KLH Model 20 TT/Tuner combo - Where's that hum coming from?
- Thread starter IanMcI
- Start date
Here's a pic comparing the old and new caps (new on the left). Saving a little space with these new caps!
This does not represent the full compliment of electrolytics in the unit. I figured I'd replace all those that were of the same make (the gray caps), leaving a number of black caps that seem different enough for me to believe that this is a good dividing line. As this is my first recap, I thought I'd take it easy. I still have the speakers to look forward to, and will do them before testing the unit.
And then, I'm replacing those larger caps as well, one of which "blew its top".
Thanks for hanging in there with me, especially you, Rsclj; your suggestions have help!
Ian
SF Bay Area
This does not represent the full compliment of electrolytics in the unit. I figured I'd replace all those that were of the same make (the gray caps), leaving a number of black caps that seem different enough for me to believe that this is a good dividing line. As this is my first recap, I thought I'd take it easy. I still have the speakers to look forward to, and will do them before testing the unit.
And then, I'm replacing those larger caps as well, one of which "blew its top".
Thanks for hanging in there with me, especially you, Rsclj; your suggestions have help!
Ian
SF Bay Area
Attachments
I've replaced the caps shown previously. Not a big deal - at least not so big a deal that I didn't enjoy the process. Things went smoothly enough. I did take photos and drew diagrams before hand - big help, as there was a discrepancy between what I drew and one of the photos!
Thanks for the tip about the dim-bulb tester. I made one, and have just tested the unit. I was disappointed to see that 15W bulb light up! But then I discovered that two RCA-type leads that are meant to connect to the turntable were touching each other - I separated them and that issue was resolved (as far as I can tell). I started with 15W, then went through 40W, 60W and 100W bulbs, so I'm hoping all is good.
I now have to stuff the chassis back in its box and attach the turntable, then the speakers. I figured I'd test without the replaced speaker caps (I haven't got to those, yet), as I'm pretty sure they won't need that for me to see if that major hum is gone.
Ian
SF Bay Area
Thanks for the tip about the dim-bulb tester. I made one, and have just tested the unit. I was disappointed to see that 15W bulb light up! But then I discovered that two RCA-type leads that are meant to connect to the turntable were touching each other - I separated them and that issue was resolved (as far as I can tell). I started with 15W, then went through 40W, 60W and 100W bulbs, so I'm hoping all is good.
I now have to stuff the chassis back in its box and attach the turntable, then the speakers. I figured I'd test without the replaced speaker caps (I haven't got to those, yet), as I'm pretty sure they won't need that for me to see if that major hum is gone.
Ian
SF Bay Area
Well, back to square one! I don't know whether to laugh or cry...
Despite my seemingly good fortune with the results of the dim-bulb test, as it turns out, I had it all wrong!
After seeing that 15W bulb glow (disappointingly), I turned things off to double check things (this is when I found the RCA leads touching), but when I tried it again (and here, I cringe at the thought), I plugged in the soldering iron thinking it was the dim-bulb tester! No wonder everything was looking up roses - and why I didn't catch it before my last post - the dim-bulb tester appears to show positive results when it shows nothing at all!
So, as I'm still not sure what the tester is suppose to be showing me, is there still hope? The 15W bulb glows far below that which it does when powered like a regular light bulb; it is, indeed, a "dim bulb". Is the only acceptable result: no light at all, or can some light be expected? What instructions I've seen for its use seem to be lacking clear explanations of what one should expect. I did read that if the 15W bulb glows brightly to turn things off! But this is glowing at about half or less than what it does in normal use.
I'll search further, but if the expected results of a dim-bulb test can be explained, I appreciate that.
EDIT: I just read a couple of other posts about dim-bulb testing and results; I'm breathing a little easier. Some suggest that a dimly glowing bulb is normal, i.e., no short. Now, these had to do with older tube equipment.
I just retested the unit with these results: the 15W bulb brightens for just a second, then settles down to dim, warm glow; the 40W does not shine at all, nor do the 60W and 100W bulbs. The unit does show that it's on with its ON light glowing. So, I figure that I'm actually OK with these results, at least in terms of a short in the circuit.
EDIT: UPDATE: The good news! It works! So far, so good. The hum is gone, the FM radio works, the phono is working as far as I've tested it (I haven't tried the automatic spindle for multiple records, or the 45 spindle).
The bad news is that the tweeters are not working. Time to follow a thread here on AK that will walk me through that process. I have high hopes.
This was my first "recap" (such as it was), and I'm pleased with what I've learned. I very much appreciate the encouragement. Still much to learn, but I feel I can do it. Thanks all!
Ian
'SF Bay Area
Despite my seemingly good fortune with the results of the dim-bulb test, as it turns out, I had it all wrong!
After seeing that 15W bulb glow (disappointingly), I turned things off to double check things (this is when I found the RCA leads touching), but when I tried it again (and here, I cringe at the thought), I plugged in the soldering iron thinking it was the dim-bulb tester! No wonder everything was looking up roses - and why I didn't catch it before my last post - the dim-bulb tester appears to show positive results when it shows nothing at all!
So, as I'm still not sure what the tester is suppose to be showing me, is there still hope? The 15W bulb glows far below that which it does when powered like a regular light bulb; it is, indeed, a "dim bulb". Is the only acceptable result: no light at all, or can some light be expected? What instructions I've seen for its use seem to be lacking clear explanations of what one should expect. I did read that if the 15W bulb glows brightly to turn things off! But this is glowing at about half or less than what it does in normal use.
I'll search further, but if the expected results of a dim-bulb test can be explained, I appreciate that.
EDIT: I just read a couple of other posts about dim-bulb testing and results; I'm breathing a little easier. Some suggest that a dimly glowing bulb is normal, i.e., no short. Now, these had to do with older tube equipment.
I just retested the unit with these results: the 15W bulb brightens for just a second, then settles down to dim, warm glow; the 40W does not shine at all, nor do the 60W and 100W bulbs. The unit does show that it's on with its ON light glowing. So, I figure that I'm actually OK with these results, at least in terms of a short in the circuit.
EDIT: UPDATE: The good news! It works! So far, so good. The hum is gone, the FM radio works, the phono is working as far as I've tested it (I haven't tried the automatic spindle for multiple records, or the 45 spindle).
The bad news is that the tweeters are not working. Time to follow a thread here on AK that will walk me through that process. I have high hopes.
This was my first "recap" (such as it was), and I'm pleased with what I've learned. I very much appreciate the encouragement. Still much to learn, but I feel I can do it. Thanks all!
Ian
'SF Bay Area
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Screw it together and see what you get out of it 
Using my MM (about whose operation, I know very little), I've contacted the two speaker leads. The speaker is out of the cabinet and not connected to anything.
There is a range of settings on the MM as such (these are in the range with the OHM symbol): 200m, 20m, 2m, 200k, 20K, 2k, 200 in that order.
I only get a reading at 2k (reading of .004) and 200 (reading of 4.4). Is this right? All other settings return a reading of zeroes.
Ian
SF Bay Area
There is a range of settings on the MM as such (these are in the range with the OHM symbol): 200m, 20m, 2m, 200k, 20K, 2k, 200 in that order.
I only get a reading at 2k (reading of .004) and 200 (reading of 4.4). Is this right? All other settings return a reading of zeroes.
Ian
SF Bay Area
Both tweeters were not working. I only pulled one, so far, so I don't have a "good" tweeter with which to swap the other.
I did try the battery test on the tweeter I pulled, using a 1.5v battery. I did get the click that is supposed to be associated with a properly working tweeter, so I'm feeling pretty good about my chances of this being a capacitor issue. That both tweeters were not working, and feeling as I do that this unit was in storage for quite awhile, I'm guessing the caps dried out. or something. Of course, I'll know more when I go through AK member, Special Idiot's, process for updated the caps for these speakers.
Ian
SF Bay Area
I did try the battery test on the tweeter I pulled, using a 1.5v battery. I did get the click that is supposed to be associated with a properly working tweeter, so I'm feeling pretty good about my chances of this being a capacitor issue. That both tweeters were not working, and feeling as I do that this unit was in storage for quite awhile, I'm guessing the caps dried out. or something. Of course, I'll know more when I go through AK member, Special Idiot's, process for updated the caps for these speakers.
Ian
SF Bay Area
Rsclj
Active Member
here is a excellent thread on speakers very much like yours...http://www.audiokarma.org/forums/showthread.php?t=102176
