CurtPalme.com Home Theater Forum

[JustGreg]

Hi mac. Thank you for looking. Yeah I only have page 1 of 3 for that version too. I didn't really expect a reply but a couple days ago I asked Spellman for a schematic. So far they've lived up to my initial expectations...bupkus. Probably because a version of it is still a current offering to VDC?
Anyway, I need to learn how to test FET's, MOSFETS, regulators, etc. In this case, Q1 and Q2-(HGT)G12N60C3D, MOS gated high voltage switching IC. (24A, 600V, N-channel IGBT) I'd also like to know how to test the three (Q3, Q4, Q5) 2SC4636 HV transistors.

I've found a couple 'teaching hospital' procedures but haven't had the time to ask someone with your skills what would be the best Go/NoGo test for the casual hobbyist like myself.

BTW..I 'think' I may have found the problem with this ps. I found a couple mismarked resistors I replaced at R3 and R4. They're supposed to be 2.2R but the ones I replaced them with tested out at 2.2K! I'm going to be eating a large portion of humble pie if it turns out to be them because I tested every other new component EXCEPT those two prior to installing. I didn't plan to replace them but picked them up at the last minute when I went out for parts for our whole house radio/intercom I was updating. And yes...the package says they're 2.2R so I DID grab the correct ones.

Another lesson learned regardless of whether it runs after or not.

[Nashou66]

Yep those are 2.2 ohm, Just measured mine and mine are out of spec at 4 ohm but that shouldn't matter too much.

The CB resistor is 100ohm as I checked on mine just now.

Those 2.2 ohm resistors are inline on a transformer so that could be the issue. Lets see what happens when you swap them out.

Athanasios

[JustGreg]

WOOOHOOOO! Let there be light!

Lesson to every newb electronics hobbyist across the internet...TEST YOUR NEW COMPONENTS BEFORE INSTALLATION!!!!

I'm still going to replace the NTE 560K's with Ohmites tho. B&R rasters are lit even when adjusted down to 10. Light output drops as contrast is adjusted down so that's working normally. I'll have to search for the answer to that...I read it somewhere recently.

Now I can finish hanging the pj in it's new TD location and move on to the part I USED to dread about a full setup.

EDIT: Found the info...I have to increase the 560K's to 680K's.

[Nashou66]

Congrats!


Try adjusting G2's for now but it might be the resistors. I found that some supplies will cause this issue even with the in spec value replacement 560k's. The ones I replaced were at 680K way out of spec. With the correct value of 560K i got the lit up raster like you mention. Not sure why but...

I have a theory and it could be wrong. All the other parts also are out of spec. I am sure wont matter but there has to be an explanation. I tested this over and over on my one 34.9 supply. No matter what, i got the same results till i put a value resistor in that was the same as the out of spec ones. G2 values went back to normal etc. A few others have also had the same results while others have never seen this after replacing them.

EDIT!!!


And greg I only went to the 680 as that was the average of the old ones I took out. I hope you saved yours so you can measure them up and then use the average, its what i did.

I still have that supply and plan to revisit it some time. I only changed out the Carbon comps , so i should look at the other resistors as well.

Have fun with the set up, i am sure we'll hear from you

Athanasios

[JustGreg]

I did (do) save the old parts. That's where I got the 2.2R's from that I just put back in. (I got that tip from one of your posts).

As a matter of fact I just got done testing all the 560k's I pulled from both supplies. All 12 averaged 639.08k. Hardly 560k. A couple of them were at 651k.

R12, 18, and 24 are supposed to be 10M. I don't know about your ps but the values in mine are higher. Due to their nature I didn't touch them and won't. For now I'll make up for their drift at the '560k' resistors until you've had time to look into it more.

I don't believe we'll be able to correct the overvoltage upstream because the problem might be resistor drift related in the potted section. Because it isn't worth it to get in there to replace anything I 'think', with the right high voltage meter, the pots at OVP-R35 and KV_R36 could be adjusted to compensate..... Something I won't be doing regardless of having the correct meter or not. I've had enough of HVPS's to last me a lifetime.

Oh yeah....humble pie tastes like $HIT!!

[Nashou66]

The potted section does not have anything to do with the G2 voltages as far as i know. Yes and really do not change anything but the Carbon Comps unless a resistor is fried or something which usually means something else is wrong.

So id go with 640 kohm ohmites then.

I want to experiment in one of my old supplies with tantalum resistors on the g2 lines. Expensive at about 10 bucks each, but i am the curious type.
Might not make any difference but what the heck, you never know till you try

nashou

[JustGreg]

I'm not going to touch anything else except for the new 640k's.

Looking at the schematic I see you're correct...G2's are fed by a single line from T2 of the flyback straight out to the unpotted section.

Strange thing about the way it is right now is that the green raster isn't lit but B&R are at contrast of 50 and default G2 values.

[Nashou66]

[JustGreg]