(Topic ID: 173729)

Data East Star Wars Burning Transistor, Literally (Q28)


2 years ago

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  • 6 posts
  • 2 Pinsiders participating
  • Latest reply 2 years ago by DANGERTERROR
  • Topic is favorited by 1 Pinsider


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#1 2 years ago

Could use some DE experts here.

DESW's L/R relay was getting flaky -- failing after a few games and firing on only flashers instead of coils. I resoldered relay pins, replaced Q29 with a TIP122 (or so I thought, the transistor I ID'd had previous, nasty work ... we'll get to that) and put the board back in. No dice.

Thought it was the relay so I Picked up a Rottedog PPB just to throw in there while doing work (this game is a big earner on location). None of this fixed the issue with the L/R relay. So: I presumed it was the PIA chip on the MPU, and, again, picked up a Rottendog MPU board to thrown in there while doing work on the other board(s).

Tonight I put in the new MPU. Things got interesting:

The L/R problems were solved! All coils and flashers fired properly.

All controlled lamps, however, weren't working.

A fuse was out above the big cap on the left (F1?). Replaced what I'll call F1 above the big cap, mounted on the backbox. This fixed controlled lamps.

Started a game. All well, but the motors were all out on the death star, bar target, and R2.

Traced motors to F2(?) above the big cap. It was blown, too. Weird. This did not fix the motors.

At this point, I thought there must be another fuse that was out that maybe I knocked out removing and testing boards or whatever. I found one, F5 on the Power Supply board. Replaced that (4A, slo blo). I also, at the same time, noticed a yellow wire connector at CN10 on the power supply board that was *not reconnected* after I removed that board. Oops.

After plugging CN10 in, and replacing that fuse, I power her on.

Q28, the GI transistor (?) spouted a 3 inch flame on my new board. Crud.

Which brings me back to "Q29" way back at the beginning. I wasn't even doing work on Q29, ever. I had replaced Q28 originally as it was loose in its sockets and had burned at some point and I just visually ID'd it and, well, made a mistake.

So I did solve the L/R problem with the new board, and I don't know how (maybe it was the PIA). But something is -and was- frying Q28.

If this is all a bridge rectifier, I just don't know what. Thanks in advance for the help!

Images attached of Q28 burned on the Rottendog, the fuses I was referring to above the cap, the fuses on the power supply board, and connector I missed.

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#2 2 years ago

Bump for the morning crew

#3 2 years ago

I suppose the TLDR question here is: What would cause a transistor to catastrophically fail on bootup when it only controls what I believe is a GI on/off switch relay.

I understand why a locked coil or bad diode could knock out a transistor, but this thing POPPED, and it simply operates a relay. I'm not really sure how to safely proceed from here to do tests.

#4 2 years ago

Replaced both bridge rectifiers above the big cap. Game plays normally even with Q28 blown (GI is always on). Moving on with my life.

#5 2 years ago

Power Supply board relay RY1: this relay controls the GI (General Illumination), and is controlled by CPU transistor Q28 (TIP122). It is very common for this relay to have cold solder joints, or to have relay switch contacts that are melted together. This relay is a 24 vdc 10 amp relay with two DPDT switches. There are a total of 8 solder points on this relay; two connect to the winding of the relay coil (to turn the relay on and off). The other six contacts (two distinct sets of three contact DPDT switches) are the relay switches. Source number FRL264 P024/02CK, Sega part 190-5003-00.

Replace Relays with the RIGHT Relay!
All of the replays used in DataEast/Sega games have at least two sets of contacts. If a relay is mistakenly replaced with (for example) a single set of DPDT contacts, it could short the power supply and start it on fire! (I have seen this happen.)

#6 2 years ago

Ah so that GI relay is on the PS! I'll take a look and resolder/replace. I've already seen one tiny fire in this machine so will proceed with caution. Sounds like that relay could have actually blown up Q28. Thanks so much for that knowledge.

I also noticed the PPB is getting 76v and 40v at the 50v and 28v test points, which could be a source of problems -- although everything is fine other than the GI transistor issue at this point. Perhaps the PS is having more issues than just the relay.

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