Toshiba dvd/hd recorder RD-88DT-K-TB dead.

[froggy]

Hi again, I hope ive listed this in the correct place, As in the title my dvd/hd recorder has gone dead, This happened after we had a power cut recently,
A visual inspection of the power board shows nothing obvious,
Im in the process of removing the fet (K3798Q)as i figure this might be the likely candidate as the diodes on the `hot` side check out fine, Now ive never tested one of these before so this will be another lesson learnt (any pointers?),
The powerboard number is,,,BE2N70F0102,,,,,Many thanks.

[popeye]

Re: Toshiba dvd/hd recorder RD-88DT-K-TB dead.

first check the fuse should read short circuit

check d2000 to d2003

check R2101 1.5 ohm

check the Q2101- Q2102

D2107 - d2111

IC 2101 optocupler & D2112

check 5W resister 0.82ohm

then check all the diods by the caps on secondery side

hopefuly by then you should have found the faulty componants.

google how to check fet.


Tony

[tom66]

Re: Toshiba dvd/hd recorder RD-88DT-K-TB dead.

Does the fuse check out fine?

Do you get 150 - 350V across the main cap?

Does the big white resistor check out okay? (1.5 ohms?)

[froggy]

Re: Toshiba dvd/hd recorder RD-88DT-K-TB dead.

Now this might be a daft question but i guess ive got to check everything off board, I am a beginner to this sort of thing so youll have to be patient with me, anyhow so far the fuse is fine, the d2000-d2003 check out fine, The Q2101 I thought was a fet or have i got that wrong?, so much to learn I guess!.

[PlainBill]

Re: Toshiba dvd/hd recorder RD-88DT-K-TB dead.

Now this might be a daft question but i guess ive got to check everything off board, I am a beginner to this sort of thing so youll have to be patient with me, anyhow so far the fuse is fine, the d2000-d2003 check out fine, The Q2101 I thought was a fet or have i got that wrong?, so much to learn I guess!.

Sorry to jump in here, but you may be going about this the wrong way. Looking at the bottom of the board, there are actually only 9 outputs. On the 34 pin conductor they are 1, 2, 3, 4&5, 6-19, 20-23, 24-29, 30-33, and 34. Pins 6-19 are ground.

The first step is to measure the voltages from 6-19 to the other 8 pins or groups of pins. Next, carefully measure the voltage across the 220uF, 400V cap. All of these tests are done with the power on, so be careful.

Ordinarily, basic tests can be done with the power off and the components in circuit. In most cases the resistance of a shorted diode will totally swamp any other resistances, so check the resistance across each diode with the DMM on the 200 ohms scale. If any check read than 100 ohms, unsolder one end and recheck.

PlainBill

[froggy]

Re: Toshiba dvd/hd recorder RD-88DT-K-TB dead.

Thanks PlainBill for the tip, unfortunately I had already removed the fet & a transistor (Q2101-Q2102) so thought it was as well to test them rather than refitting so i could power it up,
The fet as far as i can make out is suspect, I say this as ive tested it two different ways as suggested on google & it didnt do as they said it should,
I`ll be getting one ordered & in the meantime i`ll go through the rest of it just in case something else has been taken out.,,,,cheers!.

[tom66]

Re: Toshiba dvd/hd recorder RD-88DT-K-TB dead.

Thanks PlainBill for the tip, unfortunately I had already removed the fet & a transistor (Q2101-Q2102) so thought it was as well to test them rather than refitting so i could power it up,
The fet as far as i can make out is suspect, I say this as ive tested it two different ways as suggested on google & it didnt do as they said it should,
I`ll be getting one ordered & in the meantime i`ll go through the rest of it just in case something else has been taken out.,,,,cheers!.

Are you sure about the part number K3798Q? No results on Google for it. Can you post a pic of the part?

[Th3_uN1Qu3]

Re: Toshiba dvd/hd recorder RD-88DT-K-TB dead.

Here.

[froggy]

Re: Toshiba dvd/hd recorder RD-88DT-K-TB dead.

Thanks for putting the link up thatll save me a photo!, Luckily I found one for sale on an auction site so i didnt have to even leave my chair,,,,happy days!,
So far everything else is checking out but ive now got to look up how to test the optocupler,,,,,,,,cheers.

[froggy]

Re: Toshiba dvd/hd recorder RD-88DT-K-TB dead.

Im having problems indentifying a zener, The markings are `27B`, does anyone have any idea where I can get the spec for this please or know an equivalent for it?....Many thanks.

[tom66]

Re: Toshiba dvd/hd recorder RD-88DT-K-TB dead.

That is a member of the BZX27 series, a 1.3W axial zener diode. Datasheet here. You'd need the voltage too, which is usually written like "5V6" or "22V".

Zeners can fail, but why do you think it has? They usually become short circuits both ways when they fail.

[froggy]

Re: Toshiba dvd/hd recorder RD-88DT-K-TB dead.

That is a member of the BZX27 series, a 1.3W axial zener diode. Datasheet here. You'd need the voltage too, which is usually written like "5V6" or "22V".

Zeners can fail, but why do you think it has? They usually become short circuits both ways when they fail.

Thanks Tom, There is no other markings on it, to be honest it is so small that I had trouble reading the `27B` & that was with a powerful magnifier,
Ive been reading that zeners are awkward to test (like Ive said im a beginner) but thought that while it is out it would be just as well to change it as I have loads of different values I inherited from my late father,
So the probabilty of having a replacement here is quite high, If I put the meter on diode check it does read as a short both ways but no doubt im not doing it correctly, I`ll have a search on the net again & see if a schematic is available anywhere to help me along.,,,cheers.

Oh & if it helps at all its the zener D2107 which is situated behind Q2102.

[tom66]

Re: Toshiba dvd/hd recorder RD-88DT-K-TB dead.

Thanks Tom, There is no other markings on it, to be honest it is so small that I had trouble reading the `27B` & that was with a powerful magnifier,
Ive been reading that zeners are awkward to test (like Ive said im a beginner) but thought that while it is out it would be just as well to change it as I have loads of different values I inherited from my late father,
So the probabilty of having a replacement here is quite high, If I put the meter on diode check it does read as a short both ways but no doubt im not doing it correctly, I`ll have a search on the net again & see if a schematic is available anywhere to help me along.,,,cheers.

Oh & if it helps at all its the zener D2107 which is situated behind Q2102.

Zeners are just like any diode. Almost always they fail short circuit. Test both ways. If you get less than about 50mV both ways, I'd consider it failed.

[froggy]

Re: Toshiba dvd/hd recorder RD-88DT-K-TB dead.

Well, I am still none the wiser with voltage rating on the zener diode, I can find no other markings on it & can find no schematics for the board either so it seems that im stuck, So what can anyone suggest is my next approach?,,,,,,,cheers.

[tom66]

Re: Toshiba dvd/hd recorder RD-88DT-K-TB dead.

Well, I am still none the wiser with voltage rating on the zener diode, I can find no other markings on it & can find no schematics for the board either so it seems that im stuck, So what can anyone suggest is my next approach?,,,,,,,cheers.

Did you test the zener?

How did you test the FET?

Have you tested that the PSU is actually outputting anything?

[froggy]

Re: Toshiba dvd/hd recorder RD-88DT-K-TB dead.

Did you test the zener?

How did you test the FET?

Have you tested that the PSU is actually outputting anything?

Hi Tom, I Tested the Fet via a step by step guide off the net, there were two tests I could try so I tried both just to make sure & both ways it showed to be u/s,
As for the zener could you give me some pointers on how to test it correctly as its something ive never done before (meter setting etc) as I presume its not a matter of just setting the meter to diode check,
I havent tested for output as I had removed the fet & the zener first to check them, PlainBill had mentioned to check the outputs at the 34 pin ribbon mount but I had already removed the Fet, I guess im learning by my mistakes but we all had to start somewhere,
You are dealing with a total novice here im affraid,,,sorry!.

[tom66]

Re: Toshiba dvd/hd recorder RD-88DT-K-TB dead.

Hi Tom, I Tested the Fet via a step by step guide off the net, there were two tests I could try so I tried both just to make sure & both ways it showed to be u/s,
As for the zener could you give me some pointers on how to test it correctly as its something ive never done before (meter setting etc) as I presume its not a matter of just setting the meter to diode check,
I havent tested for output as I had removed the fet & the zener first to check them, PlainBill had mentioned to check the outputs at the 34 pin ribbon mount but I had already removed the Fet, I guess im learning by my mistakes but we all had to start somewhere,
You are dealing with a total novice here im affraid,,,sorry!.

Most FETs fail short circuit when they go bad, so usually the fuse goes bang at the same time. (Also check the plug fuse, this can sometimes go too.) Often this is accompanied by a loud bang while you are using it and then it goes dead.

For zeners it really is as simple as checking using the diode test mode. You should get about "500" or "0.5" one way and infinite (usually "1 ." or "OL") the other way.

I would advise you replace the FET if the fuse is not blown as it's probably not the problem.

I'm a novice too, just done a lot of reading.

[froggy]

Re: Toshiba dvd/hd recorder RD-88DT-K-TB dead.

Thanks Tom, Well I checked the fuses both in the plug & the one on the PCB & even the mains cable & they are fine,
Now back to the zener, basically I checked it on diode setting both ways & got a constant `beep`from the meter either way so im assuming it is u/s.

[PlainBill]

Re: Toshiba dvd/hd recorder RD-88DT-K-TB dead.

Thanks Tom, Well I checked the fuses both in the plug & the one on the PCB & even the mains cable & they are fine,
Now back to the zener, basically I checked it on diode setting both ways & got a constant `beep`from the meter either way so im assuming it is u/s.

Don't use the 'beep' from a continuity or diode test for anything except finding out if point 'A' is connected to point 'B'. The resistance which is considered a short can vary widely.

My preferred method - set the meter to the 200 ohms range. Check the resistance across the zener. Reverse the leads and check again. The resistance should be over-range in both directions. If it reads less than 1 ohm, the zener is shorted. THEN we can start figuring out what voltage it should be, based on where it is in the circuit.

PlainBill

[froggy]

Re: Toshiba dvd/hd recorder RD-88DT-K-TB dead.

Don't use the 'beep' from a continuity or diode test for anything except finding out if point 'A' is connected to point 'B'. The resistance which is considered a short can vary widely.

My preferred method - set the meter to the 200 ohms range. Check the resistance across the zener. Reverse the leads and check again. The resistance should be over-range in both directions. If it reads less than 1 ohm, the zener is shorted. THEN we can start figuring out what voltage it should be, based on where it is in the circuit.

PlainBill

Thanks PlainBill, Ive tested the zener as you suggest & im getting a reading of 1.1 both ways so whats next?.,,,,many thanks.