yamaha cr640

[mattx]

I recently picked up this receiver, It is fully functional except for one of the speaker sides keep losing connection also the power lights work but not any other, I am wondering what the reputation is of this amp and whether it is a real pain to change lamps/bulbs on this unit and whether it is worth it to fix 100%.

 

[MAXZ28]

If your illumination lamps are out, they're easy to change if the 640 is anything like the 840. I have some freebie twist lock lamps left over from a long gone CR840 if you need any. Just PM me your address.

What do you mean by "one of the speaker sides keep losing connection"? Does the sound cut out on one channel? May need some potentiometer cleaning.

 

[mattx]

yes the sound cuts out, also does the changing of bulbs require soldering?

 

[MAXZ28]

Depends on which bulbs you're changing.

IIRC, the dial illumination lamps are twist lock style. All the other bulbs probably require soldering [ I can't remember - it's been a few years since I had the CR840 ].

Are you familiar with Craig's Deoxit and Faderlube? It arguably the preferred electronics cleaner & lubricant duo for cleaning up potentiometers and switch contacts. I highly recommend you get some.

 

[mattx]

Yes I have removed knobs from other units and sprayed down with deoxit. How would I do that with this problem, or is it the same procedure? also Are the bulbs/lamps under the main cover or is there more to it to get at them.

 

[MAXZ28]

You just remove the unit from the cabinet and the dial illumination lamps are pretty easy to get to as you can see in this online pic. All the control pots look easily accessible as well. IIRC, I think the meter lamps may require a little more work to get to, but not too much.

 

[Tusec]

The 640's lights are soldered in, so you will have to desolder them. Once they're out you can replace them with twist-ins. It would be interesting to know the back story on why Yamaha opted to solder them into the twist-in sockets.

 

[merrylander]

Don't blame that on Yamaha, that is the work of some tech wannabee, I have seen it occasionally myself. If you get bare lead lamps you can thread them into the old twistlok bases with patience.

 

[mattx]

I am new at all this, I was one of those people that threw a unit away if the glass broke or crackleing happened. Any way is there somewhere on this board or another site for a simple step by step procedure of how to change lamps/bulb and other simple things. Sort of " how to fix vintage electronic equipment for dummies" just the basics.

 

[Blue Shadow]

I don't know of a site that discusses lamp changes, but if you pop the hood and look for the lights and (you did unplug the unit didn't you), see how they are connected, twist-loc in place or soldered, you should be able to learn a bit about how to change them. The guys that sell the LEDs or Lamps will supply correct voltage/amperage product so you don't have to figure out what parts to get. They might even talk you through a bit of the procedure.

But if you are uncomfortable taking the cabinet off the unit, don't do it and leave the work to a professional.

There is a how-to about cleaning the unit, especially the controls to remove the scratchiness that is caused by dirt in the switchgear. This page will guide you a bit in getting inside the unit and may make you feel better about jumping on the lamp project.

http://audiokarma.org/forums/showpost.php?p=2444686&postcount=1

 

[kotofei]

I just finished working on a CR-640 that was an "impulsive buy" at the SA thrift store. None of the lamps except power and stereo/local/dx worked so I ended up changing all 8 of them. The four twist-ins that lights up the dial was easy to change. The other four: three that illuminate meters and one in the dial pointer were soldered. However, it was not that difficult to change them. Unfortunately, you need to change all 4 of the meters/dial and all four twist-ins if only one is not working since they are connected in parallel. It was not that difficult to disassemble the CR-640 and get to the lamps.

The AK member dwojo sells these lamps; it was ca. $14 with shipping for the whole set.

I also ended up re-capping the 640's signal path, power supply and the phono stage. This greatly improved the sound. It was a pity that I needed to "thin the heard" so I parted with it. The tuner in this unit is extremely sensitive and the phono stage is very quiet.

I have a schematics if you need one and a user manual PDF.

 

[mattx]

thanks for all the help and offers everyone. The deoxit has cleared up the sound, so I have to decide how important it is to change bulbs. I have many other units that I am using, so maybe a side project in the next few months> btw I have a Harman-kardon twin powered 730 with almost identical problem. It kicks ass but some of the lamps are out as well as well as the case being pretty banged up. So I might practice on the cr640. also Is it ok to paint the outer shell of the 730?

 

[Blue Shadow]

The shell of the 730 is a vinyl. If it is not too bad, cleaning it with whatever and then feeding the vinyl with some car care products of your choice (for vinyl) should make it nice. If you need to paint it, there are paints that should adhere to the vinyl, but you will need to clean it aggressively to help adhesion.

 

[Tusec]

Don't blame that on Yamaha, that is the work of some tech wannabee, I have seen it occasionally myself. If you get bare lead lamps you can thread them into the old twistlok bases with patience.

Oh, they didn't come from the factory like that? I figured my soldered in lights were done at the factory. But that makes more sense that it was a tech (or some approximation thereof) who did it.

 

[Tusec]

I also ended up re-capping the 640's signal path, power supply and the phono stage. This greatly improved the sound.

So it made a pretty hearable difference, huh? Maybe I'll look into recapping mine. I know after 20+ years it's about time.

 

[merrylander]

Oh, they didn't come from the factory like that? I figured my soldered in lights were done at the factory. But that makes more sense that it was a tech (or some approximation thereof) who did it.

Unfortunately there are any number of 'techs' out there with just enough knowledge to be dangerous.:sigh:

 

[mattx]

armor all worked great at cleaning the hk case. There are a few sparkles on it, that I was thinking of trying goo gone to see I f I could get them off. Any way I will try to attack the bulb/lamp problem at some point. The hk sounds so sweet I really dont want to mess with it over something that has no effect on sound.

 

[Blue Shadow]

Glad you have the HK looking good. If the controls do not make noise, don't clean them because these HK controls will lose a bit of the silkiness of movement when cleaned. If they need internal cleaning because of scratchiness go right ahead. But you are right, enjoy and work on something else.