Threshold S300 speaker output voltage 61 Vdc after fuse blow

Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.
Hi Guys,
I am Liem from Indonesia.
I own Threshold S/300 and recently accidentally I blew one of the fuses (positive rail) after I unplugged the interconect without turning the unit off first.
After I replaced the fuse and turned it on, it blew my speaker.
When I checked the DC voltage of the speaker output terminal, I found 61 Volt output!
I wonder what has caused this problem.
What parts should be checked or replaced?

Thank you for your advice.

Best regards,

Liem
 
Blown Parts

Most likely you have blown one or more output transistors.

It might be possible to locate which one by toasted emitter resistors.
----------------------------------------------------------------------------------------------------
Thank you Sir for moving me to Pass Lab forum.

Thank you very much Mr. Pass. I am glad to get response from you. Sorry for late in responding back.

I herewith would like to attach a picture showing the blown parts after I asked a repair person to open the S300.

Can you confirm if the parts in this PCB will be the only parts to repair?

The technician also checked the output transistor (PNP and NPN) and found they were in good conditions.

Thank you for your advice.

Best regards,

Liem KF
 

Attachments

  • IMG-20210109-WA0060.jpg
    IMG-20210109-WA0060.jpg
    103.6 KB · Views: 241
Official Court Jester
Joined 2003
Paid Member
impossible to answer just on base of that picture

if tech checked all OS transistors and they're good, that's great

what you need now is to clean that pcb from burns (alcohol and cotton swabs) and check all components .... practically common troublesooting routine

locate schematic ( they're around) of your exact amp FE, inform which parts are blown
 
Blown Parts

Dear Zen Mod;

Thank you for your suggestion. The technician told me that these parts needed replacements: MPS U10, U60 A42 and A92 and some capacitors and resistors.

Hopefully only these parts that need replacement.

In regards to resistors and capacitors, please suggest the best one to use as replacements.

Thank you.
 
Quality components for Threshold S300

Hi Zein Mod;

Thank you for your sending me the schematic diagram.
My technician has limited knowledge about the High End audio unit.
All he knows is to get the unit sound again and he has no concern whether the sound quality after repair degrades or not.
So, I need advices about the quality components to bring the unit sound quality back to its original or better...

Thank you and best regards,

Liem KF
 
Tantalum

standard metal film resistors

no need to change solid/block caps

replace Tantalum caps, if there, with modern electrolytic - decent branded (Panasonic, Elna, Nichicon, whatever

if needed, ask again

Dear Zen Mod;

To replace Tantalum Cap, is it better to use Mylar 0.15uF 50 v or elcap MKP 0.15uF 250 V?

It's hard to find Elcap 0.15uF from Elna or Panasonic or others here.
 
Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.