Advice Needed - Kenwood KR 8050

[DubbleA_ron]

First, I apologize if this is posted incorrectly or out of place. Online forums are very intimidating to me to be honest. I'll get better I promise.

Recently I discovered an old Kenwood KR 8050 when going through a deceased relatives belongings. I remembered this unit as a kid and knew that it wasn't going to work 100%. Don't know exactly what happened to it just that it disappeared one day and I never saw it again. I plugged it in to see if it came on at all and did. In fact, it seemed to be in pretty good shape with the exception that it would only stay on for about 4-5 seconds before the sound would cut out.

Fast forward to this past week when I took it to a gentleman in town who is well respected when it comes to vintage audio equipment. Within a few days he got back to me with an estimate: "minimum $500". When I pressed him for an estimate that was more specific he said he expected that it would end up costing around $600 to repair.

He didn't give me specifics other than saying that it was quite dirty (obviously expected) and that it had been repaired previously and that whoever did it was "a freaking idiot". Also he shared with me that if I left it plugged in at my house I would be lucky to come home and not find my house burned to the ground. Safe to say, it sounds like it needs extensive work.

Here's what I do know:

- The sound board works. I was able to find a speaker and test them all. They all work.

- The lights all work except for the red light for the FM setting.

- The dials, switches, and knobs are all present and seem to work. The volume knob works but causes a loud scratching noise when you make adjustments.

- It is apparently a fire hazard.

- Cosmetically speaking, it's a solid 8 out of 10.

Past what I've shared above, I know basically nothing when it comes to vintage audio equipment. I'm pretty handy and I know that with some time and effort I could possibly repair the unit myself but I'm young and have a family with two kids and time is just not something I have an abundance of at the moment. Also, if I'm going to spend $600 on something I want to be absolutely sure it's not going to be money wasted.

All that to say, I need some advice and this community seemed to be the group to reach out to.

I honestly have no idea what to do at this point. My lack of knowledge of such things doesn't help. I would appreciate literally any advice anyone would be willing to give.

- Is this a fairly easy unit to repair/find parts for and I'm needlessly afraid of the commitment it would take to get it working again? How hard is it really to repair a unit like this assuming it would need what sounds like extensive work?

- Is $500-$600 a reasonable amount to spend repairing it? I can't really find any working examples online to see what they sell for.

- Should I just be looking to sell it or part it out and just wait for a working example to come up for sale?

Please help!!

 

[average guru]

I do general repairs on my personnel equipment. Doesn't sound as if it's to mager repair. I would recommend a second estimate. With a more detailed estimate. Detox all controlls.check for leaky capacitors.( I normally replace mine) may have dirty relays.clean. Their is a good repair shop 50 mile away. Similar repairs he charges less than 150.00.
Good luck !

 

[Blue Shadow]

A 5-600 buck repair must mean it is majorly messed up from the previous repair. Otherwise, that unit could be made new again for that much or less.

Maybe if you can post some decent pictures of the guts of the unit folks familiar with it can look and see if there are some majorly messed up repair work going on inside which might limit the help you could get here. There are folks that are learning to solder while repairing a unit, maybe not as big as this one, with the help of some of the techs here on AK. But if it was messed up, they may not want to try to undo what was done as that might be better done hands on.

Post you location,
Post some pics of the unit with the top off, if the bottom is also easily removed, post pics of that.
This thread has a example of a picture that is easy to look at and get an idea of what is going on inside the unit:
http://www.audiokarma.org/forums/index.php?threads/why-does-my-preamp-sound-lifeless.751826/
Different unit, different issue but gives you an idea of the pic type that might help.

 

[DubbleA_ron]

A 5-600 buck repair must mean it is majorly messed up from the previous repair. Otherwise, that unit could be made new again for that much or less.

Maybe if you can post some decent pictures of the guts of the unit folks familiar with it can look and see if there are some majorly messed up repair work going on inside which might limit the help you could get here. There are folks that are learning to solder while repairing a unit, maybe not as big as this one, with the help of some of the techs here on AK. But if it was messed up, they may not want to try to undo what was done as that might be better done hands on.

Post you location,
Post some pics of the unit with the top off, if the bottom is also easily removed, post pics of that.
This thread has a example of a picture that is easy to look at and get an idea of what is going on inside the unit:
http://www.audiokarma.org/forums/index.php?threads/why-does-my-preamp-sound-lifeless.751826/
Different unit, different issue but gives you an idea of the pic type that might help.

 

[DubbleA_ron]

Wow the response time here.

Here are some pics of the internals...


I know these probably aren't the best pictures ever but I don't want to start taking it apart and break it further without doing a little more research.

 

[DubbleA_ron]

I forgot to note that despite my lack of knowledge of vintage audio, I do know what amateur repair work on electronic boards looks like. Perhaps I'm just blind but I see nothing inside of here that looks like a "freaking idiot" got in here and messed around.

Also I think someone asked me to post my location. I'm in Little Rock, Arkansas.

 

[KingBubba]

You are getting the old scare job technique. My opinion is that your receiver has not been messed with and most likely not any kind of fire hazard. The suggestion that you use some Deoxit on the controls and switches is a good suggestion. There is a thread on AudioKarma that tells how to use Deoxit, the idiots guide. Read up on Deoxit and get some. I also would suggest setting up your receiver with some speakers and run it for a while. Feel the cooling fins on the back and see how warm they are and if there is a difference in temp between the two sides. The KR-8050 is a very nice receiver and is worth a good bit of money. You will find it sounds quite nice and is very good quality.

 

[aileenamegan]

According to the pics its possible that it had been repaired previously - but I do not see anything, that did a "freaking idiot". Some resistors have been changed, ya.

Here are some pics of a KR-8050 I have had. I still have another unit. Sorry for the poor quality of these pictures.

 

[DubbleA_ron]

The pictures are actually fantastic. Thanks for sharing. I've ordered some deoxit and an going to clean it up a bit inside and see how that goes.

I am curious about the issue with the power switch that I only briefly mentioned in my original post though.

When I had it plugged in and was testing it, the unit worked fairly well and I got sound. However, after a few seconds the sound would drop out but the unit would stay on (lights, etc.).

When I would turn the unit off the lights and everything would cut off but the sound would come back on for a few seconds and then drop out.

Is this a typical problem or has someone ever dealt with a problem like this and would deoxit potentially rectify this issue?

Thank you all, you've all been incredibly helpful.

 

[DubbleA_ron]

So now I'm hitting a new problem with the receiver: no sound at all.

At the advice of everyone here I took it apart and cleaned it and used Deoxit to try and bring it back to life.

Unfortunately, no I have absolutely no sound out of any speaker zone. I know for sure that the AUX input and speaker zone A was working before but now I seem to have no sound anywhere.

What's the best way to diagnose this issue? My gut tells me that power just isn't getting from the power board to the inputs or it's getting to the inputs but not to the sound board.

Also this is by far the most challenging project I've ever taken on

 

[roger2]

Check to see if maybe one of the Tape source/monitor switches got moved to a different position. Or the mute button. Or any type of jumpers or switches on the back panel. Check fuses. Did you power up the unit immediately after spraying a lot of Deoxit?

 

[DubbleA_ron]

Check to see if maybe one of the Tape source/monitor switches got moved to a different position. Or the mute button. Or any type of jumpers or switches on the back panel. Check fuses. Did you power up the unit immediately after spraying a lot of Deoxit?

I was told to wait a bit before starting up the unit after using the Deoxit. It was probably half an hour or more before I was able to put everything back together and turn the unit back on.

Mute button wasn't on, fuses are okay. It doesn't look like anything has been moved or disconnected. I know for certain I have not disconnected or moved any connections. It's entirely possible to guy I took it to look at it did that though.

I could take some pictures if I know what to snap a photo of so the experts here can make a judgement.

 

[roger2]

No, this receiver in 100% working condition and very good cosmetic condition is not worth $600. Maybe half that or a little better. Ebay "sold listings" search shows several examples of recent sales. As mentioned, parts to put everything right wouldn't cost a lot, maybe $100-ish for a thorough rebuild, and repair-only parts could possibly cost very little. BUT...you can very easily sink $600 (or much more) in your own labor time plus the time required to wade into the significant learning curve necessary to troubleshoot. This is not a good unit for a first-timer. It is large and complex. It has issues AND has been worked on by someone who failed to repair it....two significant red flags.

Beginners are smart if they start out with a fully working unit, learning to deoxit, set bias and DC offset, then maybe recap. Troubleshooting is more difficult and unpredictable, and requires more skill. Do you have a DMM? Are you familiar with basic electronics terminology? Do you know how to solder? Have you worked with components on a PCB before? Can you ID basic electronic components?

I don't think it is possible to infer that some previous "tech" did not mangle something based on a few pics. I just quickly glanced at your pics (nice pics!) , and didn't see anything glaring, but did not look closely. Yes, if something obvious shows in pics, then a course of action/testing etc might be possible. But not every fault is visible.

In your first post you said the "sound board works". What does that mean?

In post #9 you said "after a few seconds the sound would drop out but the unit would stay on (lights, etc.)." Is this because the speaker relay opened? Are you aware of the speaker relay? You should hear a click a few seconds after powering up the receiver. This is the relay clicking in (engaging). If the relay disengages due to some electrical fault, you would hear a similar click, but would lose audio output to the speakers. Perhaps this is what is happening? I don't know. The relay is visible in your 3rd (or 4th) pic. It is a cube with a clear plastic cover. You should watch it the next time you power-up the amp, you may be able to see the contacts move and simultaneously hear the click. This is a place to start.

Not sure what would cause sound to come back after being powered down. I wouldn't worry about that right now though.

Do you suspect a problem with the power switch? Any sparking or sounds of crackling when powering up/down?

I am not trying to discourage you if you are eager to learn, or if you have a passion for this particular receiver. It is a beautiful unit that would look impressive in a dark room, and could potentially sound great as well. Just trying to give you the low-down on what is involved so you can make an informed decision on whether or not to proceed at this time.

Good luck, welcome to AK...

 

[DubbleA_ron]

Sorry for the "train wreck" I've created but I've already established that I didn't have a ton of knowledge about these things; that's why I'm here. If I've posted something superfluous then I obviously don't understand that it's superfluous. My apologies.

Moving on, I started with a receiver that powers on. The power switch seems fine; no noise when powering up, no sparking. The sound cut out after a few seconds but the unit stayed on otherwise. The only "clicks" that I heard out of the unit occurred about 2 seconds after it powered on; which I now know is the relay engaging. Going off what you said about it possibly disengaging, I feel pretty confident in saying that it does not disengage. I have never heard any other clicks other than the initial click of the relay.

That "click" corresponded with the "protection" light on the front of the unit going out. I didn't think anything of this since I've seen several videos and photos where this exact unit is on and playing music and the "protection" light is not on. Perhaps this is an indication of an issue though?

When the sound cut out after a few seconds it literally just fell off. No clicks from the unit, no scratching; crystal clear sound all the way up until it cut out. To clarify, the volume would rapidly decrease; similar to someone turning the volume knob down quickly.

I used deoxit on the scratchy volume knob. I anticipate it won't be an issue once I'm able to figure out why I no longer have sound.

Since having the unit looked at by a professional, I have a unit that works less well than it did before. I no longer have any sound at all. I've tried every possible input and every speaker zone. Nothing. Perhaps the "professional" disconnected something?

As far as my skill level, I know how to solder. I would say I have enough knowledge to know what a damaged or poorly repaired electronics component looks like.

I don't mind investing time into this unit, it is obviously complicated but that doesn't intimidate me. I need a hobby anyway.

You've given me some things to look at later today and I'll do that and follow up with what I find. Hopefully I've provided some quality information this post that can help someone like yourself point me in a good direction.

 

[roger2]

Apologies for using the phrase "train wreck". That was a mistake on my part and I have removed it. The point I was trying to make is that in order to receive the help you seek, information needs to be presented clearly and succinctly. Additionally, readers need to feel some level of confidence in the knowledge and problem solving ability of a poster or they won't invest their time. It is about how these threads work, regardless of the problems being discussed. This thread is very confusing to me so I assume it might be confusing to other readers as well. I am just trying to help, although admittedly this type of input may seem odd.

Assuming that the goal is troubleshooting and fixing the receiver, and not trying to prove that the tech you took it to did some kind of sabotage...

Problem descriptions are confusing to me because the behavior of the receiver is described in bits and pieces at various points in time. The tech may or may not have caused harm, ditto for your deoxit treatment, but cause and effect isn't clear in the sequence. Communication in general is not as clear as it could be. You say the fuses are OK but did not clearly state that you removed them and tested them for continuity, a fuse can look OK but still be bad. You say you "feel pretty confident" that when the sound cuts out that the relay doesn't disengage, but that is key info that needs to reported with 100% confidence in order to determine the next troubleshooting step.

IMHO, a clear and succinct description of the problem as it exists now would be helpful. A report of the exact behavior of the protection light and the relay as the unit is powered-up, as well as any further activity of the protection light or relay. Can you look inside the relay and see contacts? The contacts move and correspond with the click sound, monitoring visually can add to your confidence level as to the behavior you are observing.

Then, without a complete history, what was the one last thing done to the receiver that affected a change. You had sound, then this happened, now you don't have sound. I would suggest re-checking all the items listed in post#11. Earlier you said that you didn't move any switches but the tech may have, which is vague and not really helpful as far as troubleshooting. You should determine that all of those switches are in correct positions, one tape related switch in wrong position and there will be no sound getting to the speakers.

https://electronicsclub.info/

 

[DubbleA_ron]

Roger,

I apologize for my reaction this morning. It was not a good morning for me and it started at 4:00 a.m. What you said was fair and I should've understood you were offering constructive criticism. Forgive me for taking offense.

Okay so here's what I discovered when I got home today. When I answered previously I was at work so I could be sure about the relay. I can say for 100% sure that the relay engages and does not disengage after powering up. I can see inside the relay so I can visually confirm that. However, I've discovered a few issues tonight.

I decided to take a good hard look at all of the circuit boards again just to make sure I wasn't missing anything. I've discovered two major issues.

First, I've included a picture of the bottom of the power board. Looks to me like this is what the guy I took it to might have been referring to when he said an idiot did repairs to the unit.


At the very least this seems to be in poor enough condition to warrant being replaced entirely. Being that it's the power board I don't think there's any point in risking doing anything other than replacing it entirely.

Also there is another area with significanf issues. On the board that the relay is located on (it is oriented vertically in the unit) there is obvious damage, from what I don't know. I've also uploaded a picture of it below.

Obviously I missed these things the first look over. Both of these issues are beyond repair if I had to guess.

If I find anything else I'll post pictures.

I'm assuming the easiest thing to do at this point is just replace these two boards and then continue troubleshooting from there?

Thanks everyone.

 

[roger2]

1) you said "I can say for 100% sure that the relay engages and does not disengage after powering up. I can see inside the relay so I can visually confirm that."

OK, that is one part of this particular puzzle. But what else is happening? The protection light starts on then goes off when the relay engages, and stays off? Other lights in the receiver are on and stay on? There is no sound at the speaker terminals at all? Or there is sound at first then it stops?

Can you confirm that the two tape-related switches on the front panel are in correct positions? I believe they should both be in the center but I don't know that for certain.


2) The two new pics show some ugliness on the solder side of those PCBs. But I am not able to see anything that definitely looks like it would cause a fault. So that is a firm "I don't know". The size and quality of the pics is not adequate for me. I don't know whether maybe anyone else can spot something in those pics.

"...just replace these two boards" you say? Repair is not typically done by replacing entire boards, unless there is irreparable physical damage to the board itself. Troubleshooting typically involves isolating faulty components through methodical testing, and replacing bad parts with new. And replacing a whole board is not simple. And finding a board is not easy, though people do part out units and one might get lucky, but not sure that would be the correct term to use. If you found a replacement PCB it would likely be disproportionately costly, and the condition of the components on it would be unknown.

 

[DubbleA_ron]

Perhaps these pictures are better.



I am not sure what you're referring to when you say "tape related switches". What do these look like?

The protection light on the unit turns off at the same time the relay engages. Other lights turn on and stay on. No sound.

Also, I checked the fuses on the power board, they are both fine.

 

[roger2]

On the front panel in the lower right side, there are two switches with the word "TAPE" printed below them. Above the switches one says Dubbing, the other says Monitor. The Monitor switch must be set in the middle, otherwise the symptoms you describe would result, no sound. I am not 100% certain if the Dubbing switch could have any effect, but just to be safe I would put both switches in the center position.

What is showing in the first new(est) pic certainly does not look good. And yeah, that may be a deal breaker possibly. I am still not certain what I am looking at though. Can you describe it?

In the second new(est) pic I see some ugly soldering but nothing that looks like a potential problem,. BUT I still cant see it all that clearly, and could be missing something.

 

[DubbleA_ron]

The first picture is the bottom right hand side of the largest board that sits vertically in the unit. It's the same board that the relay is located on.

The tape related switches should've been obvious to me. Oh well, I did have them all in the middle position when testing for sound.