stud mount Schottky diodes

[gretone]

hello everyone, I am looking for stud mount Schottky diodes for a 250watt amp I have to make it a class A amp, they are in the output stage, the diode are missing from the boards, I have the schematic for the amp but there is no identification for the diodes, all advice is welcome.

thank you

rob

 

[Nigel Goodwin]

Then post the schematic!.

 

[gretone]

here are the files,

thank you

rob

 

[crutschow]

here are the files,

Where?

 

[gretone]

Hi zapper,

Did you get the schematics I sent you ? if so it is CR14 & CR15

thank you

rob

 

[Galgso]

Hi zapper,

Did you get the schematics I sent you ? if so it is CR14 & CR15

thank you

rob

You don't seem to have attached the schematic to your post correctly as I cannot see it and nor can crutschow

 

[schmitt trigger]

Neither do I.

Make sure that the file has a valid extension for the forum.

 

[gretone]

hi zapper ,

please let me know if this is what you need,

and thank you both

kind regards

rob

 

[danadak]

Stud mount schottkys -

https://www.digikey.com/en/products/filter/single-diodes/280?s=N4IgjCBcoGwJxVAYygMwIYBsDOBTANCAPZQDaIALAAxxgDMFIAuoQA4AuUIAyuwE4BLAHYBzEAF9xhAExkQ2JAAsi7dgGsAngAIAJgKI7czcUA

 

[Nigel Goodwin]

Well this is a strange circuit? - what are the diodes doing?, and what are R67 and R68 doing? - and how do they survive, 2.7 ohm 10W resistors that appear to have 80V across them? (almost 3KW dissipation).

Presumably the OP is aware how hot class A amps run?, and will be massively increasing the cooling - although I'm a bit puzzled why he would want to make it class A?.

 

[gretone]

Hi ,

SAE, made a 250watt 01 series amp & a 250watt X series class A, Hypersonic amp, both amps are physically the same, ( I have two 250watt 01 amps ) But, one of them has the X series boards in it. both amps are rated at full power down to 2 ohms without forced air cooling as they have very large heat sinks like the Krell amps.

so, I thought I would try and get parts to make it a class A amp,

The parts I need are as follows :

Q15 X 2, Toshiba 2SD845 & Q16 X 2, Toshiba 2SB755

R67 X 2 & R 68 X 2

CR14 X 2 & CR 15 X 2 ( there is no identification for these stud mount Schottky diode ) My knowledge does not
extend enough to work out the which Schottky diodes I need,

At the time, SAE was using up there inventory before they sold the company, That is how I have a 01 amp with the X boards in,

All involved in helping me is greatly appreciated ,

Thank You

Kind Regards

Rob

 

[schmitt trigger]

This is indeed a strange circuit.
As far as I can tell, and I welcome corrections, the purpose of these diodes is to shift the waveform a few hundred millivolts DC, because the way it is biased causes some DC voltage to appear at the output transistor’s emitters.

Do you have a working amplifier? And a scope?
Could you take some dual channel waveforms form the anode and cathode?
It goes without saying that the ground reference of both channels must be aligned and volts/div must be identical.

Use a sinewave, not music. If you don’t have a signal generator, there are apps that generate waveforms. I personally use

https://audiogen.rf.gd

 

[Diver300]

Well this is a strange circuit? - what are the diodes doing?, and what are R67 and R68 doing? - and how do they survive, 2.7 ohm 10W resistors that appear to have 80V across them? (almost 3KW dissipation).

Presumably the OP is aware how hot class A amps run?, and will be massively increasing the cooling - although I'm a bit puzzled why he would want to make it class A?.

I am fairly sure that R67 and R68 should be marked 2k7, which would make sense with the power rating.

If the output is driven high or low by some external device (inductive surge or something similar) then the Schottky diodes will block the voltage. At that point R67 or R68 provide a bit of load for the power transistors so that the feedback circuit don't get into a mess.

 

[gretone]

Hi S & D.

Both amps work, but the one with the X series boards in do not have the stud mount Schottky diodes in,
so it is not possible to check form the anode and cathode as you advise, that is why I need help choosing
the correct one's, also where to obtain the OEM MT-200s, the part identifications are in my previous mail.

Thank You Both

Kind Regards

Rob