Does Continuity in a Pinball Transistor Mean Good or Bad

My taxi knocker isn't working but seems to be wired correctly. Transistor Q7 is involved and I'd like to test it to rule it out.

How do I test it? Black probe where? Red where? Mm set to? Game on or off?

Thanks.

Hmmm, Black probe in right ear,Red probe in left ear, and stick your tongue on the tab of
the Transistor.

Funny. I can't help my newbiness

Come on...

Haha!!

Ok,Do you want to test to see if it is shorted?
Power off,Set meter to Buzz tone-Cone shape symbol
1.Place black probe on ground(strap in backbox)
2.place red probe on the metal tab of Transistor
3.If you get a no reading/buzztone that Transistor is bad/shorted.

I think you can set the DMM to Ohms. Then put either lead on the ground braid and the center metal tab of the transistor.. You should get resistance there. No or very low resistance and the transistor is Shorted and is junk.

Also I think you can set the DMM to Continuity also . Same way either lead in the same positions, tab and ground, and if you have continuity then the transistor is Shorted and needs replaced.

Thanks bill and mike.

Game off I'm guessing.

Buzz tone is continuity(ohms) and yes with The POWER off

Thanks for the info and the chuckle.

Yep. I always turn it off.
I'm really new to this also, but am dealing with and replacing a few transistors that are locked on on my F-14 Tomcat.

Good luck, Bill in Indiana

Quoted from pinmike:

BillinIndiana said:Also I think you can set the DMM to Continuity also

Buzz tone is continuity(ohms) and yes with The POWER off

Yea, I type slow. Your reply posted while I was typing mine

No problem Bud anytime..

Here's a out of circuit test I'm going to use on the new transistors before I re-install them. Never know maybe a bad one made it past Quality control at the factory...ha

Different tests apply to different types of transistors used in pins.

Figures .. Why can't things just be simple..?

Would this be an NPN trans. test?

Quoted from BillinIndiana:

johnwartjr said:Different tests apply to different types of transistors used in pins.
Would this be an NPN trans. test?

Yep, depends on "BCE". Transistors have different configurations. Basically you have to see where the Base, Collector, and Emitter is and test accordingly. The schematics show what kind of transistor is at what location.

If the Base voltage is higher than the emitter = NPN

If the Base voltage is lower than the emitter = PNP

This affects which way current flows...hth

Quoted from pinmike:

Hmmm, Black probe in right ear,Red probe in left ear, and stick your tongue on the tab of
the Transistor.

Wow, this is how I test 9 volt batteries too!

So I tested a bunch of transistors and they all beeped. Now they all can't be shorted.

Taxis ground is cheated as it is plugged into a 3 to 2 prong conversion plug. Is this why I get continuity?

Got to my site www.ovfdfireman.com and click repair blog at the top. The tron article has details and pics

That's a nice link too Ovfdfireman.. Lot's of great pics. Thanks!

How about Pre-Drivers? These don't look to have a metal tab like the transistor. How do you test these? Can you test them in circuit?

Here you go Bill,Testing pre-drivers

Power off the game!Set your meter on diode setting
Place the red lead of your DMM on the center leg of the transistor
Probe each of the flanking legs with the black lead
.4 to .6 volts is a normal reading
Readings outside of this range indicate a failed transistor

Yes you can test them in circuit.

Quoted from pinmike:

Here you go Bill,Testing pre-drivers
Power off the game!Set your meter on diode setting
Place the red lead of your DMM on the center leg of the transistor
Probe each of the flanking legs with the black lead
.4 to .6 volts is a normal reading
Readings outside of this range indicate a failed transistor
Yes you can test them in circuit.

Thanks! Looks like I have a few of those to replace too.

I measured a couple and they are showing less than .4 on the one leg. One measures .586 on left leg and .334 on right? Another measures even lower on it's right with measurements of .574 left and .234 right..

One is very easy .. it measures .101 on the left and .001 right but what about those others?

Bill, I wouldn't replace them unless the solenoid they are driving gives some sort of indication that the transistor is failed. If they are in circuit, other devices could potentially influence the readings you get.

Also, it's good to mention that parts can test good, yet still be bad.

John, this ties back to my " New Fuse = Smoke" thread , but none of the my solenoids work on my F-14 Tomcat, besides the slings and pop bumper.. I have nothing for any of the kickbacks or the habit trail diverters. I found that the single 2.5 Amp fuse mounted to the backbox right above the flipper power board was blown. I put in a new fuse in and on Power-Up it blew again. This made transistors Q75 Q77 Q79 sorta glow and smoke. Even being a rookie I didn't think this was normal.ha

So here I am trying to work my way through this and learn a few things as I go..

Sorry Blackbeard, I really didn't mean to hijack your thread. Sorry!

If a lot of parts fail at the same time there has to be a different root cause. Find that first before replacing everything or it will just happen again.

I found a few of the Flasher Lamp resistors that are associated with the solenoids that these transistors control laying on the cabinet floor. It seems they have desoldered themselves and fallen off. I hoping this is the cause of the problem.

If you have a multimeter, you can do resistance tests on the various diode junctions. Measure each of the pairs of diode junctions. Collector-emitter, collector-base, base-emitter. Read the resistance of one junction and then read the same junction with the polarity probes switched. One side should read very high resistance, over 1 megohms. And the other should read a moderate resistance, a few hundred thousand ohms. If this is the case for all three junctions, the transistor should be a good working one.

The resource included below explains this:

http://www.learningaboutelectronics.com/Articles/How-to-test-a-transistor

Quoted from pinmike:

Hmmm, Black probe in right ear,Red probe in left ear, and stick your tongue on the tab of
the Transistor.

lol you remind me of that part in "Idiocrasy" where the doc tells him to put one probe in his mouth and the other probe up his butt, then got confused and switches the probes around.

Quoted from pinmike:

Haha!!
Ok,Do you want to test to see if it is shorted?
Power off,Set meter to Buzz tone-Cone shape symbol
1.Place black probe on ground(strap in backbox)
2.place red probe on the metal tab of Transistor
3.If you get a no reading/buzztone that Transistor is bad/shorted.

I have a question related to testing transistors. Going with the method described here, if I an testing and come across one which which I hear "tone", however retest it, and hear no tone....what gives? Is it going bad? Operating normally? 99 % of them have not tone what so ever. What would temporary show a short but upon retesting it, it's ok?

Ok, thinking through a mod idea for the machine. I previously acquired the Playmates 1701 Enterprise, I took it apart and put leds inside. Monster pain in the ass. Results were so so at best. Anyone who has tried this knows what I am talking about.

I was considering getting one of the Bluetooth Speaker Enterprise 1701-D ships, which has LEDs already installed. Here is the issue, wiring it to operate from external power, instead of battery power. Also to come on when power is applied, not by hitting a button or anything. thoughts?
01f7c27f-c1e1-456c-854c-d925823f78b1_1.15c87383112df190a171dd56f6995eae (resized).jpeg e9cba957-b0b4-43d2-877b-96ae6edd082d.0c056e85f8cc5ceb9f40518dff34bf9d (resized).jpeg img_9933 (resized).jpg

Reply

Wanna join the discussion? Please sign in to reply to this topic.

Hey there! Welcome to Pinside!

Donate to Pinside

Great to see you're enjoying Pinside! Did you know Pinside is able to run without any 3rd-party banners or ads, thanks to the support from our visitors? Please consider a donation to Pinside and get a next to your username to show for it! Or better yet, subscribe to Pinside+!

andersonhicustant1966.blogspot.com

Source: https://pinside.com/pinball/forum/topic/how-to-test-a-transistor

Share this post