Set the meter to ohms, touch each pair of terminals with the meter probes. If a pair of terminals reads a really low impedance (a couple of ohms), then the transistor is shorted.
Screwed up my Crack upgrade
- Thread starter flyfisher55
- Start date
flyfisher55
New member
I'm a little confused as I see three pins on each transistor. When you say "pair" you're referring to the two outer pins on each individual transistor?
There are 3 pins on each transistor, so there are 3 pairs of pins to measure:
1. The DC resistance between the two outer pins.
2. The DC resistance between the middle pin and one outer pin.
3. The DC resistance between the middle pin and the other outer pin.
-PB
1. The DC resistance between the two outer pins.
2. The DC resistance between the middle pin and one outer pin.
3. The DC resistance between the middle pin and the other outer pin.
-PB
flyfisher55
New member
These are my readings
QIB Outer two pins 0
R+C 35m
L+C 30m
Q2B Outer two pins 0
R+C 11
L+C 11
Q2A Outer two pins 26.5
R+C 16
L+C 0
QIA Outer 2 pins 0
R+C 35
L+C 30
QIB Outer two pins 0
R+C 35m
L+C 30m
Q2B Outer two pins 0
R+C 11
L+C 11
Q2A Outer two pins 26.5
R+C 16
L+C 0
QIA Outer 2 pins 0
R+C 35
L+C 30
flyfisher55
New member
Large Board
02A outer 2 pins 21.54
L+C 16.63
R+C 0
O2B outer 2 pins 21.43
L+C 16.59
R+C 0
Q1B outer 2 pins 52
L+C 52
R+C 1.1
Q1A outer 2 pins 0
L+C 21.62
R+C 21.23
02A outer 2 pins 21.54
L+C 16.63
R+C 0
O2B outer 2 pins 21.43
L+C 16.59
R+C 0
Q1B outer 2 pins 52
L+C 52
R+C 1.1
Q1A outer 2 pins 0
L+C 21.62
R+C 21.23
You have no units on the numbers you have. When you write 21.54, is that 21.54 ohms or 21.54 megaohms?
flyfisher55
New member
Meter shows m and ohm sign
That's millions of ohms. Your meter may also show "OL" which means "over limit", but is not 0.
flyfisher55
New member
O.L not 0
OK, so now that you know that, do any pairs of leads actually measure zero ohms?
flyfisher55
New member
Everything that I in error labeled as "0" is in fact 0.L m ohms. My apologies.
I would recheck Q1B on the big board.
flyfisher55
New member
I need steady hands, someone to teach me ohms law and a drink!
ok don't ask me where I got those previous numbers but this is what I'm seeing now .08 L+R, L+C .09, R+C 0 all M ohms
ok don't ask me where I got those previous numbers but this is what I'm seeing now .08 L+R, L+C .09, R+C 0 all M ohms
Is R+C 0, or OL?flyfisher55 said:
If it's 0, then that's a dead transistor.
flyfisher55
New member
She's toast! (I'd replace them both on that side)
flyfisher55
New member
what about the others and my wacky readings? These parts are cents ... Not better off just swapping all parts in question?
flyfisher55
New member
also the issue with small board still not working after having removed the large. Do we need to replace parts there?
You can do the same readings again on the small PC board to check for shorts.
Again, it's low impedance values between any pair of transistor legs that mean a problem. If there's an "M" in the reading or it says "OL", those are OK readings.
Again, it's low impedance values between any pair of transistor legs that mean a problem. If there's an "M" in the reading or it says "OL", those are OK readings.
flyfisher55
New member
Sorry it took me awhile...
these are the transistor readings from small board
Q1A- L+C 32.23 m ohms
L+R 0.L m ohms
C+R 37.78 m ohms
Q2A- L+C 0.L m ohms
L+R 28.10 m ohms
C+R 16.85 m ohms
Q1B- L+C 33.0 m ohms
L+R 0.L m ohms
C+R 38.25 m ohms
Q2B-L+C 11.36 m ohms
L+R 000.7 m ohms
C+R 11.52 m ohms
these are the transistor readings from small board
Q1A- L+C 32.23 m ohms
L+R 0.L m ohms
C+R 37.78 m ohms
Q2A- L+C 0.L m ohms
L+R 28.10 m ohms
C+R 16.85 m ohms
Q1B- L+C 33.0 m ohms
L+R 0.L m ohms
C+R 38.25 m ohms
Q2B-L+C 11.36 m ohms
L+R 000.7 m ohms
C+R 11.52 m ohms
