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NYAL OTL3

220.255.2.220
Posted on February 25, 2014 at 02:26:26
v_n_naidu@hotmail.com
Audiophile

Posts: 69
Joined: July 31, 2007
 Hi,

I have previously sought assistance on my OTL3s. These are the very early versions. The issue then was with V1 which started to glow orange within minutes of switch on. Many possible causes were suggested. One that suggested that V1 was not as strong as V2 and V3 as these operate as one appears to be correct. I have finally manages to find a replacement 6LF6 that does not glow orange.

As soon as this issue was resolved,there is now a new issue, V5 now starts to glow orange within seconds of switch on. I suspect that these 2 issues are related although the circuit dia. seems to suggest otherwise. Ideas on possible causes and solutions would be much appreciated. I have checked all the caps and resistors, all are spot on or just marginally off.

In view of these 2 issues I have not been able to bias the amps. Thanks in advance for your comments.

Rgds,

Nara

 

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RE: NYAL OTL3, posted on February 25, 2014 at 09:24:12
Ralph
Manufacturer

Posts: 4769
Location: Minnesota
Joined: April 24, 2002
 Try moving the tube in the V5 position to V2 or V3. Let's see if its the location or the tube.

 

RE: NYAL OTL3, posted on February 25, 2014 at 15:04:03
v_n_naidu@hotmail.com
Audiophile

Posts: 69
Joined: July 31, 2007
 Hi,

Thanks for your comments.
Sorry, my mistake, V5 (6LU8) cannot be moved to V2 or V3 as these are 6LF6 tubes. I did move it to V4 (6LU8)position, it did not glow there while V4 did in V5 position. Therefore it is the position and not the valve. I have also tried 4 other valves in this position and they all had the same problem.

Rgds,

Nara

 

RE: NYAL OTL3, posted on February 25, 2014 at 15:09:39
Ralph
Manufacturer

Posts: 4769
Location: Minnesota
Joined: April 24, 2002
 A power tube may have a certain kind of short, causing that driver tube to heat up. Try juggling the output tubes and see.

I am assuming that the components in the area don't look damaged.

 

RE: NYAL OTL3, posted on February 26, 2014 at 16:29:49
v_n_naidu@hotmail.com
Audiophile

Posts: 69
Joined: July 31, 2007
 Hi,

No changes were made except replacement of V1 with another tube that does not glow upon switch on. I am of the view that it has to do with this change in tube as there was no issue with this tube (V5) until V1 was replaced.
V4(6LU8) also started also started to glow in V5 position while V5 does not glow in V4 position.

Rgds,
Nara

 

RE: NYAL OTL3, posted on February 27, 2014 at 09:25:52
Ralph
Manufacturer

Posts: 4769
Location: Minnesota
Joined: April 24, 2002
 By any chance do you have a schematic or a link to one? That would help a lot.

 

RE: NYAL OTL3, posted on February 27, 2014 at 16:44:08
airheadair
Audiophile

Posts: 393
Location: California
Joined: October 18, 2010
 I hope the link below is a correct schematic.....

 

RE: NYAL OTL3, posted on February 27, 2014 at 18:01:13
v_n_naidu@hotmail.com
Audiophile

Posts: 69
Joined: July 31, 2007
 Hi,

Thanks for coming to my assistance. I have a copy but had difficulty attaching it to my post.

Rgds,

Nara

 

RE: I suspect that is the wrong one- it is Futterman, not NYAL OTL3 nt, posted on February 28, 2014 at 08:51:49
Ralph
Manufacturer

Posts: 4769
Location: Minnesota
Joined: April 24, 2002
 -

 

RE: I suspect that is the wrong one- it is Futterman, not NYAL OTL3 nt, posted on February 28, 2014 at 09:06:30
airheadair
Audiophile

Posts: 393
Location: California
Joined: October 18, 2010
 I think it is correct. My NYAL OTL3 says Julius Futterman OTL3 on the front and the schematic i posted. says Futterman OTL3.
I think they use the names interchangeably. Unfortunately I can't put my hands
on my own physical copy of the schematic

 

RE: NYAL OTL3, posted on February 28, 2014 at 15:32:49
v_n_naidu@hotmail.com
Audiophile

Posts: 69
Joined: July 31, 2007
 You are right, This is the version that is attached to the owners manual and that I have seen.

 

RE: NYAL OTL3, posted on March 4, 2014 at 21:13:40
airheadair
Audiophile

Posts: 393
Location: California
Joined: October 18, 2010
 Now that we think we have the right schematic, does any one have further help for
our poor patient friend naidu?

 

RE: NYAL OTL3, posted on March 6, 2014 at 17:26:32
v_n_naidu@hotmail.com
Audiophile

Posts: 69
Joined: July 31, 2007
 Yes I do hope that someone can help me to resolve this issue. Its almost 3 years since I purchased these amps. I managed to resolve the issue of the glowing 6LF6 (V1) after purchasing more than a dozen of these tubes thru ebay and now I am immediately plagued with a new problem.

I need to resort to this forum as no one here (Singapore) can help me. If I can resolve this issue I should be able to bias the amps as a kind asylum member has provided me with a copy of the necessary instructions.

Nara

 

RE: NYAL OTL3, posted on March 6, 2014 at 17:49:44
rhinohifi714
Audiophile

Posts: 174
Location: oklahoma
Joined: June 13, 2009
 What is the new problem?

 

RE: NYAL OTL3, posted on March 6, 2014 at 18:05:10
rhinohifi714
Audiophile

Posts: 174
Location: oklahoma
Joined: June 13, 2009
 I just read your entire thread, just because you purchased a dozen tubes thru ebay that doesn't guarantee a fix, the tubes need to be tested for plate current, if the tubes are not matched you can do more harm than good, by switching the tube around you should be able to find a configuration that they will align properly. If you cannot get 300ma idle current when going thru the alignment procedure then they are all probably weak tubes. If the current takes off well over 350ma within a few seconds of powering up then you need to start replacing the Zener diodes until you get a smooth rise in current hopfully around 150ma with screen controls at the lowest setting, this will give you plenty of range to align them properly.
If you don't have the alignment procedure let me know, seems like I have already sent it to you.

 

RE: NYAL OTL3, posted on March 6, 2014 at 19:37:23
v_n_naidu@hotmail.com
Audiophile

Posts: 69
Joined: July 31, 2007
 Hi,

Yes I have the biasing instructions that you sent. My original problem was V1, it started to glow upon switch on. I tried all the other tubes (V2, V3,V6-V8) in V1 position and all glowed in V1 position. V1 glows in V2 and V3 position. V6-V8 also glow in V1-V3 position.

I therefore had to get a replacement that would not glow before biasing the amp. Now that I have a replacement for V1, V5 is glowing upon switch on. V4 also glows in V5 position while V5 does not glow in V4 position.

Will try to switch on the amp with the screen controls at the lowest setting and see what happens.
Thanks for comments. Any further comments would be appreciated.

Nara

 

RE: NYAL OTL3, posted on March 21, 2014 at 06:03:06
unlisted
Audiophile

Posts: 25
Joined: March 21, 2014
 Was there a solution to this query?

I have a similar issue. On turn-on, the V5 6LU8 will slowly start to glow red and then the V3 6LF6 (vs. V5/V1 above). As the V3 6LF6 becomes more red, the V5 6LU8 less so. Using different tubes does not change this behavior, so issue is location specific. The upper grid voltage is very low for the short time I left on the amp (~6V): The plate current (~300mA), lower grid (~42V), and B+ (~325V) all look fine (even though B+ is a bit low).

If no solution known, can someone please post test point values so I may track down the root cause? I'll post any solution.

Regards,

 

RE: NYAL OTL3, posted on March 21, 2014 at 11:39:25
unlisted
Audiophile

Posts: 25
Joined: March 21, 2014
 A bit more information.

I checked the grid 1 resistor to ensure the tube was properly biased and it tested fine, but replaced it anyway: No change, V3/5 still turn red.

Wanted to take other measurements to see if that would help me track down the issue. Lowered the plate current to ~220mA and found the B+/2 a bit off. Lower grid V, upper grid V, B+, and now B+/2 all per target and stable. Adjusting the plate current and/or balance fixed the red 6LU8, but the V3 6LF6 still turns red after a couple minutes. Tried a couple other tubes and same result. (Have an unused 6LF6 matched dozen from RAM Labs I bought a long time ago, but don't want to use until I'm certain they'll be okay.)

The 6LF6 V3 was hot enough to melt the top off the jumper top, so this doesn't look normal to me.

Any inputs?

Regards,

 

RE: NYAL OTL3, posted on March 21, 2014 at 17:35:04
rhinohifi714
Audiophile

Posts: 174
Location: oklahoma
Joined: June 13, 2009
 If you have a matched set of Ram Tubes put them in and try again, make sure to back the upper and lowers to the minimum as described in the alignment procedure. Watch the current to make sure it does not run away, if the tubes don't begin to cherry then the issue was with the tubes you removed. If it has the same problem with the Ram tubes then start 1 by 1 replacing all the Zener diodes.

Question: are you placing a speaker or resistor on the output, and are you using a shorting plug on the input?
I always do that when doing the alignment,this is confirmed thru Ted Hammond. I always use an 8 ohm speaker so if something isn't right I can tell by a pop or hum when the amp is warming up, make sure the shorting plug is in place or you will hear a hum. also are you removing the 6fs5 and the 6ej7 as is also described in the procedure? These tubes are not put into the circuit until you have the uppers and lowers balanced, screens and grids! and the desired idle current is right. 275 to 300ma is plenty, then you put those tubes in prior to setting the bias voltage and final balance adjustment.

 

RE: NYAL OTL3, posted on March 21, 2014 at 18:01:52
unlisted
Audiophile

Posts: 25
Joined: March 21, 2014
 Thank you for the quick response!

No, I am not using a load on the output since not in the instructions I have (thought it was oddly missing for a tube amp). I am removing the 6FS5 for the first part of the setup, but not the 6EJ7 per the instructions I have.

It's quite possible the tubes have had it. My tube tester says they are okay, but my tube tester doesn't test them at the current necessary to be certain. I think many of the tubes I'm running are the original tubes (!), so running OTL's on electrostatics really does help. :)

I'll try the new tubes then replace the Zener diodes, if required. May take a couple days, so if any other ideas or comments, please let me know. I'll let you know how it goes.

Thanks again.

 

RE: NYAL OTL3, posted on March 23, 2014 at 11:51:57
airheadair
Audiophile

Posts: 393
Location: California
Joined: October 18, 2010
 Dear unlisted,

Very interesting post. MayI ask what electrostatics you are using?
I spent several joyful hours listening last night; one of my amps is still on the original tubes,
but I do expect that it can't last forever. A remarkable fact is how cool the amplifiers run; this seems to be quite unusual for an OTL amplifier.

 

RE: NYAL OTL3, posted on March 23, 2014 at 13:16:15
unlisted
Audiophile

Posts: 25
Joined: March 21, 2014
 For a dozen years I was using Quad ESL-988. Unfortunately, they did not like the weather and/or altitude (very dry at ~5,000ft) and kept breaking while I never had an ounce of trouble with my NYAL OTL3 amps (From all I heard....wasn't it supposed to be the other way around??). Breaking how? Not sure, never heard anything bad when listening to the Quads, but sometimes I would turn my stereo on and a speaker was toasted. The power here is really bad (noisy and variable), so tried conditioners, A/C regenerators, et al, but the Quads still kept breaking. So not sure.

Since I'm in NM and the authorized Quad repair shop is in SC, while I was getting ready to send the Quads back for repair the 3rd or 4th time I decided to switch. Since there was a near magical match between the OTL/Quads I decided to keep the OTL3's and look for new electrostatics.

I was concerned my 90W OTL3 would not have the power to drive Sound Labs, but after a number of chats with the very helpful Dr West I bought a pair of M-2PX a few years ago. The OTL3 has no trouble running the M-2PX, with the latest panel and transformer, at full tilt (though I almost never listen to it that loud). I am amazed how well they work and now have a truly full range OTL/electrostatic system that sounds (shock/amaze!) even better than the OTL/Quad match. Highly recommended!

 

RE: NYAL OTL3, posted on March 24, 2014 at 14:35:23
unlisted
Audiophile

Posts: 25
Joined: March 21, 2014
 An update.

I first checked all the diodes with my Fluke multimeter to see if anything was obviously wrong, but they all tested good. (A number of them were replaced by George Kaye when I had my OTL3's checked/upgraded about ten years ago.... Would have sent these to him already for repair, but he's a busy man.)

FYI: I attached a speaker while doing all the following work on the OTL3 per the input from "rhinohifi714" and never heard a sound.

I first took every tube out of my other OTL3 I just setup to see if they would work in the "other" one, but they didn't with V3 6LF6 turning red after the plate current had finished its slow/smooth rise to steady state.

Turned the plate current down 30% from the 300+/-25mA target per RAM Labs recommendation and placed a matched sextet of 6LF6 RAM Lab tubes I bought a long time ago into the OTL3....the V3 6LF6 turned red after a bit. Nara mentioned he changed/moved tubes around to eliminate the red glow from V1 (vs my V3), so I tried the same thing with these tubes and found a combination that worked .... at ~210mA (tgt-30%) plate current.

After new tube warm up, RAM Labs recommends bringing to target-20% then look for any plate glow in a dark room. If a glow, reduce to eliminate (I did, set plate current to ~220mA w/o any glow). [If no glow, RAM Labs recommends to leave at target-20% for 10hrs of use, then raise to target-10% for 20hrs of use, then bring to target. Check at 100hrs, then every 1000hrs after that.]

I put in the 6FS5 phase splitter and finished the setup (85V bias), with the plate current hovering ~230mA but without a glowing V3 6LF6.

After 10hrs of music (I hope!) I'll have another update.

Thanks to "rhinohifi714" for your help.

 

RE: NYAL OTL3, posted on March 24, 2014 at 18:20:42
rhinohifi714
Audiophile

Posts: 174
Location: oklahoma
Joined: June 13, 2009
 Glad to hear your going forward in solving the glow. Just wondering, are you still using the original 6lu8's 6ej7 and 6fs5 as well?
If you are you should really get them replaced as well, those 6lu8's are very prone to aging very badly, I went thru over 30 nos to get a set of 4 that tested at or near 100% spec in both sections when I did the last set of amps.

 

RE: NYAL OTL3, posted on March 24, 2014 at 18:37:03
rhinohifi714
Audiophile

Posts: 174
Location: oklahoma
Joined: June 13, 2009



One other thing, you are confusing the plate current with the bias, the current is set first by inserting a meter in circuit from the +of the bridge rectifier to the board, the bias is set after you place the 6ej7 and 6fs5 in circuit and set to 85v. I attached a pic that might help.

 

RE: NYAL OTL3, posted on March 24, 2014 at 18:50:42
unlisted
Audiophile

Posts: 25
Joined: March 21, 2014
 I changed out the 6FS5 and 6EJ7, but not the 6LU8's as they tested ~100% vs. other 6LU8's I had purchased that didn't test as well. Sounds like the same luck you had.

I bought a few 6FS5 here and there, but none of them were very strong (like many of the 6LU8 I tried). Ended up buying a couple from Brent Jessee that tested well. Have a stash of NOS Telefunken EF184's, so am good there.

Yes, I did mix up plate current (set 1st) and bias (set last); thanks for correcting and thanks again for your help.

 

RE: NYAL OTL3, posted on March 24, 2014 at 19:26:19
unlisted
Audiophile

Posts: 25
Joined: March 21, 2014
 Rhinohifi714,

You're setup looks great!

My OTL3 circuit board looks quite a bit different than the one in the picture. I know mine are one of the first built per George Kaye ... is this a latter revision board or something else?

On another note, though the 6LU8's I have test ~100% but are well used, should I replace them anyway?

Thanks again.

 

RE: NYAL OTL3, posted on March 25, 2014 at 05:34:54
rhinohifi714
Audiophile

Posts: 174
Location: oklahoma
Joined: June 13, 2009
 The 6lu8 is a dual section tube, if both sections show near 100% emission and no shorts or leakage they should be fine. The problem I ran in to was that one section was strong and the other weak, I use a Amplitrex 1000 to analyze all my tubes, it tests all parameters under load then sends it to my computer so I can test a lot of tubes then pull up all the results and compare. It differs from standard testers that are military type, those will show a tube to be 100% when it's actually only around 70% spec. It took over 30 NOS GE tubes from the same batch and date to yield the 4 that were 100% on each section. That said when I did the alignment with all the tubes verified thru testing on the Amplitrex, 6lf6's 6lu8's 6ej7 and the 6fs5, the alignment was a snap with well over 50% range remaining to keep them aligned properly as the tubes age.

 

RE: NYAL OTL3, posted on March 25, 2014 at 06:41:52
unlisted
Audiophile

Posts: 25
Joined: March 21, 2014
 I'm going to contact Brent Jessee about getting some 6LU8's too. When it comes to OTL's, my Hickok and B&K don't appear to be sufficient.

I hear the Amplitrex 1000 is a great tester.

Thanks again!

 

RE: NYAL OTL3, posted on March 25, 2014 at 09:05:27
unlisted
Audiophile

Posts: 25
Joined: March 21, 2014



Here's a picture of glowing V3 6LF6 before changing the tubes (think 4/6 were original).

Turned the system on to listen to music and hear how it sounds with the new setup, but the V3 glow is back - with the new tubes, so back to the bench. sigh. At least it sounded great for a couple minutes before I shut it down.

 

RE: NYAL OTL3, posted on March 25, 2014 at 16:00:21
unlisted
Audiophile

Posts: 25
Joined: March 21, 2014
 SOLVED - I started over. Is it plugged in? Is it turned on? Etc. Found the 6LF6 fuses for V1 and V2 were burned out: That will clearly cause 6LF6 V3 to glow red. All good now.

Thanks again to "rhinohifi714" for your help.

 

RE: NYAL OTL3, posted on March 25, 2014 at 16:00:41
rhinohifi714
Audiophile

Posts: 174
Location: oklahoma
Joined: June 13, 2009
 Can you take another picture of the area around the test socket, the sandcast resistor and the large bipolar don't look right. Are both amps the same in this area?

 

RE: NYAL OTL3, posted on March 25, 2014 at 17:05:37
unlisted
Audiophile

Posts: 25
Joined: March 21, 2014



Sure. Here it is.

This is one of the first OTL3 per George Kaye. Very late 70's or very early '80's - he wasn't certain exactly when. He mentioned some of the original caps in the power supply were WWII surplus. It has some odd bits on the front and back of the board. There are also upgraded DynamiCaps in the signal path (completed by GK). The version in your picture looks much more well finished. Mine looks more like a prototype. Sounds amazing.

 

RE: NYAL OTL3, posted on March 25, 2014 at 17:42:49
rhinohifi714
Audiophile

Posts: 174
Location: oklahoma
Joined: June 13, 2009
 Thanks for the pic, that is different in several ways.
Glad you got it up and going.
Enjoy !!!

 

RE: NYAL OTL3, posted on March 25, 2014 at 23:22:30
airheadair
Audiophile

Posts: 393
Location: California
Joined: October 18, 2010
 Is it finally working?

this is in some ways a scary thread. My OTL3's are still working well, no red glow, running cool, and sounding fantastic. But maybe this explains why one of them caught fire years back; perhaps one tube entered thermal runaway and melted the top cap, and things went bad from there. I suppose someday i will have problems again with the tubes. I've got a fair stock of spares, but who knows if they will end up being good or if I will be able to find someone to do the necessary adjustments?

Spent a couple of evenings just listening in amazement to a wide variety of music.....tonight the original LP pressing of Patricia Barber's Modern Cool. With my Stax speakers, the NYAL OTL's,
the Klyne SK5, and a van den Hul Frog, the tangible presence of her voice and band, and the beauty of the harmonic structure, was breathtaking.

By the way she has a new single release available on iTunes, a solo cover of "River" by Joni Mitchell, that is just lovely. (For her fans, I guess, if there are any here.)

 

RE: NYAL OTL3 [SOLVED], posted on March 26, 2014 at 12:46:16
unlisted
Audiophile

Posts: 25
Joined: March 21, 2014
 Yes, fixed faulty 6LF6 fuses, setup done and they're working great. They look like thrown-away prototypes, but I still can't believe the sound they produce. Just incredible.

I found this event a bit scary myself. Glad I caught it before it became a "serious" failure. Thought I checked the fuses, but clearly hadn't. Yet another good example for needing a detailed checklist to ensure the work is completed correctly.

Would really like to hear the Stax. Have heard really great feedback on those speakers, but like the OTL's they're not that common. Sounds like you have a great setup. If you like "Modern Cool", check out "This is Chris" by Chris Conner (on CD as Japanese import BCP-20).

I also bought four 6LU8's to replace the old ones I have from Brent Jesse, given "rhinohifi714" comments. I'll put them in when I check the amps again in ~10-20hrs of use (I always double check). I'm giving up buying random tubes. Better to pay and get what works rather than collecting a lot of not-quite-100% "spares".

 

RE: NYAL OTL3 [SOLVED], posted on March 27, 2014 at 14:23:39
airheadair
Audiophile

Posts: 393
Location: California
Joined: October 18, 2010
 to unlisted (and also anyone else interested, esp rhino and Lew),

Of course you are more than welcome to listen here any time you are nearby. Where do you live?
At some point I might even be able/willing/driven to subsidize a visit by a technical expert to help check things out.

I do have a local friend who has a somewhat similar setup: Soundlabs, VTL and also Atmasphere amps; we've only been able to find snatches of time to listen together. He is much more savvy about electronics than I, but like me is a university professor and hence has a negative amount of free time, so I'd be very reluctant to ask him to help me out.

 

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