Hi Tony. I have enjoyed many of your videos and just picked up this receiver. The original owner said it was serviced due to a low right output. Looking under the hood, Re57 was replaced and zener diode De10 on the main amp has one lead clipped. It measures 400mV both ways so I assume is faulty. The channel outputs look good on my scope but is this a danger to my speakers? DC is a bit high at 93 and 177mV. I will be recapping the board and obviously replacing the diode. Thanks again for all your valuable information sharing!
I know this is an old video, but if any new viewers stumble into this I would like to add more content. @ 9:00 , doing the "Maths" to convert peak to peak to RMS isn't too hard, you just divide the P-P value (from the scope) by 2.83 first, if you are looking to compare to an amp's RMS rated output value. Now, if an amp claims a "peak" power rating, that is more arbitrary, because it doesn't necessarily imply a "continuous peak" or "transient peak" wattage rating. Continuous would technically be 1/2 of Peak to peak, or, 1.4142, but a transient could be higher due to the short term power capacity of the main capacitors coming into play for a burst of signal over a millisecond time increment, and since there is no "standard" test for that it is info that a manufacture could brag about, but be hard to verify.
Just noticed at 25:46 in the video that you are supposed to adjust La8 for FM IF but you are actually adjusting Lb8 . . . La8 is on the front end board. Probably why your adjustment didn't have any affect.
You have the best video content for the vintage audio hobby. I really enjoy watching them. You are very knowledgeable, and take the time to explain things. I am a newbie so please be patient with my comments and questions. I have a non-functioning Kenwood KR-6340 that is the target of my ultimate fix-up. This KR 7400 is close to the same vintage. I have not done anything to the 6340 yet, as I am getting a lot of practice on other not-as-important gear and acquiring some test equipment. I am worried about all the wire wrapped pins in the 6340 because I don't think I will be able to keep the boards in place and still work on them. For this video, did you work on the board(s) in place, or did you remove them from the chassis first?
I Enjoy your video's very much.. I just picked up my third Kenwood and it is a KR-6020 (6400) which is working pretty good after major clean... All works fine except for Tuner... When playing tuner the left channel is half the volume of the right ch... All other functions play correct sound balance and its only the tuner that is low output on left speaker.. Ive cleaned the switches multiple times and even the switch on the back side.. So im assuming the issue is located on the tuning board ???
Bill, Thanks for the question! I am not currently taking any new jobs, as things are pretty busy at work/home. I was thinking of taking on a few outside projects later this winter, if things slow down. Check back later this year. Thanks
What is the " standard" input voltage from your tone generator to the receiver? Should it be 150mv. ? I am trying to confirm the output of my KR7600. I only got like 17 watts / Channel,so something is wrong. I think my online tone source was only reading about 40 mv and I was testing at 50 Hz. I will boost that signal through a Franken method and use 1Khz signal. Question is really how much boost on the input signal? Manual does not specify except for specs on the aux. Input sensitivity. Cool video. Thanks !
I owned a KR-6400 and it was beautiful sounding even without restoration.
Hi Tony. I have enjoyed many of your videos and just picked up this receiver. The original owner said it was serviced due to a low right output. Looking under the hood, Re57 was replaced and zener diode De10 on the main amp has one lead clipped. It measures 400mV both ways so I assume is faulty. The channel outputs look good on my scope but is this a danger to my speakers? DC is a bit high at 93 and 177mV. I will be recapping the board and obviously replacing the diode. Thanks again for all your valuable information sharing!
I know this is an old video, but if any new viewers stumble into this I would like to add more content. @ 9:00 , doing the "Maths" to convert peak to peak to RMS isn't too hard, you just divide the P-P value (from the scope) by 2.83 first, if you are looking to compare to an amp's RMS rated output value. Now, if an amp claims a "peak" power rating, that is more arbitrary, because it doesn't necessarily imply a "continuous peak" or "transient peak" wattage rating. Continuous would technically be 1/2 of Peak to peak, or, 1.4142, but a transient could be higher due to the short term power capacity of the main capacitors coming into play for a burst of signal over a millisecond time increment, and since there is no "standard" test for that it is info that a manufacture could brag about, but be hard to verify.
Just noticed at 25:46 in the video that you are supposed to adjust La8 for FM IF but you are actually adjusting Lb8 . . . La8 is on the front end board. Probably why your adjustment didn't have any affect.
You have the best video content for the vintage audio hobby. I really enjoy watching them. You are very knowledgeable, and take the time to explain things. I am a newbie so please be patient with my comments and questions. I have a non-functioning Kenwood KR-6340 that is the target of my ultimate fix-up. This KR 7400 is close to the same vintage. I have not done anything to the 6340 yet, as I am getting a lot of practice on other not-as-important gear and acquiring some test equipment. I am worried about all the wire wrapped pins in the 6340 because I don't think I will be able to keep the boards in place and still work on them. For this video, did you work on the board(s) in place, or did you remove them from the chassis first?
I Enjoy your video's very much.. I just picked up my third Kenwood and it is a KR-6020 (6400) which is working pretty good after major clean...
All works fine except for Tuner... When playing tuner the left channel is half the volume of the right ch... All other functions play correct sound balance and its only the tuner that is low output on left speaker.. Ive cleaned the switches multiple times and even the switch on the back side..
So im assuming the issue is located on the tuning board ???
Are you open to service receivers for people that do no live in your area?
Bill,
Thanks for the question! I am not currently taking any new jobs, as things are pretty busy at work/home. I was thinking of taking on a few outside projects later this winter, if things slow down. Check back later this year.
Thanks
What is the " standard" input voltage from your tone generator to the receiver? Should it be 150mv. ? I am trying to confirm the output of my KR7600. I only got like 17 watts / Channel,so something is wrong. I think my online tone source was only reading about 40 mv and I was testing at 50 Hz. I will boost that signal through a Franken method and use 1Khz signal. Question is really how much boost on the input signal? Manual does not specify except for specs on the aux. Input sensitivity. Cool video. Thanks !