WG6100 blows F100 & F101 on powerup

[scottz29]

Update:
I put everything back together and started connecting things one by one.

Deflection board alone: no problems, spot killer on

P100,P600,P700: No fuse blows! I measured -26V at the 3792, and around +1V on the 3716 on the side of the frame. Spot killer on.

P701: Deflection chatter, same volt readings, spot killer on

P101: Same, spot killer off

Neck connector: Same, 3792 -26V, and 0V to around 3V on the 3716, depending on deflection. I could see the readings go up and down based on the amount of chatter I would hear.

The only thing I have left to connect is the HV cage, which I'm reluctant to do until I verify these readings, as the 3716 doesn't sound right - should be +26V.

 

[modessitt]

Have you replaced that 3716? If you have an LV2000, are both lights on?

Spot killer is off because half your picture is up. Only half because only one of your deflection voltages is there. You can't see it because the HV section isn't plugged in yet....

 

[VectorJunkie]

Neck connector: Same, 2732 -26V, and 0V to around 3V on the 2716, depending on deflection. I could see the readings go up and down based on the amount of chatter I would hear.

The only thing I have left to connect is the HV cage, which I'm reluctant to do until I verify these readings, as the 2716 doesn't sound right - should be +26V.

As Mod said your +1v is why the spot killer is on. If you checked the transistors already, take out the deflection board and look for cold solder joints especially on the header pins where the transistors connect.

-VJ

 

[scottz29]

Have you replaced that 3716? If you have an LV2000, are both lights on?

I did replace all the frame-mounted transistors as part of my capkit. I will pop off that 3716 (on the side of the frame) and test it though. Both lights on the LV2000 are on, and I verified +-26v on pin 3 and 6 of P100 before I started connecting things.

I'll check the header pins on the transistor connectors for cold solder. I didn't reflow new solder into the connector pins like I should have.

Will update tonight...

 

[VectorJunkie]

I did replace all the frame-mounted transistors as part of my capkit. I will pop off that 2716 (on the side of the frame) and test it though. Both lights on the LV2000 are on, and I verified +-26v on pin 3 and 6 of P100 before I started connecting things.

I'll check the header pins on the transistor connectors for cold solder. I didn't reflow new solder into the connector pins like I should have.

Will update tonight...

Yeah, check the headers... I had the same problem with one side at about 1V once I plugged in the transistor. It was +/- 26 on both sides before I connected the plug. It was a cold solder joint on one of the pins.

I wouldn't remove the transistor from the mount to test it. You can test it while mounted by disconnecting it from the deflection PCB header and testing via the pins on the cable. That way your testing the transistor and the mounting in one test.

 

[scottz29]

Out of curiosity, should I check for voltages on the other 4 transistors as well, or just the 2 on the side of the frame? Should the other 3716/92s show the same readings?

 

[modessitt]

Yes, but they're harder to access than the two on the side. I'd just check the two (16 and 92) that are between the deflection PCB and the HV cage. If you get the same voltages there, then I doubt it's a header issue, unless both headers need the same reflowing. if not, then I'd check the header joints to the one that isn't reading properly.

Also, it is quite common for the wires that attach to the sockets for these transformers to break off or be barely hanging on. That would cause no voltage, too...

 

[VectorJunkie]

Out of curiosity, should I check for voltages on the other 4 transistors as well, or just the 2 on the side of the frame? Should the other 2716/32s show the same readings?

You can easily check the voltages of all of the transistors by measuring from the top of the connectors. You will see a small amount of metal exposed for each pin. You can compare those measurements to the ones on the schematic. The voltages will be off some because your lower levels with the LV2000, but they should all be off proportionate to the adjustment difference of the LV2000 which is less by about 10%-15%.

 

[scottz29]

K, I got a few hours to dink around with this again tonight. I was getting intermittent continuity readings between collector and chassis of some of the frame-mounted transistors.

I pulled the deflection board and noticed F600 was blown. I desoldered, cleaned pads, re-soldered, and re-cleaned every solder joint on every pin for every connector. Checked with my loupe and they are all good.

Placed the board back into the frame, checking the transistors along the way, and after plugging everything back in, when I finally plug P600 back in, I get continuity between the collector and frame of Q606 (and therefore Q706).

I am so ready to give up on this beast.

 

[modessitt]

That's because the connector is plugged in. You're reading continuity through the board. that is normal...

 

[VectorJunkie]

K, I got a few hours to dink around with this again tonight. I was getting intermittent continuity readings between collector and chassis of some of the frame-mounted transistors.

I pulled the deflection board and noticed F600 was blown. I desoldered, cleaned pads, re-soldered, and re-cleaned every solder joint on every pin for every connector. Checked with my loupe and they are all good.

Placed the board back into the frame, checking the transistors along the way, and after plugging everything back in, when I finally plug P600 back in, I get continuity between the collector and frame of Q606 (and therefore Q706).

I am so ready to give up on this beast.

Before you plug P600 back in, do you get continuity to the frame and the pins on the header? If you do, that just means that the ground fault is elsewhere. Figure out which pin is grounded on the deflection board header and that helps narrow down where the short is.

If you do not get continuity to ground on the header pins while P600 is unplugged, check the pins on the cable going to the transistors for a ground fault. It sounds like the transistor mounts are good, but that you have a ground fault elsewhere on the boards.

Let us know which pin on the header is grounded and we can tell you what points to test after that by looking at the schematic. If you can read schematics fine, just follow that circuit until you get to the side of a component that isn't grounded. The fault should be between the two points or on a branch between the two points. Repeat for each branch in the circuit until you narrow it down. Then you can pull the components and test them.

That is what I would be doing to find it anyway. Maybe someone knows a better way?

-VJ

 

[modessitt]

If I recall correctly, that "ground fault" you are reading with P600 connected is actually a low-resistance reading through a part on the chassis. I've gotten similar readings on 100% working monitors.

I'd check the diodes and the transistors around Q603 and Q604...

 

[VectorJunkie]

If I recall correctly, that "ground fault" you are reading with P600 connected is actually a low-resistance reading through a part on the chassis. I've gotten similar readings on 100% working monitors.

I'd check the diodes and the transistors around Q603 and Q604...

That's a good point. Is it measuring zero resistance or a small amount which makes the meter beep?

 

[scottz29]

If I recall correctly, that "ground fault" you are reading with P600 connected is actually a low-resistance reading through a part on the chassis.

You recalled correctly sir. It was a low-resistance reading around 3.5-3.9 ohms. Guess I don't always check the meter when testing for continuity - sometimes I just listen for the tone.

Only had a minute to check this before I left for work this morning. Will test the board again tonight and hope resoldering the headers fixes the bad transistor readings.

 

[scottz29]

OK, I hooked this thing back up again. Everything but the HV cage. F600 blows immediately on powerup. R612 is not open.

I have checked damn near every part on this board. Ideas?

 

[scottz29]

Bump - anybody got any ideas on what might be causing this now? Ready to get the axe out...

 

[modessitt]

Might be time to ship it to one of us who have a lot of experience with them.

Frizz beat up on one for a few months before finally crying "Uncle" and sent it to me. I had it fixed less than an hour out of the box...

 

[scottz29]

You have a PM good sir.

 

[scottz29]

Well, not being one to be beaten by an inanimate object, and with the help of a great local klov buddy, I was able to make some progress on this tonight.

Symptom: F600 (3A fuse) blowing on powerup

Found blown Q606 frame transistor! (Didn't realize they blow so easily...pretty much every time you blow a fuse) Replaced it, connected everything and fired up... no high voltage, no deflection chatter, frame was very hot & smelled burning electronics after a few minutes. Jiggled all connectors, and after P100 was touched, high voltage/deflection came on, and had a picture for a few seconds before F600 blew. Shut down, and jiggled connector again and fired up. Had a picture but horizontal collapse (vertical line).

Checked continuity from P100 to transistors Q102/Q103 and found scorched transistor mount on Q102 with poor contact. Cleaned contact & transistor legs and reinstalled. Replaced blown Q606.

Powered up with just deflection board connected. Ran for 30 seconds with no problems or blown fuses. Shut down, connected HV cage and powered back on. After about 5-6 seconds, F600 blows and I get a picture, but just a vertical line as before.

Any ideas what to check next?

 

[VectorJunkie]

Well, not being one to be beaten by an inanimate object, and with the help of a great local klov buddy, I was able to make some progress on this tonight.

Symptom: F600 (3A fuse) blowing on powerup

Found blown Q606 frame transistor! (Didn't realize they blow so easily...pretty much every time you blow a fuse) Replaced it, connected everything and fired up... no high voltage, no deflection chatter, frame was very hot & smelled burning electronics after a few minutes. Jiggled all connectors, and after P100 was touched, high voltage/deflection came on, and had a picture for a few seconds before F600 blew. Shut down, and jiggled connector again and fired up. Had a picture but horizontal collapse (vertical line).

Checked continuity from P100 to transistors Q102/Q103 and found scorched transistor mount on Q102 with poor contact. Cleaned contact & transistor legs and reinstalled. Replaced blown Q606.

Powered up with just deflection board connected. Ran for 30 seconds with no problems or blown fuses. Shut down, connected HV cage and powered back on. After about 5-6 seconds, F600 blows and I get a picture, but just a vertical line as before.

Any ideas what to check next?

You had everything connected except the HV cage and was fine? Then you connected the HV cage and it blew the fuse?

If so, then you need to go through that HV cage. Cold solder joints, visibly damaged components, testing as many components as you can in-circuit, transistor mounts, any visible signs of problems. You might even upload a picture inside the HV cage in case something isn't where it is supposed to be like the wires connecting to the focus assembly, etc.

-VJ