Kenwood KR-9600 Upgrade, Mods and Restoration

[bro4000]

Thanks for the welcome onwardjames

 

[bro4000]

Hopjohn, I think everyone on this forum has asked for advice a time or two. Yourself included. If you really think that I'm going to drain capacitors with my tongue or throw a bunch of parts into a receiver and plug it in, your assumption of me is wrong. I have several vintage receivers that I have fully disassembled, cleaned, cleaned the controls, replaced lights, re-soldered circuitboards, replaced capacitors, etc. I also have two old Hafler Dh-500's that really were my first projects. I did not fully restore them but did a lot to them. This receiver is a project for me. I want to take it one step at a time like I had previously posted. I want to do all of the required Mods first and then restore the rest. I recently acquired another 9600 for a great price. My goal is to fully go through one of them and then compare the two in a sound comparison. Does the 9600 have a shit load of parts in it? Absolutely. I build jet engines for a living and have done so for my whole career. If you want to talk about something that has a lot of parts I can show you. I have read these forms for quite some time now and felt it was necessary to join since I had gathered so much information from this site. I have no problem with you or anyone else busting my balls on this forum but in the future please do so in a pm and not in a forum where I'm seeking advice. I am asking and thanking everyone of you for your advice. I hope you guys will continue to help me through this journey. I really do appreciate your help.

 

[SicMan]

OH YES ! welcome to the forum subscriber section too.

And the tip of the day is:

Or solder in shorts.

 

[bro4000]

Haha. Great advice!!!

 

[raffman]

First, welcome to AK (you said you just subscribed recently).

Keep up the fine restoration, proceed slowly, and let others lead ya home. Watching with interest.

I'll just pass along what I learned by going through the posts just as you are doing - I hope others chime in also - I'm just regurgitating. This thread is an excellent source of info and what I referred to most often http://www.audiokarma.org/forums/index.php?threads/kr-9600-restoration-info.441957/

- I pay particular attention to posts by hopjohn, Sicman and Echowars and a few others who know their way around these things

-I should have said KSC1845FTA http://www.mouser.com/ProductDetail/Fairchild-Semiconductor/KSC1845FTA/?qs=UMEuL5FsraDCmxWozTypUA==

- Keep an eye out for the original electrolytics that are in ORANGE jackets (either dark or light orange) - these are low leakage caps. The standard advice is to use 105 degree Nichicon UKL series in those positions. The orange caps have the suffix "BR" in the s/m parts list, but In my experience their usage isn't necessarily consistent from one unit to the next

- For 1uf 50v caps - and there are quite a few, esp on the pre-amp - use film caps. There used to be some well regarded Panasonics available, but they are NLA. These seem to be the next best bet http://www.mouser.com/ProductDetail/WIMA/MKS2B041001C00KSSD/?qs=sGAEpiMZZMv1cc3ydrPrFwgzP98AO9idwFKwdAiDxsI= These are also preferable to replace the 1uf orange caps. Some will say to use film caps for 4.7uf and lower, but size becomes an issue so I have stuck to 1uf

- There are two tantalum caps on each amp board. Wisdom is to get rid of those and replace with a single 1.5uf polypropylene film cap soldered between the two (+) holes http://www.mouser.com/ProductDetail/Panasonic/ECW-F2155JA/?qs=sGAEpiMZZMv1cc3ydrPrF0%2bjlB8SXIRuAwi0zsbAaFw=

- I have used 105 degree Panasonic FM & FC on the power supply and relay boards. Others might prefer Nichicon HE & PW

- If you're good at reading schematic (I'm not) and determining which caps are in the signal path you can put fancy caps there. I've used Elna Silmic II, Nichicon UKW, UFG (fine gold), UKZ(muse) for all positions and I can't tell a bit of difference. Just beware that Silmic II and UKZ caps are big, and fitting them can be a problem, esp on the pre-amp board which is jam-packed

- I have not messed with the tuner board out of fear of all things tuner, so no help there

- I have replaced the 24V zener diode on each amp board (De3) http://www.mouser.com/ProductDetail.../1N5252B/?qs=sGAEpiMZZMvAvBNgSS9Lqm0p7KQalEG0

- If you want a little side project, you can remove the switch body from the power switch and rotate it 180 to get brand new unused contacts. You will also have to move the end wires from each side to the unused lug. Each one I have taken apart had been ridden hard and put away wet on the AC contact. Or you can just leave it be if it's working.

- Seems worthwhile to me since this is a big project to replace both speaker relays while you're in there http://www.mouser.com/ProductDetail/Omron-Automation-and-Safety/MY4-02-DC24/?qs=eORE%2bZ%2b0Crv7hRNHqogGYw==

- My best advice is to FEAR the power amp boards and make damn sure you have it right before powering up (through a DBT of course). I don't know for a fact that a mistake here could take out a TA-200W, but I certainly didn't want to find out, and I sweated BBs each time at that first power-up

And yeah - just like Mad Magazine $25/cheap!

Wonder if u mind making suggestion for minimum update mods. I am complete novice but mechanical engineer and have recapped and repaired my tuners in the past. This 9600 only works on both channels on mono now. R2 and R2 scorched. I will replace R1-4 and Q1 and Q2. What else u recommend at minimum so I can get back to cranking Zeppelin on weekends.

 

[onwardjames]

Wonder if u mind making suggestion for minimum update mods. I am complete novice but mechanical engineer and have recapped and repaired my tuners in the past. This 9600 only works on both channels on mono now. R2 and R2 scorched. I will replace R1-4 and Q1 and Q2. What else u recommend at minimum so I can get back to cranking Zeppelin on weekends.

My suggestion is to start a thread on it, there are many very helpful techs here who will literally lead you thru a resto, if you have the tools and talent. Best of luck, and warm regards to a new AK member.

 

[New2theold]

Well I’ve read the post concerning some necessary mods for the KR 9600! I have to say I am amazed and thankful for all of you who have given time, resources and encouragement to those of us investing in this hobby.
I’ve actually been trying to sell my KR 9600 but I can’t seem to get a taker. Therefore I decided to do a few of the mods/preventative maintenance things listed for the kenwood.
After checking DC at the speakers (197mv r 201mv L). I decided to replace q1&2 on the power amp. now both are under 17mv. I couldn’t get ZTX’ over 850gain/HFE. I may order more. Lol
I also did the regulator board resister upgrades replacing R1, R2, & R3 with the aluminum cased replacements. thank you gentlemen.
You are appreciated!!!

 

[Joseph G]

I have seen KR9600 receivers where the regulator transistors were changed to ONSemi MJF3055 and MJF2955, and those are mounted to the chassis (requiring no insulating hardware), while the resistors are raised up from the board, and or mounted on the heat sinks where the transistors were previously mounted. My question has to do with the heat dissipation of the regulator transistors. It seems like the newer recommended replacements actually get hotter than the originals, while their current and voltage spec is much higher, including the dissipation specification. You would think it should run cooler, right? Am I missing something? Considering there is no excessive current draw or malfunction down the line. An anyone advise me here. Thanks.

 

[Joseph G]

Hello, lots of good info here! Thanks. I went another way when I repaired and re-capped my unit. I added extra heat sink to the regulators, and instead of mounting those big metal resistors to the chassis, I got higher wattage components and raised them up from the board with ceramic spacers. I got rid of the red wire and jumped it on the bottom of the board, then I ran the orange wire from the bottom so it is away from the hot parts, instead of running right next to the resistors. It looks prettier now and It runs cooler than it did before. I actually prefer on other units to mount the transistor regulator to the chassis, using a full pack TO-220 component like the MJF3055. If you do this on the Kenwood, you could mount the metal resistors to the heat sinks.

 

[SicMan]

Just a note here on the regulator board.
I had a problem with the relays kicking out when the 9600 warmed up.
Traced it to the reg bd 34v dc drifting up a few hundred millivolts. rebuilt the reg board and used 5 watt resistors.
I use MJE15032G and MJE 15033G 50 watt xistors
I usually use the metal resistors mounted to the chassis.
Joe I like those heat sinks

John M

 

[Joseph G]

Thank you, I chose the resistors carefully, these are Ohmite with a hi temp low drift specification. I also noticed that the heat dissipation was lower after the re-cap. there were surely some leaky components drawing extra current. I noticed some people change the 60 ohm to something significantly higher. I wouldn't go any higher than 68 Ohm. I am in the process of upgrading the four filter caps to 15,000uf 80 Volt, instead of the 12,000uf 100 Volt parts currently installed. I had to replace them years ago, but did not do any other mods or improvements until now. I have done other units, (Akai) replacing the 10,000uf with 15000uf 105c high ripple parts from Cornell, and the result was positive. the amp has an openness and more punch than before. I use the Akai amp often.