Magnavox VCR model VR1841 - need transistor ID please

[Peabody]

It blows fuses immediately on pluggin in. Otherwise, it works fine.


On the power supply board, I removed Q1 and Q2. Both appear to be
all shorted out internally. I get about 1.2 ohms between any 2 pins
of each transistor. Both have pins labeled e-c-b on the circuit
board.

Q1 is still intact. It says C4418. But Q2 is partially destroyed,
and I can't read the number.

Does anyone have the schematic and parts list for this machine, or
know where I might find them? I need to identify the late great Q2.

I know, I know. You're gonna say "why bother". But you know,
otherwise it works fine, and I would just like to fix it if I can.
And with these two Q's removed, everything now seems to measure ok,
with no more dead shorts where they shouldn't be. So I think it's
worth a try. But I need to know what Q2 is.

Any help would be appreciated.

 

[Johnny Boy]

It blows fuses immediately on pluggin in. Otherwise, it works fine.


On the power supply board, I removed Q1 and Q2. Both appear to be
all shorted out internally. I get about 1.2 ohms between any 2 pins
of each transistor. Both have pins labeled e-c-b on the circuit
board.

Q1 is still intact. It says C4418. But Q2 is partially destroyed,
and I can't read the number.

I thought you just said that Q1 has about 1.2 ohms between all pins - it's
not intact, it's stuffed, unless the measurements were made in-circuit and
something else has failed.

C4418 might be a 2sc4418, check out the datasheet,
http://www.allegromicro.com/skncatlg/pwrxtr/2sc4418.pdf#search="2sc4418"


You also say that Q2 is partially intact - how do you mean - if it's also
1.2 ohms between pins, it is dead, unless, again, measurements were made
in-circuit and something else has failed.

Does anyone have the schematic and parts list for this machine, or
know where I might find them? I need to identify the late great Q2.

As near as I can tell, the Magnavox VR1841 is probably a Philips VR1841, but
I couldn't find a"schematic" or "diagram" on Google. You'll probably need to
try specialist parts suppliers. In this area, I can only help if you're in
Australia.

I know, I know. You're gonna say "why bother". But you know,
otherwise it works fine, and I would just like to fix it if I can.
And with these two Q's removed, everything now seems to measure ok,
with no more dead shorts where they shouldn't be. So I think it's
worth a try. But I need to know what Q2 is.

Can't help with Q2, sorry, except that, as I said, it sounds like it's
f...ed

Any help would be appreciated.

.... Johnny

 

[Mark D. Zacharias]

It blows fuses immediately on pluggin in. Otherwise, it works fine.


On the power supply board, I removed Q1 and Q2. Both appear to be
all shorted out internally. I get about 1.2 ohms between any 2 pins
of each transistor. Both have pins labeled e-c-b on the circuit
board.

Q1 is still intact. It says C4418. But Q2 is partially destroyed,
and I can't read the number.

Does anyone have the schematic and parts list for this machine, or
know where I might find them? I need to identify the late great Q2.

I know, I know. You're gonna say "why bother". But you know,
otherwise it works fine, and I would just like to fix it if I can.
And with these two Q's removed, everything now seems to measure ok,
with no more dead shorts where they shouldn't be. So I think it's
worth a try. But I need to know what Q2 is.

Any help would be appreciated.

This is a Panasonic-built unit. Q2 may be a 2SD1458. Can't remember the
number of the other NPN they sometimes used. Some models used a 2SB643 PNP
for Q2.

Mark Z.

 

[Peabody]

Johnny Boy says...

I thought you just said that Q1 has about 1.2 ohms
between all pins - it's not intact, it's stuffed, unless
the measurements were made in-circuit and something else
has failed.

Sorry I wasn't clear about that. What I mean is that the
body of Q1 is still intact, so I can still read the number
even though everything inside is fried.

But part of the body of Q2 is no longer there, and there's a
black burn mark on the board underneath it. So I just can't
physically read the full number because part of it is gone.

C4418 might be a 2sc4418, check out the datasheet,
http://www.allegromicro.com/skncatlg/pwrxtr/2sc4418.pdf#
search=%222sc4418%22

Yes, that looks like a match.

Thanks for your help, Johnny.

 

[Johnny Boy]

Johnny Boy says...



Sorry I wasn't clear about that. What I mean is that the
body of Q1 is still intact, so I can still read the number
even though everything inside is fried.

But part of the body of Q2 is no longer there, and there's a
black burn mark on the board underneath it. So I just can't
physically read the full number because part of it is gone.


Yes, that looks like a match.

Thanks for your help, Johnny.

Good one - wish I could have been more help. I haven't had a look at
Mark's suggestion that the chassis is a Panasonic. Try Googling "Panasonic
VR1841 + schematic" or "Panasonic + VR1841 + diagram" and see how you go.
For your future reference, often if a transistor is marked Cxxxx, it
will turn out to be a 2SCxxxx
.... J (Steve, in the real world)

 

[Peabody]

Mark D. Zacharias says...

This is a Panasonic-built unit. Q2 may be a 2SD1458.
Can't remember the number of the other NPN they
sometimes used. Some models used a 2SB643 PNP for Q2.

Mark Z.

Ok, the 1458 looks right. From what's left, I was gonna guess it
ends with 158, but the 1 could be a 4, so I think that's it.

Where I live, there's not a lot of electronic parts available, so in
case I can't find one of these, do you suppose I could use some more
familiar small NPN transistor? Physically, there's lots of room to
use any package type. So could I even use a 2N3904 or 2N2222A
(making sure to get the e/c/b right, of course), or is there
something special about "Silicon NPN epitaxial planar type"?

Here's the data sheet on the 2SD1458:

http://www.ortodoxism.ro/datasheets/panasonic/SJC00223BED.pdf

Thanks very much, Mark.

 

[Chuck]

Mark D. Zacharias says...



Ok, the 1458 looks right. From what's left, I was gonna guess it
ends with 158, but the 1 could be a 4, so I think that's it.

Where I live, there's not a lot of electronic parts available, so in
case I can't find one of these, do you suppose I could use some more
familiar small NPN transistor? Physically, there's lots of room to
use any package type. So could I even use a 2N3904 or 2N2222A
(making sure to get the e/c/b right, of course), or is there
something special about "Silicon NPN epitaxial planar type"?

Here's the data sheet on the 2SD1458:

http://www.ortodoxism.ro/datasheets/panasonic/SJC00223BED.pdf

Thanks very much, Mark.

This transistor is available from mcm but any npn transistor with
similar current ,voltage, and hfe specs can be used. Before powering
the unit up, I'd replace the faulty electrolytic capacitors and the
shorted 18v zener diode or you power supply will blow again. Chuck

 

[Peabody]

Chuck says...

This transistor is available from mcm but any npn
transistor with similar current ,voltage, and hfe specs
can be used. Before powering the unit up, I'd replace
the faulty electrolytic capacitors and the shorted 18v
zener diode or you power supply will blow again. Chuck

Ahah! It's funny you should mention that.

With nothing better to do, I removed both electrolytic
capacitors:

C4 - 82 ufd, 200V
C5 - 4.7 ufd, 200V

and found them both to be open. Well, of course they would
be open to DC, but I mean when I test them with my old
analog ohmmeter in the usual way, I get no response in
either direction. So, as you suggested, they appear to be
dead.

But the diode is a different matter. I did find one diode
(D3) which is bad (measures the same 200 ohms in both
directions), but it is a small glass diode with no markings,
and it looks the same as three or four other diodes on the
board, inclulding D4. So I assumed it was just a small
signal diode, and planned to replace it with a 1N4148.

The only other diode on the mains side of the big
transformer (which I assume is where the problem is) is the
series combination of D6 and L2 (L2 looks to be a ferrite
bead), and D6 looks different from the other diodes, but the
legend on the board doesn't show it to be a zener, and it
still measures like a good diode.

So am I wrong about the problem being on the mains side? I
see several zeners on the other side. If I'm wrong about
that, then do I also need to check all seven electrolytics on
that side as well?

Thanks very much, Chuck. I knew I was in the right
newsgroup.

 

[[email protected]]

So am I wrong about the problem being on the mains side? I
see several zeners on the other side. If I'm wrong about
that, then do I also need to check all seven electrolytics on
that side as well?

Yes, the zener is across the 12 or 15V supply line, the electrolytics are
also in the secondary side.

 

[Peabody]

[email protected] says...

Yes, the zener is across the 12 or 15V supply line, the
electrolytics are also in the secondary side.

I found a zener on the secondary side with the mark "1881".
So far I haven't been able to find that in any reference.

But, it isn't shorted. It seems to be fine. Well, I
haven't actually checked to see what it's voltage is, but
otherwise it tests fine.

So far, the bad electrolytics I've found are on the primary
side. In fact, I've found nothing bad on the secondary side
(I've checked all the diodes there). But I guess I still
need to check the electrolytics there.

 

[Peabody]

Peabody says...

I found a zener on the secondary side with the mark
"1881". So far I haven't been able to find that in any
reference.

Well, not as an 18V zener anyway. If it's a 1N1881, then
that's a 27V zener.

 

[Mark D. Zacharias]

Peabody says...


Well, not as an 18V zener anyway. If it's a 1N1881, then
that's a 27V zener.

But the Panasonixs do typically have a zener, 18V @ 1 watt, across the 14
volt line. Normally designated D15.

Mark Z.

 

[Peabody]

Mark D. Zacharias says...

But the Panasonixs do typically have a zener, 18V @ 1
watt, across the 14 volt line. Normally designated D15.

Yes, the one I found is D15. So I guess the 1881 mark means
something other than 1N1881.

Well, as I said earlier, this diode isn't shorted out,
and tests ok as a normal diode. I'll set up a circuit to
make sure it's 18V.

By the way, the power board has an assembly number of
VEPS0191. I still can't find any schematic info on the
VR1841 VCR itself, even in Sams, but maybe someone can point
me to the PS schematic, if it's also found in other VCRs.

Well so far it looks like all the damage is on the primary
side - two transistors, two electolytics, and one diode.
But I still have some electrolytics to test on the
secondary side.

 

[Peabody]

I'd like to thank everyone for their help on this.

I found a schematic for a generic Panasonic SMPS here:

http://www.repairfaq.org/sam/vcrps.pdf

I've gone through pretty much everything, and found six bad parts on
the primary side, but nothing bad (even the 18V zener) on the
secondary side. Here's the bad stuff:

Q1 2SC4418
Q2 2SD1458
C4 82UF 200V "CE"
C5 4.7UF 200V "CE-US" Marcon
R23 0.61 ohm, 1W metal film
D3 small unknown diode

But I'm kinda stuck on where to get this stuff. The only places
that have both transistors are MCM and Globalsemi, and I found this
rather distrubing review about MCM:

"MCM Electronics is an online company to AVOID! They will charge you
huge shipping and handling fees (most of it handling fees) and not
tell you how much it will be. I placed an order for a very small,
light weight item. They asked for the credit card number and other
information. But would NOT tell me how much S&H was going to cost.
It wasn't until I received the package with the invoice that I saw
the huge handling fees that they refused to fairly announce in their
online ads."

I don't know anything about Globalsemi.

I'd like to fix this thing, but Wal-Mart still has a stand-alone VCR
for $40, so if I spend $20-25 on parts, shipping and handling, that
just doesn't make sense, particularly since it may blow again
because of something I haven't found.

Does anyone have any experience with DVD recorders?

 

[David Nebenzahl]

Peabody spake thus:

I'd like to thank everyone for their help on this.

I found a schematic for a generic Panasonic SMPS here:

http://www.repairfaq.org/sam/vcrps.pdf

I've gone through pretty much everything, and found six bad parts on
the primary side, but nothing bad (even the 18V zener) on the
secondary side. Here's the bad stuff:

Q1 2SC4418
Q2 2SD1458
C4 82UF 200V "CE"
C5 4.7UF 200V "CE-US" Marcon
R23 0.61 ohm, 1W metal film
D3 small unknown diode

But I'm kinda stuck on where to get this stuff. The only places
that have both transistors are MCM and Globalsemi, and I found this
rather distrubing review about MCM:

[bad review snipped]

So find another vendor. Just for laughs, I entered the transistor part
#s into NTE's x-reference page, and found they have equivalents for both:

2SC4418--> NTE2337
2SD1458--> NTE16006

(Their site is
http://nte01.nteinc.com/nte/NTExRefSemiProd.nsf/$$Search?OpenForm)

So you can probably find all this stuff somewhere else, and hopefully
for less than $25.

 

[David Nebenzahl]

Peabody spake thus:

I'd like to thank everyone for their help on this.

I found a schematic for a generic Panasonic SMPS here:

http://www.repairfaq.org/sam/vcrps.pdf

I've gone through pretty much everything, and found six bad parts on
the primary side, but nothing bad (even the 18V zener) on the
secondary side. Here's the bad stuff:

By the way, another thought: just take all this stuff out and throw it
away. Really. It's on the primary (110 volt) side, right? Then all it
could possibly be doing is some kind of circuit protection; you could
accomplish this by simply using a decent surge protector in line with
the power cord.

 

[Jim Land]

By the way, another thought: just take all this stuff out and throw it
away. Really. It's on the primary (110 volt) side, right? Then all it
could possibly be doing is some kind of circuit protection; you could
accomplish this by simply using a decent surge protector in line with
the power cord.

Ummm... both the semiconductors are transistors...

 

[David Nebenzahl]

Jim Land spake thus:

Ummm... both the semiconductors are transistors...

So what would they be doing on the primary side of the power supply?

 

[Airioch]

Q1 2SC4418
Q2 2SD1458

Mouser, http://www.mouser.com

also carries the transistors, or at least the NTE replacements. Pretty
sure you could get all the other bits and pieces from them as well.

I'd imagine (I didn't check) that DigiKey also carries them.

But I'm kinda stuck on where to get this stuff. The only places
that have both transistors are MCM and Globalsemi, and I found this
rather distrubing review about MCM:

"MCM Electronics is an online company to AVOID! They will charge you
huge shipping and handling fees (most of it handling fees) and not
tell you how much it will be. I placed an order for a very small,
light weight item. They asked for the credit card number and other
information. But would NOT tell me how much S&H was going to cost.
It wasn't until I received the package with the invoice that I saw
the huge handling fees that they refused to fairly announce in their
online ads."

I dunno, I've never had any 'issues'. You order a 1 oz. part and have it
shipped UPS ground, you're going to get charged for the minimum shipping
weight they handle. Why would MCM eat those costs ? Now, I'd like it if
they *asked* what method of shipping to use. I've never had them ask
when I've ordered from them.

 

[Peabody]

Airioch says...

Mouser, http://www.mouser.com

also carries the transistors, or at least the NTE
replacements. Pretty sure you could get all the other
bits and pieces from them as well.

I'd imagine (I didn't check) that DigiKey also carries
them.

Thanks. And Mouser did have everything else, except the
0.61 ohm metal film resistor. But, they had 1.2 ohm.
So I ordered from them. Came to about $10 plus shipping,
which is nice if it works, but not a disaster if it doesn't.

Thanks again for everyone's help.