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In Reply to: RE: NYAL OTL3 posted by unlisted on March 24, 2014 at 19:26:19
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.
Follow Ups:
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.
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!
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.
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?
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.
Thanks for the pic, that is different in several ways.
Glad you got it up and going.
Enjoy !!!
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.)
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".
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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