Sound Amplifier PA1240A JPA_Amp_1240A_Protection_Diagram

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  • ChaosLegionnaire
    what i went through dealing with my mobo with dead onboard sound!
    by ChaosLegionnaire
    so i took out one of my spare gigabyte ep35-ds3r mobos from storage for use to do some cpu, ram and video card testing of stuff i bought from ebay and got for free from momaka. he bought 50 e8400 cpus for cheap from ebay some years ago and i decided to help him relieve him of some of his supply since he had waaaay too many!! what did we say about hoarding too much stuff and depriving others of them?! *cough* socialism *cough* lol!

    i had to blow some dust off the board and heatsinks with the datavac as i didnt clean it up before putting it in storage. after finishing...
    09-13-2022, 09:02 AM
  • UserXP
    Mackie CR4 amplifier no sound
    by UserXP
    Hi, people.

    I've got an amplifier assembly from Mackie CR4 parts. It's just an amplifier, there was no speaker housing, so I used my set of CR4s to test it.

    Anyway, upon connecting everything and hooking the "new" amplifier to an audio source, the sound played clearly and strongly for the first ten seconds. I was happy it was working. Then the sound started to fade out during the playback until it was no more. After it had "dropped to zero", there were two very short intervals of sound playing at the normal volume, as if the amplifier was trying to...
    10-17-2020, 05:06 PM
  • eduaqa
    Amplifier - bad sound when loud sound on bass
    by eduaqa
    I'n trying to fix a M&S SYSTEM DMC-1which have following problem:
    I'm using FM station to do this fix, I works perfect if volume below around 8 or if bass is set to zero, the sound can go to 20 without problem, but if I set bass to maximum and try to go over 10 the sound comes distorted ... I saw a video on YouTube the person saying about the main capacitors on the power portion, but I disconnect the main transformer and inject direct to the capacitors PINs my bench power supply -23v 0v +23v, but still distorted so I think the problem is not the capacitor neither the transformer...
    08-06-2022, 11:28 AM
  • Francesc V.
    Tele-master AS-20 amplifier. No output sound, just noise
    by Francesc V.
    Hi:

    I bought this amplifier from the 70s to try to repair it. So far it has no output sound, just noise. You can volume it up and down.

    I've checked fuses and all are ok.
    I've continued with capacitors:
    • The main black one should have 4700uF, but it has lost half of its capacity during these years.
    • The ones that I've numbered have still a really low ESR and the full capacity after ¿40 years?



    The 4 transitors are perfect. Desoldered and tested individually.
    There are also components which I don't know exactly what they are....
    02-16-2023, 07:55 AM
  • Christos Tsiligiannis
    Marian Trace Alpha sound card repair help
    by Christos Tsiligiannis
    Hello to the forum.

    My name is Christos, I am new to the forum here and i am posting from Greece.

    So i have this old German sound card from Marian, called Trace Alpha. To be exact i have 2 of them and i use them professionally for my small FM radio station here. The first one works like a charm, but the second one does not work at all.

    To be more specific in the same exact pc with windows 7 (i even tried 32bit) the one works while the other doesn't.

    So i tried asking for a schematic from the company and they would not give me one. Instead they...
    11-18-2024, 05:26 AM
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