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Kenwood KW-40 tube receiver pictures and schematics

BmWr75

BmWr75

Top octave? pfffffftttttt
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Here's the link to my prior thread on this receiver when I was thinking about buying it.

http://www.audiokarma.org/forums/showthread.php?t=375737

Well, its bought now. Time for some pictures.

First, here are the schematics that came with it scanned to jpeg images. Plus some shots of the front panel.

Anyone got a service and/or operations manual they can share for this model?

Since the seller said it had been recapped and retubed, I did an inventory today. There is a duke's mixture of tubes in it and not all the caps have been replaced, lot's of electrolytics are new though.

EL84s - one Sylvania black plate, one marked Made in Austria, two completely wiped

12AX7A - one each Sylvania, IEC?, Marshall, Fisher with a diamond mark, one wiped

12AX7WA - one Jan Sylvania

12AU7 - one G.E.

Didn't count and ID all the tuner tubes.​

Have the old gal hooked up on my bench now and playing. She's sounds good even with the tubes that came in it. Headphones sound great too. :music:
 
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I hear you BuzzK. Am certain the local Pittsburgh tube guru checked all the caps for leakage. But, I like you would rather all the caps be new. This will be in the longer term plans for this receiver.
 
I have a Lafayette LR-800 (7189 receiver, made by Kenwood) and parted out another one (no knobs or tubes, broken dial glass, etc.). Both had the output coupling caps replaced with orange drops before I got them... and both had mismatched output transformers. So both had already lost a transformer to leaky caps...

Controls will be noisy and won't respond to cleaner until the leaky caps are replaced (even millivolts of DC will make a control noisy).
 
The only noise I hear from this amp at all is a little transformer hum.....at least that is what I think it is. I have to have the volume at zero and my ear near the transformer to hear it. Can't hear the hum through speakers or headphones at all.
 
Based on the schematics and photos, this thing seems pretty similar to the Trio W-45 I have, which is a wonderful little amp. It only cost me $35 or so to replace every capacitor in it and the matching tuner with orange drops and nichicon electrolytics. Its not a terribly large amount of work, and probably well worth it.
 
I probably have all the small caps on hand. Will have to look into buting a new multi-cap can, 100uF electrolytic and one or two larger caps..
 
Noticed in the close up pictures that are in post #1, shows the front panel with knobs, etc. and noticed that the knob section to set for AM, etc. has a setting for FM, FM SUB and FM STEREO. I've never heard or seen a dial/knob section on an audio tuner, receiver, etc. for FM SUB?
What is FM SUB?:scratch2:
 
R-2-R said:
Noticed in the close up pictures that are in post #1, shows the front panel with knobs, etc. and noticed that the knob section to set for AM, etc. has a setting for FM, FM SUB and FM STEREO. I've never heard or seen a dial/knob section on an audio tuner, receiver, etc. for FM SUB?
What is FM SUB?:scratch2:
Click to expand...

I have been told this is a setting that allowed the user to determine if the station was broadcasting in mono or stereo.
 
Hey Guys,

Is the light gray Elnic 40 uF 150 V cap in top left of this picture new or original.

attachment.php
 
That is definitely OEM! The dead giveaway is the WV (working voltage rating)
no longer listed on more modern caps. (also mfd as opposed to uf is dated)

regards,

Allen
 
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R-2-R said:
Noticed in the close up pictures that are in post #1, shows the front panel with knobs, etc. and noticed that the knob section to set for AM, etc. has a setting for FM, FM SUB and FM STEREO. I've never heard or seen a dial/knob section on an audio tuner, receiver, etc. for FM SUB?
What is FM SUB?:scratch2:
Click to expand...

OK, I talked to the tech that did the restoration work on this receiver. It has no FM Stereo light and back in the day when it was built, some FM stations broadcast in mono, some in stereo. The FM SUB setting is a Left channel minus Right channel setting. If the FM station was broadcasting in mono, you would here nothing on the FM SUB setting because the left and right channels contained identical info. If broadcasting in stereo, you would hear only the differences between the two channels. Neat hunh??!!
 
I have a similar model Kenwood (Trio W38) receiver. I agree with Buzz, Tom and others about the need to replace the grey caps. I had to replace all the electrolytics in mine.
 
They really do make a nasty mess when they pop, and it will almost always take the galvy out of the metal and result in a rust spot.:thumbsdn:
 
Hey Guys,

Take a look at the picture below. The 40 uF cap is easy to ID as an electrolytic that should be replaced.

But, what about the brown butter bean shaped ones right on top and to the right of the 40 uF cap? Do these look new?

What about all the gray tubular caps scattered all over the picture that are mostly .005 uF in size and smaller which appear to be nonpolar? I ask because I usually replace these with orange drop film and foil polypropylene capacitors, which are not electrolytic (right?).

attachment.php
 
Those gray jobs are just paper capacitors. The Japanese made caps looking different than the ones made in the USA. But they are just as bad. You can use Orange Drops, IC yellow "Lemon Drops" or whatever. But they should be replaced. Did I see some green Chicklets? They may be Mylar and OK. Or, they may have already been replaced. The most important caps are the coupling caps from the plate to the grid of the next tube and the electrolytic filter capacitors. If you find any caps made by Elna, they are most likely bad.
 
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If you replace the electrolytic capacitors, don't use the terminal of the old cap as a tie point. You must isolate the old electrolytic capacitor with a terminal strip, new can or whatever...
 
kvflyer

U did see some green chicklets in a different picture connecting the power tube sockets, they are new. What about the brown chicklets in the photo above (new too)?

I do not understand this advice "If you replace the electrolytic capacitors, don't use the terminal of the old cap as a tie point. You must isolate the old electrolytic capacitor with a terminal strip, new can or whatever.". Please take another run at explaining that one.
 
Fm sub.........

Thank you BmWr75 for your explaination about "what is FM SUB" very interesting to say the least, again thanks!
 
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