Re: Source /Sub for SV-3a Diode



"Franc Zabkar" <fzabkar@xxxxxxxxxxxxxxxxx> wrote in message
news:e6bi24pgbdut2uk6mu1kq1k326mapnpo0t@xxxxxxxxxx
On Tue, 13 May 2008 01:09:07 GMT, "Bob T"
<boboranntrottier@xxxxxxxxxxx> put finger to keyboard and composed:

Dave
thanks the only thing odd I noticed is that the SV-3a diode doesn't look
like a diode using a dvm. i.e. looks open in either direction
They do look like diodes when I put them on my huntron tracker which had me
wondering if there were two devices in the case or something that might
raise the forward voltage drop
I have a few diodes from a old scott receiver that I'll try and see what
happens

Bob

See this schematic:
http://www.jmargolin.com/marantz/p750.pdf

Diodes H005 and H006 are identified as "HV0000212, SV-3A". The circuit
symbol for each diode is two diodes in series.

However, the schematic diagram for the Marantz 4240 receiver draws
them as regular single diodes.

http://www.eserviceinfo.com/downloadsm/25365/MARANTZ_4240.html

- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.

Looking at the NTE177 data sheet, I see that the forward voltage drop is 1.0
volt, pretty high for a low current rectifier.

I looked up the SV-3A unit in my old RCA SK-series catalog, and also in my old
Sylvania ECG series catalog. The SK3864 is listed as the replacement for the
SV-3A. The ECG605A is the ECG replacement.
Both of those catalogs list the replacement to be a Silicon Varistor, not a
rectifier.
ECG605A characteristics:
Vf = 1.26V - 1.36V @ 3ma
Tempco = -4.6mV per degree C

SK3864 characteristics:
Vf = 1.24V - 1.34V @ 3ma
Tempco = -3.6mV per degree C

In view of the Marantz schematic and the other observations, I would have to say
that the NTE177 part is not a good replacement. Instead, I suggest that the
NTE605A part is the proper replacement part. It has the same characteristics as
the ECG part, and is a silicon varistor, not a rectifier.

Another fly in the ointment; according to the datasheet, the NTE605A has been
discontinued. I emailed NTE and described the problem, including the fact that
the NTE605A has been discontinued. Will have to wait for their solution, if
they have one. You might be able to find a dealer or distributor that still has
an NTE605A in stock. Good luck on that.

Back to the OP... the original part is probably behaving correctly on your DMM
resistance test. Even in the Diode mode, the DMM might not have enough voltage
at the probes to turn on the junction, so it will read open in both directions.
The Huntron test should be reliable. Sorry for all the confusion.

Cheers...
--
Dave M
MasonDG44 at comcast dot net (Just substitute the appropriate characters in the
address)

Some people are like Slinkies. Not really good for anything, but they bring a
smile to your face when pushed down the stairs.


.



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