Help repairing Samsung VHS/DVD Combo - No power

[73's de Edd]

Sir WyluliWolf . . . . .

O.K. I saw the displays wild up and down, swings with ~78 VDC on the low side and up to ~160 VDC on the high range.
With that range of the swings, I believe that you will find low capacitance E-cap on the 5.8 VDC supply that the regulation circuitry makes its corrective referencing to.

Two ways to go now . . . .

Find and familiarize . .or . . mark all of the voltage pins on the white plug strip with the GREEN rectangle marking
that I added.
Take DVM and place in AC mode and select 200 voltage range as that seems the lowest offered scale on its AC mode range. . .will just have to watch the read out in smaller value digits.

Have meter negative to the STAR referenced metal shield for getting a COLD ground referencing.
Place Positive meter lead to any one of the voltages to be monitored. Power up and watch for a MUCH smaller voltage swing there. Take note of the value of swing and then move on to test all of the other voltages in the
same manner.
Of the four possibilities of output voltages, plus two possibilities for the 5.8 supply the voltage swings should be proportional to voltage output . (38 supply swings more than the 3.3 supply. )
If one is being particularly large, I suspicion there being a time related LAZY electrolytic on that supply

Get yourself a long leaded . . . . . or make it long leaded . . .1000 ufd at 25 VDC in order to meet the max voltages used and just temporarily solder tack it ACROSS one of the already in circuit 1000 ufd electrolytics and power up to see if things changed.
WATCHEE-WATCHEE POLARITY !
Continue for the two other 1000's and finally shunt it across the C1SS08 . . .470 ufd unit and power up.
Last, slightly lesser possibilities are the the two 330ufd units, try one at a time, with the 1000 being shunted across each of them.
Awaiting results . . .

73's de Edd
.....

 

[WyluliWolf]

Sir WyluliWolf . . . . .
Two ways to go now . . . .

Find and familiarize . .or . . mark all of the voltage pins on the white plug strip with the GREEN rectangle marking
that I added.
Take DVM and place in AC mode and select 200 voltage range as that seems the lowest offered scale on its AC mode range. . .will just have to watch the read out in smaller value digits.

Have meter negative to the STAR referenced metal shield for getting a COLD ground referencing.
Place Positive meter lead to any one of the voltages to be monitored. Power up and watch for a MUCH smaller voltage swing there. Take note of the value of swing and then move on to test all of the other voltages in the
same manner.
Of the four possibilities of output voltages, plus two possibilities for the 5.8 supply the voltage swings should be proportional to voltage output . (38 supply swings more than the 3.3 supply. )
If one is being particularly large, I suspicion there being a time related LAZY electrolytic on that supply

Get yourself a long leaded . . . . . or make it long leaded . . .1000 ufd at 25 VDC in order to meet the max voltages used and just temporarily solder tack it ACROSS one of the already in circuit 1000 ufd electrolytics and power up to see if things changed.
WATCHEE-WATCHEE POLARITY !
Continue for the two other 1000's and finally shunt it across the C1SS08 . . .470 ufd unit and power up.
Last, slightly lesser possibilities are the the two 330ufd units, try one at a time, with the 1000 being shunted across each of them.
Awaiting results . . .

73's de Edd
.....

I will need to order a 1000uf 25v capacitor to do the above testing. Should have it in a few days.
I pulled the remaining 1000 uf capacitor and it measured 1113 on the capacitance meter.
I pulled the 470uf capacitor and it measured 449 on the capacitance meter. This is a bit low. Should I go ahead and order a replacement capacitor for the 470uf 10v ?
I have not tested the 330uf capacitors yet.

So to summarize capacitor testing thus far:
1st 1000 uf capacitor measures 1130
2nd 1000 uf capacitor measures 1130
3rd 1000 uf capacitor measures 1113 (a little lower than the other two)
470 uf capacitor measures 449

 

[73's de Edd]

I did not know that you had a cap meter . . . test the 330uf capacitors..

 

[WyluliWolf]

Will do. I'm awaiting a circuit board holder to arrive to assist me with removing the parts. It's a bit challenging trying to hold the soldering iron, solder and board all at once ;p. Should arrive tomorrow. Will post results.

 

[WyluliWolf]

I did not know that you had a cap meter . . . test the 330uf capacitors..

Pulled out and tested the 330UF capacitors. Results are below:
330uf capacitor measures 322
330 uf capacitor measures 325

So to summarize capacitor testing thus far:
1st 1000 uf capacitor measures 1130
2nd 1000 uf capacitor measures 1130
3rd 1000 uf capacitor measures 1113 (a little lower than the other two)
470 uf capacitor measures 449
1st 330uf capacitor measures 322
2nd 330 uf capacitor measures 325

 

[debe]

ESR value of your capacitors are more important than the value of them.

 

[73's de Edd]

That's WHY his . . . . on order . . . . 1000 ufd substitute cap for shunt across testing is on order.
But . . . . with a very WARY eye on that 470 that has declined down to 433.
Poor ESR units usually show some decline in regular capacitor value testing.

 

[WyluliWolf]

That's WHY his . . . . on order . . . . 1000 ufd substitute cap for shunt across testing is on order.
But . . . . with a very WARY eye on that 470 that has declined down to 433.
Poor ESR units usually show some decline in regular capacitor value testing.

Since I have the 470 pulled out, shall I go ahead and order a replacement to solder in it's place?
The 1000uf is in North Carolina so it's getting pretty close!

 

[WyluliWolf]

Sir WyluliWolf . . . . .

Two ways to go now . . . .

Find and familiarize . .or . . mark all of the voltage pins on the white plug strip with the GREEN rectangle marking
that I added.
Take DVM and place in AC mode and select 200 voltage range as that seems the lowest offered scale on its AC mode range. . .will just have to watch the read out in smaller value digits.

Have meter negative to the STAR referenced metal shield for getting a COLD ground referencing.
Place Positive meter lead to any one of the voltages to be monitored. Power up and watch for a MUCH smaller voltage swing there. Take note of the value of swing and then move on to test all of the other voltages in the
same manner.
Of the four possibilities of output voltages, plus two possibilities for the 5.8 supply the voltage swings should be proportional to voltage output . (38 supply swings more than the 3.3 supply. )
If one is being particularly large, I suspicion there being a time related LAZY electrolytic on that supply

Get yourself a long leaded . . . . . or make it long leaded . . .1000 ufd at 25 VDC in order to meet the max voltages used and just temporarily solder tack it ACROSS one of the already in circuit 1000 ufd electrolytics and power up to see if things changed.
WATCHEE-WATCHEE POLARITY !
Continue for the two other 1000's and finally shunt it across the C1SS08 . . .470 ufd unit and power up.
Last, slightly lesser possibilities are the the two 330ufd units, try one at a time, with the 1000 being shunted across each of them.
Awaiting results . . .

73's de Edd
.....

Have the 1000 uf 25v capacitors in. Ready to start testing. Looking at the white edge connector now. In order to use Blue Star for ground I will have to put the pcb back into the unit as that metal box is not on the power supply board. I have circled the points I believe need tested? Close up photo shows connector labels and adjoining connector. Let me know if the red circled points are correct for positive lead and I will go test results. Thank You!

 

[73's de Edd]

Info forthcoming . . .tomorrow . . . .

 

[73's de Edd]

Sir WyluliWolf . . . . .

xin lỗi . . . . . . . . . .
Or, in case, your Vee-na-meese is being a bit deficient, Sorry 'bout that . . .as I have been as BUSY as a one pawed cat with the diarrhea . . .lately . . . . . .
SINCE, this is not being a . . .See Dick and Jane play . . play,play, play . . . . . see them play . . . or . . . I like green ham and cheese . . . I do . . . . . . . simplicity type of post.

So, you have received the 1000 uf 25v capacitors. ( Hopefully . . .PWEEEEMIUM BWEWED . . . at the proper /adequate DC voltage rating and having a 105 degree temperature rating. . . . . . . for operational longevity.

Ready to start testing. . . . . .

You say . . . .
Looking at the white edge connector now. In order to use Blue Star for ground I will have to put the pcb back into the unit as that metal box is not on the power supply board. I have circled the points I believe need tested? Close up photo shows connector labels and adjoining connector. Let me know if the red circled points are correct for positive lead and I will go test results. Thank You!

There is a LIKE cold ground being located on either extreme end of that WHITE power connector that you can use instead.


BTW was the board tested, when plugged into the VCR, and there were also voltage swings being encountered in that manner also ?

Using either of those cold supply grounds should let you test the power board off from the VCR proper, considering that you were testing that way before and that the output (s) voltage was / were also swinging up and down when tested that way..


Also, am I correct in . . . . if that you are monitoring one of the cold supply voltages, that it is reading low from its expected norm level of DC output, but is also swinging up and down.

Use solder tacked on wires / and / or / test clips to sequentially get your meters probes "held" across each of the supplies that you are going to evaluate.

That leaves your hands, THEN BEING FREE, to be able to take a 1000 ufd E-capacitor and then vewy-vewy cawefuwwy (a la Elmer Fudd ), shunt its two leads across an existing supply capacitor that you are wanting to evaluate . . . . . since you are suspecting it to presently be deficient in total capacitance and its decreased effective filtering capability.
OR, more importantly, finding that capacitor is having a time evolved / and / developed high Equivalent Series Resistance
That condition severely isolates its filtering effectiveness from the circuit that it is supposed to be filtering.

I have seen E-capacitors that have developed time onset / evolved ESR values, that have degraded their expected rated 1000 ufd all the way down to having only the REAL filtering effectiveness of a 10 ufd capacitor.
This is usually directly related to switch mode supplies, like this, that create sharp square waveforms that HAMMER these E-caps HARD, at tens to hundreds of thousands of times PER SECOND.

These units are not being of the older generation, linear design styles that slowly coast up and down sine wave hills at a 50/60 or 100/120 cycles PER SECOND creep.

RESULT . . . . .

What we are hoping that will be found in this sequential and individual testing of the capacitors involved in the filtering of EACH of the separate and different supply voltages of the unit, is that one of them, when receiving that extra NEW and GOOD capacitor being connected across it , is that the supply, with its present up and down GROANING . . . .by TRYING to lift its weight . . . but then DROPPING it.
It will, instead, go WHIZZZZZ - HUMMMM - PURRRRRR, and pop back into normal operation and stabilize to giving normal voltage(s) coming out from the unit.
(That, my friends, was being a run on sentence . . . . avec deux paragraphs.. )


That would be the desired monitoring procedure, to ascertain if the whole power supply has normalized and is then working as it should, just after you touch leads and substitute in a new 1000 uf capacitor ACROSS an existing capacitor associated with that supply, that you want to test..


Pick out the very lowest supply voltage (3.3 VDC) and connect the NEGATIVE lead of a 1000 ufd electrolytic to either of the terminals END cold ground connections.
Then be sure that the + connection of the electrolytic is being the one touched to the 3.3 VDC supply.connection. TRIPLE CHECK YOUR CAPS POLARITY . . . no errors are permitted.
If the supply output doesn't then stabilize, move to the capacitor to the NEXT highest supply voltage and test that cap in the same manner.
( That way, you are cumulatively transferring the caps charged up level on to the next supply level and thereby don't have to stop and discharge the cap down to ZERO, each time.)

The E- caps and their respective supply responsibilities are:

C1SS07 . . . . 3.3 VDC
C1SS18 . . . . 5.8 VDC
C1SS08 . . . . 5.8 VDC
C1SS10 . . . . 5.8 VDC
C1SS17 . . . . 9 VDC
C1SS15 . . . . 15 VDC
C1SS16 . . . . 15 VDC
And I don't suspicion 100VDC rated
C1SS12 as being bad, if you
have run the supply with
ZD1SS1 Zener diode,
being in and also floating
out of circuit

TESTING CAVEATS . . . . . .
(With some occasional need to reference back to Unit's Schematic on post # 13 )

You can both test and shunt in the test capacitor at the two different supply points of the 5.8 VDC supplies at each of their connector pins on the white connector, as well as the 3.3 and the 15 VDC supply.

HOWEVER, since there is a 10 uh inductor choke being inserted between two sets of capacitors , to make what is called a pi network filter, wherein there is being an initial filtering by a first E-cap and then inductive filtering by the choke to further cut down any ripple and then a final filtering by the second E-cap on the end.

On the 5.8 VDC supply . . . . .

To be able to bypass this circuits 10 uh of inductive isolation , you need to test at the origin point of the 5.8 VDC supply ( which is being its C1SS18 E-cap), by shunting your test capacitors + lead, right at the + lead of the installed C1SS18 capacitor.

On the 15 VDC supply . . . . .

To be able to bypass this circuits 10 uh of inductive isolation , you need to test the origin point of the 15VDC supply ( which is being its C1SS15 E-cap), by shunting your test capacitors + lead, right at the + lead of the installed C1SS15 capacitor.

Since this systems feedback sampling voltage for establishing stabilized regulation of the whole supply is taking its reference voltage from the + 5.8 VDC supply, I strongly suspicion C1SS18 or C1SS10 E-caps having drastically slacked off in their effective filtering.

NOW . . . go ye forth and . . . . . . .doittoit . . . . .

73's de Edd
.....

 

[WyluliWolf]

Since I had removed the capacitors for testing, I went ahead and replaced the three 1000uf 10v Capacitors at
C1SS10
C1SS18
C1SS07
I also replaced (though probably not needed) the two 330uf 25v capacitors at
C1SS15
C1SS16
All have 105 degree temp rating.
After soldering the new capacitors in place I plugged in the power supply (stand alone) and the buzzing noise persists.
All testing so far has been done with the power supply board OUT of the VCR.

I also have some 470uf 10v capacitors on the way so I can replace this cap if needed when they arrive (C1SS08).

Does this lead us in a new direction or shall I go ahead and do all the testing recommended in the previous post?

Thanks again!

 

[WyluliWolf]

And we replaced the 470uf capacitor. No change.