Magnavox VCR model VR1841 - need transistor ID please

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,

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.

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.

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

... Johnny

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.

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)

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

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. :-)

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

--
Met vriendelijke groet,

Maarten Bakker.

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.

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.

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.

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

I found a schematic for a generic Panasonic SMPS here:

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? :-)

Peabody spake thus:

[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

$$Search?OpenForm)

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

--
Save the Planet
Kill Yourself

- motto of the Church of Euthanasia (http://www.churchofeuthanasia.org/)

Peabody spake thus:

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.

--
Save the Planet
Kill Yourself

- motto of the Church of Euthanasia (http://www.churchofeuthanasia.org/)

David Nebenzahl wrote in news:4526f622$0$25795 $ snipped-for-privacy@news.adtechcomputers.com:

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

Jim Land spake thus:

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

--
Save the Planet
Kill Yourself

- motto of the Church of Euthanasia (http://www.churchofeuthanasia.org/)

Mouser,

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.

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.

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.