Panasonic DMR-E75V VCR/DVD Recorder combo player - Lost power

[WyluliWolf]

I recently purchased a Samsung VCR/DVD combo player. I brought it home and it had no power I'm trying to repair it and currently have another thread open as I work on it (HUGE thank you to those helping out, hopefully close to a solution).
Soon after bringing home the dead Samsung (before I thought to post on here to try and fix it) I found a Panasonic DMR-E75V VHS/DVD Recorder combo player. This is even better as it allows you to record VHS straight to DVD...well, it would if it worked.
This time I was at least able to plug in the player before bringing it home to make sure it had power! (Ha! Getting smarter I thought to myself). It DID power on but I was unable to do any other testing before purchase. Once I brought the player home I took off the lid and did a visual inspection. She was pretty dusty/dirty inside and I noticed 3 capacitors with issues. (See attached photo's). One is obviously leaking and two others were bulging. I've circled the two on the power supply side in red in the attached photo. The third capacitor was on the VHS side of the board (I can post a pic if needed).

I replaced the 3 bad capacitors, cleaned out all the dust/hair etc. and plugged in/ powered up the player. I then gleefully played some VHS tapes and DVD's with no issues for two days! Ok, there was one small issue. When I pushed the VHS tape into the player (gently) it would take the tape but then jam and eject before fully loading the tape. It was almost like the carriage would try to lower the tape before it was in all the way. A second try at loading the tape always seemed to work though, and once it lowered into place the tape would play perfectly with no issues. On day 3 I decided I would take the combo player to my work bench to see if I could determine why the VHS tapes were jamming. I unplugged the player (which had a display/clock when I went to unplug it) showing it still had power. I moved it to my work bench, removed the cover and plugged it in to do some testing. DEAD. Nothing, no lights, no reaction whatsoever, totally dead. I thought it had to be a coincidence since it just had power before I moved it! I tested the outlet I was using and it was fine. I tried another known good outlet, same results...DEAD.

The obvious glass fuse in the system is not blown. Visually everything else looks fine. I'm wondering if changing out those capacitors fixed one issue but then "blew" another part that was "on the way out". Attached is a closeup photo of the power supply side of the system with the new capacitors in place.

SUMMARY:
System had power initially but 3 bad capacitors were present.
Replaced bad capacitors with new, equivalent value, caps.
System worked 2 days. Was unplugged, re-plugged in and suddenly had no power.

I was unable to find a service manual for this system online, unfortunately. The user manual is readily available (although not overly helpful here).
I'd love to get this machine working again. I have a multi-meter, capacitance meter, soldering iron and a somewhat limited knowledge of electronics. (No fancy tools like an oscilloscope). Any advice welcome and I'm happy to provide more photo's, info etc. Thank You!

 

[kellys_eye]

Look for cracks around the tracks where the power input socket is located - strain on the lead/pcb often breaks the continuity.

 

[WyluliWolf]

Look for cracks around the tracks where the power input socket is located - strain on the lead/pcb often breaks the continuity.

Checking tracks and all looks good as far as I can tell. I have pulled the capacitors from the board and tested with a capacitance meter. All pulled capacitors measure fine, although the three 220uf 25v measured under 220 but still within tolerance range at 210uf. The two very large capacitors I left in the board and measured. They also measure fine. Photo shows power supply section of the board both front and back. I need to reinstall capacitors.
Any other advice on what to look for would be appreciated.

 

[kellys_eye]

With the board reassembled, apply power and measure the voltage across the +/- terminals of the bridge rectifier.

If you get around 150V then measure the voltage across D1 (zener). If that is ok find the device number for the controller IC (IC11150 on the heatsink) and get the datasheet for it. There may be an application schematic that shows it's basic configuration in a working circuit that we can then take measurements from.

 

[WyluliWolf]

With the board reassembled, apply power and measure the voltage across the +/- terminals of the bridge rectifier.

If you get around 150V then measure the voltage across D1 (zener). If that is ok find the device number for the controller IC (IC11150 on the heatsink) and get the datasheet for it. There may be an application schematic that shows it's basic configuration in a working circuit that we can then take measurements from.

I soldered in all new capacitors (I tested them all before install with the capacitance meter, just to be safe, and they all measured ok).
I applied power to the board and measured DC voltage on the bridge rectifier. Results were 164.
I then tried to measure DC voltage on the two Zener Diodes located at D11158 and D11155.
I had the multimeter set to 200 DC. I applied the positive lead to the anode and the negative lead to the cathode.
D11158 measured -01.3
D11155 measured -09.8
(attached is the manual for my multimeter so you can see it's functions, etc.) Let me know if I did anything incorrectly.

Device number for the controller IC is MR1521 (number 1744 is above that). From what I'm seeing it's a MOSFET.

Thank You for your input! It is greatly appreciated.

 

[kellys_eye]

The MR1521 is a MOSFET integrated SMPS controller device - now obsolete. The only datasheet I can find is this:

https://datasheetspdf.com/pdf-file/624927/ShindengenElectric/MR1521/1

which shows a very basic schematic for its operation:



From this we can see that pin 4 is the supply voltage for the device. The 164V on the bridge rectifier is also present at pin 5 of the MR1521 and should be 'switching'.

Measure the voltage at pin 4 and report back.

 

[WyluliWolf]

From this we can see that pin 4 is the supply voltage for the device. The 164V on the bridge rectifier is also present at pin 5 of the MR1521 and should be 'switching'.

Measure the voltage at pin 4 and report back.

What would be the safest point to use for Ground when measuring the voltage on Pin 4? I'll be measuring from the back side of the board as it will be easier to access the pins from there.

 

[kellys_eye]

What would be the safest point to use for Ground

Pin 3 of the MR1521.

 

[WyluliWolf]

Pin 3 of the MR1521.

Lol, well I did say I had "limited" knowledge
Ok, with the multimeter set to 200 DC it measures a steady 9.8 on pin 4 of the MR1521.

 

[kellys_eye]

Sounds about right. With the capacitors refitted are you getting DC across any of them? On the SECONDARY side of the transformer that is...

There's another device on a heatsink below the transformer - is this a regulator? Can you measure any DC on the pins?

 

[WyluliWolf]

Sounds about right. With the capacitors refitted are you getting DC across any of them? On the SECONDARY side of the transformer that is...

There's another device on a heatsink below the transformer - is this a regulator? Can you measure any DC on the pins?

The other part on a heatsink is FCQ 10A06 (N4F above that) labelled on the board as D11270. It appears to be a Diode Rectifier.
I'll have a look at the capacitors on the secondary side tomorrow and do more testing. I'll report back.

Thanks!

 

[kellys_eye]

Rectifier seems most likely. There will be AC across two pins and DC out the middle one. This DC will go to one of the capacitors you removed. Put the capacitor back and see if you can measure anything across it.

 

[WyluliWolf]

I plugged in the VCR and noticed a light buzzing noise. Prior to this the VCR had been completely dead so I went ahead and reassembled the system. I plugged it in and, lo and behold, we have power. Switching out the capacitors must have done the trick. I noticed that the fan at the rear of the case is not working at all so I'll need to test/replace that.
Hopefully we are good on power from here on out but I still have an issue. When putting a vhs tape into the cassette carriage, the carriage moves forward and lowers before the tape is completely seated and jams. If I hold the carriage, to prevent it from moving forward, and gently push the tape in until it's seated properly, then gently push the tape forward the motor takes it and lowers it properly. What would cause the carriage to move forward before the tape is properly seated? Are the gears misaligned?

 

[73's de Edd]

Sir WyluliWolf . . . .

I ran across this unit and initially thought is was the one that we were working on . . . NOT.
Seems like I was finding more caps in the other units power supply than were on the schematic and I found them within another sheet of another schema . . . I added them but have NOW misplaced that UNITIZED schema that was saved within the computer . . . it might have ended up in a Flash drive . . . I am looking.

MEANWHILE . . .

Since I am recognizing some components on this unit also . . . you might as well have a schematic for referencing also.

THE QUICKIE POWER FLOW . . . .

There is a standby power supply, at the very top of the schema, that uses one of the the 5 pin POWER ICs to generate its always present voltage, but that voltages PRESENCE, also interlocks with the LOWER supplys 5 pin POWER IC.
That circuit is where the MAIN power hungry circuitry is fed from.

On both of the circuits 160VDC comes into the top of the primary of the T11150 SBY power transformer pin 1 and into the top of the primary of the T11170 MAIN power transformer and exits as . . .respectively . . .pins 3 and 6 and pass down to the pin 5's of the PWR IC's.

Upon AC plug in, the power IC's gets jump started for just an instant and if all is well, those initial pulse streams out of the two transformers B1-2 windings feed into rectifier diodes and create DC power at their C11160 and C11170 supply capacitors.
That then creates and feeds constant DC power to the needs within the power chips.

Since you have no BLOW UP of main power components, I believe that, just as is is being suspected on the other Panny power supply, that your C11150 and C11170 E-caps on THIS unit have gone "lazy" with time and use.

Should YOU have been this units initial owner and used THIS unit daily, some short time back you should have experienced operational oddities and the need to turn the unit on several times to finally get it to latch on and work.
However, as long as it was hot and running, it would remain working . . . BUT . . . after turn off and chill down, the unit would go balky again when being stone cold.

Will re start on the other UNIT as soon as my UNITIZED schema is found . . . ..

PANASONIC DVD / VCR POWER SUPPLY SCHEMATIC . . . ..

73's de Edd
. . . . . . . . . . .

On your Facebook, if you get a friend request from someone named Jeremiah, it's ok, accept it.
He's a bullfrog. He's a good friend of mine.

 

[2tone]

Hi All,

I know this thread is a little over a year old, but I have the same problems with my Panasonic DMR-E75V and have looked at the power board and seen no evidence of bulging and discoloured caps. My limited knowledge of electronics have led me to getting a electronic tech to look at the problem. He has said that there is also a 'chip' on the under side of the power board?
I have not read any where about this chip and hope this is not being said to squeeze more money out of an easy and inexpensive repair.

Can anyone shed light on this chip ????

 

[WyluliWolf]

This unit still experiences issues. Replacing the capacitors did not resolve. It will sometimes power on and work, then spontaneously lose power and refuse to come back on. Leaving it alone for a few days may allow it to come back on later. I'm not sure what to do next to try and troubleshoot.