Yamaha CR 640 problem


New member
Username: Hurricanebob

Post Number: 1
Registered: Oct-17
My beloved 1979 Yamaha reciver has taken a hit. While testing a guitar speaker with the left channel speaker wire--it blew and took out my left channel. Now that channel has sound but cuts in and out consistently making it useless now. I replaced the 3 fuses and have spayed all the pots but to no avail, please help......

Gold Member
Username: Magfan


Post Number: 3464
Registered: Oct-07
38 year old receiver should probably be allowed to Die In Peace.

Lots of possibilities but since it is a single channel, your power supply is probably still OK.

Good chance the speaker is BAD and that's what took out the receiver. Do you have a Digital Multi-meter? And if so, do you
know how to use it?

Unless you have 'skills', you can take it to a fix it guy. HE will have trouble getting any proprietary parts.
And than he won't be able to guarantee anything, since it IS 38 years on.

The problem is probably an OUTPUT device. You have over-stressed that channel.

IMO? Go Shopping. And don't use your stereo as a guitar amp. Save up for a Pignose, a well regarded practice amp.

New member
Username: Hurricanebob

Post Number: 2
Registered: Oct-17
Was only testing the speaker to see if it worked, I do have a multi-meter but with limited skills, guess I could start checking components. I also have a Pignose amp but it hums really bad. Thanks for your suggestions--

Platinum Member
Username: Jan_b_vigne

Dallas, TX

Post Number: 18470
Registered: May-04

"I replaced the 3 fuses and have spayed all the pots but to no avail ... "

I congratulate you on having the good sense to minimize breeding between older components. Now, if only every BIC 6 speaker owner would have them neutered and tagged ...

The 640 was the second generation Yamaha into the US market and I understand your hesitance at replacing it. However, the issues of fixing anything vintage are numerous and, probably, should be obvious. Yamaha was fairly stingy with their service papers and no shop would have kept the originals in their files for nearly four decades. Parts were, to some extent, proprietary and no longer exist without salvaging another from another Yamaha of the same vintage.

Basic output stages of the 640 though are made up of rather commonly sourced parts. Since the channel still operates to some degree, this probably means the output devices may have survived the incident but that the component parts ahead of transistors have failed to some extent. On the other hand, and I don't remember the inside of a 640 well enough to say, it may be a matter of a relay being damaged. Either way, parts may be available if someone wants to search long enough and hard enough. The problem becomes how much you will pay anyone to do such a search after they have allotted some time to diagnosing the actual problem. Yamaha won't help, they have lone ago moved on from the 1970's models.

You can, if you prefer, search out repair shops which specialize in vintage restorations. A few big cities have someone close who will take on such a project. Of course, if the shop isn't close to you, then you need to add in shipping costs both ways to your final bill. And any guarantees on such repairs are typically very limited.

You should be able to see the final and potential cost of repairing vintage gear often far exceeds the original cost of the component. It pretty much always runs more than the cost of a new replacement component. Though, ...

For good and bad, the old phrase "they don't build 'em like that any more" is very true in consumer audio.

I would suggest you consider your options with the 640 and try to find a dealership with anyone who might remember the receiver. You don't say what your speakers are but many vintage speakers might be less than happy with many of today's "modern" receivers.

You might also try buying a replacement from a specialty retailer such as Audio Classics;

Audio Classics was started by a group of McIntosh Lab employees and they are as well versed in classic audio pieces as anyone I know. They can discuss with you your options and possibly suggest an even better component than the 640 for no more money than you paid back in 1979. They stand behind their goods and are truly some of the good guys in audio.

(I would though suggest you avoid the Lirpa products being offered by Audio Classics. As unique as their designs were, they generally proved to be laughably unreliable.)


New member
Username: Hurricanebob

Post Number: 3
Registered: Oct-17
Its hard to part with my old Yamaha, she was the life blood of my whole youth. Was running her through Bose and JBL speakers, the sound was fantastic. My 1980 Phillips 685 turntable also took a turn for the worse, only plays really fast now. Belt looks floppy, motor makes grinding noises, yes I live in an analog world. Thanks for all the comments
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