• The move to the new server is done. There are some software and database maintenance updates in process. This has us passing the hat around to help out. We appreciate any donations. Seriously, even a dollar helps. The payment page may be found here - https://www.audiokarma.org/support.html

Yamaha cr-820 Output transistor Mouser part numbers

M

MiKokomojoe

New Member
Hello fellow Yamaha AK members;

I am working on a cr-820 which has the "no output, lights up, no relay click" syndrome. I have gone through the older threads which were helpful in focusing me in on the right areas.
I have a TR721 transistor which reads 230 degrees when I point my thermometer gun at it, so I am going to order and replace that.
The other suspect is that one of my output transistors on the heat-sink side of the chassis ( the one nearest the front panel) reads ol and ol when I check the continuity of each pin against the back of the transistor. This one is labelled 2SB555. I need to be able to find the Mouser part number for this, but the mouser site is too overwhelming for me to get through it. I am thinking of just replacing all 4 of the output transistors while I am elbow-deep in this. The numbers on these, from left (Back corner-to front) are D424_2SB554_2SD425_2SB555.
I don't know why my transistors are marked differently from what I see posted on other threads; is there a difference between a 2SB557 and a 2SB555? This unit has been in the shop before for power issues. Maybe they went with a different part.
I am not any good with my DMM or terminology, so please don't throw a lot of numbers at me. I am good at buying and replacing parts. Thats just the way it is.
Thank you in advance for any assistance; I value the AK brain trust very much.
 
Register to hide this ad
Thanks for your reply, avonic.

Yes, under your tutelage I will do my best.

I am including an image of my meter, so you can see what I have. I don't usually know which settings to use to read; or if I have the red lead

plugged in the right spot.
 

Attachments

  • DSCN0584.JPG
    DSCN0584.JPG
    115.9 KB · Views: 153
  • DSCN0585.JPG
    DSCN0585.JPG
    97.2 KB · Views: 145
index.php

MiKokomojoe said:
if I have the red lead plugged in the right spot.
Click to expand...
Yes you do..
 
How are you at locating specific components in a schematic?
 
Do you have the service manual ? If so look at page 10.
 
OK.. Here is what I want you to do. Fasten your meters black lead to the metal chassis (ground). With your red probe.Check the voltages ,one at a time ,at TP-1,2,3 and 4. Looking for less than 1 volt DC on each test point.. Set you meters selector switch to V with the dotted line and straight line above the V. This is voltage DC function.
Be extra careful not to slip off the test points and short out anything.
 
Last edited:
Thanks for the clear meter instruction.

TP1 44.01
TP2 44.02
TP3 -.004
TP4 -.002 (3 and 4 jump around a lot, all below 1.0 v)

Is this ok to do with no speakers attached.
 
Unplug the unit. and remove the two output transistors closest to the power transformer.

The (2S)D424 and 2SB554...
index.php



Do you know how to test these transistors for " shorts" with your multimeter?
 
Last edited:
MiKokomojoe said:
No.
Click to expand...
I'll try to teach you then.
upload_2020-3-22_16-31-54.png

Set your meter to the resistance Ω function. Measure the resistance between the transistors case ( C,collector) and the pin E (emitter). Repeat the measurement with the test leads reversed. Both ways should read (open or infinite) resistance.
I suspect one or both will read zero or close to zero resistance.ie. shorted
 
Last edited:
MiKokomojoe said:
2SB554: C to E reads O.L even with leads reversed.

D424: C to E reads 3.2 bothways
Click to expand...
Need to replace both.. The 2SD424 is shorted.. These outputs need to be replaced with complementary pairs.ie. 1-NPN and 1-PNP.

Post # 3 has the mouser part numbers. One of each for this channel.
 
Last edited:
You must log in or register to reply here.
Back
Top Bottom