0.09 ohms This one is rated in picofarads, but my result was in nanofarads. Right numbers, but wrong scale. I should have got 0.3904pf.
What do you guys think is the biggest issue here? The yoke, Q418, or these last couple capacitors? Or all the above?
Rocketeer2001:
Apologies, I'm trying to upload all the photos but I keep getting errors. I'll try again in a bit, I guess.
grantspain:
the transistor reading seems odd to me, i would expect collector/base 0.450 and emitter/base 0.500 or around that sort of range
your yoke looks pretty bad, the yoke in my experience are one of the most common failures on d9200 - they just corrode due to the crt suface paint flaking off and rotting the windings or actually burning out. One of the horizontal pins on the connector has been burning for some time, it could be poor connection
c455 is well out of spec but are you going from the component marking or the schematic, c475 looks to be completely wrong but if its marked 394 then the cap is 390nf
I think first thing to do is check all the codes on the caps and if they all match then replace the yoke connector pin
I am leaning towards corroded yoke but that normally causes dead short to HOT and blows, the fault you have on a chassis with a good yoke would be down to an out of spec high voltage poly cap - it could be any of the poly caps rated from 250v to 1.6kv . An example of this is a polo 25 chassis i had this week whereby the 3.3nf 1.6v cap was bad, chassis ran but eht was high and the width control had no proper range
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