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SAE 3000 Preamplifier diodes

Discussion in 'General Audio Discussion' started by 70smidfiguy, Aug 12, 2018.

  1. 70smidfiguy

    70smidfiguy New Member

    Messages:
    46
    Location:
    British Columbia
    Hello all,

    I need to replace the power supply diodes on an SAE 3000 Preamplifier.

    These are marked on diode as "4436-24" and are baby blue in colour.

    Their designation on the circuit board is CR501 thru CR506

    Any substitute part information would be much appreciated.

    Also could not find schematic or service manual anywhere on the net!

    Many thanks in advance.
     

     

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  2. DaveVoorhis

    DaveVoorhis Super Member

    Messages:
    3,907
    Location:
    Behind you.
    "4436-24" is probably a house number, though it is numbered somewhat like a Zener diode, which would (usually) make it a 24 volt Zener.

    Without the schematic or service manual, it's only possible to guess at the exact replacement, but it's easy to figure out a replacement that will be just as good. Some information will help:

    1. Are CR501 - CR506 used as rectifier diodes in the power supply, or as Zener regulators? Are there 6 of them or 4?

    2. Assuming they're rectifiers, what voltage are the associated filter capacitors rated for? Alternatively, what voltage is the associated secondary(s) of the power transformer?

    3. What is the rated power consumption of the preamp. Is it, per what I found online, 25 watts?

    Note that rectifier diodes (if they're rectifier diodes) rarely fail by themselves. If they're burned out, it's probably due to the associated power supply rail(s) being shorted. Have you checked for this?

    If they're Zener diodes and not rectifiers, this will do: https://www.mouser.co.uk/ProductDetail/Taiwan-Semiconductor/2M24Z-R0?qs=sGAEpiMZZMtQ8nqTKtFS/MD6hg66KrTa95ikKCZYBuc=
     
    Last edited: Aug 12, 2018
  3. 70smidfiguy

    70smidfiguy New Member

    Messages:
    46
    Location:
    British Columbia
    There are 6 of them all in a parallel placement.
     
  4. sregor

    sregor AK Subscriber Subscriber

    Messages:
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    Location:
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    Last edited: Aug 13, 2018
    DaveVoorhis likes this.
  5. DaveVoorhis

    DaveVoorhis Super Member

    Messages:
    3,907
    Location:
    Behind you.
    Per @sregor's posted schematic, they are rectifier diodes, but not strictly in parallel -- it's a conventional full-wave rectifier arrangement. There are two 18volt Zener diodes, CR507 and CR508.

    How have you determined that CR501 - CR506 need replacement, and have you determined what caused them to fail?
     
  6. 70smidfiguy

    70smidfiguy New Member

    Messages:
    46
    Location:
    British Columbia
    Hi and thanks for responding.

    My goal is to restore the unit and would like to replace those now.

    When I said parallel it was not meant to be electronically speaking rather physically.
     

     

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  7. 70smidfiguy

    70smidfiguy New Member

    Messages:
    46
    Location:
    British Columbia
    Steve,

    Thanks for schematic link, I use HFE all the time and dont know how I missed that.

    Cheers
     
  8. triode17

    triode17 Super Member

    Messages:
    1,315
  9. DaveVoorhis

    DaveVoorhis Super Member

    Messages:
    3,907
    Location:
    Behind you.
    Silicon rectifier diodes don't degrade. (Unlike old selenium rectifiers, certain germanium transistors, and electrolytic capacitors, for example.)

    Unless there's evidence that they've overheated or are defective, there's no reason to replace them. Replacing them when they don't need it only risks damage to the circuit board, with no benefit.
     
    Bill Ferris likes this.
  10. 70smidfiguy

    70smidfiguy New Member

    Messages:
    46
    Location:
    British Columbia
    Good to know, thank you.
     

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