GreatSage is right, that was a PNP transistor, and was shorting the C and E ... what put energy on the coils, and i didn't read this before, so first i though was N Channel, as I replace had the same problem (N Channel act as a diode and keep coils energized)
below i'm posting all step that could help somebody if need:
#1 meter was turning on, but all reading was showing OL in all functions
#2 I open it and I detected that transformer was just generating like 4-5v where it should be generating around 10V
#3 Disconnected the transformer from the board and than it...
eduaqa
Member
Last Activity: 07-10-2024, 12:35 PM
Joined: 06-06-2022
Location: Orlando, FL
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Thanks
I used that method to detect the 2 ICs i discovered in short (in the first round when rail was 0ohms) ... those 2 in the first picture (see the green wires connected to the 7805)
I have a fluke thermal camera so I used it to detect what was warming
But now the only thing warming was the relays after a few minutes,
So I focused on that ... note on the new picture i desoldered 3 of the 5 relays ... after that the rail went to 140ohms (what is still high, should be Open Link)
Now look the pictures ... relays a connected direct to the 5V rail and if I'm...Leave a comment:
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Understood … those 2 (16 pins)cycled on the picture are new from DigiKey , the 2 that was there before was short circuited (0 ohms between gnd and vcc)
on that situation it was not even turn on because of the short circuit on the rail and the rail was measuring 0ohms
after I removed the 2 old one the rail become around 24 ohms , and here is my problem it’s still too low , should measure near open link
so something more on the rail is still almost shorting the rail
After soldering those new rail keep reading around 24omhs , so the 2 new should not be the ones causing...Leave a comment:
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sorry, what you mean? the quantity of 8pin chips? or those 2 that were replaced (16 pins)? Those that were replace are onsemi HC573A, exactly as was before, and just in case ... I tested pin by pin on those replaced to detect maybe jump solder between pins or not soldered pin and they are all good (not short between pins, no desoldered pin)...Leave a comment:
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Fluke 8808A not measure
I bought this multimeter as part, and I'm trying to fix
Initially when powering on, it was beeping, beeping and display was come on and off fast
Doing a initial investigation I notice that the 7805 marked was warming ... I removed it and test the rail that it supply voltage and was short circuited
I discovered to IC (latches) marked on the picture in short ... I replace the 2 IC and the rail now is having around 24ohms resistance, which still seems having some type of short circuit, because is cause a consumption of 370mAH, what seems too much, because when compared with the... -
Amplifier - bad sound when loud sound on bass
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... -
Re: What is this "processor"
Found the processor, it's a Hitach HD404328, still didn't help a lot, but checking the pins and where connected to the main unit board to try to track what is causing the processor understand the RELS (door release) is been requestedLeave a comment:
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Re: What is this "processor"
I draw the schematic for the Q1 to Q4 which are MPS2907A, but I don't understand
the collector goes to the PINS 5,7 of the main CI and has about +4.5v
The pin 6 of the CI comes from the board and has around 5v when no button pressed, 3.8v when talk external pressed, and 1.6 when talk to the room pressed, and 0.5v when both button pressed what means release
But for now stay in release independent of the voltage on the pin 6
So seems or other factor is making the main CI understand the release is been requested or...Leave a comment:
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Re: What is this "processor"
Some adicional information for the main IC on the board
PIN 4 goes to the main power line
PIN 8,9 goes to the main ground line
PIN 11,12 has a 4mhz xtal
PIN 16 goes to the main ground lineLeave a comment:
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Re: What is this "processor"
The super capacitor I replaced and it can hold the charge (clock)
Q1 > Q4 at least without unsoldering seems OK
but the trigger has a strange behavior ... if I touch the pin 1,2 with the finger, of course after discharging static it reset the clock (turn off, and comes back as 12:00)
about wiring I'm testing the board isolated from the rest, I'm powering it with 5.1V from a regulated power supply and it's disconnected from the rest
I put a 10k resistor on the PINs that comes from the main board where the talk buttons...Leave a comment:
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Re: What is this "processor"
Let see if the pictures goes...Leave a comment:
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What is this "processor"
I have a M&S SYSTEMS, and not working well. The display keep showing Realz ... meaning release, like if a had push the 2 talk button simultaneously, I already disconnect the processor board and still show the same. I put a 10K resistor on the connection that comes from the board, because otherwise it would be expected that behavior, but even with that still the same, it's like something on the board is not able to compare voltage as reference.
Seems to be a exclusive chip made to this, but I believe should be based in some other.
If was able to find some data sheet would at list... -
Re: What is this SOT23-5
Thanks, and seems your are correct.Leave a comment:
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What is this SOT23-5
I have a home decorator fan that use DC motor
In the controller there is what i believe some kind of power regulator in an SOT23-5 format
I receive 170vdc that comes from the 120vac rectified
It has as few components around like resistor and capacitor and diode
On the top it has the letter IAFAK and in the bottom says C278
Any idea what is that? I would like to find the data sheet for it -
Re: New Members - please post your introductions here
Hello everybody, I'm just starting here, and will try to help as much I canLeave a comment:
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