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
Badger237
Member
Last Activity: 05-26-2020, 12:15 PM
Joined: 05-02-2020
Location: Wisconsin
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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.Leave a comment:
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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?Leave a comment:
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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.Leave a comment:
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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....Last edited by Badger237; 05-07-2020, 11:26 AM.Leave a comment:
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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...Leave a comment:
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Re: PE0702A, V28A000962A1 (5V Yes, 12V/24V NO)
Parts are ordered will update in five days...Leave a comment:
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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...Leave a comment:
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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.Leave a comment:
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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.Leave a comment:
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Re: PE0702A, V28A000962A1 (5V Yes, 12V/24V NO)
POW-TV has 3.2V
5v1 has 5V
Everything else is Zero
The power button changes nothing.Leave a comment:
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Re: PE0702A, V28A000962A1 (5V Yes, 12V/24V NO)
And, as a third note, it appears that it is actually SR80 rather than SR81Leave a comment:
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Re: PE0702A, V28A000962A1 (5V Yes, 12V/24V NO)
Also I should add this TV was rendered inoperable by a lighting bolt that hit my chimney and arc'd over to the antenna and continued to destroy every TV in my house that was connected via coax. I'm guessing the main board is toast, but the power board is showing promise after putting in about an hour and 1 dollars worth of parts. If I can prove to myself that the power board works, I plan on confirming the main board is dead and then replacing it.Leave a comment:
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Re: PE0702A, V28A000962A1 (5V Yes, 12V/24V NO)
Hi everyone,
I have this exact board... The problem I found is that the 5V relay (SR81 I believe) gets 5V at the coil ( When I short 5V1 to POW-TV), but doesn't close because there is no current flowing. Where does the circuit for the coil of SR81 go to ground?
Also, as of right now I have replaced R850 and do get a steady 5V on 5V1. Finding a service manual has proven impossible. I am an electrical engineering student so I know a thing or two, but I have checked all of the capacitors, diodes, shottky diodes, optocouplers,...Leave a comment:
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