What is telephony? where does the VCC come from?

[scampo77]

Re: What is telephony? where does the VCC come from?

The voltage defiantly drops to 0v on the remote board when I unplug the phone line. on the main logic board I get an unusual result, I get 4.2v when I unplug the remote and then I get 3v when I plug the rj11 in.

I have 0v on both sides of the F thing located below the 483ECN

while taking measurements for this photo. I moved the board someway that it didn't like and one of the big relays clicked and now everything is 0v, DAMMIT!!

now as soon as I connect the B+ it clicks the relay and now I have no remote to visually see what the hell is going on, I am so discouraged.

[fzabkar]

Re: What is telephony? where does the VCC come from?

The F is near the RJ11 jack right above the TP10 on your picture of the main board. You can do that, but you still are going to have to determine which board is causing your problem.

ISTM that the "logic" board has a problem.

The A&D differential pair appear to connect to the data pins of the SP483 transceiver, so that's OK. The B&C pair are the power pins. C is ground, so that looks OK, too. The OP needs to determine where the -1.1V is coming from. AFAICT, that should be a positive supply. I would look for any chip that might be a regulator. In fact I can see at least one LDO (Sipex SPX2951ACS) in the earlier photos.



There is also a DF04S bridge rectifier (near CON111). I wonder if that's the source of the negative voltage.

https://cdn.badcaps-static.com/pdfs/...415d4937ea.pdf

[keeney123]

Re: What is telephony? where does the VCC come from?

The F is near the RJ11 jack right above the TP10 on your picture of the main board. You can do that, but you still are going to have to determine which board is causing your problem.

[fzabkar]

Re: What is telephony? where does the VCC come from?

The component marked "F" on the logic board appears to be a polyswitch resettable fuse. I would expect that it would be protecting the outgoing supply. What voltage do you measure there? Does it connect to the RJ11 jack?

[fzabkar]

Re: What is telephony? where does the VCC come from?

Sipex was acquired by Exar.

Here is the current support page and datasheet for the SP483E:

http://www.exar.com/connectivity/tra.../rs485/sp483e/
http://www.exar.com/common/content/d...et&part=sp483e

R5F21256SNFP, Renesas, R8C, SINGLE-CHIP 16-BIT CMOS MCU, 2.2V - 5.5V (f(XIN) = 5 MHz):

[keeney123]

Re: What is telephony? where does the VCC come from?

If the voltage goes away between pin 8 and pin5 with the R11 connectors disconnected we will "assume" the 5 volts is coming from the main board.If it is coming from the main board we need to determine which board is causing this. So now I would measure the voltages on the R11 connector while it is unplugged from the remote board in reference to the gnd pin on the R11 connector that is unplugged. See if the voltages change their reading while unconnected as oppose to connected. If they do we will again "assume" the problem lays in the remote board. Also when the R11 connectors are unconnected from the remote bd. go the the main board and measure the same points on the main board. This will verify what ever the main board is putting out it is getting to the end of the cable if both readings are the same.

[scampo77]

Re: What is telephony? where does the VCC come from?

There is no other connectors, only these 4 conductors on the phone cord. I am pretty sure the power comes from this logic board leaving on the red "D" terminal.

I was wondering if I could just jam 5v to this D terminal, to see what happens? I don't know if this is a good idea or not.

[keeney123]

Re: What is telephony? where does the VCC come from?

So this is the problem 2 volts at pin8 when you need a minimum 4.75 VDC to operate that chip. I am not sure but I would say the 5 volts is being generated on this remote board and is being fed by another connector. If you unplug this R11 connectors and leave the other connectors connected then measure the same two points again pin 8 and pin 5 what do you get?

[scampo77]

Re: What is telephony? where does the VCC come from?

Please ignore post #17, the logic board slides into the inverter like a video card on a PC. I was trying to probe around a corner and I was measuring the wrong port. I have since pulled all of the tin heat shields apart. The previous post (#18) is actual measurements. Moving forward I will do my best to keep the letters and colors the same.

The IC on the remote pin has only 2V at pin 8 with my ground lead on pin5

I have enclosed photos of the micro controller on the remote board. before I started this thread, I found the VCC pins on the controller and they are all at 2v

[keeney123]

Re: What is telephony? where does the VCC come from?

So I am confused as one place you list A,B as ground and another place you are listing C as ground. This is a very simple circuit. Do you measure 5Volts DC when you measure from pin 5 to pin 8 on the 483ECN on the remote board? If you look at your picture of the remote the microchip seems like lines are shorted in the middle of the pin on the bottom part of the chip. I can not make out where pin 1 is or the number of the chip.

[scampo77]

Re: What is telephony? where does the VCC come from?

Here are some more measurements and some more photos.

there is no loss between the output of the logic board and the input of the remote.

I have negative voltage at one pin, I do not know what this means.

the IC in the photo of the logic board has 483ECN and 0448 on it and also possibly SIPEX ?

the IC above it are LM393 and the one below it are LM358A.

on the photo labeled "back of logic" there is an image of terminal B -1.1v and its very close to solder dot, I don't know if these are supposed to be connected or not. I have enclosed a closer photo, the "dot" has 5v.

please don't forget, this stopped working, Then I pulled it and replaced the female connectors and now its still not working (or at least the same as it was before)

[scampo77]

Re: What is telephony? where does the VCC come from?

C .25 vdc
D 3 vdc

A,B, Ground

E.F, 0 vdc

The connections are good between the remote and the logic board. I have 0 ohms straight across each lead

terminals E and F don't seem to do anything and terminal D doesn't seem to be strong enough to light up the remote. I think this is possibly the problem??

[eccerr0r]

Re: What is telephony? where does the VCC come from?

VDD Voltage Drain (MOSFET, N-Channel)
VSS Voltage Source (MOSFET, N-Channel)
VEE Voltage Emitter (BJT, NPN)
VCC Voltage Collector (BJT, NPN)
B+ B battery positive

Maybe? At least it's a guess? Just pulling this out of ... eh... nevermind.

[keeney123]

Re: What is telephony? where does the VCC come from?

Dammit!! No I am not!!! I had a problem with the original cable that came installed with this thing. It stopped working so I bought a new phone cable to replace it. It worked and lasted a few months. After 3 phone cables and all worked, I realized the female jack was corroded. I thought the corrosion was my problem. I pulled the unit from the vehicle and replaced the female jacks, now I am in this predicament where the new or old phone cords don't work.

Did you check the phone cable that had work and then stop working? This is where I would start. If one of the lines opened up you could have a short that melts that cable line. I know on converters that they are not protected against such a thing happening even with all there fuses. A friend of mine had a RV converter and it was literally smoking and all the fuses were fine. I know this is different as it is an inverter. I just would not trust that it is protected. Also RJ11 connectors and lines on phone systems can carry 45VDC on hook and 110VAC for the ring. Twisted pairs have an impedance of 128 ohms. Used to get rid of AC Hum in old tube TVs.

[budm]

Re: What is telephony? where does the VCC come from?

I would find out which pin of the female phone jack is the VCC pin, GND pin the check out the resistance between the VCC supply pin of the main unit to see if you do have conection all the way to the remote unit VCC pin of the female phone jack, do the same for 3 other pins.
You should verify that one pin of the Remote female jack on the main unit has VCC (5V? 12V?), and one or more pins are GND. It only uses 4 wires.
Then you should at least find out if you do have good connection between the two unit first.
It is double sided board when you removed all those pins, the feed through between the top layer and the bottom layer may be damaged.

[fzabkar]

Re: What is telephony? where does the VCC come from?

I would identify the RS485 transceiver ICs at each end. One or more of those 8-pin ICs should be likely suspects. Then examine the IC's datasheet. This will tell you its power and data pins. Then trace these pins to the respective jack(s).

[scampo77]

Re: What is telephony? where does the VCC come from?

I seem to have 2 sets shorted, it appears to be by design, I can follow the traces. the other pins are free and clear of each other.

these female jacks have 6 pins

I have only replaced the 4 female jacks on the main unit and I have not replaced the female plug on the remote.

[fzabkar]

Re: What is telephony? where does the VCC come from?

The OP mentions an RJ45 jack, but that's 8-pin. The ME-ARC uses a 6P4C RJ11/RJ14 connector. Moreover, I didn't realise that phone cables had reverse pinouts at each end, so I had to check my own. Sorry about the mistake.

[budm]

Re: What is telephony? where does the VCC come from?

' I thought the corrosion was my problem. I pulled the unit from the vehicle and replaced the female jacks,' So you replaced the FEMALE phone jack on the main unit or on the remote unit? Did you do the resistance test on all four pins between the main unit and the Remote unit? Correct phone wire per post 7?

[SteveNielsen]

Re: What is telephony? where does the VCC come from?

Recheck your work. Perhaps you've got a solder bridge short or a bad solder joint.