Another Sansui 4000 question

Discussion in 'Exclusively Sansui' started by stereoguy70, Aug 8, 2017.

  1. stereoguy70

    stereoguy70 AK Subscriber Subscriber

    Messages:
    433
    Location:
    Salem, NH USA
    Ok, so like the title says....another question as I'm new to the Sansui fold.......

    A little back story first. I recently was given this 4000 from a guy I work with who was cleaning out his brother's estate. His late brother was the original owner of this fantastic piece of audio artwork. Anyway, sometime in its past the right channel had a minor meltdown on the power amp side of things. Seems that resistor R829 (100ohm) fried and the 2sa537 transistor got taken out, as well as both 2sc213 output transistors on that channel. I found the "repair" to this failure when cleaning out the years of dust from the inside of it. Well, whoever did the repair did some transistor substitutions......they used a sylvania egc129 as a replacement for the 2sa537, and two sylvania ecg128's for the output transistors and a rather sorry looking carbon comp 100ohm resistor to replace R829, but they soldered it to the BACK of the board rather than on the front of the board where the original one was! I also found an 8amp fuse in the main power supply fuse holder (supposed to be a 5amp for 117v...I'm in the USA so....) and I found two 5amp 32v fuses in the speaker output fuse holders where there should have been 3.5amp fuses!

    I also found that the ecg129 transistor was barely soldered into the power amp board! Hence the crackling noise I was chasing too.......anyway, my plan is to replace the ecg129 with the proper 2sa537 (NOS of course) and the two ecg128's with the proper 2sd213 sankens (also NOS....not an easy find as it turns out, but I found them) and putting the proper 5amp fuse in the power supply fuse holder.

    Now here comes the question.......(sorry for the long rambling backstory but I thought it pertinent to the question).......I can only seem to find 3amp fast acting fuses locally, not the recommended 3.5amp fuses for the speaker protection fuses. Can I get away with 3amp fuses in place of the 3.5amp that is recommended, or will they blow fairly quickly? I wouldn't think that 1/2 an amp lower would be that big of a change, but maybe it is.

    I'm figuring by replacing those "close enough" transistors with the proper numbers and then resetting the bias, etc. It should be closer to the proper specs than it is now. BTW, I have already repaired the bogus resistor "repair" with the proper 100ohm carbon film 1/4 watt fuse and on the correct side of the board as well!

    So, I guess I'm asking if 3amp is going to work even though it will be a "close enough" repair......
     
  2. N8Nagel

    N8Nagel AK Subscriber Subscriber

    Messages:
    5,094
    Location:
    Sterling, VA
    lower is always safer. Worst case they blow when they don't have to. No danger.
     
  3. The Fuxtor

    The Fuxtor AK Subscriber Subscriber

    Messages:
    1,888
    Location:
    Calgary, Alberta
    Better to go lower in amps than increasing the fuse size!! 3 amp should be completely fine...
     
  4. stereoguy70

    stereoguy70 AK Subscriber Subscriber

    Messages:
    433
    Location:
    Salem, NH USA
    Ok, I thought so guys, but wanted opinions to confirm my suspicions. I found I had some 3amp fuses in my spares bin. Four left out of a five-pack......I seem to remember using one for an Advent 300 I restored, and I believe that called for a 3.5amp in it as well.....never had any issues with the 300 after its restoration, so I guess "close enough" worked in that case too......
     
  5. KingBubba

    KingBubba "Too Much Stuff" Subscriber

    Messages:
    8,695
    Location:
    Brooksville, Fl.
    The majority of the glass fuses you see these days are 250volt fuses. It always concerned me, until I asked on AK. Higher voltage is okay as opposed to amperage and lower voltage is not a good thing as opposed to amperage. If your fuse is too low, you will find out sooner than later, but at least you will be safe. Some amps I have run into called for ultra fast fuse in the manual. I have never come across anything named that way on the market; so I just used fast-blo. I have a 4000 and was always amazed at its power. It also weighs a ton for it size. Nice find, enjoy.
     
  6. N8Nagel

    N8Nagel AK Subscriber Subscriber

    Messages:
    5,094
    Location:
    Sterling, VA
  7. stereoguy70

    stereoguy70 AK Subscriber Subscriber

    Messages:
    433
    Location:
    Salem, NH USA
    Well, the repair to the previous "repair" that someone did to the RH power amp board is complete as is the replacement of the "close enough" output transistors. I used the 3amp fast blow fuses I had on hand in the speaker output fuse holders and so far no issues. I also replaced the 8amp main power fuse that someone installed with the correct 5amp fuse. Again, no issues as of yet. My problem with the crackling channel is now gone as of right now. I plan on testing this receiver for a while to make sure it is going to work as they intended and to make sure the crackling noise doesn't come back. I'm pretty sure the issue was the bad solder joints on the poorly done previous "repair".

    All of the electrolytic caps are original to the receiver and all seemed to test fine on my capacitor tester, so I think I'll leave them be for now. I'm usually of the camp that they should be replaced because of the age of them, but it seems to be working fine and sounding fine with the originals still in there. Rather impressed by the quality of those old Elna caps to be honest with everyone. Caps aren't supposed to last this long!
     
  8. N8Nagel

    N8Nagel AK Subscriber Subscriber

    Messages:
    5,094
    Location:
    Sterling, VA
    you won't have issues with 3A fast blow for the speaker fuses... unless you do

    long term, you may want to get some of these

    http://www.woodang.net/qafuses.htm (I'd offer you some as I ordered extras, but mine are 5A) those are the originals used by Sansui

    alternately, a "Very Quick Acting" or "FF" fuse would be a current production rough equivalent as I understand it, like this:

    http://www.mouser.com/ds/2/358/typ_SA_5x20-793336.pdf (3.15A not 3A, that's as close as I could get in that series)

    the Littelfuse equivalent is also 3.15A but non stock at mouser

    http://www.mouser.com/ProductDetail/Littelfuse/23013150021

    note that while searching for ideas for you I found a Velleman brand "K/FF" fuse set but those are not the same. The Littelfuse Type FF fuses will break in max 1 sec. at 200% rated load, the Velleman will break in 5 sec. max. Big difference.
     

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