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i have a very nice vintage DBX BX3 amp on which at least one channel fused.
power transistors literally burned down.

it is a very nice piece of hardware (4 channels with BTL capability 4x125W or 2x300W)
I would like to fix it myself. Having an electronic engineering degree, i think I should be able to undertake that venture but I never practiced (i've been in software for the last 40 years...)
So I need some guidance on the methodology to diagnose and track what went wrong.

I do have a scope, signal generator and I guess all required tools, as well as the schematics of the amp.
what I need is some help on locating the key parameters to measure and how to incrementally explore the different stages of the amp to find the faulty sections.

I guess I need to isolate the different sections of the amp but then, what ?

any help and advice will be highly appretiated.

 

Hello, I am in the process of repairing the Mackie ProFX12 V2 mixer for a client, and am running into the unavailability of schematics. Does anyone have a copy they could share? I have already reached out to Mackie directly but am still waiting for a reply.

Additionally, I am having trouble identifying the failure mode for the two channels that have failed: one produces loud static (indicating bad op-amp or feedback resistor perhaps?) and the other has the right channel producing a 60hz hum, the other is functional. (see board photos, with the two failed channels being marked with "F". The browned area is residual flux from having replaced two opamps, and having reflowed other components around them)


Any help on either of these fronts would be invaluable. I have mainly worked in laptop and computer repair, and am just getting started with my first scope and first set of board level repairs. 

Hi,
My column Marshal Acton 2 , is dead . Power suplyy is it ok ... 18 V , but not light and not power on. 
I need some help, and i try to find schematic !

Do tou can help-me ?

Best regards

Sziasztok.

Van egy ilyen Samsung HT-WS1 Crystal Surround Air Track  Soundbar-om amihez van gyárilag egy Wireless Subwoofer PS-WWS1 is ami vezeték nélkül kapcsolódik a Soundbar-hoz.
Az a problémám, hogy amit találtam manual-t hozzá, abban pont erről nem esik semmilyen említés. A problémám az, hogy a Subwoofer, egyik napról a másikra egyzser csak elnémúlt.
Ez annyit takar, hogy nem néma, hanem olyan halkan szól, hogy csak kézzel érezhető hogy van hang, azaz mozog a hangszóró, közelebb hajolva hallani is, de élvezhetetlenül halk.
Amit találtam a PCM azonosítója:  Samsung AH94-02239B PC Board-Amp, Ht-Ws1

Képek (netről) a PCB_ről:

Wifi panel:

Ezen kívül semmit nem találtam róla.
Esetleg valaki nem javított ilyet vagy nem tudjam merre induljak el, mindihol neten annyit írtak, hogy szervízbe vigyem be, vagy cseréljem az erősítő PCB-t egyben:(, ami nem egy gazdaságos megoldás..

Köszönöm szépen előre is.