Source /Sub for SV-3a Diode

I have a marantz 4230 receiver with a blown amp looking for a SV-3a temp compensating diode (or an entire amp board) Can I use any temp compensating diode or is there something I should be looking for Thanks Bob

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Bob T
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The NTE177 is a sub for that diode, which appears to be an ordinary 200V silicon rectifier. You can probably use any rectifier with the same case as your original part.

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Dave M
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DaveM

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

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Bob T

When checking a diode (rectifier or other semiconductor junction), make sure that you use the Diode function on your DMM. If you use a normal resistance range, the applied voltage from the DMM isn't enough to cause the junction to conduct. If it checks OK with a Huntron, then it's probably OK. There are devices that have multiple PN junctions, and are usually used for setting bias levels and temperature compensation in audio circuits, but according to the NTE reference, the SV-3A is just an ordinary (low current) 200V silicon rectifier. If you're concerned about a proper replacement, then you can see the NTE177 datasheet at

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Cheers!!!!

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Dave M
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DaveM

On Tue, 13 May 2008 01:09:07 GMT, "Bob T" put finger to keyboard and composed:

See this schematic:

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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.

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- Franc Zabkar

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Franc Zabkar

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...

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Dave M
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DaveM

On Tue, 13 May 2008 08:57:08 -0400, "DaveM" put finger to keyboard and composed:

An ordinary 1N4001 has the same forward voltage drop according to its datasheet.

IIRC, a silicon PN junction has a tempco of approximately -2.2mV/deg C. Therefore the "varistor" behaves like two series silicon diodes. Would two series Schottky diodes fit the bill? AIUI, Schottky diodes have a slightly lower tempco which may be consistent with the SK3864.

- Franc Zabkar

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Franc Zabkar

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Bob T

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