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Kenwood KA-7300 Integrated Amplifier Issues

captainclock

captainclock

Pacifist Otaku
Hello everyone, a few years back I had bought from a local electronics repairman a 1970s vintage Kenwood KA-7300 Integrated Amplifier for $60 to install inside an old Knight Kit Console that a friend of mine from Church had given me to monkey around with that he had built when he was in High School back in the 1960s.

Anyways everything on that old Knight Kit console still worked except the amplifier which when I took it to the aforementioned repairman he told me the power transformer was dead and to get a new one would be impossible because of the fact that it used a type of power transformer that was apparently NLA, which is why I bought the Kenwood Amplifier from the repairman, the way it came was that it had all of the metal panels except for the top and bottom ones and and also the price was good.

Anyways a couple of months after buying the amp from the repairman I started having issues with the safety relay acting erracticly where it would randomly just start triggering itself out of the blue and it would trigger itself several times in a row before settling down and then it would be fine for a while and then it would start triggering itself again etc.

Anyways to the present day I wanted to try and use the old Kenwood amp to power the audio for my LCD Projector I have in my basement for movies and I hooked it up and now the relay doesn't seem to want to kick in at all (at least not to allow the amplifier to fire up properly so that it can put out audio) and for a while the relay was doing the erratic triggering thing but then it even stopped doing that.

So now my biggest question is, what could be causing this amplifier to act this way?
And Also how would I go about trying to repair this amplifier?
Because none of the circuitboards in this amplifier look like they would be that easy to remove without having to cut some wires which I don't think I would want to do that.

Any help would be greatly appreciated.
 
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The driver transistor (IIRC, its a 2SC1213) for the relay circuit in the KA-7100 and KA-7300 are known to fail over time, just replace it.
 
Leestereo said:
The driver transistor (IIRC, its a 2SC1213) for the relay circuit in the KA-7100 and KA-7300 are known to fail over time, just replace it.
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OK, but how do I even get the relay circuitboard out of the unit without having to snip wires? because all of the wires that are used to go between the relay board and the rest of the amplifier are wrapped tightly around some binding post style wire retainers and there are about 20+ wires that would need to be removed and I don't have a service manual and I don't want to try and monkey around with taking those wires off and then not be able to get them back on again and there's no wiggle room as far as trying to remove the circuit board with the wires intact.
 
Leestereo said:
You don't have to snip any wires, there is enough wire "slack" to work on the relay circuit in situ, you might want to un-mount the board from the chassis for easier access.

The service manual is here: http://akdatabase.org/AKview/albums/userpics/10004/Kenwood KA-7300 Service Manual.pdf
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No there isn't enough slack to do anything with that board that board is fastened to a couple of brackets inside the amplifier and then it has the pegs that the wires are attached to on the bottom side of the board and then the wires coming up from the bottom and then the wires are tied to those wire mount pegs on the circuitboard using a tight wire wrap similar to what one would find in a cheap set of bookshelf speakers, and the wire has very tight clearance there would be no way for me to take that circuitboard out without damaging wires.
 
Well aparently the 2SC1213 and its substitute the 2SC1959 are NLA because I just checked Digikey and they didn't show that transistor in their stock.
Also Apparently Mouser doesn't have it either so it definitely is NLA, unless there's some place else that I didn't check that would have it but seeing as if Mouser or Digikey didn't have it then I doubt anywhere else would have it.
 
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Leestereo said:
You don't have to snip any wires, there is enough wire "slack" to work on the relay circuit in situ, you might want to un-mount the board from the chassis for easier access.

The service manual is here: http://akdatabase.org/AKview/albums/userpics/10004/Kenwood KA-7300 Service Manual.pdf
Click to expand...

Nope try again, there is absolutely no slack in the wiring whatsoever to allow for the relay board's removal without having to monkey around with the wiring.
And I have photographic proof to back up my claims.
 

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Hmm, my Pioneer SA-8500II integrated has the driver boards mounted kinda like yours. Unfortunately, I just had to sit down and make a drawing and label every wire and then unsolder each one. Sure would have been nice to have a plug-in board huh.
 
captainclock said:
Nope try again, there is absolutely no slack in the wiring whatsoever to allow for the relay board's removal without having to monkey around with the wiring.
And I have photographic proof to back up my claims.
Click to expand...

I fixed the same problem your having by following this thread:
http://www.audiokarma.org/forums/showthread.php?t=277328&highlight=ka-7300

I did not need to remove any wires from the bottom of that board. Loosen the back panel to get some room and then unfasten the vertical supports holding the board in place and you can tilt the board towards the back some for better access.

The relay transistor in question is the three legged black thing between the orange cap and green resistor in your 2nd picture.

If I were you, I would rebuild that whole board as described in the link. Caps, relay, diodes & transistor. My 7300 is still going strong since I did.
 
sake said:
I fixed the same problem your having by following this thread:
http://www.audiokarma.org/forums/showthread.php?t=277328&highlight=ka-7300

I did not need to remove any wires from the bottom of that board. Loosen the back panel to get some room and then unfasten the vertical supports holding the board in place and you can tilt the board towards the back some for better access.

The relay transistor in question is the three legged black thing between the orange cap and green resistor in your 2nd picture.

If I were you, I would rebuild that whole board as described in the link. Caps, relay, diodes & transistor. My 7300 is still going strong since I did.
Click to expand...

yeah but how much is that gonna cost? I think as far as the capacitors go I might already have some of those laying around in my parts bin, but as far as the diodes and the transistor and the relay goes I don't have access to those parts and I looked everywhere that I could think of as far as online parts stores go and I couldn't find that 2SC1213 transistor or any of its substitutes.
 
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bktheking said:
2sc1213 --KSC2383YBU
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OK... Then why the heck did that not show up in my search results when I went to google substitutes for the 2SC1213 transistor? Is it really a correct substitute or are you just throwing random numbers out there?

Also nobody answered my question as to how much it would cost to completely redo the relay board, and this is a rather important question because I don't make a whole lot of money and if its going to cost more than $40 to do all of that work then I might as well just junk the unit because I only paid $60 for the unit initially and its not even complete so its really not worth sinking tons of money into the unit to get it working again especially since all it was going to be used for was to power the audio system for my LCD Projector Home Theater system.
 
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I'm not sure how to answer your post. 12k posts from me generally don't contain bullshit although I have admittedly made mistakes, I haven't in this case. I googled two separate threads on ak in which this sub was mentioned. Ben also tried telling you that you didn't have to snip wires and you discarded his post as if he didn't know. There are always ways of doing things that you may not know, I know for a fact that boards in kenwood units can be worked on without snipping wires, I've done it, he's done it. The advice is free, listen to it.

As far as cost, make a list and submit it to get a quote from mouser, that's the easiest and guaranteed approach to parts pricing.
 
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bktheking said:
I'm not sure how to answer your post. 12k posts from me generally don't contain bullshit although I have admittedly made mistakes I haven't in this case. I googled two separate threads on ak in which this sub were mentioned. Ben also tried telling you that you didn't have to snip wires and you discarded his post as if he didn't know. There are always ways of doing things
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Well I'm not sure either because you and everyone else on here are trying to make this sound like its going to be an easy repair even though I'm not seeing anything easy about any of the stuff you guys are suggesting I do with this unit, and like I said I want to try and do this repair with as little effort and money as possible because like I said I'm not made of money like you guys on here seem to be.

Also Considering that you guys are suggesting I completely rebuild the relay board (which is NOT going to be an easy job to do to say the least) and you can't even give me a rough estimate as to how much those parts are going to cost (I can't imagine that a relay like what this thing needs is going to be all that cheap considering its a specialized part.)

Like I said I might as well just junk this thing and be done with it because it doesn't seem like there's going to be a cheap and easy way to do this repair without having to completely dismantle this unit and what not and then having to source scarce hard to find and more than likely expensive parts to fix this thing...
 
If it's a transistor failing for the relay drive it's a $2 part. It could also be a cap. It's a simple repair for a person who is used to repairing electronics , for someone who isn't it may be difficult.
 
bktheking said:
If it's a transistor failing for the relay drive it's a $2 part. It could also be a cap. It's a simple repair for a person who is used to repairing electronics , for someone who isn't it may be difficult.
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Yeah, if it was a piece of tube electronics it would be a piece of cake for me, but its solid state, I'm not used to working on solid state stuff, the last time I worked on solid state electronics I burned off the circuit traces by accident with my soldering iron because it got too hot while I was trying to remove a bad capacitor from a power supply on a VCR and also when I was trying to repair a video output module for a VCR, I actually hate working on Solid State stuff unless the Circuitboards are made well enough to not disintigrate under my soldering iron.
 
bktheking said:
If you were local I'd help, unfortunately I'm due north.
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Yeah, Although actually Ottawa, Ontario is actually about a half a day's trip from where I live I live in Northern Indiana about 6 Miles from the Indiana/Michigan Border and then you're actually right immediately across the US/Canada Border from Detroit which is about a 4 hour drive from where I live, so not too far.

Although like I said its not that I couldn't do the repair work, because I could, its just that I don't know how structurally sound so to speak the circuit traces are on these circuitboard in this amplifier because like I said I would hate to have to run into an issue where the solder won't come off cleanly from the circuit board with my desoldering bulb and then end up tearing up the circuit traces because the soldering iron was on the board too long and because of that it got the board too hot and basically does irreversable damage to the circuit board, and then the unit won't work at all period.
 
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Yeah, I removed all of the screws holding the back cover on, and its not budging, there are way too many wires in the way that are keeping the back cover from coming offcompletely and I don't want to break any wire connections.
 
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