Did I kill this chassis?

HornNerd

Member

Donor 2013
Joined
Aug 5, 2013
Messages
71
Reaction score
4
Location
Henderson, Nevada
It was working pretty good except for some curling. I read about how to adjust the B+ voltage to 120v. I did. I was pretty happy up to this point then.....I dropped my screwdriver into the chassis. Sparks flew and now I have nothing.

Since then I've replaced voltage regulator, horizontal transistor, fly back, b+ filter and 1.25 pigtail that was blown after the screwdriver drop. 3 Amp pigtail is testing fine.

Caps had been replaced recently by previous owner so I haven't touched them.

Please see the photo to see w
cb55d6614378e8802a8479f0a0924d6f.jpg
here the screwdriver landed. Maybe that will help in finding the problem. Any help is greatly appreciated. Please advise.
 
remove X701 and see if it fires up and if it does your VR is crapped out.
 
Stuck at 160v. I tried turning the pot and it won't change.

You are in HV shutdown.

You probably just shorted and ruined the voltage regulator. The flow chart would have you pull x701, plug it in and see if you get a picture.

I'd skip that step, pull the VR and test it.
 
Sorry I'm still learning. Is this the x701?
4ba3588b05c107267d5802277e7b9101.jpg


I don't remember tge part # off hand, but it is similar to that. If you pulled it from position x701, that was the proper thing to do.

Also I replaced the VR after the short.

I forgot that you had said this.

Hard to say with certainty at this point. Pull r908 and r912 and test. Also FR401.
 
Ok so I pulled x701 and it didn't fire up. Then I noticed that one of the pins from the fly back I had either missed or did a poor job on so I reflowed all pins and it fired up.
A couple more issues though.
1. B+ voltage is now between 99.3 and 100.3 at maxed out position. How can I correct this?

2. I want to put back x701 right? But I didn't make note of what direction it came out. I see three letter on the board for each leg. E C and B?
Picutres attached.
cac55b39c6824d2774d8d53d057f56c3.jpg
cb9cbe2c92671c0886b90d4b4936e213.jpg
 
The center leg is your collector (C)

The flat part with writing will face away from the flyback.

It should kind of go in only one way unless you tweaked the legs a bunch. :)

Give us a B+ measurement after you put X701 back in.
 
pull and test R908 first

If it's 47k ohms (or very close) it's not the problem

Then try R912 (I forget the ohms on it off hand)
 
Correct me if I'm doing this wrong on the multimeter.
R908
116c115198f429f4e383bc2351f1aedf.jpg


R912 color bands are grey red yellow gold
65cf01bbbecbdeb508889eb36f77384d.jpg


They look good to me but let me know.

By the way I truly appreciate all the help so far.
 
Correct me if I'm doing this wrong on the multimeter.
R908
116c115198f429f4e383bc2351f1aedf.jpg


R912 color bands are grey red yellow gold
65cf01bbbecbdeb508889eb36f77384d.jpg


They look good to me but let me know.

By the way I truly appreciate all the help so far.

yeah I think those measurements are good. I think 47k and 820k are the 2 values now that I think about it.

Double check your solder work again.

Throw the old flyback in just for kicks and see if the b+ changes.
 
Oh crap. I threw out the old fly back. I knew I should of kept it. I'm new at this I don't have more parts on hand.

You had mentioned to test FR401 earlier and upon visual inspection it looks pretty baked. Should I try this? If so how do test this?
44a0f2159d3a1369b40f9084013b1ca7.jpg
 
Oh crap. I threw out the old fly back. I knew I should of kept it. I'm new at this I don't have more parts on hand.

You had mentioned to test FR401 earlier and upon visual inspection it looks pretty baked. Should I try this? If so how do test this?
44a0f2159d3a1369b40f9084013b1ca7.jpg

it's 68 ohms , same as you tested the other resistors, only not on as high of a setting.
 
When you dropped the screwdriver, you likely blew transistors X901 and X902 in the power supply section. There's also the possibility that fusible resistor FR901 (220 ohms at half watt) has blown.
 
FR401 tested fine
I'm considering running jumper wires from each of the 8 fly back pins because I noticed that the pads on some of them where damaged. I don't know if I did it or if it was done by the previous guy. Do you think it's a good idea? Could this be causing the he B+ voltage to be too low if one is not making contact?
Hi Ken, thanks for chiming in.
Can I buy X901, X902 and FR901 somewhere? Haven't tested them yet, just wondering.
 
Never mind I think that was a dumb idea. I did continuity test on all pins and they passed. Except 2 and 6. I don't know where they trace.
 
FR401 tested fine
I'm considering running jumper wires from each of the 8 fly back pins because I noticed that the pads on some of them where damaged. I don't know if I did it or if it was done by the previous guy. Do you think it's a good idea? Could this be causing the he B+ voltage to be too low if one is not making contact?
Hi Ken, thanks for chiming in.
Can I buy X901, X902 and FR901 somewhere? Haven't tested them yet, just wondering.

i stock about every part for that chassis and others. let me know if you have trouble finding anything on our site.
 
Back
Top Bottom