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In Reply to: RE: Lazarus basic preamp posted by Uncle Mike on December 18, 2016 at 03:46:11
Yes! Make that Lazarus rise from the dead!
Dave
Follow Ups:
All he will have to do is say,preamp,wake up,just as Jesus did with Lazarus.
An Xmas miracle possibly?
"For every complex problem there is an answer that is clear, simple, and wrong" H. L. Mencken
Edits: 12/20/16
It works to certain extent.
Phono section hums with 60hz motorboating/ oscillation at every 5 seconds apart that is volume dependent. After doing some measurements, HV regulator decoupling cap is the suspect for now.
The original parts in this preamp are marginal at best. The 250v metalized coupling/ decoupling caps everywhere are destined to be ruined with constant stress. The decoupling cap at HV regulator is constantly stressed at 280v with 250v specs. The filament cap is a cheap 50v cap but is designed to take 48v. What a joke!
In terms of the cookbook, to spend 50 EU from a foreign country simply doesn't make sense. I respect the designer's copyright, however he has passed away. I am actually very puzzled by the lack of info for this preamp. Schematics seems a secret of some sort purposely hidden by this manufacturer. I don't understand the mentality of that, and no wonder this company cannot survive the real world. I guess I will just hand trace it.
Your 50 Euro would have been spent in vain, there is no mention of a Lazarus preamp in Allen Wright's Tube Preamp CookBook. However, there is an article by Mike Vans Evers about this preamp in the March 1993 issue of Glass Audio.
Thank you for the pointer!
"In terms of the cookbook, to spend 50 EU from a foreign country simply doesn't make sense. I respect the designer's copyright, however he has passed away. I am actually very puzzled by the lack of info for this preamp. Schematics seems a secret of some sort purposely hidden by this manufacturer. I don't understand the mentality of that, and no wonder this company cannot survive the real world. I guess I will just hand trace it."
If you knew how Allen worked you would understand this.
Allen was generous with his knowledge, time and help. He had at one time (he passed some time ago)schematics posted on the Vacuum State web site. They were, by design, generic in nature so that others could not copy and implement his work on their own (read Chinese knockoffs). I know at one time he had several lawsuits regarding intellectual theft. If you were proficient you had a good chance of ciphering your layout from his basic premise.
As an aside, I was looking for a MC phono stage to work with my SP6 that did not use transformers. Allen was helpful to a fault setting things up to have it added to my preamp however he would not send me the schematic for my own use.
OK, I hear you But your solution is pretty much the standard solution. Replace the filter caps with new electolytics and replace the coupling caps. I don't mess with the resistors unless they are carbon composite. You don't have to spend a lot of money. you just have to solder carefully. Just youse defiant polly propylene capacitors as decouplers and dece t elecrp;tics in the power supply and clean all the pots and switches.. Even without the schematics, you should be able to read the values of the existing parts. Good luck!
Dave
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