Kenwood 700M vs. the newbie

If the front panel really needs to come off, the switch cap can be removed. There are some Marantz units where this had to be done, and I heated the cap with a hairdryer and it came right off. Have to pull straight off, or risk breaking the switch stem.
 
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Good tip :thmbsp: I'll do my best to work around it and only attempt to remove the switch plunger as a last resort.

In the mean time, this is where I've left things; with the A-speakers wired direct and the rest capped off. I'll come back to the switch later, as I have been making good progress with the driver boards.

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The left channel driver board has received the same parts previously mentioned in the right channel rework. After a test run, the left channel DC offset came in at less than 10mv. :thmbsp:

As of now, I'm commencing with some basic housekeeping. I've removed the heat sinks and polished up all the pins on the output boards. Also time to clean out all the cobwebs and mop up the stray thermal grease.

When you have these heat sinks removed, it really becomes apparent just how much surface area there is. It is quite impressive.

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Take a close look where the TO-3 socket tabs are bent over and soldered to the PC board pads on those assemblies. Not uncommon to find one or two that are failing to make contact and need careful re-soldering.
 
Indeed!! You called it. Thanks for the heads up. :thmbsp:

This is the most obvious one that can clearly be seen with the naked eye.

I found a couple others that only appear as a hairline under the eye loupe.


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Getting ready to button some things up. My testing thus far has been done retaining the original transistors on the protection board. Went back and re-read the thread.

...the 2SC1416 and the 2SC1451 are being used as switches on the protection board, so their replacement simply needs decent gain and low saturation voltage. A Zetex ZTX694B for Qp1 and Qp2, and an On-Semi 2SC3902T for Qp3.

Did you mean to say ZTX694B for Qp1, and 2SC3902T for Qp2 and Qp3 ? :headscrat
 
Qp2 is only a driver for Qp3. Qp3 is the one that does the heavy lifting (such as it is). I mean you could use the C3902T for Qp2 and Qp3 (it's not exactly a crucial area), but from an engineering standpoint, makes more sense to use a small driver transistor and larger transistor to close the relays.
 
Ok, I see. I had just been wondering about that when I saw the factory used the same transistor for Q2 and Q3. At first glance I thought perhaps they had used one each per coil, but I see the coils are in series and the emitter of Q2 is tied to the base of Q3. Thanks.
 
At this stage I have things functionally assembled. I've been testing conservatively up to this point on a set of small speakers. I lugged her down to the man cave and hooked things up to a pair of RtR IIF's. Time to open up the throttle some.

http://www.audiokarma.org/forums/showpost.php?p=8414117&postcount=63

Well, there's no question, this amplifier is definitely amplifying! :guitar:

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One thing that does jump out at me is the right channel meter is reading a bit below the left. Not sure what's going on there, but I'm going to clean up the contacts on the meter board and see what happens. I plan on getting something set up with my scope and a signal generator, just not there yet. But I can say that I can't hear a difference in the channels and what I do hear sounds purdy darn good. :D


...I'm just thinkin' I may have to git me some bedder spiggers...:scratch2:
 

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Well, there's always those funny little adjustment trimpots on the meter board, in case you tire of scrubbing pins.

RE: Listening. Are we having fun yet?
 
Well, there's no question, this amplifier is definitely amplifying! :guitar:


One thing that does jump out at me is the right channel meter is reading a bit below the left. Not sure what's going on there, but I'm going to clean up the contacts on the meter board and see what happens. I plan on getting something set up with my scope and a signal generator, just not there yet. But I can say that I can't hear a difference in the channels and what I do hear sounds purdy darn good. :D


...I'm just thinkin' I may have to git me some bedder spiggers...:scratch2:

Wow DrumminDaddy now that was quite an accomplishment! If I ever seriously held out the fantasy that I would rebuild mine myself this thread was a reality check.
"A man's got to know his limitations"
Yes better speakers!
Again well done!
 
Wow DrumminDaddy now that was quite an accomplishment! If I ever seriously held out the fantasy that I would rebuild mine myself this thread was a reality check.
"A man's got to know his limitations"
Yes better speakers!
Again well done!

Thanks Alobar. I will gather my thoughts and post a summation a bit later.

Unless I find something amiss when I get to scoping it, everything else at this point is ancillary, like the speaker switch and light bulbs.

My comment about the speakers was slightly tongue in cheek. Not to side track this thread into a speaker discussion I will just make these few observations;

I am not an audiophile. I'm just a dude that likes music. I've had the good fortune to be able to acquire some very nice vintage gear lately. To me, it all sounds damn fine. I'm well aware that the 700m is capable of driving speakers of a much higher pedigree. These RtR's ain't too shabby, though. Those dual 10's can throw some respectable bass. And as I'm sure you know, the 700m has some serious balls to push that bass. The other speaker options I have at the moment are a couple pairs of HPM-100's, and some CV RE-38's. Honestly, I don't feel like lugging them around, as much as I'd like to just try them out. Maybe a summer time project with my son. If I did step in shit, I'd love to try out some high end speakers. I'm just afraid my weary ears wouldn't hear any orders of magnitude difference. Until then, as they say at the races, I run what I brung.


RE: Listening. Are we having fun yet?

Fun?? Hell, I'm haulin' wood just looking at the thing! Haha! (TMI ??)
 
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Listening....Listening...

A cold, snowy day, hunkering down here in the northeast. Sitting with my son and listening to music. Driving the 700M with my KA-9300.

As I listen to music, my minds's eye tends to key on the bottom end. Listening to The Yes Album. Following every note of Chris Squires' bass performance. Hearing it...Feeling it...I can close my eyes and watch his fingers play.

Carter Beauford's incredible drum performance on DMB's Crash CD holds me in a trance. The attack and resonance of his tom hits flow through my body. What a masterful performance and superbly engineered recording.

Listening through this amp is such a pleasure. I turn to my son and ask, "Do you like this amp?" "Yes," he says, nodding his head firmly. "Do you want it?" I ask. "Yeah!" he says, grinning widely. "OK it's yours," I say, "On the day that you plant me, and not a day sooner!" :D


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I just happened to notice that the header for post number 92 has an 'unhappy' face. I just wanted to post here for the record that there has been nothing unhappy about this experience with the amp or with anyone on AK. In fact, I don't know how it even got there except maybe a case of fat thumbs on the touch screen tablet that I sometimes use to post. Unfortunately, the edit function will not allow me to remove it.

Soooo...... How can I possibly express how much I have been enjoying this experience?? Well.... so much, in fact, that I bought another one....
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What the hell is wrong with me??? ... :dunno:
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Many congrats on your second 700M... sure is worth having two :thmbsp:
BTW,your just gettin' addicted to Kenwood :D
 
Woah!:thmbsp: 700M v not quite a newbie!

Hmmmm. "Not quite the newbie." Funny you should put it that way because I've been giving some thought as to what point does one graduate beyond newbiedome. My mind harkens back to the days I was in the military. When I first arrived at my duty station, I was referred to as a 'JEEP'. The military, being fond of their acronyms, this unofficial title meaning 'Just Enough Education to Pass'.

I will say that I did not just wake up one day and start ripping this amp apart. I did quite a lot of tutorial reading and studying of the schematic. I printed out every thread I could find on this model and read them over several times. I made a point of not being in a hurry.

In my initial stated goals, I should have made a point regarding safety. After all, we are working on live electrical devices here and this shit can kill you. I had to calmly remind my very loquacious wife to please not disturb me when I was working on it.

I remember reading in another thread that EW remarked this wasn't a complicated amp. I guess as far as amps go, that's true. But when your new to this stuff, it's intimidating. Mechanically this amp is certainly easy to access. Electronically, I suppose it's pretty straight forward as well, since your not dealing with any preamp or anything.

I must say that when working on it, I'm struck with a sense of history and felt as much as if I'm preserving it as fixing it.

Having said all that, this newb's journey is still very much at the beginning. There is a colloquial phrase that describes one's competency level as not knowing 'shit from Shinola'. While I did manage to not turn this project into a turd, there is a can of Shinola that's not within my grasp yet. But I'll keep reachin'.
 
Does anyone know what the resistance should be on these things on the protection board on the Kenwood 700M?
 

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It appears to be an inductor; if so a resistance near zero would be expected. Do you have the schematic? It will help a lot to identify components.
 
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