Magnavox DRV power supply SMPS

[johnfin]

Re: Magnavox DRV power supply SMPS

Ok, will test, thanks

[momaka]

Re: Magnavox DRV power supply SMPS

OK, try this...

Using a PC PSU, insert 5V at the EV+5V pins on the output of the Magnavox DRV power supply and 12V on the EV+12V. Do NOT plug the Magnavox PSU in the wall. With your multimeter, measure the voltage across either capacitors C2204 and C2205 or directly at pins EV+5V and EV+12V with the PC PSU powered On. Post what voltage you get here. Next, with the PC PSU still powered, measure voltage on pin 1 of IC2201 (KIA431 shunt regulator). It should be 2.5V or close, but again, please post exactly what voltage you get with your multimeter. Then also measure the voltage on pin 3 of the same IC (IC2201) and post the results.

Once I know what values you get for these, I will modify this test a little bit so that we can determine if IC2201 is providing feedback to the primary side, as it should. If not, that could be the reason why your PSU is "stuck" On.

[johnfin]

Re: Magnavox DRV power supply SMPS

I did not pull the transformer. I still believe its the source of the problem. I am 90% sure the primary side is fine So tell me how to isolate the secondary side into sections that I can connect and turn on one at a time. Breaking down the sections may help me find the problem easier.

[momaka]

Re: Magnavox DRV power supply SMPS

There's no definite answer to that question.

The fault(s) could still be anywhere. First make sure you have no short-circuit on the primary side WITH the transformer in there - that is, check with a multimeter (a glowing bulb is not always an indication of a short-circuit, particularly with these 2-transistor designs). Same goes for the secondary-side outputs. Usually, there's no need to remove the transformer when troubleshooting. But now that you have it out, you can check most of the small diodes on the primary side more easily (i.e. D2109, D2111, D2112, D2107) and transistors (Q2102, Q2101).

Also, for us to get a better picture of what's going on, please take a piece of paper or a notebook with you and record what you have tested and what values you get. For example, if you test a diode with diode check, post the forward and reverse readings you got like this:
D2109: 609, inf
D2111: 590, inf
and so on.
If you get something for the reverse reading of a diode, also measure and post the reverse resistance. I'm mentioning this, because D2110 has a 150 Ohm resistor in parallel with it, so you'll probably get something like 100-200 and 100-200 again for both the forward and reverse measurements. Doing a resistance test should show 150 Ohms, or very close to that.

[johnfin]

Re: Magnavox DRV power supply SMPS

True or false, when i pull the transformer and there is no short, the majority of the fault would point to the secondary side.

[johnfin]

Re: Magnavox DRV power supply SMPS

It was actually a dumb idea, i dont want a bunch of power supplies running 24-4. I need to start back at square one and look at the components again.

[momaka]

Re: Magnavox DRV power supply SMPS

I have no clue what would be an alternative compatible part number in terms of using another power supply. But I imagine that as long as you provide the right voltages on the right pins, you can get your DVR going.

Looks like you need only 2.8, 5, 12, and around 30V. So with a PC PSU and a ungrounded/isolated 19.5/20V laptop adapter, you can get 3.3V, 5V, 12V, and 32V (to get 32V, connect the laptop adapter's negative output to the 12V rail, and the adapters positive output to the EV+33. As for the EV+2.8V, either connect it directly to 3.3V or use a schottky rectifier rated for 6-10 Amps and connect the EV+2.8V through that to the PSU's 3.3V rail. This will give you around 2.8-3V, depending on the schottky rectifier's voltage drop.

That said, I'm not sure if the lack of voltage on F1, F2 and -FL pins will matter, so you may need to use another independent ungrounded/isolated power adapter for F1 and F2 (probably 5V or less, judging by the 6.3V caps used to filter F1) and maybe another for -FL, which I'm not sure what it should be.

[johnfin]

Re: Magnavox DRV power supply SMPS

Well I went to test the voltages and I am back to square one with the 100watt light bulb on full. I really dont want to pull any more parts on this board to test AGAIN. Is there any way these DVD-R's can use other power supplies?

[momaka]

Re: Magnavox DRV power supply SMPS

OK, so it looks like where we last left off, the PSU was no longer making the incandescent bulb stay glowing, but the input fuse would still blow without it.

So, with that said, it seems like I never asked you to check the output voltages when the PSU was doing that. With the incandescent bulb in place, do you get any voltage on pins EV+5V, EV+12V, and EV+33V ??

If not, try connecting one or two more incandescent bulbs in parallel with the incandescent bulb you already have. Ideally, you want the total power of all the bulbs added together to be about 180-200 Watts (i.e. 3x 60W bulbs in parallel is 180W or 2x 100W bulbs in parallel is 200W). Then, connect the PSU to the rest of the DVR and see if these voltages above come up. If not, try adding another bulb or two to raise the total power to about 250-300 Watts. The reason behind paralleling the incandescent bulbs is to stop the input voltage going to the PSU from dropping too much. With a single 60-100W bulb and the DVR requiring probably around 10-30 Watts, the input voltage could drop significantly - and most 2-transistor PSUs don't like that too much.

Let me know what you get back from these tests.

[johnfin]

Re: Magnavox DRV power supply SMPS

Well, the reading were erroneous. Its hard taking those readings you want, guess there is an electrolytic in the mix. The R2274 is a 223 resistor = 23kohms BUT its not, the readings bounce, one way its 2.8k ohms, the other way its 22K ohms.
Pins 28-30 are about the same way, around 22k ohms.
Used the Digital VOL this time. The analog gives different and and strange readings
I checked the large diodes 2204 2205 and they look ok.

There are a couple of tiny transistors that were never checked and too hard to check also. Q2209 Q2221

On to some better tests?

[momaka]

Re: Magnavox DRV power supply SMPS

Ooops, almost forgot about this thread with the holidays. (but not really ) Happy new year!

The resistance of pin 27 to ground (10 Ohms both ways) seems very suspicious. What is the supposed value of resistor R2274? If it's not 10 Ohms, then that means either you have a shorted output rectifier (either D2204 or D2205) or the regulator circuit for the P-ON+12V rail is bad (which consists mainly of transistor Q2203 and IC2204).

The 100 Ohms to ground on Pin 28-30 also doesn't look too good, as that's a regulated voltage rail derived from the EV+12V rail through Q2203. So that also suggests Q2203 may be bad. But nevertheless, check rectifiers D2204 and D2205 first.

[johnfin]

Re: Magnavox DRV power supply SMPS

Here are some simple tests I did with an analog meter on x1 for the most part. DVOM was too jumpy. Gnd lead on 9-18 - if reversed inf. reading.
-You were right about diode 2274, its a resistor
-No traces on 19&21


1-gnd nothing
2-3 (across cap 2207)= 200k after bounce
2-+cap to #9 gnd = 200K
3- -cap to #9 gnd = 10K
5-8 to #9 gnd 5ohms with neg lead on #9 inf if reversed
22-26 to #9 gnd = 5 ohms reversed leads bounces to inf.
27 to #9 gnd = 10ohms
30 to #9 gnd = 100ohms

Hope this provides some inside and clues. Let me know the next step/

[momaka]

Re: Magnavox DRV power supply SMPS

Ok, so here's your pin out then:

Pins 1, 2, and 3: same as the schematic attached in POST #50... i.e.
1: Low Power
2: F1
3: F2

Pins 5-8: that should correspond to EV+2.8V on the schematic in post #50.

Pins 9-18: GROUND

Pin 20: EV+33V

Pins 22-26: EV+5V

Pin 27: I don't see a diode labeled 2274. Are you sure it's not resistor 2274? (And diodes 2204 and 2205). If yes, then that's your EV+12V rail.

Pins 28-30: P-ON+12V (i.e. a 12V rail derived and regulated from EV+12V, and probably only turned ON when the PSU is signaled to turn ON fully).

Also, you say pins 19 and 21 are not connected, but do you not see any traces going to them? It appears these pins should correspond to SAFETY2 and PWRSW2 to the schematic in post #50.

p.s. I thought we were going to connect a PC power supply to this SMPS

Well, that's on the backburner for right now. Reason being the test without the incandescent bulb. Did you verify all components on the primary side again after one of the Zener diodes blew? Every time you remove the incandescent bulb and something blows/smokes, you need to re-check everything on the primary side. Otherwise, if we perform any further tests and expect everything on the primary to be okay, we could get some unexplainable results.

So we are back to square one. Test primary-side components. Then test the resistances to the output pins I mentioned in post #86 (but with the updated/corrected pinouts from this post). And then, if everything appears to check out, we might put an ATX PSU to feed power into the 5V and 12V lines of the output of this PSU to see if the bulb will go off. Really, it's mainly the EV+5V rail that is responsible for the majority of the PSU's regulation. However, EV+12V is also needed, as that supplies power to the optocopupler. And EV+33V seems like it could be partially responsible for the regulation as well, so you might also need a 12-20V *ungrounded* power adapter to feed that on top of the 12V rail to get something closer to 30V output. The idea with the ATX PSU is: if we feed this PSU with the correct output voltages (or close), its primary side should not have to work as hard or at all. Thus, we can more easily pinpoint where the problem is (primary or secondary), then go from there. I hope you have lots of jumper cables and aligator clips for the PSU test (if we even need to get to it), along with 3-5 spare resistors in the range of 10-100 Ohms, as we will need all of that.

[johnfin]

Re: Magnavox DRV power supply SMPS

Here is the interpolation:

1-same
2-cap +2207
3-cap -2207

5-8 connected to large diodes 2203-2209
9-18 Connected to pin 13 of transformer and diode 2229
19 n/c
20 resistor 2241 ev+33v(stamped on board not reading)
21 n/c
22-26 connected to large diodes 2206-2207
27 diode 2274
28-30 npn transistor c2026 (q2203)

p.s. I thought we were going to connect a PC power supply to this SMPS

[momaka]

Re: Magnavox DRV power supply SMPS

One problem is that schematic is not exactly the unit is I am working on. Close but no cigar. The output pins on the schematic are 34, mine is 30. I can tell you which ones are grouped together or where they go. You will have to work kinda of blind or interpolate the differences.

Okay, that will do.

If possible, try to see to which output diode/rectifier these pins connect - that should allow us to pinpoint what the pins are connected to.

ALSO important, where is the real ground. Can I use the - on the electrolytics?

For the secondary side, YES, most of the electrolytic caps will have their negative (-) leads connected to ground - but don't assume they are until you verify with a multimeter. Basically, try to see which caps have their negative leads connected together. The most that have them connected together should be your secondary ground (which, of course, is different from primary-side "ground").

[johnfin]

Re: Magnavox DRV power supply SMPS

One problem is that schematic is not exactly the unit is I am working on. Close but no cigar. The output pins on the schematic are 34, mine is 30. I can tell you which ones are grouped together or where they go. You will have to work kinda of blind or interpolate the differences. ALSO important, where is the real ground. Can I use the - on the electrolytics?

[momaka]

Re: Magnavox DRV power supply SMPS

After you check all of the primary side components, there are a few resistances I'd like you to measure - basically all of the output rails. Here is how they are grouped:

Pins 5-10 appear to be labeled as a 2.8V rail. Measure the resistance between any of these pins and ground (just one measurement is sufficient.) Make sure to use multimeter's lowest resistance scale (if it's a manual one) and also leave the meter connected to the test points for at least 3 seconds - this will allow the meter to charge the output caps so you don't get any false "short-circuit" readings.

Pin 22: it's an always-ON 33V rail, same like Pins 5-10. Thus, do the same resistance test as for pins 5-10 to ground.

Pins 24-29: an always-ON 5V rail, so do the same resistance test as pins 5-10.

Pin 30: an always-ON 12V rail (that should read closer to 13.2V if performing a voltage test). Again, do the same resistance test as pins 5-10.

Pins 31-34: a 12V rail that is derived from the same voltage rail as pin 30, but it is NOT always on (the DVR controls when this rail turns on through a low voltage signal on pin 23 (PWRSW2). Again, check resistance to ground for this pin.

Finally, for pins 3 and 4, check resistance to ground, same as like the other pins above. But for pin 2, check resistance between pin 2 and pin 3.

Report back what numbers you get. And again, make sure to leave the multimeter connected for at least 3 seconds when measuring these resistances in order to avoid false-positive short-circuit readings.

[momaka]

Re: Magnavox DRV power supply SMPS

So the new symptom is it still blows the 2amp fuse but when I put the bulb in series with the fuse, it flashes for a second then goes off and the power is still on. Its like there is a surge. Wonder if I should try to connect it to the dvr player with the bulb in tact.

It's normal for the bulb to go bright for a second and then go off - that's because the primary cap charges up when the PSU gets plugged in, hence the "surge" in power draw.

But since your input fuse blew again, now you must re-check all parts on the primary side again before we can continue with any other troubleshooting or experiments. You should not remove the series light bulb until we know the PSU is fixed for sure. (Actually, when it comes times to testing the PSU with the load from the DVR, then you can add 2-3 more bulbs in parallel with the bulb you have now - this will allow you to pull more power from the PSU without the input voltage dropping too much and causing the PSU to not work. I usually do light load testing on my repaired PSUs with a 450W heating element in place of the bulb.)

[johnfin]

Re: Magnavox DRV power supply SMPS

So the new symptom is it still blows the 2amp fuse but when I put the bulb in series with the fuse, it flashes for a second then goes off and the power is still on. Its like there is a surge. Wonder if I should try to connect it to the dvr player with the bulb in tact.

[johnfin]

Re: Magnavox DRV power supply SMPS

I replaced a zener and it doesn't blow the fuse now but I would like to see if it's working but I have not made a new cable yet and.....the actual unit I have has 30 output pins, the schematic here has 30. I measured a cap at the output and it measured 2vdc. Can someone give me some test points at the output so I can see if it's working.