Kenwood KR-5600 relay/recap project; open relay needs help

[tusntuk2]

Thanks, Steve! I will check it soon. Funny how life happens while you have other plans...Meanwhile, I finished recapping the audio and power supply of the second 5600, and Holy Smokes! This machine has more power than I ever thought, and now it's sparkling clear, too. And I thought the recapped Pioneer SX727 sounded good - well, it does, but the Kenwood seems to overlap the bass and the treble with more range and more specfic (accurate?) control. Such an engaging hobby! You get to challenge yourself with new things while improving your old favorite things, which benefits your most favorite thing, music. Once again, many thanks to the kind folks here in this forum and all who offered guidance to restore this receiver. When I learn how to format a BOM for Mouser I will contribute to the library.

 

[onehander]

tusntuk2, I also have a my original untouched KR-5600 with a Dual 1228. I have just started setting them up so I checked the receiver first to see what worked. Powers up, lights and meters work, AM and FM work. Hooking up the turntable regardless of phono A or B and Aux, I get no sound. I plan to take my TT somewhere to insure it is sending a signal to receiver. Hopefully I can get this sweet little hot rod cranking as well as yours That's just where I stand now, but what I am really interested in is following your recap project, your pending BOM and most importantly hoping you will upload your KR4600/5600 service manual. I have spent the week reading through AK site and very impressed with the concise information and quality of the members.

 

[tusntuk2]

Good luck with your project onehander! You may want to start a new thread to help find the answer to the lost phono/aux signal. There could be many causes, and I am not an EE, just a retired musician with a hobby interest in old amps. The KR-5600 uses op-amps in the preamp section, of which I know nothing, so ask those who do. It is also recommended you thoroughly clean the controls and switches and inputs with deoxit, it can solve mysteries sometimes. I was told not to deox the little button switches (top row) in the glass.

As for the BOM, I am working on it, but with two caveats - first, I only swapped electrolytics in the PS and the Audio boards, not the muting or FM boards, and not the preamp. Secondly, Trio/Kenwood made several changes to their receivers throughout this period, some documented, some not, and even in my two receivers there are different PCB's. So this makes it hard to create one BOM that will fit every KR-5600. I will try to list what I did, and for what model boards, and that is the best I can do. The list will need more contributors. There is also considerable discussion about sizing and fitting different main filter caps, so look around AK for that.

Finally about the service manual. It has been noted hifiengine et all lack this manual. I took a chance and paid for a "manual" from a foreign supplier, and I got a good listing of bias adjustments for many models, and a better copy of the schematic, with several models of the small PCB's. I was disappointed for as much as I had paid, but the good schematic did prove useful. i would be happy to share the s/m with you, and the bias is 40mv.

Good luck with the project, and welcome to AK!

 

[Number Nine]

I have heard the phrase "Recap" numerous times on different forums.
I have the impression that this is targeting the electrolytic caps.
Are you doing this wholesale or to correct a specific performance issue?
For instance my 5600 is very slow to engage the relays at turn on, so I have stopped using the receiver.
My intention is to troubleshoot this issue.
However, while I have it apart I do not mind a little extra work / cost if there is a rational reason.
So in this context what does recap mean?

Thanks in advance for any information.

 

[tusntuk2]

Good answer rjsalvi. Hello Number Nine (...number nine...number nine...) and welcome to AK! Changing all of the electrolytics is a common project for many AK'ers and others who want to help preserve and maintain their favorite vintage gear the best they can. Most folks believe (me too) that some of these vintage analog units made the best sounding music, and the debates rage on. Many of us were probably raised on it, so we know what we like. Restoring the amps and tuners with modern parts, often stronger values and specs, is a way we can ensure "our" favorite equipment will last well into the future.

Search in AK a little for the relay problem, there are various solutions. All of them can be fixed/altered with an understanding of the parts involved, which are conveniently soldered separately. With modest soldering and DVM skills you can get a lot done.

 

[Martinvb]

Update: Got some parts ordered, and meanwhile I tacked the receiver back together and Voila! Music! Actually sounded very good, and it has not been recapped yet. I'll be glad to leave another update as I go along, but once again a HUGE THANK YOU! to all who offered help.

Thanks for this useful discussion, guys! Based on your analysis I was able to fix the delay (>4 min.) in the protection relay circuit of a Kenwood KR-5600. It took replacement of the culprit transistors Q25, Q26 and a local 100uf capacitor. Very happy with the result. @sregor @petehall347