WG 19K7601 blowing fuse

[CICA2]

Need a little help with my new Street Fighter II arcade game which got damaged during transport. The top fell and was caught by a bystander while we were trying to lay it on its back. A few capacitors were bent and some of the terminals were yanked off. The bracket which held the P447 monitor circuit board was not secured properly.

I noticed that the CRT cathode (with the suction cup) was ripped out. I aligned the terminals to 6 and 12 o’clock position and plugged it back into the monitor.

Upon reassembly, the game powered on and blew a fuse after a few seconds. I checked the board and found a few capacitors and resistors bent; also one of the legs of the 10K pot controlling the contrast was broken.

I found the Service Manual for K7000 on-line, straightened all of the caps and resistors up. Everything looks good but every time I turn it on, it blows the F1 fuse. 

The monitor is a Wells-Gardner Model 19K7601.

I noticed the R105 thermister has a crack as shown in the picture. Although the circuit diagram shows it being in proximity of the fuse, it is in the degaussing coil circuitry, so I don’t know if it has anything to do with the fuse blowing. I have a replacement thermister on order.

I don’t think the broken contrast 10K pot has anything to do with it either. Nevertheless I am replacing it tomorrow.

I noticed some discoloration on the T2 transformer (Transf – Horiz Driver)

I checked the supply voltage 119.5 VAC, within limits.

Any ideas what is causing the fuse to blow? 

----------------------------------------------------------------
Update:

I replaced the contrast 10K pot.

I isolated the circuit by disconnecting the R103 resistor. Fuse is holding steady proving that R105 thermister is not the problem. The rectifier circuitry outputs 151.1 VDC.

Reconnected R103; disconnected  P5 and P6 terminal strip going to the P456 board.
Also disconnected P1 and P2 coming from the JAMMA board.

I tried to further isolate the board by disconnecting R101. Fizzzz… blown fuse.

Am I going in the right direction here? What should I check next?

[Ken Layton]

Common causes of the fuse being blown:

Shorted power supply diodes.

Shorted degaussing coil. Try leaving it unplugged.

Shorted capacitor C36.

Shorted diode D18

Shorted yoke.

Shorted horizontal output transistor.

Bad flyback (known to fail suddenly on this chassis).

[CICA2]

Many thanks for replying Ken.

1. I think the power supply diodes are D19, 20 21 and 22 on this board. They all look fine physically. I can not check them without unsoldering them. But 151.1 VDC seams like a reasonable 119.5VAC once rectified. Plus the fuse did not blow when I isolated R103 which is feeding the rest of the board. Correct me if I'm wrong but these diodes are ok.

2. Done that. I left the degaussing coil unplugged. No help.

3. C36 I will check this first.

4. D18 I will check this second.

5. Shorted yoke? hmm... I disconnected P6 and P5. No help, although the hardwired T1 Trans Flyback leads were still connected. I will try unsoldering these.

6. Shorted horizontal output transistor. I will need some help locating and diagnosing it. Please understand my background is robotics. Aside from repairing my 37" Mits TV last year, thanks to helpful people and forums similar to this one, I know jack all about monitors.
Is it (what the service manual describes as) the T1 Trans Flyback? I did notice a crack in the housing (I'll post a close up picture next). Again how do I diagnose it?

7. Bad Flyback? er...same as # 6.

Again Ken I appreciate any help I can get. I bought this (perfectly working prior to transport) arcade game for the guys at work out of the goodness of my... bonnus, to boost workplace moral. Unfortunately it backfired when the monitor fell off 

[Ken Layton]

Whenever moving a game, ALWAYS make sure everything inside it is properly secured.

[CICA2]

Update:

Ok, I looked around D18 and C36.

1. I noticed that one of the D18 legs soldering was completely disconnected from the board due to heat damage. I removed it and measured 4.22 M ohms one way and infinity the other.
I think this will have to be changed.

2. All 4 legs of C36 looked shorted at first, but once removed, it checked out ok.

3. The reason C36 looked shorted is because the two leads of Q11 transistor 2S1398 had continuity.
Also I noticed that the input of Q11 was grounded.

4. The only three components on the input of Q11 is C35, R14 and T2 transformer horiz. driver. I removed T2 and found that pin 3 and 4 had continuity, while pins 1 and 2 measured 53 Ohms.

So… change D18, Q11 and T2, right? Anything else I should check?

Oh also attached is the pic of the cracked flyback.

[Ken Layton]

Replace the damper diode (D18), the Horizontal output transistor (Q11) and the flyback.

Transformer T2 is fine --- leave it alone.

[alexred]

It looks like your flyback is cracked and your HOT is shorted which will cause the fuse to blow every time.

[CICA2]

Darn, I was hoping that I would not have to change the flyback.

Got it, D18, Q11 and the T1 flyback.

Is $25 plus $7 shipping reasonable for this new flyback?

[tta583]

Man that looks JUST like the one I just went thought.  D18 had been on fire at one point in time but was replaced by the time I got it.  When you fired up the chassis there was a strong burning smell.  Turned out to be the big sand block resistor on the side of the chassis.  It was getting hot enough that it cracked.  The underside of the board showed several burned up traces as well as some repair attempts.  Further investigation found a 10amp fuse in it.  Apparently it was burning them up so someone decided to give it all that it would eat.

To be honest I just banked on the flyback as bad.  I understand them to be flaky.  I guessed someone started upping the fuse till it started other components and traces started to burn.  I put in a complete bobroberts rescue kit.  Flyback, caps, HOT.  The hot was shorted.  I also had to replace the voltage regulator (Can not recall the component number.  Its and STR something or other.  Its mounted to the inside of the metal heat sync on the left side of the chassis as viewed from the back.)  It was shorted.  That came from Bob as well.  I also replaced D18 for good measure as I did not trust the one in there.  Google NTE cross reference and plug in that Sanyo number for the common NTE PN.  I have some NTE folks in town so I could just walk over and pick one up.  I bet Bob has them as well I just did not think to look.

Bob gets $28 for his rescue kit:
http://www.therealbobroberts.net/k7000.gif
Flyback, caps, hot, and a fuse.

Given that I would say the flyback you found is not a good deal.  Bob starts shipping at like $6 then actual cost if you go over what $6 will ship weight wise (if memory serves).  Even if you don't need the other parts the difference is only like $2 (total) and you have a spare HOT and complete cap kit for a 7000.

[alexred]

I just replaced the flyback and hot on my K7000.  You could try just replacing the other components but if the flyback is bad it will cause your hot to short out and you will be down at least $5.00.  Probably best to replace all the suspect components while you have the chassis out to work on.  To get the old flyback out, I cut all the pins down as close to the pcb as I could without breaking a pad and then sucked all the solder out.  It still took me around 20 minutes to get is out...

[CICA2]

Thanks for the great advices guys. I will do this right the first time and get the kit along with the high speed diode. Bod's prices are far better than I've seen anywhere else or what I would pay locally. His no paypal policy is somewhat of a pain in the rear. Anyway, I will get them on order tomorrow.

Thanks again!

[tta583]

Yeah, no paypal is srot of a pain but not that big of a deal.  I can not blame him.  If for nothing else his margins seem low enough that by the time PP gets a cut it stacks up.  Factor in the games PP plays time to time and I don't blame him one bit.  If it was not for pure convenience and low volume of miscellaneous stuff that I sell on rare occasion I would not mess with them either.

[CICA2]

well? I finally received the parts from Bob Roberts.

Ken, per you suggestion I replaced the Flyback, the horizontal transistor Q11 and the damper diode (D18), for which Bob sent me a FR106 Diode (NTE 558). (see pic below)

I soldered everything in place. Used a continuity tested to test all soldering points. All good. Reconnected all wires.

Power on! ... No picture. 

I can hear the crackling sound of the screen turning on when applying power. No picture. I tried playing with the contrast on the board, screen dials and focus on the flyback... no picture.

Fuse is holding steady. Measured 65 VAC in at the fuse in reference to the frame ground. Measured 120 VAC on the inputs (black and white wire going to the screen).

What should I check next?

Oh BTW I checked continuity on the damper diode D18 right out of the package. No continuity either way. Shouldn't a diode have continuity one way and not the other?

Again, what should I check next?

[Ken Layton]

This is easy. I just had a chassis come in with the same thing. Flyback was shot, Cap c36 was shorted, Horizontal out transistor was dead shorted, fuse was blown. I replaced all those and went to fire it up. Heard the static crackle but no picture and tube filament was not lit. Stuck the high voltage in the anode cup to measure the high voltage as I'm powering it up. Just as I thought: high voltage immediately tries climbing way up to 30,000 volts and shuts down. The only thing it could be is the B+ regulator bad.

This is probably what's happened on yours. Replace that B+ regulator (the STRxxxx one).

[SirPeale]

Oh BTW I checked continuity on the damper diode D18 right out of the package. No continuity either way. Shouldn't a diode have continuity one way and not the other?

Continuity?  No.  Use the diode check.  You should see a junction drop voltage of ~.400-.800 or so.

[CICA2]

Thanks Peale, I didn't know that.

Ken is it IC4 Regulator STR3123 as pointed on the pic attached?

[SirPeale]

Thanks Peale, I didn't know that.

Ken is it IC4 Regulator STR3123 as pointed on the pic attached?

That's the one.

[segasonicfan]

I've ran into this problem many times.  What I find is that it's the diodes to the left of the GIANT capacitor (up right corner of board).  There are 2 diodes and the AC voltages run through and when the fuse keeps blowing it's usually cause these are blown.  check with a mulitmeter test, I bet that's what it is

-Segasonicfan

[alexred]

If the fuse is holding steady, you can lift one end of D10 to disable the HV shutdown and verify it is IC4 that is causing the problem.  Do not keep operating it this way, this is only to troubleshoot.

[CICA2]

Sweeeet, I changed the STR3123 regulator and tha-thaaam! I got picture! 

Took a bit of adjusting, but it looks as attached. As Borat would say, "Niiiice, yes?"

One minor detail, both sides of the screen are cut off. I found the "vert size" pot, but I can not find one for horizontal.  How am I ... Never mind! I just found the black cylindrical shaped thingy on the schematic, entitled "horiz size". I will adjust this next.

Now, I will start restoring the box and figure out why the sound isn't working.

Thank you very much Ken and everyone else for your input. You guys helped me save face and will make a whole bunch of blue collars very happy.


Should I start a new strings for the sound in the audio area? Again the game is Street Fighter II with a Jamma board. The seller said that the sound works "intermitently". The speakers are in place. They are connected to the board. Tried adjusting the volume, not one peep. Any advice on where I should start?

Cheers

CICA