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ronybc 4th September 2005 06:07 PM

TV Horzontal Output Transistor for output stage..?
What are the disadvantages of a TV Horizontal Output Transistor...? for using in the output stage of a AF amplifier.

Eg: BU508 instead 2N3055.

CBS240 4th September 2005 06:49 PM

2 Attachment(s)
Horizontal outputs are basically fast switches and not very linear. They are designed to drive the flyback transformer for hi- voltage to the picture tube anode. Besides, 2N3055 isn't a great audio device either.

This xls file of some On Semi devices may help you...;)

wrenchone 4th September 2005 08:43 PM

The gain is generally pretty horrible for horizontal output transistors as a consequence of the very high collector voltage ratiing. There's enough good stuff around at reasonable prices that you dont have to mess with the likes of horizontal output transistors or 3055s. If you look at the specs for a 3055, they are pretty much optimized for cheapness rather than performance.

tlf9999 4th September 2005 09:40 PM

I would say give it a shot. It may work. From the datasheet, it does seem to be a slow device (which can be desirable) and hfe drops pretty fast when hot.

But I guess as long as you don't push it, it should be fine as a driver or even output device in low-medium power applications.

I have been using switching devices in linear applications for a long time with good success (to me anyway). So i don't buy the stigma that some of us believe in.

BTW, Nelson also uses lots of switching devices in his amplifiers as well. Last I heard, they sound pretty good.

I guess there is to do with how one uses them, not what they are designed for.

mbates14 4th September 2005 11:32 PM

you CANT use the ones with built in dampers. on a side note.......

anatech 4th September 2005 11:53 PM

You can use the ones with damper diodes, they are not going to conduct unless you put the transistor in backwards. The gain is dreadfully low with these.

I'll agree with wrenchone 100% here. Not only that, but these are normally more expensive than audio transistors. Unless they are fakes ('cause you got them cheap or for free).


mastertech 5th September 2005 01:02 AM

as i recall from memory (which is not very good) bu208d and bu508d have internal damper diodes beta
here is not as importand as in amps as you may know these are mostly driven by
transformers and high current

the 2n type is not high voltage type


mastertech 5th September 2005 01:13 AM

"Not only that, but these are normally more expensive than audio transistors. Unless they are fakes ('cause you got them cheap or for free)."

even fakes work well in this application anatech,and most cost less than amp transistors around $4

cheers mate

anatech 5th September 2005 01:19 AM

Hi mastertech,
I guess the cost depends on your local market.

I can't see why a fake horizontal output would be more reliable than a fake audio output. We've had trouble with fake horizontals for years. Guess what? They blow up too.


mastertech 5th September 2005 01:31 AM

local market? for sure

fakes? i have no idea, thanks for telling me

cheers mate

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