Another Kenwood KA-5700 Recap & BOM

12v on an led assembly designed for 8v ac or dc will dramatically overpower it- led will burn out for sure. If you have a spare, you could put another resistor in series- to reduce the current- which would let the 8v led assembly operate normally. I like the bright spectrum though I also like the cooler incandescent if its a clear bezel- the 5700's is a great candidate for that, I did an onkyo a while back with an incandescent indicator liked that too.
 
I was able to get to Advance Auto Parts yesterday and dropped in the clear, 14V incandescents. They are dimmer but at least I am not having a voltage issue anymore and hope they last longer in the tuner and amp. @gpounce32768 was correct, I think the 8v LEDs were getting overpowered in the circuit as I was seeing 12v at the first buld in series.
 
@Spenser @hopjohn @gort69

I did a total re-cap of my KA-5700 last night using the BOM that @Spenser posted.

I am having issues with the amp. The amp was working perfectly prior to the re-cap. On power up the older relay pinged at approx. 2 seconds. Now, the amplifier is dead, no ping with the new diodes, relay & transistor. I would like to ask, where should I start looking for the problem? There are no blown fuses. Is it possible that I might have reversed the polarity of the transistor, diode or cap? I will re-check my work but wanted to put a post up on AK for some help.

Thank you.
 
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So you did a recap and made diode and transistor changes? Check everything. Cap polarity, diode polarity. Check transistor datasheets new and old to see if there were differences in pinout. If you're relatively new to this I'd suggest only going in small stages before testing. That way if something goes astray you're not at a loss as to where to look. Fortunately, the 5700 doesn't have too many things to change.
 
Thank you @hopjohn

I just double checked the polarity and parts numbers of all the caps. All were OK.
 
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So you did a recap and made diode and transistor changes? Check everything. Cap polarity, diode polarity. Check transistor datasheets new and old to see if there were differences in pinout. If you're relatively new to this I'd suggest only going in small stages before testing. That way if something goes astray you're not at a loss as to where to look. Fortunately, the 5700 doesn't have too many things to change.

@hopjohn

Your advice was spot on. Right away, I decided to go for the transistor relay Q26 2SC1213 512-KSC2690AYS BJT NPN. I pulled and reversed it on the board then tacked it back in,... got relay 'ping'. Amp is up and running now, will let it break in a little bit at low gain.

Again thank you!

EDIT: Below is the mistake I made. C2690A-Y was reversed.

FC1A0868.JPG
 
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The marking on the board will look similar to this >I or this I<, (for zeners, more like this Z>, <Z) and the diode will have a band around one end. The band on the diode goes to same end as the vertical line (or Z) on the board. (You really should make a note that the board marking is correct before removing the original diode since board mismarkings are not unheard of. I don't recall that being the case on the KA-5700 though).
 
The marking on the board will look similar to this >I or this I<, (for zeners, more like this Z>, <Z) and the diode will have a band around one end. The band on the diode goes to same end as the vertical line (or Z) on the board. (You really should make a note that the board marking is correct before removing the original diode since board mismarkings are not unheard of. I don't recall that being the case on the KA-5700 though).

Thank you @gort69

I went with below and had installed them correctly first go.

diode-markings.jpg
 
@Spenser

My apologies for the repeat thread hijack. Thank you, very helpful and a timely one!

Did you start the KT-5500 project yet?

FC1A0869.JPG
 
Congratulations on getting it running :) I like my 5700 a lot, sounds great, it was fun to fix up and the tone control circuit built into the feedback is very interesting.
 
Great thread.. I just started with a KA-5700 myself after spending the last year in Marantz land :) I put up a separate thread before I found this one :)
 
Great thread.. I just started with a KA-5700 myself after spending the last year in Marantz land :) I put up a separate thread before I found this one :)

Great amp. Once modded it sounds terrific!
 
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So replacing the protection relay just because might be a bad idea. I have one of the blacl DEC TYPE MS4U relays and I took the cover off. It's a well designed relay with gold contacts. At least it looks like gold. Mine had zero pitting or scorching on the contacts. I plan to put it back into service after checking the coil. None of my Marantzs were gold contacts.. this is pretty sweet.

IMG_6642.jpg IMG_6645.jpg
 
Hey thanks on the thread.

With respect to the relay, if it aint broke...

On the other hand, since you've done the work to get it out of there, maybe you should go ahead and replace it with a new one that will be good for another thirty or forty years instead of maybe only 5-10.

I don't actually know that the original part may only have 5-10 years left. Just playing devil's advocate.

There are people on here with way more experience than me who would have a better idea. There is probably a generally accepted protocol.

In any event I WILL venture that these relays are indeed a marvel of engineering and manufacture. How the contacts are made and getting them to mate so precisely, amazing.

I believe you are right. I think the contacts are made of a base metal plated with a highly conductive material, like silver or gold.

I think the flexing of the armatures when the contacts come together makes the contact surfaces rub laterally against each other ever so slighly, which helps keep the contact surfaces free of corrosion. I just made that up. No I'm kidding. I did not make that up.

You would probably need quite a magnifier to effectively inspect the surfaces for wear I'm guessing and who knows what you would be looking for or how one would judge.
 
Hey likewise 8xlaxx! Thanks for asking. Sold one KT-5500 as-is and have not touched the remaining one. Two or three other tuners are in line ahead of it. About half way through a Pioneer SX-939 receiver at present. What are you up to?
 
Not gonna lie to you, I miss the 5700 and 5500 combo. Sounded great and was really durable, easy to work on too. I have the KT-7500 waiting to be modded after the monoblocks.
 
Coincidentally a KT-7500 is one of the three in my tuner queue.

The Heathkit tube amp looks like great fun! Nice guys you have involved there.
 
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