STV-03h diode replacement

[mrmodify]

Anyone know of a replacement or a good substitute for a STV 03h biasing diode. Thanks

 

[mrmodify]

STV 03h

[Anyone know of a replacement or a good substitute for a STV 03h biasing diode. NTE no longer has replacement. Thanks

 

[davenn]

[Anyone know of a replacement or a good substitute for a STV 03h biasing diode. NTE no longer has replacement. Thanks

not familar with that part # and cant find any reference to it
what is it out of (equip type) what part of the cct is it in ? can you draw or photo the relevent part of the cct for us guys and we may be able to help

cheers
Dave

 

[mrmodify]

Thanks Dave for reply
It is out of the amplifier section of a Marantz 4300, The manual calls it a varistor STV-3H(Y) marantz p/n HV0000508. It is mounted on the heatsink with the switching transistors. I have attached some info. If you look on schematic it is to the left of H712. I have found some info on a substitution but I am not smart enough on electronics to understand it. If interested I can send this info to.

 

[davenn]

OK I see it there its circuit part # H728, shown as 3 diodes in series

Its providing thermal control over the driver transistors, decreasing the drive to the final transistors as they heat up.
I was trying to figure a way to explain it and gave up after 3 deleted attempts haha
maybe some one else could do a better cct description

Dave

 

[shrtrnd]

A varistor is basically a surge protector for voltage spikes.
If you can figure out your peak/peak voltage and amperage from your circuit, you should
be able to get a cheap NTE equivalent. (Which will be rated above your p/p voltage).

 

[davenn]

A varistor is basically a surge protector for voltage spikes.
If you can figure out your peak/peak voltage and amperage from your circuit, you should
be able to get a cheap NTE equivalent. (Which will be rated above your p/p voltage).

yeah he was a little off in that description see my comments in previous post as to what the diodes are there for namely a temperature sensor

Dave

 

[stephen]

diode

Anyone know of a replacement or a good substitute for a STV 03h biasing diode. Thanks

We have a stv3 if you are interested

 

[poor mystic]

OK I see it there its circuit part # H728, shown as 3 diodes in series

Its providing thermal control over the driver transistors, decreasing the drive to the final transistors as they heat up.
I was trying to figure a way to explain it and gave up after 3 deleted attempts haha
maybe some one else could do a better cct description

Dave

I think Dave wanted to explain about thermal runaway.
Thermal runaway is a problem for designers because the biasing circuits for transistors are usually made up with resistors, which maintain the same voltage as they heat up. With transistors the situation is different - as they heat up they pass more and more current for the same biasing voltage. So then they heat up some more, because in passing current they dissipate power within themselves, and the whole situation can get out of control in a poorly-designed circuit.
One way to get around the problem is to use a thermally-responsive bias circuit, and diodes (which are made of the same stuff as transistors) are sometimes chosen for the job. (Another method is to use a well-chosen emitter resistor, which is inappropriate in the circuit topology Marantz has used here.)
Is that helpful Steven, and is it like what you wanted to say, Dave?

 

[mrmodify]

Morning Stephen, Thanks for the reply, Yes I am interested. Let me know how much. I think I would posible need 2. I have built 2 replacements and installed them. The unit will now power up with out burning parts but I still have no signal going to the amplifier section so I have not been able to test. Summer is here and I only play with electronics durning the winter.

 

[mrmodify]

Back to work on my Marantz 4300, AM, FM, and all inputs are now operable. Now have signal on head phones and amplifier on right channel only. Left is very weak almost non existent. Currently trouble shooting that problem. The only thing left that has not been researched is when volume is turned up past 1/4 knob dim bulb tester will go to flashing slowly then to a very fast bright pace. If volume is kept very low with a speaker or dummy load problem does not exist.

 

[flyingtele]

Hi Stephan, do you still have the STV3? I need two for a vintage JVC amplifier. Can you please email me at flyingtele at yahoo dot com dot au

Thanks very much.

 

[Bertil Andersson]

diode



We have a stv3 if you are interested

Do you still have varistors STV-3H-0?
Do you know of any equivalents?

 

[Bertil Andersson]

Hi Stephan, do you still have the STV3? I need two for a vintage JVC amplifier. Can you please email me at flyingtele at yahoo dot com dot au

Thanks very much.

Did you find any varistors STV-3H-0? If so, I would like to have.
Did you find a supplier?

 

[stephen]

I have looked one up way back in 2011 and one of the members here gave me a part number for it but I do not remember what it was. I still have the old Morantz circuit board that had one chanel working and there may still be 1 used part on it with this part number that works. I can look if you are interested in the part. Let me know and I will get back to you to for sure.

 

[stephen]

Did you find any varistors STV-3H-0? If so, I would like to have.
Did you find a supplier?

I wrote an answer on the page this was posted on thats the best I can do as of now.