Threshold S/300 Repair

[Cambe]

Hi,
Trying to help a friend with his S/300. One channel went out. Looking for a repair tech. recommendation to send it to.

 

[gary s]

Jon Soderberg at Vintage Amp Repair in CA is the go to man I believe. Link below.

Contact Us – Vintage Amp Repair

NP has mentioned him in the past in other Threshold repair threads.

 

[Cambe]

Thanks Gary!

 

[Nelson Pass]

Yes, Jon Soderberg was a tech at Threshold for years.

Knows where most of the bodies are buried.

😉

 

[gary s]

Get your friend to get the amp upgraded while getting the repairs done - well worth it.

 

[Cambe]

Thank you Nelson and Gary. I will try to urge him to do the upgrades. 🙂

 

[audiodoc]

My Threshold 300 II left channel went out this past Sunday.The sound just faded away. No sudden lost of sound. I still get the turn on thump from the same channel. I got the amp apart and have checked all of the individual parts on the input board (after removing them).No burned parts. Capacitors check OK.Plan to replace caps anyway. Could be one leaking. Power transistors all check as good .Any help would be greatly appreciated.

 

[gary s]

Check PSU DC rails, does the 300 have DC rail fuses?

 

[audiodoc]

I checked all fuses, continuity of ps wires.When a fuse goes-sound stops abruptly.I still get turn om thump so I think something is bad on the input board.

 

[Mikerodrig27]

What is the DC offset?

 

[audiodoc]

I have no idea. Never had any issues with the amp. No chance to check before it went down.

 

[gary s]

Compare components on the good right channel input pcb to the faulty left channel to see if you can highlight/measure any big differences. Also check all solder connections on the pcb.

 

[audiodoc]

All components seem to test fine on pcb but I have replacements and will change them all: transistors and caps of exact values. Hope it works.