Semanon
Super Member
I agree. The replacement Omron relay was far superior. I'll be long dead before that new relay fails.
KENWOOD KA-4004 Recap & Restore
- Thread starter Zeus12
- Start date
Zeus12
Active Member
Hi there fellas @Semanon and @kwayde 
I think WE FOUND THE CULPRIT!!! Yes, it was the relay ALL ALONG!
Changed ALL TRANSISTORS, CAPACITORS, DIODES, was going to even change resistors, and never bothered to think about the relay.
The little metal cover can be easily removed --just 2 screws holding it.
Under it is a "DAIICHI Type MSS and it has a black diode "FR2" across 2 of its pins.
Diode FR2
Close-up of pins:
I couldn´t find anything online for this exact type of relay but from the looks of it, it should be fairly easy to replace since it´s not soldered on to a PCB board. In case I wanted to bypass the relay, what wires would I have to jumper? Wires Red, Yellow and Blue go to the Main AMP board from what I can see.
In the meantime poking around and looking at it carefully, I noticed that the little plastic tab has a little hole that can be gently lifted which would allow to spray some DEOXIT. I did this on both sides, and turned it on and off a good number of times.
I cleaned the dirty goo that came out of the bottom, the contacts as well, and then plugged it and guess what fellows???
It looks like IT´S WORKING!!!
So excited that it´s working great from the start now. I have turned it on and off for more than 10 times and it has gotten better and better each time. Who knows what is going on in there but I would imagine something DIRTY in the contacts. The relay was working/clicking great before so I guess that DEOXIT does miracles. Should I change it anyways? In case somebody knows the best match from Mouser please let me know which one to get. I´m sure it wouldn´t hurt to change it for a new one. Poor thing has been "clicking" for almost 50 years now!
So I guess, I will have to close the chapter on this--hey, almost 5 pages on audiokarma is pretty good. Built like a little tank and one of the SWEETEST little amps I have come across. Learned so much and I think the pain and frustration paid off. At least now I now NOT TO FORGET about the relay...
I couldn´t have done it without the help of you guys and this wonderful forum.
Wish you guys the best!!! Now I´m on my next GEM, the HK 730. Oh, what a beauty that one is.
https://audiokarma.org/forums/index.php?threads/harman-kardon-730-left-channel-bias.994791/
Happy is the man that findeth wisdom, and the man that getteth understanding.
For the merchandise of it is better than the merchandise of silver, and the gain thereof than fine gold.
(Proverbs 3:13-14)
I think WE FOUND THE CULPRIT!!! Yes, it was the relay ALL ALONG!
Changed ALL TRANSISTORS, CAPACITORS, DIODES, was going to even change resistors, and never bothered to think about the relay. The little metal cover can be easily removed --just 2 screws holding it.
Under it is a "DAIICHI Type MSS and it has a black diode "FR2" across 2 of its pins.
Diode FR2
Close-up of pins:
I couldn´t find anything online for this exact type of relay but from the looks of it, it should be fairly easy to replace since it´s not soldered on to a PCB board. In case I wanted to bypass the relay, what wires would I have to jumper? Wires Red, Yellow and Blue go to the Main AMP board from what I can see.
In the meantime poking around and looking at it carefully, I noticed that the little plastic tab has a little hole that can be gently lifted which would allow to spray some DEOXIT. I did this on both sides, and turned it on and off a good number of times.
I cleaned the dirty goo that came out of the bottom, the contacts as well, and then plugged it and guess what fellows???
It looks like IT´S WORKING!!!
So excited that it´s working great from the start now. I have turned it on and off for more than 10 times and it has gotten better and better each time. Who knows what is going on in there but I would imagine something DIRTY in the contacts. The relay was working/clicking great before so I guess that DEOXIT does miracles. Should I change it anyways? In case somebody knows the best match from Mouser please let me know which one to get. I´m sure it wouldn´t hurt to change it for a new one. Poor thing has been "clicking" for almost 50 years now!
So I guess, I will have to close the chapter on this--hey, almost 5 pages on audiokarma is pretty good. Built like a little tank and one of the SWEETEST little amps I have come across. Learned so much and I think the pain and frustration paid off. At least now I now NOT TO FORGET about the relay...
I couldn´t have done it without the help of you guys and this wonderful forum.
Wish you guys the best!!! Now I´m on my next GEM, the HK 730. Oh, what a beauty that one is. https://audiokarma.org/forums/index.php?threads/harman-kardon-730-left-channel-bias.994791/
Happy is the man that findeth wisdom, and the man that getteth understanding.
For the merchandise of it is better than the merchandise of silver, and the gain thereof than fine gold.
(Proverbs 3:13-14)
Semanon
Super Member
Glad it is fixed.
It is your choice about replacing the relay. If it sounds good and it is all closed up, leave it. The problem will return well before another 50 years have passed. My recommendation for a relay is probably right. Still, I would verify the size and voltage first.
Enjoy this little gem!
It is your choice about replacing the relay. If it sounds good and it is all closed up, leave it. The problem will return well before another 50 years have passed. My recommendation for a relay is probably right. Still, I would verify the size and voltage first.
Enjoy this little gem!
Joe Kraft
Member
This seems like the right thread to jump into. I have a Trio KA-4004 that I have been working on for a while. Started with it doing nothing. I now have replaced all the transistors, caps, a couple of the diodes and the trimmers on the amp board (outputs are good) and have solid 20mv bias on both channels. DC offset in the single digits of mV. Hooked up speakers and it plays for a few minutes and then the right channel fades out. Trying to figure out where the issue is. Where did the test voltages come from earlier in this thread? Zeus12, is your KA-4004 still working well? Thanks for any help.
Zeus12
Active Member
Hi @Joe Kraft
Yes, this little gem is still working GREAT!! Did you check the relay? That was the final "fixer" for me, at least.
Cheers!!
Yes, this little gem is still working GREAT!! Did you check the relay? That was the final "fixer" for me, at least.
Cheers!!
Zeus12
Active Member
Hi @Joe Kraft
I wish I could help you some more buddy but I´m a newbie myself...
What relay did you use? Was it from Mouser? I should also change mine but I couldn´t find one on Mouser which is where I buy normally.
All I can say is that IT´S WORTH fixing this little beauty. Stereo imaging is ROCK SOLID!! Dead center!! Perfect for voices. I don´t think these little "Kennies" get all the love they deserve!!
Cheers!!
I wish I could help you some more buddy but I´m a newbie myself...
What relay did you use? Was it from Mouser? I should also change mine but I couldn´t find one on Mouser which is where I buy normally.All I can say is that IT´S WORTH fixing this little beauty. Stereo imaging is ROCK SOLID!! Dead center!! Perfect for voices. I don´t think these little "Kennies" get all the love they deserve!!
Cheers!!
Zeus12
Active Member
Greetings fellow audiophiles,
You were right @Semanon . The acting up of the relay came back and the spraying DEOXIT in there is not the best solution.
I decided to use the "paper strips" solution and that seems to have really worked well--SO FAR.
Has anyone seen this much dirt and gunk on the relay contacts?
Next step will be to obviously change it and put in a brand new relay in there. If anyone knows a Mouser equivalent to it, I would greatly appreciate it.
Cheers!!!
You were right @Semanon . The acting up of the relay came back and the spraying DEOXIT in there is not the best solution.
I decided to use the "paper strips" solution and that seems to have really worked well--SO FAR.
Has anyone seen this much dirt and gunk on the relay contacts?
Next step will be to obviously change it and put in a brand new relay in there. If anyone knows a Mouser equivalent to it, I would greatly appreciate it.
Cheers!!!
See post #55. Be sure to check your voltage. Mouser has plenty in stock.
https://www.mouser.com/ProductDetai...d-Safety/LY2-DC24?qs=Pjd0UV7BHP8x1Q3nVd1B1A==
Zeus12
Active Member
@kwayde
Big thanks for the link! That looks like a good relay which should last more than what I´m going to last.
So far, it is working like a charm, not one hiccup from it. On the next Mouser order I put in, I´ll get the relay as well and save on shipping charges.
This little amp is SOOOOOOOOOOOOOOO SWEEEEEEEEEEET and musical that just invites you to listen.
One thing I noticed. There is a slight hiss/background noise--independent of volume but when using Headphones (SPEAKERS OFF) it is DEAD SILENT. I would imagine it´s because the main filter caps, which are still the original ELNA ones, that is causing that. What function is that 100 uf axial cap doing there? Here are the reading I got with my cheap cap meter. Should I change those caps as well?
Cheers!!
Big thanks for the link! That looks like a good relay which should last more than what I´m going to last.
So far, it is working like a charm, not one hiccup from it. On the next Mouser order I put in, I´ll get the relay as well and save on shipping charges.
This little amp is SOOOOOOOOOOOOOOO SWEEEEEEEEEEET and musical that just invites you to listen.
One thing I noticed. There is a slight hiss/background noise--independent of volume but when using Headphones (SPEAKERS OFF) it is DEAD SILENT. I would imagine it´s because the main filter caps, which are still the original ELNA ones, that is causing that. What function is that 100 uf axial cap doing there? Here are the reading I got with my cheap cap meter. Should I change those caps as well?
Cheers!!
Attachments
Semanon
Super Member
The 470 and 100 uF caps are filter caps for the phono pre board, tone board and protection circuit. The 6800 uF caps are the filter caps for the main amp board.
The hiss could be a lot of things, but taking it one step at a time is the wisest approach.
When you separate the preamp from the main amp, do you hear the same noise? On my 6004, the amp was silent, while the tone amp had a lot of noise and needs to have the dreaded 2SC458LC transistors replaced. The 4004, fortunately, has none of those noisy things.
The hiss could be a lot of things, but taking it one step at a time is the wisest approach.
When you separate the preamp from the main amp, do you hear the same noise? On my 6004, the amp was silent, while the tone amp had a lot of noise and needs to have the dreaded 2SC458LC transistors replaced. The 4004, fortunately, has none of those noisy things.
Last edited:
Zeus12
Active Member
@Semanon
Hey there buddy!!! So nice to hear from you again!!
Yes, forgot to mention, that the Pre-Amp part is DEAD SILENT--likewise, when using the headphones. Not one little hiss. The Pre-Amp has been fully recapped and the transistors as well--all small transistors in this amp for that matter.
By the way, that tone board looks so simple and "clean" that this could also be used as a PRE Amp?? The less signal path = the cleaner and more faithful the signal??
I don´t use PHONO, just the AUX (connected to a DAC), so then it can´t be those "white" axial ELNA caps and it must be one of the big black ELNA caps. What does that 1000uf Black Elna do? The one right next to the transformer? There are in total 3 big black caps---2 ELNAS 6800uf (have crept up in value, by the way) and 1 1000uf cap
Apart from the light hissing, coming from the tweeter, I can also hear a very slight "hum" from the woofer. Isn´t that a tale tale sign that the "filter" caps need to be changed? Nothing major, and it is only heard when you put your ear right next to the speaker.
Cheers!!!
Hey there buddy!!! So nice to hear from you again!!
Yes, forgot to mention, that the Pre-Amp part is DEAD SILENT--likewise, when using the headphones. Not one little hiss. The Pre-Amp has been fully recapped and the transistors as well--all small transistors in this amp for that matter.
By the way, that tone board looks so simple and "clean" that this could also be used as a PRE Amp?? The less signal path = the cleaner and more faithful the signal??
I don´t use PHONO, just the AUX (connected to a DAC), so then it can´t be those "white" axial ELNA caps and it must be one of the big black ELNA caps. What does that 1000uf Black Elna do? The one right next to the transformer? There are in total 3 big black caps---2 ELNAS 6800uf (have crept up in value, by the way) and 1 1000uf cap
Apart from the light hissing, coming from the tweeter, I can also hear a very slight "hum" from the woofer. Isn´t that a tale tale sign that the "filter" caps need to be changed? Nothing major, and it is only heard when you put your ear right next to the speaker.
Cheers!!!
Semanon
Super Member
The early Kenwood’s had very simple preamp sections. The 4004 has two transistors and a few caps when the tone controls are not engaged.
I missed the 1000 uF cap when I first looked at the schematic. It is The filter cap for the tone and phono. It comes right after the diode. If you have no noise or hum in the preamp section, it’s probably fine (but at 50 years is probably due for retirement).
Hum in both channels would point to the filter caps. Hiss is harder to pin down, but could be the filter caps. Based on your measurements and description, that’s where I’d start.
Keep us informed.
Zeus12
Active Member
@Semanon
Thanks for enlightening me!! Will order those 3 big black caps next time I place an order with mouser, along with the relay, and in the meantime...........I will continue listening to this little gem. Sounds so musical and warm that I´m keeping it in rotation for an extended period of time. By the way, that relay cleaning seems to have really fixed it. I haven´t heard on hiccup from it. Knock on wood!!
How does that KA-6004 compare with this one? Does it have more low end? I saw one for sale and I´m seriously thinking about it. The one I would really like to hear is the KA-8100 with those dual transformers....Oh, that should be a pleasure!
Cheers!!
Thanks for enlightening me!! Will order those 3 big black caps next time I place an order with mouser, along with the relay, and in the meantime...........I will continue listening to this little gem. Sounds so musical and warm that I´m keeping it in rotation for an extended period of time. By the way, that relay cleaning seems to have really fixed it. I haven´t heard on hiccup from it. Knock on wood!!
How does that KA-6004 compare with this one? Does it have more low end? I saw one for sale and I´m seriously thinking about it. The one I would really like to hear is the KA-8100 with those dual transformers....Oh, that should be a pleasure!
Cheers!!
Semanon
Super Member
The KA-6004 sounds lovely. However, it is more complex and requires a rebuild of the preamp to remove the 2SC458LC transistors. Mine sounded awful when I got it - like wind blowing through the speakers. The amp was dead quiet, but the preamp needed lots of work, and it's a bit of a pain to work on. I don't think you would hear much difference between the two. If the power of the 4004 works for your speakers and your room, stick with the 4004.
The KA-8100 is different animal. When I was downsizing, I had to choose between the KA-6004 and the KA-8100. I chose the 8100, mostly because of looks/styling (I have the handles!). Both sound wonderful, but different. The 6004 is warmer, but the 8100 just feels more powerful with better bass control. I also think 8100s are under rated, as most folks want the 9100 with the meters.
The KA-8100 is different animal. When I was downsizing, I had to choose between the KA-6004 and the KA-8100. I chose the 8100, mostly because of looks/styling (I have the handles!). Both sound wonderful, but different. The 6004 is warmer, but the 8100 just feels more powerful with better bass control. I also think 8100s are under rated, as most folks want the 9100 with the meters.
Zeus12
Active Member
@Semanon
OK. You convinced me again!!! Thanks for that sound description on the 6004 and 8100. I prefer the warmer sound and one thing I have learned is that "paper measurements" don´t equate with "musicality" --those feelings and pleasant emotions you get when listening to music. Gonna stick with the KA-4004!
Speaking of measurements and "paper specs"--here´s a personal example:
NAD 319 vs. Kenwood KA-4004 --- On paper the NAD should KILL the little Kenny---But to my ears---I prefer the 4004 BY FAR. The NAD might have a lot of power and dead silent but it doesn´t "invite" you to listen to music. It is missing that "warmth", "musicality" and "emotion". By the way, got another speaker relay issue, jajaja, with the NAD. Here´s my post on it, just in case you want to check it out.
https://audiokarma.org/forums/index.php?threads/nad-319-relay-cleaning-change.1019616/
Big thanks for all your help buddy!!! Learning something new everyday thanks to this wonderful forum.
Cheers!!
OK. You convinced me again!!!
Thanks for that sound description on the 6004 and 8100. I prefer the warmer sound and one thing I have learned is that "paper measurements" don´t equate with "musicality" --those feelings and pleasant emotions you get when listening to music. Gonna stick with the KA-4004! Speaking of measurements and "paper specs"--here´s a personal example:
NAD 319 vs. Kenwood KA-4004 --- On paper the NAD should KILL the little Kenny---But to my ears---I prefer the 4004 BY FAR. The NAD might have a lot of power and dead silent but it doesn´t "invite" you to listen to music. It is missing that "warmth", "musicality" and "emotion". By the way, got another speaker relay issue, jajaja, with the NAD. Here´s my post on it, just in case you want to check it out.
https://audiokarma.org/forums/index.php?threads/nad-319-relay-cleaning-change.1019616/
Big thanks for all your help buddy!!! Learning something new everyday thanks to this wonderful forum.
Cheers!!
Reliving.
Active Member
What transistors did u use to replace them all?Greetings fellow audiophiles,
Thanks @Semanon for enlightening me along the way!!! I will get a Fluke (used one). Saw a 179 for a fairly good price. The 87V, which is what many say would be the best for electronics use, is way too expensive for my budget.
Changed the Diodes De12-15 (S-1.5-02) with a 1N4003. I checked them and they all measured more or less around this value:
View attachment 2542385
Also checked the two oil filled caps (Ce22,23) and they checkout within specs so I left them in there. I lifted one leg for the measurement. Original value 0.022uF:
View attachment 2542386
I rechecked the Bias, connected it and for a moment I thought it was fixed. I was getting ready to start jumping up and downI still have the De5-De10 pending to change. Could it be one of those little "thyristors" close to the Bias pots? Or one of the "ceramic" (Ce1,2) or "mylar" (Ce15,16) caps? The symptoms normally take place at start-up and I have been listening to it since yesterday and it´s working GREAT! Maybe those De3,4 Diodes (STV-3). They are screwed to the heatsink so maybe it has something to do with temperature?
So far, this is what I have changed:
View attachment 2542390
Oh, forgot to check the relay that you mentioned before. Gonna keep trying!!
Cheers buddy!!!
Zeus12
Active Member
Hi @Reliving.
I replaced them all according to the "el maestro" dlucy, following this thread:
Cheers!!
I replaced them all according to the "el maestro" dlucy, following this thread:
Top Ten Worst Transistors - noisy, failure-prone, whatever... and replacements
I've followed AK advice for several vintage solid state receivers now and the difference in sound, from recapping and from replacing "known-to-be-noisy" small signal transistors to be amazing. While following along with others' threads and trying to help out with "consider replacing these...
audiokarma.org
Cheers!!