thebes Posted July 19, 2020 Share Posted July 19, 2020 A fellow Klipscher dropped this off at my house month ago. Model number is 2540U and it's one big puppy with AM, FM and Shortwave. It was missing it's tubes but otherwise in pristine shape. Had some of the tubes here and ordered up a couple more. Checked all resistors, and was quite surprised to find that all read within specs, something I've never seen before. I did have to lift only a couple to get a true reading. Fired it up, dialed in a station or two and everything works fine except for two issues. The first is volume. It's way too high. Anything above 8:30 on the volume dial and the sound starts to distort. Above 9 on the dial you can feel the wind coming off the woofer. (One 6x9" woofer, two tweeters). By 11 there is so much wind coming from the woofer you could use it as a fan. The 2nd problem is directly related. This thing sounds very boomy on the bottom end, and if you move the tone control very far to compensate the sound grows very harsh, very fast. Now, I'm sure everybody will suggest that I replace all the caps, but I got to tell you, there are some incredibly fine wires in this radio and I'm pretty sure I'd manage to inadvertently burn through one of them with my soldering gun, so I'm really reluctant to start popping new pieces in this radio. I'm also incapable of doing an alignment on this beastie. I'll post the schematic shortly but I'm looking for suggestions on two fronts. First is the volume issue. This radio uses a dual pot incorporating both volume and tone control and is probably unobtanium, and from my testing it both appears to be in spec. Second is the woofer. I do believe its 5ohm, yes a 5ohm speaker. Although the surround is completly intact, I'm wondering if age is affecting it's performance and if it should be replaced. I'm thinking a stock car woofer, but am wondering if a 4ohm or a 8ohm would work best with the existing tweeters. So there you have it. Thoughts? Quote Link to comment Share on other sites More sharing options...
thebes Posted July 19, 2020 Author Share Posted July 19, 2020 Left side schematic: Quote Link to comment Share on other sites More sharing options...
thebes Posted July 19, 2020 Author Share Posted July 19, 2020 Right side schematic: Quote Link to comment Share on other sites More sharing options...
tube fanatic Posted July 19, 2020 Share Posted July 19, 2020 Hi Marty! Before anything else, hit the volume and tone controls with a touch of Deoxit. It wouldn’t hurt to do the same with the switches. .Also, measure the dc voltage between pin 8 of the eabc80 and ground, and pin 3 of the EL84 to ground. Also measure pin 2 of the EL84 to ground to verify that there is no dc present. Use the lowest range of your meter for the latter. Maynard 1 Quote Link to comment Share on other sites More sharing options...
thebes Posted July 19, 2020 Author Share Posted July 19, 2020 Thank you Maynard. I knew I could trust in the Forum brain trust, and of course, your own incomparable knowledge. Will report back. Quote Link to comment Share on other sites More sharing options...
thebes Posted July 19, 2020 Author Share Posted July 19, 2020 Well one problem solved. While removing thee knob for the volume and tone control pots, I learned that the volume knob was mis-aligned. Corrected that and now it has a better, not perfect, but better range of sound. Hitting the pots with Deoxit may have also helped. While here are the measurements, radio warmed up: EABC80, Pin 8: 1.8vdc El34, Pin 3: 6.9vdc EL34 Pin 2: 20mvdc Quote Link to comment Share on other sites More sharing options...
tube fanatic Posted July 19, 2020 Share Posted July 19, 2020 Not too bad. Just to be complete, measure the voltages to ground on pin 9 of the eabc80 and pin 7 of the EL84. Clean the pins of those tubes well, coat with Deoxit, and insert/remove a few times. C67 is a little leaky, so if you have something close in value with the correct working voltage, replace it for good measure. Will try to look in later on in case you do this today..... Maynard Quote Link to comment Share on other sites More sharing options...
thebes Posted July 19, 2020 Author Share Posted July 19, 2020 Ok. Here's the latest measurements: EABC80, Pin 9: 88vdc EL84, Pin 7: 253vdc I'll clean the pins and remeasure later. Got to run some errands. I have located a good .022 cap, but it's an orange drop. Will that work in this position? Most of the caps in this radio have are the round things plasticy/glass things which have a direction marked on them. Quote Link to comment Share on other sites More sharing options...
tube fanatic Posted July 19, 2020 Share Posted July 19, 2020 Yes, an orange drop is fine. Keep me posted. Maynard Quote Link to comment Share on other sites More sharing options...
thebes Posted July 20, 2020 Author Share Posted July 20, 2020 Ok. Dropped in the orange drop and retested. All voltages read the same except pin 8 of the EABC80 which now reads -1.1vdc down from 1.8vdc, although the later measurement was probably minus dc and I simply missed the minus sign on my meter. Either I was mistaken yesterday, or something is not right, but the volume is still too high at way to low on the knob. Turned fully down I can still hear the radio station. While the distortion is not overt, the thumpyness is and while fiddling with the tone control does effect it but not the overall character of the sound which is forward and thumpy at the same time. Quote Link to comment Share on other sites More sharing options...
tube fanatic Posted July 21, 2020 Share Posted July 21, 2020 Marty, do you have a an audio signal generator with variable output and a shielded test lead? I can take you through a simple troubleshooting process if you do. Maynard Quote Link to comment Share on other sites More sharing options...
thebes Posted July 23, 2020 Author Share Posted July 23, 2020 Sorry Maynard, this heat wave is knocking me back a bit and making me slow to respond. I have a general radio 1312 Descado Oscillator, which I do believe fits the bill. Has various control for frequency and output voltage. Output is 600ohms and has the test lead can be plugged into something called "Ext Sync" which I take to be exterior synchronization. Haven't used it in a long time. I have three test leads, I have a clip type test lead 10x, another 10mohm and a third that has the additional ground lead, and can be set for either 1x or 10x 100mx with includes a ref *(reference?) setting. Sadly it lacks the push on spring loaded clip lead. Oh yeah, I also have a Heathkit RF Signal Generator. Here's a pic of the signal generator: Quote Link to comment Share on other sites More sharing options...
thebes Posted July 23, 2020 Author Share Posted July 23, 2020 Better yet. Here's a pic of the actual radio. In pristine condition and very cool looking: Quote Link to comment Share on other sites More sharing options...
tube fanatic Posted July 23, 2020 Share Posted July 23, 2020 Sent you an email a little while ago..... Maynard Quote Link to comment Share on other sites More sharing options...
OO1 Posted July 24, 2020 Share Posted July 24, 2020 On 7/22/2020 at 8:02 PM, thebes said: Better yet. Here's a pic of the actual radio. In pristine condition and very cool looking: I have quite a collection of these -older radios ---------- Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.