Elecrohome G05-805: Small fire on HV Board

[csa3d]

Elecrohome G05-805: Small fire on Deflection Board

So today I performed the R100/R101 wire mod and game my G05-805 a test run, now that I have recieved working and verified game PCBs for my Asteroids cocktail. I also reflowed all the pins which looked like they could have had loose solder joints.

When I gave everything juice, I neglected to first plug in the anode cap to the monitor. This resulted in a small fire on the HV board.

While I am kicking myself for this mistake, it brings about a few questions as well. Before the questions, here's what parts appear to have been affected going only off visuals:

• 2amp FB fuse at F700 blown
• Small fire around the center most big 6800uF Cap
  
  *note: These caps have both have been replaced with a kit from Bob Roberts prior to this incident *
  • two pinholes around base of said cap at C101
  • R713 fried
  • R718 fried
  • R705 has possible damage due to residual damage

Questions:

1.) What's the repercussions of not having the annode cap hooked to the monitor and giving it juice? Would this have been the sole cause of everything going wrong here or was this a situation where It would have no affect, and I was just lucky it wasn't shorting out on the monitor frame or something other.

2.) I'll assume it's plausible that the anode cap had no effect, and the parts which were burned weren't going to work anyways. Is it as simple as cleaning up the damage, replacing the parts, then give it another go?

3.) What now? Any other suggestions other then replacing parts and giving it another go?

Thanks all. I guess if this was easy it wouldn't be fun... stupid asteroids..
-csa

 

[csa3d]

I picked up a few packs of resistors and replaced four of them which were either fried or slightly charred. I've also removed the the large cap at C101 which had some charring on it, but I'm unsure if it blew or if the resistors around it charred it. Either way, I'm putting in an order for a new one (since I've not found these locally).

So when I get the new one back and installed, should I just plug her in and see what happens? Is this how this hobby works? Unless someone else chimes in, that's the approach I'm going to take, hoping that it was a combination of me being stupid with anode cap not attached and some bad parts on the deflection board which weren't getting juice because R100 and R101 were previously open.

Anyone?

-csa

 

[Dokert]

There is no one standard answer here. It all depends on where the anode was laying as to what you smoked. Normally, if you leave the anode off and it smokes parts all you have to do is replace the toasted parts and everything will fire up.

 

[csa3d]

There is no one standard answer here. It all depends on where the anode was laying as to what you smoked. Normally, if you leave the anode off and it smokes parts all you have to do is replace the toasted parts and everything will fire up.

Ahh, well here's to hoping this was a fluke once my C101 cap arrives and is replaced.

The anode cap was hanging so that the rubber side was resting on the HV cage, which was far away from the mounted deflection board, which is where the fried parts caused a small fire. I don't suspect the anode shorted out anything, but I also wasn't sure that because it was unconnected, if the parts fried due to some open circuit drawing more power, etc.

-csa

 

[csa3d]

Well crap!

I replaced all charred parts mentioned above, plug'd her in after I tripple checked all connections, and the same thing happened again! There is something clearly wrong with this Deflection board other then bad parts.

This time around:

R718 caught fire again, this time damaging C100
R713 burnt up once again
2amp Fuse F700 blew once again.

​

I'm attaching pics, hopefully this will spark some discussion of what do I do next?? This is a repeat situation, and if I don't modify something then replacing the parts will likely yield similar results.

What would be causing those two resistors to keep blowing? Meanwhile, I'll be cleaning the board..

-csa

 

[csa3d]

Ok, I have cleaned the board and replaced (for a second time) all the parts which were damaged. There's no way I'm plugging this in until I test some things.

I have a multimeter handy, just tell me what to check and where to start. I'm thinking the fuse blowing at F700 is where I'd start, but you tell me.. I've got the schematic open, trying to make sense of it all.

Anyone?

-csa

 

[csa3d]

I am attaching a portion of the schematic where my problem is occuring. The parts highlighted in yellow keep blowing. They all seem to be contained in this one area, so the problem seems like at least it's isolated?

So if I remember correctly, electricity flows from positive to negative. This would lead me to believe that power comes in through pin 7 and pin 10 of P100. Can anyone help me trace through this logically, and help me figure out what to test here to ensure that next time I plug this in, these parts don't fry again?

-csa

 

[csa3d]

According to the B&W Vector monitor Faq...

If 2 amp fuses keep blowing:
A. Check the large heat-sinked power transistors.
B. Check D608 and D708 (1N4001)
C. Check semiconductors, especially the transistors in the "X" and "Y" amplifiers.
D. Bad yoke.

What are they referring to with A) the large heat-sinked power transistors? Also, what specifically should I check with C.) ?

I've pulled the Bridge at DB100 to test it out of the circuit. All diodes only conducts in one direction, which is good.. but one of the diodes reports a voltage of almost 1volt lower then the rest of them. I think I'm going to pick up a new one locally and replace it just for piece of mind. Does this have any affect on the issue or not at all? I'm not blowing F100 nor F101, which replacing the bridge seems to fix.

-csa

 

[csa3d]

Who do I need to throw some money at to get some help with this? I'm willing to do so to make some forward progress on this project.

-csa

 

[vctrcollectr]

Have you checked the 4 transistors with the heatsinks for shorts? Also check the diodes,you probably have a short somewhere near the burnt spot.

 

[KevinMullins]

Agreed.....
Typically anytime you have blowing fuses AND burning up parts you have a dead short in either the transistors or diodes.
In your case you need to check ALL the 700 components. ( i.e Q701, Q702, Q703, etc, etc)
Setting your meter to it's "Diode" function and test between the leads of each component looking for anything dead shorted. (.000)
Diodes should read in one direction, but not when the meter leads are reversed.

You can unplug the yoke at P701 and check the resistance on both windings.
Black and Yellow should be your most concern.
Should show minor resistance, but not dead shorted. (.000)

Also double check the entire chassis for bad solder joints.

 

[csa3d]

Just got finished checking the board some more tonight.

Tested all the diodes with the board pulled and diodes all still soldered in place. Four of the diodes reported two-way voltages, where a majority of the diodes work as they are supposed to, only reporting one way voltage. The two way culprits are D606, D607, D706, and D707.

Do I pull these and test again or do I assume they are bad and replace them since they are pulled anyways?

I found one diode at D708 which reported 0.00 voltages on both directions (shorted?) I assume this is a bad guy and needs replaced.

What does shorted vs a reading where you get voltage readings both way mean?

I did a diode test on the four heat sunk transistors. Only one of the three transistors seems to give me a one way voltage reading. The others all give me reading going both directions. On that matter, a bunch of the transistors on the board appear to give me two way readings.

Do I need to pull transistors to test them properly? All the documentation on testing transistors leads me to believe I should be getting only one way readings per leg pairing, yes?

Thanks again for the help!
-csa

EDIT: D606, D607, D706, and D707 are all IN914 diodes (switching). Do I test these differently then regular diodes? Are these considered Zener diodes?

 

[vctrcollectr]

Definately replace d708,the others will sometimes give you a reading both ways in circuit.Sounds like you might have found the culprit.

 

[csa3d]

I did a diode test on the four heat sunk transistors. Only one of the three transistors seems to give me a one way voltage reading. The others all give me reading going both directions. On that matter, a bunch of the transistors on the board appear to give me two way readings.

Do I need to pull transistors to test them properly? All the documentation on testing transistors leads me to believe I should be getting only one way readings per leg pairing, yes?

So any opinion about these here transistors?

-csa

 

[Maxstang]

You have to remove the transistors to test them correctly. If you have the 6100 monitor faq there is an excellent section on testing transistors. With your meter set to diode test you're going to check these three readings in BOTH DIRECTIONS (reversing your black and red probes). 1) between the two legs of the transistor. 2) between on leg and the body of the transistor and 3) between the other leg and the body of the transistor. Here's a relevant portion of the faq:

Set your meter to the diode test. Connect the red meter lead to the base of the transistor. Connect the black meter lead to the emitter. A good NPN transistor will read a JUNCTION DROP voltage of between 0.45v and 0.9v. A good PNP transistor will read OPEN. Leave the red meter lead on the base and move the black lead to the collector. The reading should be the same as the previous test. Reverse the meter leads in your hands and repeat the test. This time, connect the black meter lead to the base of the transistor. Connect the red meter lead to the emitter. A good PNP transistor will read a JUNCTION DROP voltage of between 0.45v and 0.9v. A good NPN transistor will read OPEN. Leave the black meter lead on the base and move the red lead to the collector. The reading should be the same as the previous test. Place one meter lead on the collector, the other on the emitter. The meter should read OPEN. Reverse your meter leads. The meter should read OPEN. This is the same for both NPN and PNP transistors.

 

[csa3d]

You can unplug the yoke at P701 and check the resistance on both windings.
Black and Yellow should be your most concern.
Should show minor resistance, but not dead shorted. (.000)

I've read this a few times and for whatever reason, this isn't making sense to me. If I unplug the 4 pin connector at P701, what am I testing resistance on? Am I doing this while powered off still? I'm not familiar with a yoke, so maybe that's my blocker.

Thanks in advance, slowly getting through this

-csa

 

[csa3d]

You have to remove the transistors to test them correctly. If you have the 6100 monitor faq there is an excellent section on testing transistors. With your meter set to diode test you're going to check these three readings in BOTH DIRECTIONS (reversing your black and red probes). 1) between the two legs of the transistor. 2) between on leg and the body of the transistor and 3) between the other leg and the body of the transistor. Here's a relevant portion of the faq:

Set your meter to the diode test. Connect the red meter lead to the base of the transistor. Connect the black meter lead to the emitter. A good NPN transistor will read a JUNCTION DROP voltage of between 0.45v and 0.9v. A good PNP transistor will read OPEN. Leave the red meter lead on the base and move the black lead to the collector. The reading should be the same as the previous test. Reverse the meter leads in your hands and repeat the test. This time, connect the black meter lead to the base of the transistor. Connect the red meter lead to the emitter. A good PNP transistor will read a JUNCTION DROP voltage of between 0.45v and 0.9v. A good NPN transistor will read OPEN. Leave the black meter lead on the base and move the red lead to the collector. The reading should be the same as the previous test. Place one meter lead on the collector, the other on the emitter. The meter should read OPEN. Reverse your meter leads. The meter should read OPEN. This is the same for both NPN and PNP transistors.

Ah, makes sense then why the readings I were getting all seemed off. Do you think I should just go purchase 4 new sinks and replace them? Are they expensive? Removing parts seems like a lot of hassle to put the old ones back in personally. Though, searching RatShack I didn't seem them locally available.. just curious.

Thanks
-csa

 

[KevinMullins]

I've read this a few times and for whatever reason, this isn't making sense to me. If I unplug the 4 pin connector at P701, what am I testing resistance on? Am I doing this while powered off still? I'm not familiar with a yoke, so maybe that's my blocker.

Absolutely OFF .... do any of these tests with power OFF.

Set your meter to the resistance scale, the Omega looking symbol, say on a 200 range.
Doesn't matter which color lead you put where, but probe the 4 wire connector directly where the wires come into that connector.
So one lead will be in where the yellow wire is and the other lead will be where the black wire is.
They should NOT show a direct short.
And you can also do the other pair of wires, but I'm certain the yellow and black are the ones you need to be concerned with.

My 6100 is not accessible at the moment otherwise I'd grab a pic and draw arrows up for ya.

Removing parts seems like a lot of hassle to put the old ones back in personally.

But it's better to be certain rather than to burn other stuff up.

Though, searching RatShack I didn't seem them locally available.. just curious.

Doubt you'll find much of anything for that 6100 at RS.

 

[csa3d]

Absolutely OFF .... do any of these tests with power OFF.

Set your meter to the resistance scale, the Omega looking symbol, say on a 200 range.
Doesn't matter which color lead you put where, but probe the 4 wire connector directly where the wires come into that connector.
So one lead will be in where the yellow wire is and the other lead will be where the black wire is.
They should NOT show a direct short.
And you can also do the other pair of wires, but I'm certain the yellow and black are the ones you need to be concerned with.

Gotchya. This is super clear now, thanks!

But it's better to be certain rather than to burn other stuff up.

Yeah, burning up stuff sucks some fun out of it for sure!

Ok, thanks again to all who have suggested things. Looks like my battle plan for the weekend is to replace the shorted diode, unsolder and check Q707,Q706, Q607, and Q606, and also all transistors in the 700 range, and check the P701 connector for shorts. That should keep me busy over the weekend.

-csa

 

[csa3d]

OMG.. super frustrated.. R713 and F700 continue to blow!!

Today I yanked every single transistor (including the heat sinked ones ) off the deflection board and tested each one out of the circuit.. even the 500s and 600s just because I was in the mood. I found one transistor at Q703 which was shorted, and has since been replaced. Yay.. progress.

I replaced R713 again and F700 and plugged her in. Fire in the HOLE! (literally). *Insert swears like Cubert* Looks like I'm no further then I was before with the problem.. which means there's something else I've overlooked.

I metered my Yolk's yellow and black pair as Kevin suggested. I get readings around 2.1 either direction. Doesn't look shorted to me.

Any suggestions here? I had thought for sure I now have this issue licked seeing how I found and replaced a shorted diode and a shorted transistor in the 700 range...

The only things I can think to do is yank every 700 diode off the board and test them out of the loop.. is that necessary though? I've tested each on the board and is how I found the first one shorted.

Also, do I need to start looking outside this deflection board for problems coming in? Those four transistors on the side of chasis (which I had replaced as well)? Something on the high voltage board coming into the deflection?

Please send me a beacon pros!

-csa