PE0702A, V28A000962A1 (5V Yes, 12V/24V NO)

[Badger237]

Re: PE0702A, V28A000962A1 (5V Yes, 12V/24V NO)

Good call on the FET's! Q821 was showing shorts between all pins, I removed it from the circuit to confirm that and that the pads were not shorted to each other. I should also point out that there are marks around the two power resistors near the FET's where it looks like it got a little hot. Will be ordering a new FET today.

[dick_barton]

Re: PE0702A, V28A000962A1 (5V Yes, 12V/24V NO)

Check the gate resistor when replacing the FET. I would also change Q820 to be on the safe side and again check the gate resistor

[Badger237]

Re: PE0702A, V28A000962A1 (5V Yes, 12V/24V NO)

If by the gate resistors you mean R827 and R828, they check out, those are the resistors I had mentioned had burn marks around them. Their resistance is still spot on, so I'll let them stay. While checking those, I discovered one of the fusible resistors had opened, R821. Will replace Q821 and R821. R820 is still closed and Q820 still checks out, so I plan on letting them go as well, if I was fixing it for someone else maybe I would change them.

[Badger237]

Re: PE0702A, V28A000962A1 (5V Yes, 12V/24V NO)

I can't seem to find a replacement for R821, it is a 3W 27mOhm cement resistor from Noble, every one i find is either the wrong wattage or the wrong resistance. Maybe I'll just solder a wire there instead...

[Badger237]

Re: PE0702A, V28A000962A1 (5V Yes, 12V/24V NO)

Parts are ordered will update in five days...

[dick_barton]

Re: PE0702A, V28A000962A1 (5V Yes, 12V/24V NO)

Are you certain R821 is 27mOhms?
If Q820 & Q821 are in the same circuit then when one goes it can put a strain on the second one and weaken it.

[Badger237]

Re: PE0702A, V28A000962A1 (5V Yes, 12V/24V NO)

So here is the update:
Parts installed, when powered they are still good
However, these parts made no difference at the output. I still have 5v1, but everything still reads zero referenced to board ground. The 5 volt relay still isn't closing, I have tested it out of the circuit and it works fine, that's whats holding up the 120vAC to the second bridge rectifier. When I short the contacts, the rectifier kicks back up to 160vdc. Even this doesn't allow 12, 18, or 24vdc to be seen at the output. The relay still has 5v at the coil, but there is an open circuit somewhere that isn't allowing the current to flow to fire the relay.

Is there a way to bench test this board properly? What pins do I have to send voltage to in order to get it to switch? I have been shorting 5v1 to POW-TV. Whats even more confusing is that there appears to be a path to ground from the relay coil through possibly a diode and a capacitor. Is it possible that one of the IC's is controlling the coil?

[dick_barton]

Re: PE0702A, V28A000962A1 (5V Yes, 12V/24V NO)

Have you found a schematic for the power supply. You have four red wickman fuses, the red circular fuses. Are they all OK.
There's a resistor alongside one of the relays with a dark mark on it but the picture is not well focused. It could be R853. Have you checked it out?

There are also 4 white large ceramic fuseable resistors that you can test are not open circuit. Also check R850 which should measure 1.8 ohms.

https://www.youtube.com/watch?v=ttrSsgkI5TE

[R_J]

Re: PE0702A, V28A000962A1 (5V Yes, 12V/24V NO)

Does POW_TV connect to JP051 (near the relays)? Also does Q8510 emitter connect to hot ground (JP062)
If the above is correct, POW_TV connects to R8510 which turns on the base of Q8511, Q8511 collector connects to 5v so when turned on the emitter supplies 5v to Q8510 base, which when turned on connects the relay coil to hot ground.

[Badger237]

Re: PE0702A, V28A000962A1 (5V Yes, 12V/24V NO)

Here are my findings:
I will say I cannot confidently determine the direction of the coil diode or that the transistors are NPN or PNP without removing them from the circuit, and they are SMT and small which is a huge pain for me. I will energize the circuit and take voltage measurements tomorrow.

[R_J]

Re: PE0702A, V28A000962A1 (5V Yes, 12V/24V NO)

The diode is backwards, the cathode should be to the supply (5v) Do the transistors have any markings? you may need to clean them with alcohol or something similar to read them.
Q8511 might be (LY)
Q8510 might be (CCA)(CCB)

[Badger237]

Re: PE0702A, V28A000962A1 (5V Yes, 12V/24V NO)

Good call on Q8510, I powered the circuit (shorting 5v1 to POW-TV with 1k Ohm resistor) and found sufficient voltage at the base. After removing the transistor from the board, I tested it and found an open in all directions between all pins. Will attempt to find a replacement, as the transistors I have are all THT.

[R_J]

Re: PE0702A, V28A000962A1 (5V Yes, 12V/24V NO)

Q8511 (LY) = 2SC4116
Q8510 (CCA) = 2SC3326

POS software keeps changing upper case to lower case??


Q8511 (ly) = 2sc4116
q8510 (cca) = 2sc3326

[R_J]

Re: PE0702A, V28A000962A1 (5V Yes, 12V/24V NO)

Q8511 (ly) = 2sc4116
q8510 (cca) = 2sc3326

I enter this:
Q8511 (LY) = 2SC4116
Q8510 (CCA) = 2SC3326
and it changes to the top two lines??

[Badger237]

Re: PE0702A, V28A000962A1 (5V Yes, 12V/24V NO)

Howdy everyone!
Good news, after soldering in the new transistor (I ordered a CCA and they sent a CCB) the relay now closes when the 1k ohm resistor is placed between 5v1 and POW TV. I still get no rail voltages, however. Is there another pin that needs 5 volts? both bridge rectifiers are at full power (160V), and I am testing it on the bench. What do I need to do to get 12, 18, and 24 on the meter?

[Badger237]

Re: PE0702A, V28A000962A1 (5V Yes, 12V/24V NO)

After reinstalling the board, I get 5 volts on 5v1 and 3.2 (pretty much 3.3) on POW-TV, which closes the relay. I have found 11.6 volts on the rectifier side of T880, and zero volts on the other side. Still no voltage at the output pins.

[nomoresonys]

Re: PE0702A, V28A000962A1 (5V Yes, 12V/24V NO)

.

[R_J]

Re: PE0702A, V28A000962A1 (5V Yes, 12V/24V NO)

Check the voltage across the large cap C820, You can use JP027~029 as ground and F820 as positive.

I have found 11.6 volts on the rectifier side of T880, and zero volts on the other side

Transformers operate with ac voltage. If you say you are measuring +12 volts, Where exactly, T880 has rectifiers on the primary side and the secondary side.
What voltages do you have on plug PJ90?
Have you checked ALL the small fuses on the board?

[Badger237]

Re: PE0702A, V28A000962A1 (5V Yes, 12V/24V NO)

All fuses are good
The side of T880 with 11 volts is the side with the large bridge rectifier (Away from the plugs for the main board)
Only voltages I have at PJ90 are 5 on 5v1 and 3.3 on POW TV. The relays close when everything is hooked up and I plug it in. I have strong reason to believe that the main board is toast due to the lighting strike, so at this point I am only trying to make the power board turn on by itself before I order a new $75 main board