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Sound Master STIX 305 schematic request

Discussion in 'Electronic Repair Modifications DIY' started by valvusmusicus, Feb 27, 2012.

  1. valvusmusicus

    valvusmusicus Active Member

    Strange one this-All the digital chips (4011's, counters, RAM,etc,) have the correct power going to them, yet the 7555 counter/comparator strange $*^t, dont know what it does chip, only has 3v. Should work between 5-12v. replace all electrolytics-NADA
    Anyone have the schematic please
    I have plenty of swaps for vintage gear

    Cheers all
  2. Boswell

    Boswell Moderator Distinguished Member

    The 7555 is a CMOS version of the 555 and many makes of it will work on as low as 2V power rails.

    You haven't told us what problem you are trying to fix and where you are located, although I see from your post on the DIYAudio site that your STIX 305 has "died" and that you are in the UK.
  3. valvusmusicus

    valvusmusicus Active Member

    STIX 305 problem

    Thanks for the reply. The problem is, the unit will not function. No tempo/prog LED illumination, No sound, or even background noise (noise floor on these is bad usually). There is the correct power going to all the chips. No form of on-board regulation that I can see-cant work out the PSU circuit, if there is one. I have replaced all the, what seem to be electrolytics concerned with decoupleing. I guess I should replace the whole lot as they do measure a little low with and ESR meter. Cant figure out the audio side of it-seems to use all discrete transistors. It does have a 4011 chip-which are notorious for dying-might replace this I guess
    Can you think of anything else please?

  4. MrEase

    MrEase Active Member

    It is unlikely, even with all leaky cap's, that you would get the total silence you mention. Did the unit die a slow death or just pack up overnight? 4011 chips are only unreliable in poorly controlled circuits, otherwise they are just as good as anything else. I guess you don't have anything to probe this with.

    From what you say, this will be a nightmare to diagnose remotely. Where are you in the UK? PM me if you don't want to expose yourself!!!
  5. MrEase

    MrEase Active Member

    That reminds me, I need to update my profile as I'm now in West Sus***!
  6. valvusmusicus

    valvusmusicus Active Member

    Thanks for the reply. I can probe it-I have a scope, meters etc, but if I had the schematic-it would help. It was working OK on the main out to start with, the only problems being the individual output faders. They were the open type vertical ones. I clened those, checked for cracks in the carbon tracks, and they all seemed OK. I powered it up, and it just made noisey tickin clock type sounds from the main mix output, with all the individual outputs dead. Now its completely dead, but as I said, all the power rails seem OK
    A schemop would be such a help

    Im in sunny Bour***outh
  7. MrEase

    MrEase Active Member

    Sunny Bournemouth! I guess you know roughly where I am even with a seemingly overzealous profanity filter!

    Did you take antistatic precautions when doing your cleaning? If not, it is quite possible you have fried a CMOS chip. Have you tried probing around the 4011? If there is audio going through it (or trying to) you should be able to check it out with just the chip datasheet. Any gate that is supposed to be "on" from the logic control should show similar signals on both in and out. Sorry if I'm being too basic here but in the absence of schematics you have to start somewhere!

    If you fancied a 4 hourish, 200 mileish round trip I could maybe take a look at it for you......but no promises on a quick fix.
  8. valvusmusicus

    valvusmusicus Active Member

    New Problem!! Replacement buttons

    Ive got it going after cleaning the switches butit's still pretty flakey
    The SPST push button switches are US. They are the big square type, with a plunger that pushes a flexible rubber membrane coated with a music Kbd type conductive plastic nipple onto a metal contact area to complete the circuit
    Its a bit like a computer Kbd switch, but much bigger#
    Nightmare trying to find them-any ideas
    Have lots of info/schemos to swap

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