Yes, have complete diagram. I have replaced or replacing caps (like the main 5v supply) and regulator. I'll try and post, its large.

 

 

I hope you can find a way to look at first image and zoom in, it helps.

 

Got it. Thanks.
I will look it over.

 

The issue i'm having is LD56 10 point and LD54 (mislabeled as 66) 1000 point are both flashing together and sending a signal to the displays which are advancing both the 10 and 1000 point digits. This is after the ball in play switch has been cycled and the logic (playfield logic reset) is released. I've followed it back to the 555, LD53 is flashing at the same rate. It also looks like it might go to another area. This is where I am, trying to locate what might be happening. There does not appear to be a stuck on switch on the playfield.

 

Do you have access to an oscilloscope?
At this stage in trouble-shooting an oscilloscope would be your greatest asset.

 

No unfortunately not, however, good news, I was double checking my 10 point circuit and discovered a previously overlooked contact that was stuck closed. After I isolated it the 10 point problem has gone away. It was the contact, so I’m guessing the 1000 point is the same but no direct 1000 point contacts on playfield, going to look further.

 

How would an oscilloscope help? I’ve used one in the past

 

How would an oscilloscope help? I’ve used one in the past

With an oscilloscope you can probe exactly what is going on at any node in your circuit.
Here are some examples of things that can be observed:

1) when there is excessive noise on the power supply lines, e.g. defecting filter capacitors
2) a drooping power supply voltage or transient, for example, when a solenoid is activated
3) noise or artifacts on signal lines and power supply lines
4) invalid voltages on a signal line, for example, missing or faulty pull-up resistors, bad switch contacts
5) weak output signals from a gate output pin
6) too slow or too fast rise-times caused by defective capacitors on signal lines
7) actual frequency or pulse widths on clock signals, e.g. 555-timer circuits
8) malfunctioning switches, gates, components etc.

In other words, the oscilloscope is your best and essential diagnostic instrument in this line of work, much more useful than a DMM (but also complements it) .

 

High for TTL is 3.4 volts minimum, and no more than .7 volts maximum for a low. Open inputs on TTL are treated as a high.

 

Thank you, I shall consider it. Post 23 above, the 78H05 regulator , its a 5A, is smoking hot and as it warms up the voltage will slowly sink to 4.8. There is a modification memo to this that it is an issue, not big enough. I'd like to increase the capacity of this i.e. get a bigger one, what would you folks suggest as an upgrade to power capacity here? The caps are new and 10,000 mfd. AC ripple as measured by VM is very low.

 

Why not use a USB power cube for power. They are already at the right voltage.

 

I am not familiar with a USB power cube. I started to trace back the circuit for the thousand point and I found a bad solder connection on an ic pin, it fixed the problem. Moving forward. Re solder tomorrow.

 

Here is another 2 circuits I'm having trouble understanding. First is a lamp driver circuit and second is a relay driver circuit. Seem simple enough, I've included several from the page, they are all the same in each. I'm not getting a light to work on the lamp driver (#47, 6V) and a relay wont operate from the relay driver. (24V). The light has positive to all lights, so its looking for a ground to light, and the relays the same. I've checked with my hi/lo and dvm, in the light circuit, when the light is calling to be off, the input is H, and when calling to be on, its L. I get that, but the 75492 driver, (which I think has a bad inard) is stuck on H no matter what. Question is, on the other lamp drivers, when calling to be on, there is neither H or L at the final output here, but there is 6V and the light lights. ? The 100 ohm is a warm up resistor. which gives about 1V when off. Second, how do I check the MPS 6531 on the relay driver board? I think I may have either a bad transistor or bad ic.

 

hi Earl,
The label Output means what.?
How is the Load connected to the Output, update your images to show the Load and voltage sources.
E

 

How are you wiring the lamp and relay?
It will not work by connecting between output and ground.
These outputs are called open collector.

The 6V lamp has to be connected between output and 6V supply.
The 24V relay goes between output and 24V supply.

 

I'll update this when I get home later today, i'm sorry my explanations may not be clear at times.

 

The light will not light, but will glow dimly when off. (100 ohm) as it should. The relay will not close when called for. First two are for the light circuit, the bottom two are the relay circuit. Sorry for the poor penmanship, i'm using a mouse. just trying to understand the workings here, especially the relay one.

 

hi Earl.
I guess you know that a 7404 is an Inverter.?
A High on its input will set its Output Low, so the Transistor will not be switched ON.
What is the rating of the Lamps.... Wattage/Voltage.?
E

 

they are standard #47 6V .15A it says. there are 50 or so on a typical machine. Yes, the 7404 is an inverter, but they didn't include the bubble on some places in the schematic. Also the 75492s are also inverters, being used as a lamp driver. The ics on this board are quite warm, more so than i would think from past experience. The 6531s are simply passing ground when activated, am I right? Then why when I put my logic probe on the output, when on, do I get neither high or low indication? is it above/below the threshold for the probe to register?