wanted amplifier module triac

[Phil Woollard]

I have a amplifier module with a blown triac, thyristor im not sure what they are as i cant see any details or values on the component, the offending articles are bolted to the heat sink, there being four of them. The sound function is still working but at two thirds volume.
could any of you techy guys tell me which type they are and the best place to buy replacements
Thanks Phil

[Detlef Giessmann]

Hi Phil,

you have to remove the heatsink to be able to name a name.
With the circuit diagram you are able to do it.
Without name is not possible.
Manufacturer and model year of the amplifier is not bad!
With the component name I can look for a shop.
If the component is very exotic, I can look in my portfolio.

Greetings,
Detlef

[Phil Woollard]

I will have a look again tomorrow Detlef and get back to you many thanks Phil

[Phil Woollard]

Well Detlef , the writing was very faint indeed and reads as follows I think! PDS 36 , G401D VW, CHN 236, it looks like it was made by "ST", it has three legs and is 16mm x 10mm x 5mm (without the legs), it looks like a mosfet with the two semi circular indentations on the body sides..... regards Phil

[John Hill]

Hi Phil, ST is STMicroelectronics an American/ Italian company.
CHN 236 I think is the number of the component, which would indicate it's a MOSFET.
Will have a look later, regards John

[Phil Woollard]

Many thanks John regards Phil

[Detlef Giessmann]

Hi Phil,

I have to look.
Housing is definitely TO220.
I'll get back.

Greeting,
Detlef

[Detlef Giessmann]

Hi Phil,

this component is not present in the current databases.
Probably the part has been manufactured specifically for the amplifier.
Also, a licensed production is possible.
The name CHN probably means Chinese production.
The question is whether additional components are defective in the amplifier.
With the wiring diagram a similar component could be determined, but this is a gamble.
I don't have this component in my inventory.
TO220 transistors may include internal components such as diodes.
Without wiring diagram, the reparation is not possible.
Contact the manufacturer directly. That's still a possibility.
Use and effort is the question.

Greetings,
Detlef

[Phil Woollard]

There must be an equivalent mosfet/transistor? Many thanks for your time Detlef regards Phil

[Detlef Giessmann]

Hi Phil,

there are different types of MOSFETs / Transistors.
Please only install the same, otherwise other components are destroyed.

https://en.wikipedia.org/wiki/MOSFET

Greeting,
Detlef

[John Hill]

Hi Phil, this is tricky one, the PDS means it is a P channel field effect transistor, the 36 will be the max input volts. Cannot identify the next bit but the CH is also a mosfet number. Mouser is the UK dealer for ST semiconductors but most of their listings is now in surface mount form.
P type mosfets are common in the output/power stages of amps, controllers and the like. You may end up substituting a general purpose one. I assume it looks blown and as you say the circuit works but at reduced volume, this would indicate the rest of the components are ok. What caused it, first thoughts would be a short in speaker wiring. Are both speakers working ?, could something have moved and caused a temporary short?
The standard of component today is very good and usually only fail for a reason.

Hope this helps, still looking

Regards John

[Phil Woollard]

Hi John, interesting stuff, both speakers are working although the offending channel is down on volume by say 40%, I could live with it but you know how it is I want this thing to be perfect .
How it happened, ....a rouge 3mmm screw shorted the speaker output connections which resulted in the triac/mosfet/transistor thingy blowing clean in half, but despite that everything else is working just fine!
These units are very robust indeed, I do tend to ad a fuse to power supplying leads, which has proved invaluable on more than one occasion.The power supply module is well protected as standard with fuses on each output.
A substitute component is the way forward , I just need to know what to order as I quite like repairing these things myself ..regards Phil

[John Hill]

Hi Phil, that makes sense, not many survive amp output shorts. The fets will be in complimentary pairs, one P and one N channel. You have blown the P fet and that output is running on the N fet. This would account for the 40/50% reduction in volume in that output channel.
There are plenty of general purpose fets on EBay, 100volt , 20 amp peak. You may end up replacing the pair as they are complimentary .
You could email the part number to Mouser or STmicroelectronics and ask if they have a replacement/equivalent

Regards John