robbie010

Identifying unmarked Transistor & circuit type......

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Super Wammer

Ok, I've made some progress on my project amp today and have now started drawing out a schematic! It looks a bit like spaghetti junction at the minute but I am starting to get my head around the layout of the componets and the purposes they serve.

I pulled one of the output transistors to try and identify its make / model / values and found there is not a single mark on it. Now, due to its placement in the circuit I believe it to be a fet transistor of some sort, as the positive supply from the large smoothing capacitors connects to the base of the transistor, rather than the emmitter of collector. Would this be correct?

Transistor1.jpg.86d466135fb16260484ecbeeaca46ab6.jpg

Also, the bank of output transistors are grounded to the chasis via a small ceramic fuse, coupled to what I believe is a 100nF polyester capacitor. Am I correct in thinking this would make it a common drain circuit? Sorry I know its crude but its just for illustration purposes!! :$

2062142065_OutputTransistors.jpg.d0cd132c30dcf58e07702cb58d6b4f5c.jpg

1075599725_polycap.jpg.8857d27a80d9aae6200e3b0a1111d50b.jpg

Thanks in advance. :)

Edited by robbie010
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Super Wammer

IMHO what you call a ceramic fuse is more likely to be a resistor.

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57 minutes ago, Radioham said:

IMHO what you call a ceramic fuse is more likely to be a resistor.

Thanks for posting here today :)

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The can is usually the collector for a bipolar transistor, 

see complementary emitter followers in link below:

https://www.nutsvolts.com/magazine/article/bipolar_transistor_cookbook_part_2https://www.nutsvolts.com/magazine/article/bipolar_transistor_cookbook_part_2

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In your multiple posts I may have missed it, but would it be possible to have a nicely lined up well illuminated photos of both sides of the amplifier board(s)

:D

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Super Wammer

See below:

646965623_Boards1.jpg.ceb33fa23b23ca93184e861df10bf116.jpg1724016486_Boards2.jpg.4d5eb661bbad4b2bada8733de7b2c86b.jpg

Edited by robbie010

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Super Wammer
5 hours ago, dave said:

In your multiple posts I may have missed it, but would it be possible to have a nicely lined up well illuminated photos of both sides of the amplifier board(s)

:D

See above. :^

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wow, is that it?

you picked a good amp as a first project......

d

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Do an image search for "hitachi mosfet amplifier circuit" I would imagine it could be a derivative of one of those, due to the absence of big driver transistors, and temperature compensation. that would make the output devices complementary lateral mosfets...

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Super Wammer

Your amplifier "could " be a kit with a circuit like this ?

Image result for everyday electronics  45 watt amplifier

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Spoiler alert, He says modesty. happy to delete......

My guess of the circuit. Drawn in LT switcher Cad.

Capture2.thumb.JPG.a91fae4180d571e2e093851672656c13.JPG

Edited by dave

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Super Wammer
2 hours ago, dave said:

Spoiler alert, He says modesty. happy to delete......

My guess of the circuit. Drawn in LT switcher Cad.

Capture2.thumb.JPG.a91fae4180d571e2e093851672656c13.JPG

Thanks Dave,

I have really struggled with the schematic as I have been drawing what I can see rather than what may be the most efficient way of representing the layout.

I've been using a free software to try and draw-out the schematics but it only a free trial. I think I may need to pass this on to someone who has the technical knowledge to draw it up properly.

What do you think?

346319967_Input-PowerStage.thumb.jpg.9559945cf960b028faf73327ecc673e8.jpg

84901280_AmplificationStage.jpg.266a9a99dfa27d179ddd8af88acd1f51.jpg

391615925_OutputStage.thumb.jpg.3a7197331694036199f56c91a9779560.jpg

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Switcher Cad is free, and an excellent simulator. I did what you did and then rearranged it to look like an amplifier. I have never done it like that before, I am looking forward to doing a few more now, like a fun puzzle.

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Super Wammer
4 hours ago, dave said:

Switcher Cad is free, and an excellent simulator. I did what you did and then rearranged it to look like an amplifier. I have never done it like that before, I am looking forward to doing a few more now, like a fun puzzle.

I think I have found it!!! 

I accidentally stumbled upon the attached PDF online, the circuit layout and the parts list look very, very similar........

If correct, the amp is a DIY Nelson Pass A40!!

:D

Nelson Pass Art A40.pdf

https://www.passdiy.com/gallery/amplifiers/a40-part-substitutions

Edited by robbie010

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Result. Having a nicely documented circuit makes all the difference, and lots of web tweaks. If you post in the right place on DIYaudio you can communicate with the Pass himself. (Be warned), I was a bit taken aback when he responded in person to some of my slightly tongue in cheek comments.

Edited by dave

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