Need a Circuit Schematic for a Lambda Model LPD-424A Power Supply

[Cerberus]

I am repairing an old (1970s-1980s) Lambda Model LPD-424A dual channel, regulated power supply and have hit a dead end trying to locate a circuit schematic for it, which is not in the Lambda user manual, not on the Lambda website for legacy instruments, and not found from a serious web search. Also, I tried to find similar designs from Lambda, again with no relevant results. Further, I requested help from TDK-Lambda technical support, but have had no success there, yet. If anyone has this schematic, I would appreciate it if you would kindly upload a copy of it for me. I am new to electronic test & instrument repair but am learning. Thank you in advance!

 

[EastCoastToast]

Might want to consider posting in the datasheet subsection here: https://www.electronicspoint.com/forums/datasheets-schematics-manuals-and-parts.87/

I did a quick search and this was returned although not a schematic it could be helpful:

http://exodus.poly.edu/~kurt/manual... 422AFM, 423AFM, 424AFM, 425AFM Operation.pdf

 

[Cerberus]

Thank you for your excellent suggestion! I posted my request in the datasheet subsection today. I have the LPD-424A manual already, but appreciate your effort.

I am checking the circuit, section-by-section, but have no reference given their is no schematic on-hand. So far, the power supply appears to be working properly, except the dual, coaxial potentiometers for controlling voltage and current on each channel are "twitchy" in that the gauge-indicated output voltage and current swing wildly as I adjust the knobs. I gave each of the pots a thorough spraying with contact cleaner and it helped somewhat, but the problem remains. These are ten turn coaxial pots with the outer knob course and the inner one providing fine control. If I could find them from one of the component suppliers (e.g., Mouser, Newark, Digi-Key, etc.), then I would replace them and be done with the issue. I know that I can use a DVM and other instruments to monitor voltage and current outputs, but I prefer to have the power supply working correctly by itself. My "Plan B" is to disassemble the pots carefully and manually clean them of corrosion and contamination. I've seen Dr. Shahramian use this technique successfully on TheSignalPath.com but it is not the optimum solution. I appreciate any helpful suggestions from the forum. Thank you!

 

[davenn]

Have only been able to find a user manual, I saw one link to a schematic but it was behind a pay wall

 

[Cerberus]

Would you please let me know what website claims to have the schematic? I was unsuccessful in finding it on any site; pay or free. Thank you!

 

[73's de Edd]

Sir Cerberus . . . . . .


https://www.google.com/search?q=katzenjammer+kids
+cartoons&newwindow=1&source=lnms&tbm=isch&sa=X&ved=0ahUKEwjjn_nJ8I_KAhVE32MKHRoMCtsQ_AUIBygB&biw=1536&bih=710#imgrc=_



"I gave each of the pots a thorough spraying with contact cleaner and it helped somewhat"

I don't think that you REALLY got enough cleanser, penetration WAAAAAAAAAY DEEP into the units, along with all of the circular area that is actually being encompassed within those types of units..


Stand back . . . .waaaaaay back . . . . brace yourself . . . . . here it comes all 47 pages of it !
Herewith is your treasured info:

http://www.davmar.org/pdf/LambdaLPD.pdf

73's de Edd

 

[Cerberus]

Dear 73s de Edd:

Many thanks!!!!!!!!!!! I did the best I could with the contact cleaner without de-soldering the pots from the unit, so you are correct that the spray may not have penetrated far enough to make a large difference. However, now that I have the schematic and all of the great information in the manual you so kindly sent to me, I will be able to have a great day! Thank you, again!

Und now, dis Katzenjammer Kid bids du und grosse 73,

Mike (WA1MB)