Transistors for Hitachi HMA 7500 amplifier

There are several reasons. If you find one shorted transistor in a push-pull stage you should always replace both. One might be faulty but not shorted, but when in operation it does the other one in. You might have also missed another shorted part such as a diode or voltage regulator. Hunt around looking at the circuit of the confirmed shorted parts and test or replace anything off that circuit.
Finally check your speakers and wiring to them. Shorted output transistors have generally two ways of going like that. Wires touching each other or bad speakers, or having it too loud!

hi zm_16dec,

Right chanel fully dead , output transistor burnedout ,

Without knowing the make and model of your amplifier

all i can advise is to replace the unknown part number of

the transistor.


Look for the working left channel output transistors and

replace the bad transistors in "pair". These may include

other components but check on it as well.


Check the speaker system, especially where that channel

is connected.Inspect speaker wires or cable up to the speaker

itself.


Amplifier wont blow without reason.It could be from the wirings,

speaker or volume settings of the unit.

Thanks for choosing Fixya for assistance!

Yes it depend on how much damage is on the system. What you need to do is to identify the transistor model and look for replacement parts.

you can get parts from digikey.com.

look at the transistor you want to replace, they all have part numbers on em.

type it into the search frame on the site.

Service manual:
http://elektrotanya.com/?q=showresult&megnev=Compaq%20&megnev2=7500&kategoria=monitor&kat2=all

The VGA cable and pins are OK.
Look for bad solder joints on the circuit board mounted on the end of the picture tube socket. There should be transistors that drive each colors.

they are a Driver Transistors 2SD718 & a 2SB688, these are Complimentary, PNP & NPN power transistors. try Radio shack, or your local parts supplier they are quite common and have replacements, equivalents too. google for them.

I would try looking for 2SJ6357. Japanese transistors tend to drop the 2 when putting the numbers on the parts.

The parts that are missing are likely to be the convergence ICs. These are STK392-110 and should be available online from any electonics parts supplier. Expect a cost of around $25 each.

Dan

Well that means it is done. There is no magic button to stop this I am afraid. You could replace the board but cost wise just easier to buy a new one.

This is straight from the 1989 Japanese Transistor Substitution Manual.......

2SA 1011--------use 2SB 1085 A, made by Rohm

2SC2344---------use 2SD 1562A, made by Rohm

Good luck...Rob