Valley Spectra IV

Note: This page is a work in progress. Please help get it to a completed state by adding any useful information to it.

This section is dedicated to the repair, preservation, restoration and maintenance of Valley's Spectra IV.

1 Introduction

This section is dedicated to the repair, preservation, restoration and maintenance of Valley's Spectra IV. These are very special and unique machines. It was the only pinball machine manufactured by the Valley company (known for Billiards equipment) and one of only two solid state pinball machines where the entire playfield could rotate for additional players instead of trading positions in front of the machine. Players still have the option of leaving the playfield in place and the players can move as traditional pinball games.

2 General Information

Before working on the machine you need to know how to get into it! The top sets on the machine and can be locked into place. The locks are somewhat unique in that the whole cylinder moves in and out. They push in place to lock the top. To remove all four have to be unlocked and pop out to release the top. The key should be the same for all four of those locks. Once the top is unlocked it just lifts straight off. When reinstalling it fits in any position. If you look carefully at the corners one will mention about inserting coins so you can tell how it should set on the machine.

Once the top is off you can raise the playfield. This is done by grabbing onto the thick metal guide rail at the top of the playfield and lifting up. It helps to pull out the shooter rod for clearance. Just be careful NOT to grab the playfield by any of the plastics to avoid breaking any of those.

2.1 Unique features

Besides the rotating playfield there are some other unique things going on with this machine. One was the way the difficulty level is adjusted on the machine. On traditional pinball games it is common to adjust logical settings via DIP switches. Often they have a moveable post by the outlanes or slings to adjust the size of the opening. Instead, Valley took a different approach by having two voltage settings for coil power. This is set by a toggle switch on the underside of the machine. Lower voltage made it harder to make some shots while on the high voltage setting it is much easier to reach the top. Oddly that operator setting is exposed on the bottom where players could just make it easier if desired. It's a mystery why that toggle wasn't hidden inside the coin door.

Another unique feature is related to the two kick-out holes. Each one has a set of 4 screws to adjust how the ball sets in the hole. By adjusting the height if them the angle that the ball is kicked out can be adjusted.

2.2 Getting access to circuit boards

Accessing the circuit boards to remove them for servicing is not obvious or intuitive! They are all mounted in a card cage that is directly attached to the underside of the playfield. If they need to be removed first all the cables need to be unplugged from the boards. There are edge connectors (similar to what Gottlieb used) that go to each of the three boards in the cage. Some boards have these on both sides. The lamp board which is the one exposed also has 6 standard .156" molex plugs that pull off. After that there is one screw (the original was supposed to be RED) that needs to be removed. It is screwed into the side of the cage that holds one end of the plastic rails that the boards slide into. Once that screw is removed the rails pivot on the other end allowing the cards to tilt out and then then can slide out of the cage. There is a picture in the manual for the game that also explains the process.

The tilt board is directly accessible when the playfield is propped up.

2.3 Removing the playfield

Removing the playfield is a relatively easy task. The only tricky part is reaching up inside the drum to unplug the cable from the display board. Once that is unplugged just disconnect the two cables from the playfield to the the drum. After all the electronic cables are disconnected just lift out the entire playfield.

2.4 Removing the Rotating drum

With the playfield out of the way the drum can be removed. There are only 4 screws securing it to the lazy suzan assembly. After removing the screws and washers just lift off the drum and set it aside. That will allow access to the lazy suzan.

3 Technical Information

3.1 MPU board

The MPU is based on the 6503 processor which is a 28-pin version of the 6502. This is not a common processor and seems that one of the few other places it shows up is on an early Gottlieb System 1 sound card as used in Buck Rogers. Having access to another board using a 6503 is a good method of validating at least the CPU chip is ok.

Many of the IC's may be soldered to the board. In order to test out of circuit it will need to be carefully unsoldered to remove. If it tests ok it is recommended to carefully clean the leads and install a socket for easy service in the future.

While the 6503 controls the show there are several other important pieces. There is a 6532 RIOT chip onboard to handle many of the I/O tasks. This chip has a small amount of RAM that is used for the Stack memory. If the RIOT chip is bad the MPU board will NOT run.

There is also a pair of 5101 RAM chips which hold the variables for the game and also the battery backed game settings/configuration. This is an important detail! If the battery power is ever lost the first time the MPU is powered up there will be random data in these chips. The code controlling the game is fairly simple and does not no how to deal with this. As a result the game will do odd things and act like there is a hardware or other problem. After servicing the boards it is critical to RESET this memory (with special tool) then reset the remaining settings through the control door interface. The 5101 RAM chips are known to fail so those need to be tested. It is best to test them out of circuit.

The main controlling program is typically stored in three mask programmed ROM chips. Some boards have a single larger ROM chip instead. The ROM must me ok and working otherwise the 6503 will not know what to do and how to control a pinball machine. This is another common issue as the ROM chips are located right in the corrosion zone.

There is a zero crossing circuit on the MPU but it doesn't just keep track of zero crossing events. If that signal is not present it can prevent access to the 5101 RAM chips so nothing will work. If bench testing the MPU there must be an AC source that the zero crossing circuit functions to allow the CPU to access the working RAM.

It appears that at some point there was an undocumented small daughterboard installed on the MPU board. It seems that the function may be to keep the MPU in RESET if the zero crossing isn't seen. There needs to be more research on that. However that board can be removed and a 4093 chip installed in it's place. If that happens a jumper has to be removed and a diode installed otherwise that new 4093 chip will be blown. The original schematic shows the 1n4148 diode but when the change was made to install the daughterboard was done it was changed to a jumper.

4 Problems and Solutions

4.1 Summary of Issues

The main cause of non-operating Spectra IV machines is the same the number one killer of all pinball machines. Leaking rechargeable batteries. The MPU board has a set of three 1.2V AA NiCad batteries soldered to the MPU board. In most machines these ended up leaking and caused considerable corrosion on the MPU board that would etch away traces causing open circuits and even up into the sockets on the board. Because the MPU is the top board in the stack they could leak down on the Solenoid/Sound driver board right below it causing damage to that board as well. To get one of these machines going all the corrosion has to be properly dealt with.

As is the case with 40+ year old technology, many of the active components on these boards are obsolete and may at times be difficult to find exact replacements. They do share many of the common electronic components but there are a few unique parts that are not so common. To date, some "drop in" substitutions have been found for several difficult to find components. This information is contained in the Technical page.

4.2 Troubleshooting (Electronic)

4.2.1 First Time Power-Up

Before attempting to power on one of these machines the MPU and boards in the card cage have to be inspected for battery damage. If there is that will need to be addressed and resolved first.

For a first power up or after the RAM or battery backup power source has changed the memory contained in the 5101 chips has to be reset. Otherwise you will see abnormal behavior even if the boards themselves are ok. In order to reset the memory the machine has to be powered off, playfield lifted up, and the connector to the sound section of the Solenoid/Sound driver temporarily disconnected and a special RESET card be plugged in. Then power on the machine and you should see all 0's on all displays indicating that the RAM was reset. Power down the machine, remove the card, then plug the connector back in and lower the playfield.

Once the RAM is reset the game should boot normally. However it may not play normally until you use the coin door interface to adjust and set the remaining settings. From that point on it will be fine unless the battery backup to keep the memory fails resulting in garbage data. When that happens you need to go back and use the RESET card again after addressing the memory power issue. This will mess up a lot of people if the reset process isn't followed.

4.6 Re-Pinning

The most likely area to require repinning would be the connectors right near the MPU batteries. Any that show signs of corrosion should be replaced. They use the same pins as many of the Gottlieb System 1 or System 80 so they are still available. Along with replacing any bad pins the edge connector on the PCB should be reconditioned so that there will be a solid connection again.