Help with Kenwood KA-7300 (Protection Relay?)

Owl said:
Well, I can't find a decent view of the control-amp. I got my SM manual off of hifiengine. The hifiengine pc-layout is pretty bad. The schematic is OK, though. Al had better copies. I don't know where he got them, though.

So... I did the brute force method. Pulled off the top and bottom sheet metal, looked around and took a few pictures (attached). This is what I found.

1. I don't see any 220 uF caps. I see one100 uF/25v cap, and maybe the other cap is the same. Hard to tell. On the SM parts list though... there are no 100uF caps. Go figure.
2. Look at the pictures I took (attached) for reference.
3. Note that sometimes a manufacturer will substitute parts. However, subbing a 100 for a 220 cap seems a bit out there, but it does work, so what do I know!.

Good luck!
Click to expand...
Much appreciated with doing this. Your board looks the same as mine - no 220uF caps at all. I knew about looking out for components that don't match values, but for so many (at least 6) to be different, and such a different value, it just threw me off a bit.

Here's a screenshot from a YouTube video:
1000008132.png
I can just barely make out 220uF on the far left cap, so we know for certain at one point at least some of the values lined up...

But like you said, what do I know? lol! I'm going to replace them with the same values of what's installed. If someone with advanced knowledge sees this and has an idea why please chime in!

re:bad service manual, I have an original hard copy on the way from eBay. I have a really film nice scanner I use for my other hobby so once it gets here I'll make a good scan and share the file.

Thanks again!!
 
Hey @Owl,

Yesterday I did an (almost) complete recap of the Control board. If you ever want to do this you unfortunately will need to take it apart just to take stock of what's actually on your board. The service manual is way off, even with me partially taking it apart last week and trying to build a list of caps to get, I was still short and had to leave 2 or 3 original caps in. I took them out and measured all of them, and put the ones that measured best back in. I wish I would've taken more photos, but this was about 5 or 6 hours into my nearly 9 hour session yesterday so frustration was a little high. Since I didn't take photos or take notes, now I will need to go in again to see the values of the caps I left in if I ever want to replace them. Oops, lol.

I did also replace some transistors on the Power Amp boards and the 0.47uF caps (Ce2) with a 1.5uF WIMA cap, per Echowars.

I also replaced Qe1 and Qe2 with matched KSA992FBUs, which brought my DC offset at the speakers from ~55mV and ~75mV to ~ -20mV (negative twenty) and ~12mV. I am doing more research to see if I can do anything to get these values closer to zero, but from what I'm gathering so far, the 7300 is difficult to get perfect and these values are pretty close to ideal for this amp. Even EW had to build a servo circuit to tame these values in the 7300.

I hope your repair goes well, keep me updated on your progress. If you have any questions I will do my best to help out. My knowledge level is still very basic, but I am good at searching the web and AK for answers.
 
Last edited:
Got the parts, but I'm working on my KR6600 right now. I've got the TS done on the 6600, and I'm waiting on parts. That will hopefully be done next week. I know it seems like I should have time... but house projects have sucked up my spare time (story of my life).

I will update you on the 7300 once I've got back to work on it. Maybe I should change my handle to "Turtle".
 
I realize this is an older KA7300 thread... but can anyone tell me what the function of DK4 (not DK2) is in regard to controlling the relay on the protection circuit? I'm having problems with my relay going on, but when I disconnect DK2 everything seems to work fine.

Thanks!
 
Last edited:
I was wondering if anyone that knows this 7300 protection circuit can tell me what DK4 actually does? I can't figure that one out.

I know this is an older thread... just got me curious.
 
I have a KR-7200 that the protection goes in and out. It's a "click" and it goes off then "click" and back on. It's in a shed that gets hot in the summer, so I thought it was heat related, but it still does it even with a fan on it and the few times I've used it this winter while cleaning the shed out. This sounds like an issue across many units. If I unplug it and leave it for 30 seconds or so, it generally fixes it for a time, but it does return - usually when initially turned on the next time.
 
It turned out to be CK7 was the main culprit here. It was 1 uF instead of 10 uF. I replaced CK9 also, but everything worked fine after CK7 was replaced. Got to make sure the + and - are done correctly.

I tested DK4, and it was OK. I therefore soldered it back in to the circuit.

Everything fine again.

Thanks for your response "drjohnnyfeva"!
 
The 1st time my KA-7300 went bad I had left it on overnight when the temp was about 80 (overnight). Next day it wouldn't come out of protection. As I stated before... replacing CK7 was the problem (for me).
 
You must log in or register to reply here.
Back
Top Bottom