Tuesday, August 10, 2010

SuperSprint Repair - Pt 9 - Repair complete!

I played my game last night for the first time in 10 years. I am VERY grateful to all who helped me on this project.

Monday, August 09, 2010

SuperSprint Repair - Pt 8 - Drawing a blank, or not!

Victory! Well, actually just progress. I replaced Q201 & Q202 in the blanking circuit. That gave me a picture (FINALLY!), but it was still heavily blue biased (see pic 1). For good measure, I also replaced Q205 & Q208 in the main board blue drive circuits. For a few glorious minutes, I had correct color. Then it returned to blue biased again???

Next, I swapped the Red and Blue neck board transistors (Q401, Q403) with no change. After that, I pulled all the pins from the RGB feed to the neckboard (except T) and began playing mix-n-match with jumpers. No matter what happened, sending a signal to the blue input resulted in a blue that was too strong. Diagnosis; Problem is not in the mainboard.

To diagnose the problem further, I lifted the final current limiting resistors (3) feeding the RGB pins on the tube. No picture (black) as expected. But to my surprise when I cranked up the screen control near max, the image began appearing faintly on screen. (cross talk?). Anyway, I jumpered from the each drive circuit to KR, KG, KB. Consistently, whenever any signal was applied to KR or KG, it looked normal (pic 2). But when that same signal was applied to KB, I got an overly bright blue screen (pic 3). Diagnosis; Problem is not in the neckboard.

At this point, I believe there is a problem with the blue gun. But, testing it against H, and every other pin on the neck I get no short and >1Mohm resistance. And the blue ends at the well defined edge of the raster. However, if I turn up the screen, I get raster lines that are blue, and a blue "background" where there should be white raster.

By playing with the drive pots and the screen control, I manage to get a proper picture (pic 4), but the blue pot is all the way down and the other pots are all the way up. Also, the screen seems set a little high at about 11o'clock. At 9 o'clock there is practically no image at all. It's usable, but I wonder about running these pots hard at one end or the other.

Conclusion: It's playable but I'm still not certain where the blue problem lies. I had speculated that the problem was a "hot" blue gun and a weak red and green because of how I set the pots. However, with a good picture on screen, final K voltages are R-87.2, G-88.7, B-101.0 vs 88.3VDC spec for all. What confuses me is that *dropping* the blue gun to 88.3 dramatically increases blue bias and creates raster lines on screen. Perhaps's an inverse coupling of K voltage and screen brightness is normal and I just don't understanding completely how the CRT works.

SuperSprint Repair - Pt 7 - Feeling Blue

A fellow collector suggested it may be the tube and reminded me that it is possible that the blue gun is shorted and staying on when the heater has power, creating the blue screen. I'm not sure about that as I thought losing blue when I left the blue gun out of circuit would contraindicate a gun failure?  Also, I was under the impression that a shorted gun wouldn't leave a clean black border between the image and the tube edge. Hmmm.... To be sure I tested H-KG, H-KB, H-KR and found no shorts between the heater and any of the colors.

Next, I unseated two of the resistors before the neck socket, removing input to those guns. With only green remaining, I got the image above, only in green. When I jumpered in Red off the green drive next circuit (pre-resistor), same image in yellow (red+green=yellow). When I jumpered in blue, I got a light cyan. From this, it appears that all my tube colors are functioning properly as yellow and cyan are the secondary colors of the respective pairs.

Not knowing where to turn, I tested all the resistors on the neck board (in spec), checked the pots against one another (same), swapped Q401 (green) and Q403 (blue), and re-flowed ALL of the neckboard (400 series) connections. When tested, I get the same image pictured above, only in white (YEA!!). Not there yet, but it appears I may have solved the dominant color issue.

Before calling it quits, I pulled and tested Q201, Q202 in the blanking circuit. I don't have a control to compare them to, but they tested similar to one another with ~0.694 across one junction and open across all others. I think I will replace these for good measure.

SuperSprint Repair - Pt 6 - New Voltage Regulator

Replacing the VR & HOT brought my B+ back up to 122.5V got me raster. Not white raster, but bright blue. Still not out of the woods yet, as all I can get is a blue screen with regularly spaced horizontal and diagonal lines (see green pic earlier in this, substitute blue for green). Lines are present in the screen shown, but not visible in the photograph.

I removed the Q403 (blue drive - neckboard) and the main body of the screen is light blue with bright blue diagonal lines. Top and bottom edges are well defined with a black border. L&R are scalloped in, forming a sort of letter "I" shape. Removing the RBG connection between the main board and the neck board cleaned up the edges nice and straight once, but that may be a fluke as I haven't been able to reproduce it again.

So far;

- Removed game PCB feed, no change.
- Removed RGB feed from chassis to neckboard, no change.
- Removed Q403 (blue drive transistor), colors lightened, images remained the same.
- Lifted R415 where it meets the neckboard. Color changed to yellow, but the image is the same.

I'm stumped. Fromm diagram suggests Q201, Q202, but with the neck feed disconnected, they are out of circuit. Am I seeing a failure in the oscillator and hence no change when it's disconnected from the neckboard?

Monday, July 19, 2010

SuperSprint Repair - Pt 5 - Flyback replacement

Yea!! The replacement flyback for my K4900 monitor arrived from ArcadeCup today, and tonight I may get to see my SuperSprint's face for the first time in almost 10 years! First, I begin by getting all my tools and parts together.

Fig 1 - Chassis and new flyback.

Desoldering the old flyback is a tedious process involving lots of time, patience, and soldering wick. The posts are fairly large solder joints, so braid was a little slow. Here is where I really wish I had a solder sucker.

Fig 2 & 3 - Old flyback removed from chassis.

Taking the old flyback out took forever, but installing the new one took just a few minutes. The trickiest part is holding it still until you can get a few colder connections in place. To simplify that, I press the flyback into position and use a pair of hemostats to grip the legs and hold it tight to the circuit board. One connect on each side, and you can remove the hemostats. Since the legs are all in a circle, and the flyback is large, the next 8 connections are quick and easy.

Fig 4 - Brand new flyback in place

With everything in place, it's time to give her a test run. At first, she displays a very nice playfield, a little out of focus, small, and washed out but otherwise colored correctly. A few degrees on the focus pot, and she looks better. Suddenly, the screen goes pure bright green with horizontal lines every 1" or so. I shut her down and check all connections but find nothing amiss.

Second try is a repeat of the first. Starts out normal, goes green, and then after awhile, the screen goes dark for about 60 seconds and comes back with a definite blue tint.

Fig 5 & 6 - Blue shrunken screen
Note: Circular "waves" are a camera artifact.

Checking B+ at TP91 reveals it's only 100VDC and Fromm's points to the voltage regulator. This is a new regulator, but it's a slightly different part number (STR381 vs STR380). Not having another STR380, I decide to try the original. Bad move. She blew the main fuse immediately on power up. After replacing the main fuse and STR381, she no longer has a picture or heater glow. To make matters worse, while testing various voltages I see a ribbon of smoke and smell R503 overheating. I shut her down, and find the HOT is shorted. Man I hope it's just the HOT and VR IC.

Tomorrow I'll call Zannen again and order another VR and HOT...

Friday, July 16, 2010

SuperSprint Repair - Pt 3 - Power supply circuit

My parts arrived last night, and that means that the Super Sprint might be about to open her eyes for the first time in 10 years.  To be replaced are a 3.3ohm resistor (R601), a horizontal output transistor (2SD870), and voltage regulator (STR380).

Fig1 - The new parts

First, we replace the horizontal output transistor (HOT)

Then the voltage regulator. That's the quarter sized component
located in the square metal box.

And last, the open power resistor (3.3ohm, 10W) that sits between the rectifier and
the voltage regulator. In this picture, that's the smaller white rectangular
component bolted to the chassis on the right.

With the repairs completed, it's time for a power on test. And......  No joy.
Quite the opposite in fact. The large power resistor (R503 - 180ohm, 25W)
became very hot and the output transistor blew again. Looks like it's the
flyback after all.  Now to go find one of those. Man is working on 30yr
old technology a challenge...

EDIT: Found a reproduction K4900 flyback thanks to Chad at ArcadeCup.

If you've made it this far in the series, you're probably a geek. If so, you can find the technical details of the repair on the KLOV forum

Thursday, July 15, 2010

Golden Tee '97 - A new project for the Arcade

Not quite sure what I'm going to do with this one yet.  Might refinish it, might part it out, might sell it.  Whatever happens, here is my newest project.

Fig. 1- The new machine

Fig. 2 - The control panel needs a little work and someone murdered the coin acceptor trying to make it play.

Fig 3 - Left side

Fig 4 - Wells Gardner 25K7131 monitor works perfectly.

Fig 5 - Rear view of the coin mechs and bill acceptor.  Obviously one coin acceptor is badly damaged by efforts to make it free play.

Fig 6 - Cabinet needs some work

Fig 7 - The serial plate

To be continued.....

Foosball Table rejuvenation

Today my wife calls and tells me to pickup a foosball table she bought on Craigslist for $25. Expecting a WalMart Christmas toy, I do my husbandly duty. When I arrive, I am surprised to see a rather nice looking table that hasn't been cared for.  The play surface is practically new, and the cabinet shows little sign of wear, except for some scratches.  But, the legs are loose, the top is racked, and one end comes off completely when you try and lift it. Most of the damage came from not tightening the leg bolts and letting the glue joints take the load for mechanical fasteners.  Since I'm a woodworker, I can see that she needs some TLC but is far from a lost cause.  Here's what followed over the next few hours;

Fig 1 - Taking the table apart
Notice the cabinet end laying in the floor?  No tools neccessary to remove it...

Fig 2 - The Leg Brackets
Almost all of the brackets were removed, pre-drilled for screws, glued with polyurethane glue (Gorilla Glue), and reattached. This picture shows on after reattachment.  Shortly after this picture was taken, polyurethane foam would bubble out these T-nut holes.  Messy cleanup....

Fig 3 - The playfield
The playfield was flat and supported by these MDF struts, but as designed it could easily warp in the future..  I removed them, reattaching them edgewise with with glue and screws and "clamped" them to a smooth flat surface. Once dry, this playfield will remain flat for a long time.  It was attached with drywall screws but will be reattached with proper furniture screws.

Fig 4 - The end plates
One plate (shown) required a lot of work to get right.  Brads were used for fasteners, and the glue appeared to be hot glue?!?  All joins were broken, cleaned, and reassembled with poly glue and screws.

Fig 5 - Reassembly
During reassembly, all joints were clamped to keep them flush and tight.  This will result in a cabinet that is tight with no gaps.Many bolts were completely missing and had to be replaced.

Fig 6 & 7 - The end result
Now back together the table is tight and solid.  Total costs was about $5 worth of parts and glue (all on hand) and about 3 hours time.

So was it worth it?  I think so.  For $30 and a few hours work, we got a great looking foosball table that retails for $475 new.

Tuesday, July 13, 2010

SuperSprint Repair - Pt 2 - Installing a cap kit

With the monitor removed and on the bench, the repairs begin.

Fig 1 - Game disassembly

Diagnostics indicate that the chassis has several problems.  At the least, it needs a new power resistor (R601, 3.3ohm 10 W), horizontal output transistor (HOT - Q352, 2SD870), and "cap kit"

Fig 2- Well Gardner 19K4915 Medium Resolution Chassis

First, we install a "cap kit".  This means that we replace all the electrolytic capacitors that may have dried out with age.  In the pictures below, these are the little black can shaped components

Fig 3 - Getting Started

With the cap kit installed, it's time to double check my work and resolder any connections that look iffy

Figure 2 - Chassis Board solder side.

More parts are on order, so the next steps will have to wait for now.  In our next installment, I'll install a new horizontal output transistor (HOT), power resistor and voltage regulator.

SuperSprint Repair - Part 1 - It begins....

Many years ago, I purchased an Atari Super Sprint arcade game. It entertained visitors at my house in Stone Mountain for years, including one all night "drinking and driving" marathon.  Sadly one day the screen of this beloved game suddenly went dark.

The game will play "in the blind", but basic troubleshooting (fuses, power) revealed little other than the monitor was the not working.  So, I hauled the monitor off to an arcade repair shop where they declared the monitor chassis dead,unrepairable, and parts unavailable (it is a 1982 machine, after all).  After 2-3 unsuccessful attempts to purchase parts off eBay, it appeared my Super Sprint was doomed to stay dark forever.

About that time, I got engaged to my beautiful bride Michele, and video games took a back seat to weddings, houses, and picket fences.  During the move, my Super Sprint got relegated to the corner of my new workshop where it would sit for almost 10 years....

Recently during the process of converting an old Mortal Kombat arcade cabinet to run MAME, and discovered an active community of arcade collectors who repair and restore classic arcade games like. With their guidance and experience, I hope to repair my Super Sprint game so it can once again entertain family and friends. This series or articles will document the repair/restoration process as it unfolds.