(Topic ID: 190796)

Sys80b Display Board Frying R1

By adamtoth

6 years ago



Topic Stats

  • 3 posts
  • 3 Pinsiders participating
  • Latest reply 6 years ago by ForceFlow
  • No one calls this topic a favorite

You

Linked Games

#1 6 years ago

Hello,

I am trying to bring a sys80b alphanumeric display board back to life. Tested R1 and it was toast, and after replacing it, the display works (so the glass is fine), although the new R1 is blistering hot within seconds, and I'm sure won't last. What would cause R1 to get too hot?

I replaced the big 470uf cap, and also replaced R2 (R2 checked out fine though).

I checked the two zener diodes VR1 and VR2, and they are not totally open or closed both ways.

On my working display board, checking the voltage across VR2 and C2 when on, I get ~14v, and ~17v on the one that's burning R1 (also get ~17 on the bad board across cap C2).

I've checked R4, R3, and R5, and they check out.

I have not checked CR1-CR4 yet, nor R6-R15. I though someone might have an idea what to look at before I start lifting everything up.

Would the Q1 transistor have anything to do with R1 getting too hot?

#2 6 years ago

I can't be certain, but I'd sure test, or just replace CR1 through CR4. Next would be R2.
Strictly guesses.
Sometimes, it's just easier to replace everything in the circuit and move along...
--
Chris Hibler - CARGPB #31
http://www.ChrisHiblerPinball.com/Contact
http://www.PinWiki.com - The Place to go for Pinball Repair Info

#3 6 years ago

Also, sometimes components may test fine with the power off, but fail while under load or when heat enters the picture.

Promoted items from the Pinside Marketplace
$ 83.00
Electronics
PinballReplacementParts
Electronics
$ 15.00
Cabinet - Sound/Speakers
Gweem's Mods
Sound/Speakers
$ 5.95
Playfield - Protection
The Pinball Scientist
Protection
From: $ 2.99
$ 99.00
Playfield - Other
RGP Models
Other
Wanted
Machine - Wanted
Gainesville, GA

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 anext to your username to show for it! Or better yet, subscribe to Pinside+!


This page was printed from https://pinside.com/pinball/forum/topic/sys80b-display-board-frying-r1 and we tried optimising it for printing. Some page elements may have been deliberately hidden.

Scan the QR code on the left to jump to the URL this document was printed from.