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» Can anyone help me understand this schematic for my Stern Viper?

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Can anyone help me understand this schematic for my Stern Viper?

By n1teowl

2 years ago

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Latest reply 2 years ago by n1teowl
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Viper Stern Electronics, 1981

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Stern_1981_Viper_Rotor_Schematic (resized).jpg

#1 2 years ago

OWL

I've been having some interesting issues with my Stern Viper turret mech. I've tried a ton of different things to fix its wonky behavior and am hoping someone can help me understand the attached schematic. The issue I have been having is very intermittent. The turret will start to rotate when the ball drops in, as it is supposed to, and then the "reverse" and "fire" buttons will quit working. The next time it might not register the ball has gone in and will just sit there. The next time it works fine. I have questions specifically about the capacitors near the motor and motor relay. There is a big one right before the power that goes to the motor, and there are a couple of smaller ones near the relay. Can anyone shed light on what they are supposed to be doing? Is it for filtering on the circuit? Could a bad one be causing this behavior? The big one is an electrolytic capacitor (which I'm sure has dried out after 45 years) and the smaller ones are ceramic discs. Thanks!

Stern_1981_Viper_Rotor_Schematic (resized).jpg

#2 2 years ago

CHS

Chuck_Sherman

Pinside member

Vancouver, WA

11y 77,050 873 12 9

Replace the big cap, disc caps are probably ok. I would also look at the zener diodes

#3 2 years ago

OWL

n1teowl

Pinside member

9y 61,300 544

Quoted from Chuck_Sherman:
Replace the big cap, disc caps are probably ok. I would also look at the zener diodes

Thanks for the suggestion, I'll try that. Do you think the symptoms I described sound like a bad capacitor or diode?

#4 2 years ago

OWL

n1teowl

Pinside member

9y 61,300 544

Chuck_Sherman I have one more question. Which diodes on this schematic are zener diodes? I know they have a slightly different symbol, but I'm not seeing it here. Thanks!

#5 2 years ago

CHS

Chuck_Sherman

Pinside member

Vancouver, WA

11y 77,050 873 12 9

OP
Quoted from n1teowl:
Chuck_Sherman I have one more question. Which diodes on this schematic are zener diodes? I know they have a slightly different symbol, but I'm not seeing it here. Thanks!

I`m thinking as the caps deteriorated, they might take the zeners with them . assuming all traces and contact points are good, not seeing much else to go wrong

zener (resized).png

#6 2 years ago

OWL

n1teowl

Pinside member

9y 61,300 544

Thanks for the explanation, but I think that those are disc varistors. I do have some spares of those so I will potentially replace them after the new cap goes in. My new cap is on the way so I'm hoping that takes care of the issues.

#7 2 years ago

CHS

Chuck_Sherman

Pinside member

Vancouver, WA

11y 77,050 873 12 9

OP
Quoted from n1teowl:
Thanks for the explanation, but I think that those are disc varistors. I do have some spares of those so I will potentially replace them after the new cap goes in. My new cap is on the way so I'm hoping that takes care of the issues.

Ya know, I think you are right, was fooled by the number below looks like they are varistors those rarely go ban unless you get a large voltage spike

Sorry, I tried

#8 2 years ago

OWL

n1teowl

Pinside member

9y 61,300 544

Quoted from Chuck_Sherman:
Ya know, I think you are right, was fooled by the number below looks like they are varistors those rarely go ban unless you get a large voltage spike
Sorry, I tried

Hey, no worries! I appreciate the help and I'm hoping the new cap takes care of it.

#9 2 years ago

???

pins4u

Pinside apprentice

Gaborone

3y 34,400 1,037

They aren't strictly required so for a test you could just lift one leg.

They are there to suppress any back EMF from the motor windings - for a test it won't matter if they are there or not.

For future reference, the symbol for a zener diode is exactly the same as a regular diode with two extra arms added - here;

zener (resized).png

#10 2 years ago

OWL

n1teowl

Pinside member

9y 61,300 544

Well @chuck_sherman, I replaced the cap and everything seemed to be working okay. And then... magic smoke! The cap blew up. Not sure if I got the polarity wrong, or got the wrong cap. I've inclined some pics, what do you think? I assumed the side that I drew the positive symbol on really is the positive.

20220304_171759 (resized).jpg20220304_171835 (resized).jpg

20220304_172652 (resized).jpg

#11 2 years ago

OWL

n1teowl

Pinside member

9y 61,300 544

Hmmm. I am now noticing that this is a DC capacitor. I did not realize there is a difference...

#12 2 years ago

JWH

Shogun00

Pinside member

6y 60,550 948 60

OP
Quoted from n1teowl:
Hmmm. I am now noticing that this is a DC capacitor. I did not realize there is a difference...

There is a major difference between VAC and VDC. Alternating Current (AC) and Direct Current (DC) have different voltage readings sort of like temperatures measured in Fahrenheit (F) and Celsius (C).

Edit: Using a AC to DC calculator 150 VDC = 235.8491 VAC.

#13 2 years ago

DBS

Skidave

Pinside member

6y 63,550 1,288 9

You need what is called a non-polarized capacitor.

https://www.parts-express.com/Dayton-Audio-DMPC-8.2-8.2uF-250V-Polypropylene-Capacitor-027-426?gclid=CjwKCAiAjoeRBhAJEiwAYY3nDGEJkBKto7h1NbqMnVlJ5R2fbXs6Ze9tjyXIp87oZfJc4EGiLf8JpRoCKPkQAvD_BwE

Screenshot_20220304-212221_Chrome (resized).jpg

#14 2 years ago

OWL

n1teowl

Pinside member

9y 61,300 544

This makes much more sense. Thanks for pointing me in the right direction.

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