The last pin on the right is #22, so of course #19 is the fourth from the right.
Totally normal for the bias to rise slowly. Monitor it for 45 min ~ 1 hour, and set as necessary.
Kenwood L-07M II Issues
- Thread starter EchoWars
- Start date
Totally normal for the bias to rise slowly. Monitor it for 45 min ~ 1 hour, and set as necessary.
Thanks a lot Echowars. I adjusted them all. Sound wonderful. I paid $50 on garage sale and didn't not know anything about them until I got home and did a research on internet. I hook to Nakamichi TA-2a as preamp play by a pair of Timeframe 350. The best sound ever since I got Marrantz 2285B. I will play for a while before hook them to my brother B&W CDM7SE to see how their sing.
PS: Does I need to replace those main caps (18000uF) ??
PS: Does I need to replace those main caps (18000uF) ??
Last edited:
lorne
Sonic Lizard
Lots of blah-blah on these forums in the past on this matter, and I don't criticize anyone one way or another!
As for me (only) ... I replaced the big supply caps in my L-05M's. I did this a year after replacing all the other caps, adjusting bias, reflowing some solder and so on. I really thought I had a better pair of amps after I put in the new supply caps. But it's a tough call. I did not put the units on a scope. I did not do anyting empirical to get measurements. (BTW, the new supply caps i installed in my SA-8900 in the same month resulted in a dramatic difference. I don't think any of these were leaking).
Big caps like this are not cheap in Japan, but I'm glad that I did it. Just another opinion — my two bits. But something else ....
EW has said in the past that reflowing old solder is very, very important in the vintage machines. And, in my L-05M's it turned out to be vital. I don't know if your 7 Mark II's have the same weakness as my 5's ... but I gotta tell you that the boards in my 5's were really showing some signs of nasty deterioration, despite their running very cool in even the most humid Japanese, summer weather. One pad actually went open and made the amp a silent door-stop. It was one of the pads I had not touched up with the iron! There was also a pile of flux, which I removed mechanically and then swabbed with flux remover and Q-tips. I've not seen your model. Maybe it is a nicer board in something other than the phenolic ones that I have.
I also made an effort to be sure that the massive copper ground bus was cleaned up where it was terminated. And I rewired some of the hard wire in/out when I installed some new I/C plugs. Good for another 30 years!
These L series amps were a high watermark of the era. Your finding the 7's was a stunning score. WOW!
restorer-john
Addicted Member
Very true. I always test and empirically benchmark BEFORE and AFTER. That way I can be honest with myself AND my customers. That's not to say no measurable improvement is a waste of time, as we are talking reliability here, and long term viability. If a customer tells me they want the amp to last another 20 years, I have to look at everything in it and make an educated decision and recommendation. What they do with that is up to them. I have NEVER seen on these forum boards any publication of a before and after test sheet for anything...ever. I will do it for anyone that asks and many that don't.
restorer-john
Addicted Member
by the way, my L07ms performed EXACTLY the same after a rebuild- the distortion was still below 0.003% at full power and the bandwidth was beyond my computer based sweep withing 0.01dB.
lorne
Sonic Lizard
I have to admit that I would have to submit a unit to be analysed by somebody like you — before and after a rebuild — in order to properly understand the results of a rebuild. I'm not ashamed to admit it; hopefully, there are other areas where perhaps I am more masterful than in electronics. But your comment is apros-pos. And all the more so for your startling results — an amazing report considering the years.
And I appreciate your inference: all of us in these forums should be made abundantly aware that there are two distinct assessments — anecdotal and empirical. The latter reports to science, and the former reports to our subjective, received reaction to an experience. Both have validity, but the awareness of the distinction needs be constantly reminded. The constant battle that takes up so much space and time in so many forums need not be so contentious — as long as we remain aware of what these two approaches mean. I lean towards the science — if only to balance the subjective by way of an antidote, and because I am not equipped to do same.
There may be a number of reasons for this, but the greatest one may be that there are more people like me than more skilled people like you writing on the forums. Again — there is no need to despair as long as we keep in mind our respective limitations in regards to objectivity. Moreover, many enthusiasts are more concerned with scraping some time together so as to get the work done — to hell with measuring the raw, untouched, unrestored unit.
I hope that am still on topic, if only I can underline the significance of your measurements, and what place they have in the history of these vintage Kenwood specialities. I remain amazed. I am assuming that you restored a virgin pair of amps??
restorer-john
Addicted Member
Lorne, yes the pair was 'virgin'. Internally, they were essentially untouched. One was totally unopened, ever. In the other, none of the boards had been touched, one fuse was non-original, but this was no doubt due to the fact that amp was not turning 'on'. (the owner probably thought it was 'just a fuse'...) The fault was simply a leaky transistor on the protection sub board. It resulted in the amp taking anything from 5 minutes to several hours to connect the speaker relay. The amplifiers themselves were as original as the day they were made.
They were therefore, after inspection, perfect candidates to have 'baseline' measurements made. I had purchased around 7 L0xx amps at that stage with some needing work.
The issue with vintage hifi is it often comes to me when it needs 'fixing' as it has ceased functioning correctly and 'while you're at it, why not 'bring it up to spec' ' recap it' etc' What usually happens from that point on is:
1) find and fix the fault/s, do the commisioned work and test at completion.
I decided several years ago that was proving nothing and compromising my integrity. I now (only on the good stuff):
1) find and fix the fault/s.
2) make any adjustments needed
3) test and do up a simple report for myself in excel
4) do any extra commisioned work (recaps, tweaks etc)
5) test and add to my previous report.
I keep all the information along with pictures of every item repaired or sold with serial numbers and my test data.
The pair of L07ms are packed in two boxes, along with their original rca and triger leads as a reference.
They were therefore, after inspection, perfect candidates to have 'baseline' measurements made. I had purchased around 7 L0xx amps at that stage with some needing work.
The issue with vintage hifi is it often comes to me when it needs 'fixing' as it has ceased functioning correctly and 'while you're at it, why not 'bring it up to spec' ' recap it' etc' What usually happens from that point on is:
1) find and fix the fault/s, do the commisioned work and test at completion.
I decided several years ago that was proving nothing and compromising my integrity. I now (only on the good stuff):
1) find and fix the fault/s.
2) make any adjustments needed
3) test and do up a simple report for myself in excel
4) do any extra commisioned work (recaps, tweaks etc)
5) test and add to my previous report.
I keep all the information along with pictures of every item repaired or sold with serial numbers and my test data.
The pair of L07ms are packed in two boxes, along with their original rca and triger leads as a reference.
I like to replace these caps, but the L-07M uses a solder-tab cap that is a pain to source. Michael Percy Audio here in the US has a 22,000µf Nichicon cap that might work, but I'd need to recheck measurements. Other than those expensive caps from him, I can't think of any suitable replacement.
I do it all the time, but simply see no real purpose to publishing the results here. I've got plenty of 'to-do's' on my list as it is.
lorne
Sonic Lizard
EchoWars wrote:
The fasteners and the copper gauge take up some height. But then a stroke of luck: a dry-run pre-fitting showed the tops to be just shy of the cage. Anyway, after mounting the pair in the collar and carefully assuring alignment blah-blah, I turned up the thermostat on the iron and soldered the copper tabs onto their respective trace plains. Hot damn — it's satisfying when it all goes together! I've used this solution elsewhere on a vintage amp.
Now, for you (EW) and and restorer-john, I can understand how this may not be a very happy option if and when you are restoring units for a client. This work-around is not exactly commensurate with a stock restoration. Nevertheless, screw terminal types seem to be available in a lot of values because it would seem that industry is consuming them — communications and aero-space would be my guess. The screw/bolt terminal increases the effective length, but the reduction in overall size (due to technical
developments) can leave you with a suitable fit.
The Chemicon series I've been using is a robust, serious capacitor with a pressure relief plug on the base. In some applications, one might have to drill the board to create a port for the plug — due respect payable to the engineering.
Yes, I know exactly what you are talking about. The same in the L-05M. I quickly passed over even attempting to duplicate the originals and concentrated on ordering cans from a local HAM shop that would fit both the case and the collar-brace for the pair. The catalogue came up with some Nippon Chemicon, screw-terminal types that if memory serves me were close or identical to the original capacitance. I cut tabs out of solid copper then drilled, formed and screwed them in.
The fasteners and the copper gauge take up some height. But then a stroke of luck: a dry-run pre-fitting showed the tops to be just shy of the cage. Anyway, after mounting the pair in the collar and carefully assuring alignment blah-blah, I turned up the thermostat on the iron and soldered the copper tabs onto their respective trace plains. Hot damn — it's satisfying when it all goes together! I've used this solution elsewhere on a vintage amp.
Now, for you (EW) and and restorer-john, I can understand how this may not be a very happy option if and when you are restoring units for a client. This work-around is not exactly commensurate with a stock restoration. Nevertheless, screw terminal types seem to be available in a lot of values because it would seem that industry is consuming them — communications and aero-space would be my guess. The screw/bolt terminal increases the effective length, but the reduction in overall size (due to technical
developments) can leave you with a suitable fit.
The Chemicon series I've been using is a robust, serious capacitor with a pressure relief plug on the base. In some applications, one might have to drill the board to create a port for the plug — due respect payable to the engineering.
Share and share alike
EW, I hope you dont mind me adding these docs into this thread.. but I figure this would be a good a time as any to post these manuals for the L-07M, models MK1 and MKII.
I hope you guys can make use of these and keep more of these great amplifiers running for years and years to come.
Mike
EW, I hope you dont mind me adding these docs into this thread.. but I figure this would be a good a time as any to post these manuals for the L-07M, models MK1 and MKII.
I hope you guys can make use of these and keep more of these great amplifiers running for years and years to come.
Mike
Have a Kenwood L-07 MII... is it a HUGE PAPER WEIGHT?
Hello all, went into my closet the other day, at my wife's urging, and found my old Kenwood L-07 MII sitting there all wrapped up. I haven't used the amp for over three years; it was, originally, one of 3 that I owned and, when last hooked up, powered a large Canton passive sub woofer I have long since parted with.
I have attempted to see if the thing still works and powered it up; the only thing I get is a "click" and the small light up front does not work. I have checked the fuses and they are good... is this worth pursuing to repair and resell or should I confine it to trash yard history?
Thanks for your thoughts and suggestions.
Willy
Hello all, went into my closet the other day, at my wife's urging, and found my old Kenwood L-07 MII sitting there all wrapped up. I haven't used the amp for over three years; it was, originally, one of 3 that I owned and, when last hooked up, powered a large Canton passive sub woofer I have long since parted with.
I have attempted to see if the thing still works and powered it up; the only thing I get is a "click" and the small light up front does not work. I have checked the fuses and they are good... is this worth pursuing to repair and resell or should I confine it to trash yard history?
Thanks for your thoughts and suggestions.
Willy
Attachments
lorne
Sonic Lizard
The relay is working if you hear the click. Two clicks, and it's shutting down. Does it attenuate a signal? If source is a problem, just put a line-out on yer computer and any junk speaker on the LM. You will know instantly.
As for junking it? I wouldn't. There is munch unobtainium in there — some specific thermistors that are as rare as dragons teeth ... if I remember rightly. Relays ... lots of cool stuff. Somebody will want this as either parted out or whole. There may be lots of old stuff that is more trouble to get rid of than they are worth. This unit, despite missing its mate, is not one of them.
As for junking it? I wouldn't. There is munch unobtainium in there — some specific thermistors that are as rare as dragons teeth ... if I remember rightly. Relays ... lots of cool stuff. Somebody will want this as either parted out or whole. There may be lots of old stuff that is more trouble to get rid of than they are worth. This unit, despite missing its mate, is not one of them.
There are two relays...one that is triggered by a remote source through the back panel or triggered by flipping the rear panel switch to 'Mains On', and there's the speaker relay, which should come on about 3 or 4 seconds after power is applied.
The non-functional LED may just be a coincidence. I'd check the fuses with an ohmmeter to make sure, and pull out the amp driver board and see if the speaker relay comes on.
The non-functional LED may just be a coincidence. I'd check the fuses with an ohmmeter to make sure, and pull out the amp driver board and see if the speaker relay comes on.
Anyone interested in a "free" amp (you pay shipping) from Naples, Florida?
Sorry for the late response.. had a death in the family and have been very busy with family and friends.
I really have no use for this amp now and looking for someone who may be able to repair or use it for parts rather than disposing of it. All you would need to do is pay for packing and shipping from Naples, Florida. Anyone interested? Let me know in the next week or so and I will have it packed and shipped and on its' way to you.
Sorry for the late response.. had a death in the family and have been very busy with family and friends.
I really have no use for this amp now and looking for someone who may be able to repair or use it for parts rather than disposing of it. All you would need to do is pay for packing and shipping from Naples, Florida. Anyone interested? Let me know in the next week or so and I will have it packed and shipped and on its' way to you.
Hello all, just got the message from Artie and my intent was to send it to the first person to reply so I'm going to be doing exactly that; I have, also, asked Artie that if he can't get the amp fixed that he make the same offer I have made to members of this thread and have the amp shipped to that person. I just want a great amp to end up in "good home". Good Group Here! Best Regards!