[etcarroll]

So I moved speaker leads from indoor floorstanders to monitors on deck for outside enjoyment, and let positive and negative leads touch at right monitor on powering up the amp, blows fuse.

Replace fuse, check connections, blows fuse immediately.

Pull amp out of rack, replace fuse, nothing attached to amp while it's on bench, power up, and it blows fuse immediately.

It's a 30 year old 4B that I sent to Bryston when I bought it 2 years ago and had upgraded to 4B-ST status.

Popped cover, replaced fuse on bench, nothing attached, powered up and looked for arcing when fuse blew, (it did), but saw nothing.

Everything appears ok to my eye, but what do I know. 

I see an internal fuse at each set of speaker posts, they seem ok, though middle of right fuse is hidden from view by a cap.

Any thoughts of what else I can try before I box it up and bring it in?

Gene

[avahifi]

If you are lucky, the issue might just be an internal B+ or B- fuse blown.  Most solid state amplifiers have external speaker fuses (the ones you are blowing I suspect) and also two internal power supply fuses per channel.

If the speaker fuse is too big, then shorting the outputs will also blow an internal power supply fuse.   If one internal supply fuse is blown, then replacing the speaker fuse only can cause the amplifier output to go full DC offset and blow that speaker fuse over and over again.

Again, this is assuming pretty normal construction and layout for your amplifier.

So, maybe you should replace all the internal fuses and try one more time. Don't connect the amp to the speakers again unless replacing all the fuses results in no further fuse blowing.

Regards,

Frank  Van Alstine

[Diamond Dog]

No local service option available, Gene ? That unit is, as you said, 30 years old and it ain't gonna be cheap sending it across the border to the ancestral homeland. FWIW I had a pre that was blowing fuses on start-up - turned out to be a resistor or some such ( let me know if I'm being too technical  ) and it was an easy and inexpensive fix. I was fortunate enough to avoid sending it back to the manufacturer - the freight alone would have cost way more than the actual repair.

D.D.

[James Tanner]

So I moved speaker leads from indoor floorstanders to monitors on deck for outside enjoyment, and let positive and negative leads touch at right monitor on powering up the amp, blows fuse.

Replace fuse, check connections, blows fuse immediately.

Pull amp out of rack, replace fuse, nothing attached to amp while it's on bench, power up, and it blows fuse immediately.

It's a 30 year old 4B that I sent to Bryston when I bought it 2 years ago and had upgraded to 4B-ST status.

Popped cover, replaced fuse on bench, nothing attached, powered up and looked for arcing when fuse blew, (it did), but saw nothing.

Everything appears ok to my eye, but what do I know. 

I see an internal fuse at each set of speaker posts, they seem ok, though middle of right fuse is hidden from view by a cap.

Any thoughts of what else I can try before I box it up and bring it in?

Gene

Hi Gene

Check with Mike Pickett at Bryston but if it blows immediately I suspect the output devices have been shorted.

james

mpickett@bryston.com

[budcook]

You can also contact:

Dennis Hawkins
usaser@bryston.com
Bryston Service USA
79 Coventry St
Newport,VT.05855
(802) 334-1201

This is where US Bryston gear is serviced.  He replaced a power switch on my old 4B a while back.  Dennis may be able to give you some advice.

[etcarroll]

Thanks all. 

The fuse in question is the right fuse replaceable from out side the body of the amp.

There are also 2 internal fuses, I guess I can try to get the right side one replaced, though not sure my fat fingers can work it out, will have to tear apart my garage looking for my fuse puller.

Gene

[etcarroll]

Unfortunately I live in SE PA. in the middle of nowhere. The nearest authorized dealer is in Wilmington DE.

I bought the amp from a stereo shop in Queens, NY, guess I could drive it back to him if needed.

G

No local service option available, Gene ? That unit is, as you said, 30 years old and it ain't gonna be cheap sending it across the border to the ancestral homeland. FWIW I had a pre that was blowing fuses on start-up - turned out to be a resistor or some such ( let me know if I'm being too technical  ) and it was an easy and inexpensive fix. I was fortunate enough to avoid sending it back to the manufacturer - the freight alone would have cost way more than the actual repair.

D.D.

[etcarroll]

Frank -

When you say "..... and also two internal power supply fuses per channel", are you saying 4 internal fuses? I see two internal fuses located by the speaker posts, I hadn't noticed 2 others. But I'll try replacing all I see.

If you are lucky, the issue might just be an internal B+ or B- fuse blown.  Most solid state amplifiers have external speaker fuses (the ones you are blowing I suspect) and also two internal power supply fuses per channel.

If the speaker fuse is too big, then shorting the outputs will also blow an internal power supply fuse.   If one internal supply fuse is blown, then replacing the speaker fuse only can cause the amplifier output to go full DC offset and blow that speaker fuse over and over again.

Again, this is assuming pretty normal construction and layout for your amplifier.

So, maybe you should replace all the internal fuses and try one more time. Don't connect the amp to the speakers again unless replacing all the fuses results in no further fuse blowing.

Regards,

Frank  Van Alstine

[SHV]

"It's a 30 year old 4B that I sent to Bryston when I bought it 2 years ago and had upgraded to 4B-ST status."
*********
What is the warranty policy on Bryston upgraded analog gear?  Sound like the best option is to call Bryston, Vt.

Steve