KLH Model 20 TT/Tuner combo - Where's that hum coming from?

I just picked up this nice little system, knowing it was a "pig in a poke", but I was told it worked fine.

Quite a major hum going on. Much more in one channel than the other.

This is present whether in Phono, FM (no AM on this model) or Aux. Volume does not have any effect - it is constant.

I thought maybe a speaker problem, but tried a good speaker from another KLH system and no difference.

There is a switch on the back of the TT labeled IN/OUT (see photo, which is not mine, but one I grabbed from online). I wonder if this is to switch from speakers to headphone (1/4" jack. I haven't tried the headphone option as I don't have any). The hum is present with the switch in the IN position, but is not present when this switch is in the OUT position (in the OUT position there is no sound at all, as if I've shut off the system). By the way, the photo shows an AC plug jack with what appears to be a ground prong. Mine uses a hardwired AC in with no ground.

I haven't opened it up, but may. Just want to take it slow, and who knows, maybe it has a simple explanation.

What do you think? Simple issue? Easy fix?

EDIT: I just opened it up, and the problem seems very apparent. There is a large capacitor whose top has come off (see pic). I realize that some, as a matter of course, replace all caps from something of this vintage. I've never replaced a cap, but have done small soldering jobs on bass guitars and other light electronics. Is this something I can do? Or would it be better to take it in for repair (and where would I take it in the SF Bay Area?). Expensive repair?

Ideally, I'd like to repair it myself, but I don't know if I want to learn on this unit. And, well, caps...

Ian
SF Bay Area

Yup....replace all electrolytics and the hum will go away. Obviously, the one that flipped its lid is suspect.

The caps used in those were fairly crap quality. Its due for new ones by now.


Something else to check is the routing of the phono wiring. I had a 24, and it did not use shielded leads from the phono, just twisted pair. If it wasn't laid in there right, it got too close to the AC power switch and it would pick up hum. I always meant to upgrade that bit of wiring but sold it before I ever fooled with it.

I've taken things apart a little further, and can see that this isn't anything I've done before. But it is something I'd like to learn.

Is a recap very expensive? That is, if I take it to a stereo repair person? I can solder, but these have heavy leads soldered to a board, with the lead soldered to whatever you call the sheet-metal like conductors on a board. Pic attached. And just what danger am I in of "lighting up" as I go rooting around in here? It's unplugged of course.

It looks like I'll have to do a bit of detective work to figure out how to get this board out to work on it. There's a component soldered to it that is also soldered, or wired, in a way that inhibits any movement more than what you see. Hope I'm not biting off more than I can chew.



Ian
SF Bay Area

Nothing unusual there. Just need a solder sucker and a decent iron.

Will solder wick work well in this case?

I'm not sure the photo shows it, but I have very little room to work with, as I'm not able to pull the board out without getting over my head.

It also looks like I can snip the lead that's further in the works; maybe then solder the new lead to the old?

Will replacement capacitors be essentially the same size and shape, or have things progressed to the point that I can replace these with something smaller, lighter, etc.? The reason I ask is that these are attached to a metal plate using prongs from the capacitor that are twisted to hold the caps on. In fact, now that I think of it, I don't see how I can Untwist those prongs to remove the caps - that metal plate is attached to the circuit board with screws that have been soldered in place.

Would I expect a professional to completely dismantle this TT in order to get at what are seemingly easily replaceable parts? There are quite a few wires attached to this one board, so that to remove it, it looks like I can expect to de-solder about 20 or more wires to replace the caps with their six total leads.

Sorry to invite you down a rabbits hole - I'm hoping to do this myself, but am not sure if I'm thinking it through thoroughly enough. I've worked on bass guitars, which a very simple in comparison; vintage sewing machines, which are mainly mechanical; other and sundry projects over the years, and I really want to have a go at this. It's the tangle of wires that's holding me back.

Lastly (for now, anyway): does it help (will I save myself a few bucks) that I have this somewhat disassembled, should I find it more realistic to have someone who knows what they're doing tackle this for me? I'm older and "between jobs"; I'm into this as a hobby and want to continue without having to shell out for any work I can do myself. I'm thinking I need a class in electronics.

Thanks for hanging in there.

Ian
SF Bay Area

I would be surprised if the recap parts cost more than $40.00 including shipping (I just ordered an entire Receivers worth and it was $32.00 with shipping from Mouser) The replacements will likely be much smaller than what is currently in there (particularly if you go with the Nichicon UPW series) you can do this!

the schematic is available here...http://www.hifiengine.com/manual_library/klh/twenty.shtml

you will need to register to download it but they DO NOT spam and its VERY EASY to do...use the schematic to keep track of the caps you need and be sure to replace any that don't match what the schematic says they should be with what is in the actual unit...match the uF rating on the cap and the voltage second...if you NEED to you can go up slightly in the voltage with no real issues but do not change the uF rating.

while your ordering the caps you might as well order the replacements for the speakers as well...the model 20 had good speakers from what I've read they are identical the the KLH Model 17 (but the drivers for the twenty are 4 Ohm not 8 Ohm) and the Model 17's get rave reviews

I use a combination of solder wick and this...
http://www.radioshack.com/radioshack-45-watt-desoldering-iron/6402060.html#.VJMzTyvF9Yc

It works really well for what it is...and right now radio shack is running a 25% off sale (at least out here they are) so for $11.00 it's already paid for itself in wick alone.

lastly (for now) I'm not familiar with this piece (beyond looking into them some time ago when one popped up on my local craigs list) but I have recapped about 10 or so receivers, a half dozen turntables and countless speakers...I am still learning myself...but I have never had to desolder wires from a board to recap it...not saying you wont have to but I would look long and hard before I pulled 20 wires from a board...if you do have no choice take copious notes and lots of pics so you are damn sure it goes back the way it was

Thanks, Rsclj, for the vote of confidence that you and others have provided! I do think I can do this, but feel I'll have to take a step back and approach this knowing that it will be slow going with a lot of learning to be done along the way.

I do have the schematic for this - it's on the bottom panel. I'll have to better understand this before getting much deeper into it. Looks like about 100 caps total on the schematic! I'm hoping I won't have to replace them all!

As replacing caps is essentially de-soldering and soldering (let alone, for the moment, finding and identifying them), I feel confident it's nothing I haven't done before.

It's disassembling the entire TT (bear in mind, this has an FM radio in it as well) that has me hesitating. But I know it's all up to me, and it won't fix itself just sitting there, so I may as well start from the beginning, take my time, and hope for the best.

Of course, I'll be back here for help with any particulars. Thanks all!

Ian
SF Bay Area

you should only need to replace the electrolytic caps...the ceramic ones "should" be just fine.
Take lots of photos as you go...especially with the TT...get an empty egg carton (or two) to put the parts into or a bunch of zip lock bags that you can label

I have a pair of the Twenty-seven receivers and only can say they are not friendly to the beginner for repairs. Things are tight. Yours looks similar. You may want to have a tech do the work and maybe concentrate on the speakers. The tech at the same time get the changer cleaned, lubed and adjusted. These units are well worth the investment as the system approach KLH took yielded a well balanced and good musical sounding system.

I'm attaching a number of photos of the electrical components with assorted arrows for some reference. I'm hoping to identify what needs replacing and what can be left alone. Thoughts (comments)?

The pic labeled "A" shows the board to which the large electrolytics are attached: note the screws (orange arrow), which are filled with solder. Those screws hold a metal plate through which the "twisty posts" of the electrolytics pass and then twisted to attach. I guess I'll have to de-solder the screws to detach that metal plate.

The green arrow points to one of the electrolytic leads. I'm hoping it's cool to snip these where convenient in order to remove the old caps, then solder the new leads to these.

"Exhibit" "B" has an arrow pointing to what I figure is a cap. Should all that look like this be replaced?

"C" shows other electrical components - are they caps?

I've heard that the ceramic caps, the round, brown "wafer" type for instance, don't need replacing unless they test bad.

Brian, I'd love to have the services of a tech willing to look over my shoulder as do this, but it isn't something I can afford, and I do want to persevere in my learning process. But thanks for the fair warning! And, yes, I will be getting to the speakers as well.

I was able to remove the turntable proper, after removing a couple of clips and a few connections. I had no idea what I was looking at, but once done, it seemed simple enough in hindsight. I also loosened another board and component that allows be better access to what I'll replace. I'm feeling a little more confident. However, I'm sure that those pesky screws that were difficult enough to remove, will be a bear to replace.

For now, looks like I need to identify what I'll be replacing, then head to my local electrical supply store for proper replacements.

And better late than never with this question: in what danger am I from any of this. I've had dire warnings in the past from some, while others have assured me that after some time the caps are harmless. This has been unplugged for 24 hours and counting.

Ian
SF Bay Area

Any thing that looks like a little can (some will be axial like the grey ine in your second pic) some will have two leads from the bottom...like the little black one in your third pic (blue arrow) try to order from Mouser or digi-key...they will have a MUCH larger supply to choose from and likely be cheaper than your local supplier...even "You-do-it" which is one of the largest suppliers around me has nothing compared to mouser or digi-key

24 hours should do it...the smaller ones even less...unless its plugged in your biggest danger is burns from the iron

The white arrow 3rd pic is pointing to a resistor likely not on the hit parade for replacement ...the black one look like replacements and the grey ones look like the originals...deffinately tight working space but take your time and tripple check the polarity before you finalize...and solder it...it will always be indicated in some way on the cap you are removing...the black ones for instance have a, looks like lt grey or white stripe on one side... the grey ones have a plus on one side

The metal cans in you second pic, with the 3 protected leads, are not caps...do not remove them...the caps should all be marked with an xxV and xx uF (the xx representing some value like 63v 220uF)

I'll plan on first replacing all gray electrolytics, as they are easily identified. Then perhaps the black.

Looks like I have no paper/wax caps to worry about.

First, I'll have to replace the large caps as seen in post #1. The one has obviously failed.

Ian
SF Bay Area