Yamaha CR-640 to CR-1040

merrylander

AK Member

• Oct 5, 2011

• #1

These are the three receivers in the CR-n40 lineup that use the NLA pre-driver chip. I have been advising an AK member about a retro-fit to these units and really should put it here for everyone who owns them.

In all of the blown pre-drivers I have opened up there is one transistor that seems to be the one that always blows. Looking at the backside (metal) of the pre-driver it is located about 1/4" down and 5/8" from the left. The retro-fit is to JB Weld a TO-220 size heatsink to the metal backplate at that location. As Pacific Stereo has noted the OEM supplier of the pre-driver said heat sinking was unnecessary - sure. But a little extra sure won't hurt.

 

Blue Shadow

Waiting for Vintage Gear from this century

• Oct 5, 2011

• #2

Thanks for posting this. I have added heat sinks to my list of parts to order so I can do this mod.

 

ehoove

Old & New - Carpe Diem

Staff member

Super Mod

Moderator

Subscriber

• Apr 8, 2013

• #3

I have done this upgrade to my CR840, and thought a bump for those CR-n40 owners who missed this was in order.
Regards,
Jim

 

4seatPilot

"Broker"

• Apr 8, 2013

• #4

Good CR-n40 information!

Also... chazix has put together a custom built replacement out of discrete components. I have not used one, but all indications are that testing has been successful.

Here is his thread in BT

Some apparently original 640 drivers have been available on eBay for awhile, I know he bought a couple as did I - "just to have."

This thread is also full of useful information on testing, heatsinking etc.

These n40 series receivers need no longer be doorstops!

 

Last edited: Apr 8, 2013

Rasputin47

Woad

• Apr 8, 2013

• #5

I picked up a CR-840 a while back and aside from a few dead bulbs it is in good working order.

Adding heat sinks to the chips sounds like a good idea to keep it working well.
Any recommendations for heat sink size etc?

 

4seatPilot

"Broker"

• Apr 8, 2013

• #6

Rasputin47 said:

I picked up a CR-840 a while back and aside from a few dead bulbs it is in good working order.

Adding heat sinks to the chips sounds like a good idea to keep it working well.
Any recommendations for heat sink size etc?

Click to expand...

Here's what I went with...

May be a bit overkill, but it certainly won't overheat! Old computer motherboards, video cards etc are great sources for heatsinks.

 

Tom B

AK Subscriber

Subscriber

• May 15, 2013

• #7

Output Modules for the CR-1040

I am working on a 1040 that may have a bad output chip. as these IG chips aren't easy to find, i looked at finding possible alternatives. It seems that the STK 0080 Type II may be a match, or a little heavier one would be the STK 0100 type II. Has anybody tries using these??

 

merrylander

AK Member

• May 15, 2013

• #8

Yes in fact the Yamaha chip is just a re-badged STK00n0 type II.

 

janikphoto

Lunatic Member

• May 20, 2013

• #9

Hmmm... I just put a 640 into service. It is mated to my JBL L220's right now. Looks like I should crack it open and do this mod. Anyone have pics of a new heatsink in place?

 

4seatPilot

"Broker"

• May 20, 2013

• #10

there is a link in my post above... #6

4seatPilot said:

Here's what I went with...

Click to expand...

 

janikphoto

Lunatic Member

• May 20, 2013

• #11

4seatPilot said:

there is a link in my post above... #6

Click to expand...

Thanks!