I'm looking for modern replacement parts for obsolete SV02YS and SV03YS used in below circuit. Any suggestions?
Not something I would design into an audio amplifier but each to his own .
If they are standard (old ) silicon based then they are non-linear and add noise , they have been replaced with MOV=Metal Oxide Varistor,s .
As I am not keen on them I will let somebody else advise as to which type of MOV to install.
If they are standard (old ) silicon based then they are non-linear and add noise , they have been replaced with MOV=Metal Oxide Varistor,s .
As I am not keen on them I will let somebody else advise as to which type of MOV to install.
MOV's ?
The circuit shows diode packs which were commonly used years ago. About the best you can do is to replace with appropriate series chains of small signal diodes and perhaps tweak the appropriate current setting resistor to get similar current flows to the originals.
In other words if it still works then measure the appropriate volt drops over the resistors concerned and tweak these resistors to get identical currents with the new diodes in place.
The circuit shows diode packs which were commonly used years ago. About the best you can do is to replace with appropriate series chains of small signal diodes and perhaps tweak the appropriate current setting resistor to get similar current flows to the originals.
In other words if it still works then measure the appropriate volt drops over the resistors concerned and tweak these resistors to get identical currents with the new diodes in place.
SV02YS are silicon varistors -
SV02YS Datasheet PDF, Sanken Electric co.,ltd. :: QDATASHEET ...
MOV,s are a later replacement.
SV02YS Datasheet PDF, Sanken Electric co.,ltd. :: QDATASHEET ...
MOV,s are a later replacement.
I've always known the term MOV's to mean metal oxide varistors used for overvolt transient suppression and these have a totally different symbol.
I agree these (in the circuit above) seem to be something different to that being very low voltage and low power devices... interesting 🙂
I agree these (in the circuit above) seem to be something different to that being very low voltage and low power devices... interesting 🙂
Your right on the symbols completely non-standard display they used two diodes placed anti-parallel ---but that symbol was taken over by DIACS and a new Varistor symbol introduced--- two opposing triangles .
Thats the problem with old school amplifiers they have old school schematics that aren't updated from non-standard symbols.
Thats the problem with old school amplifiers they have old school schematics that aren't updated from non-standard symbols.
The specs look exactly like strings of 1N914 diodes. Nothing like the varistors on my RS232 modem or 117V circuits.
I also doubt they would get "more modern", or fail in our lifetimes.
I also doubt they would get "more modern", or fail in our lifetimes.
Thank you all for input. I do not intend to replace the parts in existing equipment, I just want to build this circuit from service manual and can't find SV parts. I will use a string of 1N914.
The symbols tell you how many diodes are in them.
I would expect to find them bolted to the heat sink especially the one between the bases of the output pair. It looks like it has three diodes in it. If you get cross over distortion with two it will not harm the amplifier as you would be under driving the output stage. Just add another diode.
I would expect to find them bolted to the heat sink especially the one between the bases of the output pair. It looks like it has three diodes in it. If you get cross over distortion with two it will not harm the amplifier as you would be under driving the output stage. Just add another diode.
Those that keep on talking of "diodes " instead of the indisputable FACT that the actual CIRCUIT DIAGRAM shows them to be ===SV02YS =silicon VARISTORS---as PRINTED on the schematic please explain why what is shown is a LIE and in effect simple "diodes " I don't want ---well they look like diodes I want facts because what you are saying is that the circuit the company produced has a major discrepancy that has never been picked up over the decades by any audio engineer and relayed back to the manufacturers as a major flaw in the schematic ?
Show me other audio websites/top end electronics magazines /debates that say- they got it wrong and it should be simple diodes , in this case --no speculation but facts .
I don't like the circuit with them there but that doesn't dis the fact that they are and printed on that schematic even the OP mentions that fact in his first post .
Show me other audio websites/top end electronics magazines /debates that say- they got it wrong and it should be simple diodes , in this case --no speculation but facts .
I don't like the circuit with them there but that doesn't dis the fact that they are and printed on that schematic even the OP mentions that fact in his first post .
These parts were also commonly used in many Sony amps of the mid 70's era (eg TA3650) and they are always both drawn as and referred to as 'diodes'. Replacement with diodes (such as the 1N4148) is a recognised repair procedure.
Apart from that Sanken reference to the 'varistor' in the data sheet do we have any other reference of that term being used for these parts?
Is there another word or term that would be used to describe a series diode pack... I can't just think of one.
A more comprehensive data sheet shows these parts to have what appears to be the expected characteristic of a series diode chain.
Apart from that Sanken reference to the 'varistor' in the data sheet do we have any other reference of that term being used for these parts?
Is there another word or term that would be used to describe a series diode pack... I can't just think of one.
A more comprehensive data sheet shows these parts to have what appears to be the expected characteristic of a series diode chain.
Attachments
If they are (as you say ) just like several series diodes in their operation then please comment on -
What Is A Varistor vs TVS Diode? How To Select The Best Varistor To Protect Your Circuit
Are you saying that normal diodes have the same qualities as varistors ?
Here is the professional engineering website -Stack Exchange where an electrical engineer gets seven approval ratings from fellow engineers for his reply that ---quote---" a varistor isn't two diodes in series ---any rebuttal ?-
Is a varistor basically two diodes in series, with opposite polarities? - Electrical Engineering Stack Exchange
What Is A Varistor vs TVS Diode? How To Select The Best Varistor To Protect Your Circuit
Are you saying that normal diodes have the same qualities as varistors ?
Here is the professional engineering website -Stack Exchange where an electrical engineer gets seven approval ratings from fellow engineers for his reply that ---quote---" a varistor isn't two diodes in series ---any rebuttal ?-
Is a varistor basically two diodes in series, with opposite polarities? - Electrical Engineering Stack Exchange
Without being combative I'd say your first link shows exactly what I understand a Varistor to be. A two terminal bidirectional device used for transient suppression. It is a voltage dependent resistor or VDR. I've always regarded them as a bit 'vague' in operating parameters, in other words pretty loose tolerance. I consider them fairly robust in service unless they meet with a catastrophic overload.
TVS diodes I have plenty of experience with, typically seeing them fail short circuit in consumer equipment where they are placed directly over regulated SMPS rails. I would class these as 'diode' like (somewhat like a Zener in operation but very fast and with high energy capability) and in practice prone to failure for no obvious reasons.
I just wonder whether its a case of the terminology being confusing. All the amplifier circuits show the equivalent of diode chains and if you were designing the circuit you can see how the appropriate number of diodes would be correct such as for setting a current source or sink.
I can't offer any more than that really. You also have to ask whether manufacturers would be using something oddball and exotic back in the 70's and I'd hazard a guess that the answer is no. They all draw them as diodes, refer to them as diodes and number them as diodes.
TVS diodes I have plenty of experience with, typically seeing them fail short circuit in consumer equipment where they are placed directly over regulated SMPS rails. I would class these as 'diode' like (somewhat like a Zener in operation but very fast and with high energy capability) and in practice prone to failure for no obvious reasons.
I just wonder whether its a case of the terminology being confusing. All the amplifier circuits show the equivalent of diode chains and if you were designing the circuit you can see how the appropriate number of diodes would be correct such as for setting a current source or sink.
I can't offer any more than that really. You also have to ask whether manufacturers would be using something oddball and exotic back in the 70's and I'd hazard a guess that the answer is no. They all draw them as diodes, refer to them as diodes and number them as diodes.
Long ago Philips used to make multiple series silicon diodes for voltage reference work.
They were just normal 1N4148 type die, but tested for Vf
They were just normal 1N4148 type die, but tested for Vf
Okay then that's a logical point of view Mooly , Usually in designs presented to EW there is much talk about the design structure, its pros and cons and even difference of opinions as not all designers agree as to an audio philosophy .
Thats okay just a difference of opinion but never have I come across a gross misrepresentation ( if that's what it looks like ) in actually publishing a circuit where the component name for a (semi) active device was so misnamed .
I know for a fact that at least one well known engineer would have torn the designer in two .
That nobody in the audio world has queried this over many decades either means it was not a well known designer or the manufactured design never sold well.
But now DIY Audio has queried it and if you are correct then that is obviously a plus point in the audio world.
Thats okay just a difference of opinion but never have I come across a gross misrepresentation ( if that's what it looks like ) in actually publishing a circuit where the component name for a (semi) active device was so misnamed .
I know for a fact that at least one well known engineer would have torn the designer in two .
That nobody in the audio world has queried this over many decades either means it was not a well known designer or the manufactured design never sold well.
But now DIY Audio has queried it and if you are correct then that is obviously a plus point in the audio world.
I am neither PC nor woke and have watched even engineering terms being "moderated " elsewhere just because it upsets somebody even terms used for about 200 years .
I realise in the USA you are not allowed to say lie .
In engineering only the truth will do to say otherwise gets 1000,s of the public killed as in sub standard concrete/steel used to build bridges in civil engineering , corners are cut for profit .
If it is the truth contrary to what you posted (" today we call them 1N4148" ) then why criticize me ?
I realise in the USA you are not allowed to say lie .
In engineering only the truth will do to say otherwise gets 1000,s of the public killed as in sub standard concrete/steel used to build bridges in civil engineering , corners are cut for profit .
If it is the truth contrary to what you posted (" today we call them 1N4148" ) then why criticize me ?
Agreed David I remember that name from a long time ago.
Its an American invention -
A new electronic rectifier - IEEE Journals & Magazine
and yes an early symbol was series diodes a circuit used by the Bell Telephone company and from what I remember the UK GPO .
Its an American invention -
A new electronic rectifier - IEEE Journals & Magazine
and yes an early symbol was series diodes a circuit used by the Bell Telephone company and from what I remember the UK GPO .