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Kenwood L-09M Caps and Restorations

M

megasat16

Well-Known Member
I picked up a pair of L-09M amps and one unit has some problems. I checked the power caps and they seems to be working fine. I found a lose connection in the RCA socket that is causing hum when the I/C is connected.

RCA cable is sort of acting like an antenna and it scares the chit out of me when I am hearing that hum. I wonder should I be doing an overhaul since it's about time.

I read some old threads that EchoWars has caps for the L-09M.

Paging EchoWars! Would you chime in please?

TIA!
 
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The only ones that are hard to get are the two large filter caps. I put together a group order a few years ago and shelled out $2000+ of my own money to get the caps, only to be abandoned by about 1/2 of the guys who said they wanted them. It took a while, but they are all long gone.

Mouser has one (1) United Chemi-Con 18,000µf 160V cap measuring 76mm x 93mm (Mouser part number 661-E36D161HPN183ME9) for what is actually a pretty reasonable price of about $51. They also show a minimum order of only one, and a lead time of about 90 days. All reasonable. If you want replacements for the original power supply caps, you can't do much better than that. Get 'em on order and they'll hopefully show up.
 
Thanks Glenn for your input! I wished you had some power caps left but since they are long gone, I will try to order a set of 4 caps from Mouser and hope they can fill the order.

I have been following your threads and I guess the fan replacement and the the lytics replacements are the only things I need with these monsters, right?

The other thing I need is the bulbs for the meters, do you happen to remember the correct bulb substitute? If not, I think I will just use the 12V LED. I measured the voltage across the pins and looks like 12V DC is what's going to the lamp.

Thanks!
James
 
megasat16 said:
Thanks Glenn for your input! I wished you had some power caps left but since they are long gone, I will try to order a set of 4 caps from Mouser and hope they can fill the order.
Click to expand...
No reason they can't. They show a lead time of about three months and I have no reason to doubt that. I'd simply get them on order before someone changes their mind about it.
I have been following your threads and I guess the fan replacement and the the lytics replacements are the only things I need with these monsters, right?
Click to expand...
Fan, new voltage dropping resistors for the fan, new electrolytics, new speaker relays, and clean off the old thermal compound from the outputs and mica insulators and put fresh stuff on.

Speaker relays:
Omron MY4-02-DC24 (two of these)
Omron MY4-02-DC48 (One of these)

I've changed my recommendation for the fan resistors since my old post on this amp. 1.2K for the big resistor, and 400 ohms for the small one. Mouser part numbers 588-B12J1K2E and 588-B8J400E.
The other thing I need is the bulbs for the meters, do you happen to remember the correct bulb substitute? If not, I think I will just use the 12V LED. I measured the voltage across the pins and looks like 12V DC is what's going to the lamp.
Click to expand...
8V to the lamp. If you measure with an open bulb, there's no current through a 10 ohm 2W limiting resistor, so your voltage reading is skewed.

A small 5mm LED won't light the meter very evenly. SuperbrightLEDs.com sells a 360° 8mm LED that might work reasonably well with the proper current limit resistor, but it's just easier to replace the lamp with a new 8V 250mA lamp from AK'er Dgwojo. He'll sell you one with leads attached to make things a little easier.
 
EchoWars said:
No reason they can't. They show a lead time of about three months and I have no reason to doubt that. I'd simply get them on order before someone changes their mind about it.Fan, new voltage dropping resistors for the fan, new electrolytics, new speaker relays, and clean off the old thermal compound from the outputs and mica insulators and put fresh stuff on.

Speaker relays:
Omron MY4-02-DC24 (two of these)
Omron MY4-02-DC48 (One of these)

I've changed my recommendation for the fan resistors since my old post on this amp. 1.2K for the big resistor, and 400 ohms for the small one. Mouser part numbers 588-B12J1K2E and 588-B8J400E.8V to the lamp. If you measure with an open bulb, there's no current through a 10 ohm 2W limiting resistor, so your voltage reading is skewed.

A small 5mm LED won't light the meter very evenly. SuperbrightLEDs.com sells a 360° 8mm LED that might work reasonably well with the proper current limit resistor, but it's just easier to replace the lamp with a new 8V 250mA lamp from AK'er Dgwojo. He'll sell you one with leads attached to make things a little easier.
Click to expand...

Oh Wow! :ntwrthy: :ntwrthy:

:jawdrop:

Thanks for such a detail response! I am floored by the details and the insights you provided for these L-09M. You've made my life a whole lot easier.

All parts are in my mouser cart now. I got the broken RCA socket fixed this evening so I got both amps singing beautifully now. I think people are right when they says about these Kenwood sings very nicely. I also got a couple more L-07MII that are oscillating and I saw you recommendations to replace some caps to resolve that. I will get to those too!

Thanks a lot for the bulb recommendations as well. I will contact AKer Dgwojo to get a handful of these bulbs just in case they go out again in the future!

Without your help and input for them, I will probably be reading the parts and searching for them for about a week before I know what to order. :beerchug:
 
Mouser shows no stock on the MY4-02-DC48, but they apparently will be in by about the time the big caps show up...just order the relay along with the rest.
 
Yep, that and the caps are backorder but I am in no hurries. I think it'll be a good winter project for me to recap the L-09M.

While I am at it, I think I am going to order some parts for the L-07MII too.

Do you happen to keep mouser part numbers for the stuff I need to order too?

Thanks Again, Glenn!
 
Thanks! I got those pF caps and the sand cast resistors and the cap for the zobel added to the mouser cart as your recommendations in that L07MII thread.

I also wonder you can tell me the test points for the Bias adjustment on this one? I can't seems to find it in the service manual I got.
 
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Page 16 of the manual (there's also a good visual on page 13 of where to connect the probe leads). On this one, you really, REALLY need minigrabber clips for the meter...way too easy to short pins here and blow the whole thing to hell.
 
Thanks EW! I printed out the SM and found what you are talking about. The problem was that I am a tree hugger and tried reading the SM and the schema from my laptop screen.

I got a full manual printed out (sorry tree!) now. I also pop the cover from both amps and spent a few minutes adjusting offset. The offset is about -1mV in one amp and about 4mV in another. Very minor drift about 2-5mV but I suspect that's due to the line voltage variation. The full recap will be underway in a couple of months so I am not concerned about it.

For Bias adjustment, I got to delay that to the full recap too. I got a few mini grabbbers on hands but my scope quits since a year ago. I don't want to mess with it a lot before I can get everything done in one time.

By the way, the fans in the L-09M are really quiet. I got to put my ears next to them to hear very faint whizzing at idle. I think it's a good thing!
 
Most stay pretty quiet in slow mode. But short pins 13 and 14 on the power supply board to kick the fan into high-gear (which is what the thermal switch does when the amp heats up) and a lot of the fans suddenly sound like a bag of marbles.
 
Bumping this thread.

I'm about to make the same trip as megasat16 but also want/need to change the cap Ck5 on the power supply board, it's 1000uF 16V. Any suggestions what brand/type to go for? A Mouser part number would be marvelous, of course! ;)

Also want to praise EchoWars for sharing all his knowledge about this amp.

Thanks in advance,
Tommy

Edit: Found the answer on page 3 in this thread: http://www.audiokarma.org/forums/showthread.php?t=487718
 
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I am happy to be a new member of the Owner-Club Kenwood L-09 M. Last week i picked up a pair of working L-09M and now i can hear them at my home.
The previous owner changed one of the Fans to a new one,- it is louder than the original Fan in the other Amp. I disassembled the original Fan which was given with the Amp.
There are two roller Bears inside, the size is R-1560 ZZ. I bought a Pair of them on EBay and reassembled the fan. It is perfectly quiet now!

I opened one of the old Bearings. Here is the look inside:
PC150022.jpg
the grease is soiled and desiccated. I Think it is a good solution to change the Fan- bearings and get a quite Working Fan.

Richard
 
I am going to try these bearings they come shipped with a light grease lube. I like the idea of replacing the bearings and keeping the original motors.

https://www.bocabearings.com/products/smr696c-yzz-5-nb2-8116

Ceramic Lightning, shielded bearings are specially designed for relatively clean operating environments. These bearings have ceramic balls, with stainless steel races, retainers and shields. Ceramic hybrids are lighter, capable of achieving higher RPMÆs and sustaining higher operating temperatures than traditional bearings. Bearings that are packed in grease will require a short break in period to loosen up. Grease can be removed before shipping upon request. Grade 10 SI3N4 Ceramic Balls, ABEC #5, (6x15x5)MM
 
We
EchoWars said:
The only ones that are hard to get are the two large filter caps. I put together a group order a few years ago and shelled out $2000+ of my own money to get the caps, only to be abandoned by about 1/2 of the guys who said they wanted them. It took a while, but they are all long gone.

Mouser has one (1) United Chemi-Con 18,000µf 160V cap measuring 76mm x 93mm (Mouser part number 661-E36D161HPN183ME9) for what is actually a pretty reasonable price of about $51. They also show a minimum order of only one, and a lead time of about 90 days. All reasonable. If you want replacements for the original power supply caps, you can't do much better than that. Get 'em on order and they'll hopefully show up.
Click to expand...
Well, what are the dimensions of the original filter caps?
 
Kingbleu said:
I am going to try these bearings they come shipped with a light grease lube. I like the idea of replacing the bearings and keeping the original motors.

https://www.bocabearings.com/products/smr696c-yzz-5-nb2-8116

Ceramic Lightning, shielded bearings are specially designed for relatively clean operating environments. These bearings have ceramic balls, with stainless steel races, retainers and shields. Ceramic hybrids are lighter, capable of achieving higher RPMÆs and sustaining higher operating temperatures than traditional bearings. Bearings that are packed in grease will require a short break in period to loosen up. Grease can be removed before shipping upon request. Grade 10 SI3N4 Ceramic Balls, ABEC #5, (6x15x5)MM
Click to expand...
These bearings are not that quiet. I ordered some EBMPAPST 9909 axial fans. I will see if theese are any better.

​

 
I am wondering about the two caps on the power amp board Ce13 and Ce14 they are 1uf 50v. Since the UPW,UPM and FC have dried up what would be a good replacement. I don't know what theese are doing in the circuit. Are they in the third stage differential amp? Would this be a place to use film caps?
 
The capacitors C13 & C14 are for damping the current limitation. This makes the triggering a bit less sensitive. A voltage rating of 50V is more than sufficient for this part of the circuit in this amplifier. I would choose a small Wima film type capacitor with a 50V voltage rating. However, a regular electrolytic capacitor would also work perfectly fine here
 
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