• 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-1020

H

Hifibythekg

Super Member
Hi,
Can anyone offer advice for replacing a transistor on a Yamaha CR-1020 power supply board?

At location TR714 lives a 2SA844.

KSA1015 was many times recommended as a substitute on Audiokarma but I believe it's no longer available from reputable distributors.

Will a KSA1220AYS work in this location?
If not, is there a specific transistor model currently available that would work?

Many thanks.
 
Register to hide this ad
Thanks for the speedy reply Avionic.
My issue was that I couldn’t get the bias adjust to adjust. Put in Bourn multi turns and got identical results (15mV and 25mV no matter what was turned.)
So, I’m going to take out and check the board as there are some burn marks around the TO234’s.
Also the red fusistor on the left has melted both itself and the skin of the neighbouring cap.
I thought that while I’m in there I should check the renowned 2SA844 and have replacement to hand without additional shipping later on.

I’m a first time hobbyist, so feel free to advise on any other components I should examine or replace, or have to hand.

Thanks again for your help.IMG_4837 copy.jpg
 
Are you getting a relay " click" shortly after power on ?
 
Need to check your +/- B voltage on the output transistor cases (collectors). With your multimeters black lead securely fastened to the metal chassis( ground). Use the red probe to check the DC voltage on the output transistors metal case. The outputs are the four TO-3 transistors fastened to the large heatsinks. We are looking for +/- 49-50 vdc.
 
Thanks.
Are the settings on the multimeter, and the setup for testing looking ok to you in this photo? If so, I'll switch on the amp and do the test.
Background: the CR1020 is working 'fine' in all regards except that the sound from each speaker sounded different. One was clearer and more forward than the other. (I swapped speakers around to double check that this was so.)
I hoped that just biasing the amp would fix this, and then discovered the known problems with this model. So I'm hopeful that swapping the worn out fusistors, some out of spec caps and transistors will fix and improve things.

IMG_4840.jpg
 
Hifibythekg said:
Are the settings on the multimeter, and the setup for testing looking ok to you in this photo? If so, I'll switch on the amp and do the test.
Click to expand...
Yes.. Don't let the red probe slip off the transistor and short the case to the heatsink. There will be a nasty spark. And likely a blown fuse.
 
Thank you for the warning, I really don't want to damage anything.

But why would brand new pots for bias not affect any change on bias?
And the board shows burn marks around the 2SD234 and a molten red fusistor. I'm thinking that these need checking?
 
You must log in or register to reply here.
Back
Top Bottom