Scott LK-72 & LT-110 clean & 100% original

Great news on your LK-72. A true classic!


Was listening to my LK-72 last night. Just back from a going over by Mr T DeWick. Mine is a factory wired and with the gold front panel.

I have been using the Tung-Sol Quad 7591's first because they fit in the cabinet and sound rather nice.



Barney
 
Had a nice long listening session using my 3Pi horns last night. The LK-72 is smooth & warm. Still evaluating the degree of sonic detail, but very enjoyable in a vintage way. I'll let the orange drops break in some more because this system keeps getting better and better with use. At first, vocals and mids seemed to be pulled back and dry. But listening to jazz, echo effects and delay was noticeable. My favorite test album, "Ella and Louis" had nice detail and clear vocals. Maybe 80% of the sense that Ella is standing in the room that my DGSE gives. But can still hear Louis opening his mouth to sing ( gross, but true...amazing what mics can pick up). So maybe it was just the particular recordings that sounded dry and recessed. The bass is just wonderful. Full, even with my 3 Pi speakers (that roll off at about 50Hz) and with the "loudness" switch off. I love what I call "rubbery" bass and this amp gives the rubbery sound. I've never experienced an integrated with such huge OPT.

I tested the phono section this morning. Had a Tele 12AX7 tube that needed to be wiggled and may be starting to die or may still have dirty sockets or pins. One channel will start to sound scratchy, but I fixed it by wiggling the tube. Then it came back. But wow, I think this unit may save vinyl for me. I was seriously giving up on vinyl cause I couldn't find a decent phono pre. Listening to the Carpenters this morning (yeah, I'm a fan, superb recordings and lovely melodies) and the stereo separation was very satisfying. The sound was smooth and quiet with no hum or hiss. Vinyl now sounds at least as good as Spotify, with some added analog warmth. Very happy about that and excited to start to collect vinyl again!

Finally, about the tuner, I haven't recapped anything, but I brought it up over 24 hrs on a variac. First test revealed that the output was a squeal. Today, I realized that V1 just needed to be rocked and re-seated a bit. The squeal went away, leaving slight static, but no signal. When I went downstairs to snap some pictures, I turned it on again and lo and behold, I got about 5 stations (with a T antenna....in the basement!). So, thankfully, everything works now. Amazing how these amps seem to fix themselves and get better with use. The tuner sounds smooth and warm as you'd expect from a tube tuner. I just wish that there were some good jazz stations in KC. :(

Pics aren't as nice as some others', but here ya go!

index.php



index.php


index.php




'
 
Last edited:
I was listening to the radio on mine last night. They were playing an hour of blues, and the harmonica on one song sounded so life like. I also have a 233 and a 299C and my favorite is the LK72. All are in tip top condition one (299C) total recap. The other two went thru Mr DeWicks shop recently.



Barney
 
Phono section has some "rushing" sound to it. I swapped out the 12AX7s for V1 and V2, but no change.
The rush starts when the tube warms up and goes away when I switch RIAA to NARTB-Tape.
So, is this some problem with the phono PEC? Noisy resistors?

I would probably go ahead and try to rebuild the RIAA circuit on a breadboard and get rid of the PECs.

Even with this pretty loud rush in the background, phono is still about the best experience I've had in almost 10 years.
What a superb phono section!!
 
Last edited:
I'll start by replacing resistors around V1 and V2 first. Then, the PECs. Old carbon resistors could make weird noise sometimes.
 
Good advice.

I tried to deoxit the sockets today and now lost one channel all together (still a tiny signal I can hear, maybe it's cross talk).
I tried both the V1 and V2 tubes in another amp and they work fine. Worked the switches, tried another TT.

Hmmm tube rush, then kaput.

I'm on business until Thursday, so I won't get to tinker with it until the weekend.
 
Thanks Al. Glad you're happy. :thumbsup:

Last night I tested voltages on V1 (channel A phono preamp tube) and they looked good. Then I checked continuity from the phono RCA jack as much as possible (gets a little complicated near the selector switch) and really couldn't find any Rs or Cs that were dead or had cold joints, so I focused on the RCA jack and after wiggling it and connecting/disconnecting the interconnect from the turntable, suddenly got volume in channel A. :)

So, it looks like I have some more deoxing to do and also change some resistors (plate voltage was 30% high on V1A compared to V1B. These should both be 100V and I was measuring 130 on V1A....strange because the V1A plate 270K plate resistor was closer than the V1B plate resistor. I wonder if I should replace with two new 270Ks and then investigate whether the voltage on the upstream side of these is higher than it should be?)

Enjoyed some vinyl again to celebrate solving the problem. The LK was hooked up to the ADS 1290's. First up Don Williams "Cafe Carolina", sounded like it was recorded in the 80's, but smooth and warm. Then, The Nightfly, which was shockingly clear and punchy! I'll say it again, I can't wait to start collecting vinyl again. The only real difference between vinyl and CD now is the analog warmth that vinyl has. I have never heard the vinyl copy of Nightfly sound as good as streaming or CD, but last night, I was truly hearing things I had never noticed before. Actually experiencing something I had never noticed. I suppose it would be called dynamics? I have listened to The Nightfly a hundred times, so I know it well. Here's what I heard: decay that I had not noticed before, vocal note changes (like 1/4 tones), very subtle notes played in the background (harmonicas / triangles, extremely subtle guitar fills). This phono section is the best I've heard (ref: Bottlehead Seduction (which is AS GOOD and maybe better, but lacked bass IME), Muffsy phono pre, Boozehound Labs, Music Hall MM2, Marantz 2230, Fisher 500t).

Stereo balance is great. Very good transparency, less good sound stage I would say (but only listened to 3 mass produced pop albums (except The Nightfly which is a special recording...maybe that will improve with some jazz recordings) Great balance. Bass is very much there but well balanced. Highs, again, are light and clear. My only criticism is that Fagan's lead vocals (and any lead vocals ) seem dry and not as clear as the rest of the instruments. We'll see if it was just that recording, or the speakers or the pronounced instruments that overshadow vocals.

This weekend, gonna spin The Best of Stan Getz (Verve) and Little Feat Time Loves a Hero (ah heck...ALL my Little Feat albums) :music:
 
Congratulations on the Scott gear. It is truly some great stuff, every bit as good as fisher but less known. I have found with my HH Scott amps, that you really can't make any judgements about the amp based on the first side you play. It takes a half hour for the cathode to really get hot and everything to stabilize and produce the best sound. Anyone who gets so own and use a restored HH Scott amp is a very very lucky person in my book. I have been blessed with a LK72, 299D, and a Scott model 208 power amp. I have restored all 3 with new power supplies, bias supplies, tung sol power tubes, and fresh coupling caps... The joy I get from turning on my 299, and dropping the needle, is immeasurable, sounds like you're feeling it too.
 
When measuring OPT's with a DMM, set the range, and freeze it. The auto-ranging function most of them employ hates the radical amount of inductance present in an OPT.
cheers,
Douglas
 
In a moment of upgrade-itis, I ordered K40Y-9 coupling caps to replace the orange drops that I just installed. :oops: OD's didn't sound bad, but I was curious to try something cheap, but different. Wanted some variety because I have OD's in my Pilot. Surprised that I gave them another shot, because my last experience with them on a preamp wasn't good. They sounded dark.

I don't want to go overboard with enthusiasm, but the Russians are a very nice improvement. Smooth as silk, but also crisp and clear and MUCH more transparent.
All this with only about an hour of break-in. ( I noticed a little bit of 2D behavior and smearing of sound for the first hour of listening last night...didn't worry cause I know these have a 100-400 break in....supposedly)

I was starting to think I was reaching a plateau of decreasing returns (in my budget, anyway) but this feels like a major step up. Each familiar song I listen to now has like a new personality. Vocals and instruments appear in places where before I never noticed. The smoothness is something I've not really experienced before. Such a richness.

K40Y-9's don't need my endorsement, but I'm really happy with this decision & recommend to others with Scott gear. :hug::rflmao:
 
Nice job getting it going again JD -- and a very nice amp! I've got one just like it that I restored nearly 3 decades ago now, and it still sees weekly if not daily use, still operating perfectly. Gorgeous sound. However, because of its original failure mode, and the point in time that I restored it, it's restored in such a way that you would never imagine. I just went through it not long ago, and because it has been so uniquely restored, decided at the time that it might be worth throwing up a quick thread about it which I hope to do in the next day or two.

Congrats on bringing it back to life!

Dave
 
byoungman1 said:
Back to the OP, polyester caps tend to sound pretty bad in audio circuits...orange drops would be a much better choice.
Hope you get the resto worked out!
Click to expand...
Orange Drops are polyester I believe. Replace all the resistors with overrated (higher rated voltage) metal film, go easy on the deoxit (all that oily stuff is gross). Those Scott slide switches are culprits and hard to clean unless you disassemble them. The filter switches should be hardwired out of circuit IMO because you will never use them and they can cause problems with a leaky (high resistance) slide switch. My 299C also had a front panel headphone jack that caused sound problems solved by pulling the circuit and shielded cable entirely.
 
^ There are several lines of Orange Drops; some are polyester, others are polypropylene.
 
Took apart the LT 110 tuning meter and found that the white dial back "card" was warped, which is what bound up the indicator pointer.
The only way to fix ( without bending the delicate needle ) was to put some stand-offs on the inside of the plastic bezel.

It worked little. I glued a couple of transistor bodies in there ( just happened to have some and figured they were about the right height) to hold the warped backing card away from the window and allow free movement of the indicator. Buttoned it all back up and tested. Well, the needle moves now, but just slightly and it does help to indicate maximum tuning on some of the strong stations, but doesn't have full range. I'm sure it's gonna bug me and before the weekend is up I'll have to go back in there and do it right. :rolleyes: ( should have tested before buttoning back up.....I'll never learn )

Worth doing cause this tuner is awesome. It pulls in more stations with a regular ribbon type T antenna and IN THE BASEMENT, than my Rotel digital receiver which has a powered antenna and is upstairs.
It's dead quiet and sounds even better after I replaced a few of the larger value caps.

I'll take some pics when I go back in. Sounds like a sticky meter dial is a common problem.
 
Update:
I was becoming dissatisfied with the quality of the high frequencies on this amp. I replaced the cericaps on the treble tone control pot with orange drop caps and didn't notice any difference at all.
Next, I replaced the parallel 0.05uF ceramic disc coupling caps (C23&24 and C123&124) with 0.1uF IC lemon drops .......THIS is a WINDEX treatment! Major ( like 25% or more) improvement in highs and overall clarity. I was having to crank the treble pot to 3 o'clock to get satisfactory HF. I have to have crystal clear highs. Now it is quite clear at the 12 o'clock position. :)

After recapping the HF tone control pot, and getting no change, I found an article about the LK-72 stating that the sound was dark. I figured that's just the signature of the amp and I would have to either live with that, or sell the amp. Well, not any more. This baby is approaching the detail of an SE amp. I really thought I was an "SE only" guy (and I still very much appreciate SE amps) but the LK-72 has now tempered my bias. Today, it was hard to turn the amp off.

WRT the LT-110, no sound. Everything was working OK, and then nothing. I don't have an O-scope to trace signal, but I've checked voltages and they measure high. My guess is that I have a bad tube somewhere. I've swapped out all the 12AT7 and 12AU7 tubes and no fix. So I've now ordered one of each of the other tubes in the tuner. Good thing is that the 6U8A are the alternates for 7199, so I ordered 2 for if/when my original 7199's die.
 
Last edited:
JD -- A quick test you can try to determine whether the problem is in the tuner section proper, or the MPX unit -- which in this design, has all signals (stereo and mono) flowing through it:

See if you have audio at the RCA jack located on the Multiplex sub-chassis. If so, then the tuner section is fine and the problem is in the MPX section. If no audio there, then the fault is in the tuner section.

Good luck with it!

Dave
 
Hey, how about that! Great advice Dave. There IS a signal on the test point jack.
So, now I know that it is in the MPX section and probably the 6BL8 Yes! :thumbsup:
 
Last edited:
You must log in or register to reply here.

Similar threads

E
Scott LK-72-B and LT-110-B
Replies
16
Views
2K
Patrice B
Patrice B
vannozzi
2-Scott LK-72 Tube Amplifiers
Replies
16
Views
2K
century tek
century tek
radioterry
Scott LK-72-B
Replies
7
Views
3K
heekma
heekma
djef
My new Scott LK-72
2 3
Replies
48
Views
4K
FalconEddy
FalconEddy
AFpay
Found a Scott LK-72
Replies
6
Views
1K
richfro
R
Back
Top Bottom