MS8-26SU Schematic and more info! (was "Horizontal Transistor- quick question")

[segasonicfan1]

Note: edited to reflect the great info shared in this thread!  Scroll down for lots of MS8-26SU repair info
 
I feel silly asking this question but i want to make sure...
ordered a two of the 2SD1880 HOT for the nanao MS8-26SU to repair it.  When they came in the mail (new supposedly, though it looked like it was desoldered) the collector to emitter resistance was 35 ohms on one and 45 ohms on the other.  These are shorted/broken, right?  I put one in anyway (doubting myself) and it blew the chassis fuse, shorted to hell, and shorted out the 2SC3306.

[MonMotha]

Sounds like you probably got screwed.  If it looks like a pull, it very likely is.  Bonus points in this case for it apparently even being a defective pull.

Where'd you buy them from?

[tolias3]

I have exact the same problem!!!!!!!
Anybody help 

[segasonicfan1]

Sounds like you probably got screwed.  If it looks like a pull, it very likely is.  Bonus points in this case for it apparently even being a defective pull.

Where'd you buy them from?

http://www.ebay.com/itm/171259710461?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649

   I opened a case with ebay to get a refund, but their response is entirely in spanish, doh.  Lesson learned: don't buy blurry-photo inexpensive transistors from Peru.

[MonMotha]

Try MCM:  http://www.mcmelectronics.com/product/2SD1880

[tolias3]

I have already change with new transistors and it fail again!!!!! The problem is somewhere else!!!!!!

If someone have any ideas please tell us

[segasonicfan1]

tolias, there are a lot of posts on this subject, if you do a search you will find the common failures and parts to replace.  Like here:
http://forum.arcadecontrols.com/index.php?topic=62428.0

C433 and R433 were obviously bad on mine.  Still waiting for parts to finish the job.

[segasonicfan1]

NOW im confused.. bought 3 more of these HOTs off ebay, these look new but base-collector resistance is ~45ohms on one and ~75ohms on the others.  Could someone measure a known working one for me?  I don't wanna blow up the chassis I'm repairing with bad parts.  Seems odd that both these sellers would be giving me broken ones.
Thanks,

-Segasonicfan

[ed12]

if u are reading b->e
u will find a resistor in there
if u are going c->e u will find a damper diode
look at the attached .pdf

ed

[ed12]

ok
here is what i would sujest u do
pull the fuse out
and do the 60-100watt light trick,what this will do is
a=save a fuse
b=save a hot
what u do is put the light in >in place of the fuse<
now if it light's up bright u have a dead short
if it glows dim ? u are drawing current
if  bright i would look at the flyback or yoke
ehiter will hall enogh current to make the bulb glow
also well u are at it place a new mica between the hot and the heat sink
just go get your a once of heat sink compound and a mica insulator
that will be more then enough

ed

[MonMotha]

In general, testing transistors on the resistance setting is not useful.  If your meter has a diode test setting, you should get ~0.7-1V from B to E.  E to C will have a damper diode on many HOTs and should measure similarly or maybe down near 0.5V if it's a schottky type (uncommon on BJTs).  The reverse of those should read "open", and neither should read as a short.

[segasonicfan1]

In general, testing transistors on the resistance setting is not useful.  If your meter has a diode test setting, you should get ~0.7-1V from B to E.  E to C will have a damper diode on many HOTs and should measure similarly or maybe down near 0.5V if it's a schottky type (uncommon on BJTs).  The reverse of those should read "open", and neither should read as a short.

thanks for all the really helpful input guys.  When I do a diode test for B > E (also a beep test on my fluke) I get a constant beep and a reading of 0.015.  It just seems like a direct short to me.  It reads around 40ohms and this is the same for the entire set of new 2sd1880s I ordered.  I've done some HOT replacements over the years but I've never come across this. 

Thanks to user "notherngames" I now have a schematic of the MS8-26SU which I am attaching here.  It's fairly difficult to read, but the HOT is on the very bottom of the diagram toward the middle, just left of the 4 pin connector.  Emitter is attached to ground and Base is the input, which is connected to a small transformer.  Collector is 130v i believe coming from pin 1 of the large transformer and there is a protection diode connected to pin 2 of the transformer which goes back to the fuse F902.

The last HOT I connected blew my fuse (F902 2A) and the 2SC3306.  I replaced more parts this time around hoping to avoid the calamity again but I'm afraid to turn it on with this HOT reading being so strange.
I would just love it if someone with a working Nanao would take a reading for me.

[ed12]

segasonicfan1
did u read the pdf i posted for u ?
it explains a reisiter inside of the high-gain out put transistor

ed

[segasonicfan1]

segasonicfan1
did u read the pdf i posted for u ?
it explains a reisiter inside of the high-gain out put transistor

ed

Yep, I see the resistor, it doesn't say the value though >_<

I feel MUCH better now that I found this(!!) thanks to use "phi lo" on this thread:
http://forum.arcadecontrols.com/index.php?topic=83816.0

Just for your information:
Take those transistors out of the circuit ,  with the DMM set for diode measuring and the following values are what I read from my known good transistors
Q901:
Red test lead to B,black to C: .499
============B,===== E: .536
Black test lead to B,red to C: OL
============ B, ==== E: OL
Red test lead to C,black to E: OL
Black test lead to C,red to E: OL
Q533:
Red test lead to B,black to C:.452
=========== B,====== E:.027
Black test lead to B,red to C: OL
============ B,===== E:.027
Red test lead to C,red to E:OL
Black test lead to C,red to E:.464
Hope this will help

.027 is close enough to my meter of .015.  I'm pretty confident about the HOT being okay now.  Especially since my values were a little bit lower overall compared to theirs.  I'm going to swap it into the cab on Saturday and hope for the best(!)

[ed12]

your gold now

your horz output is on the far left
the 1 on the right is for position
ed

[segasonicfan1]

yep, put the chassis in the cab today and fired it up and IT WORKED!!! 

thanks for your help guys!

-Segasonicfan