Two blown fuses in one day

[hpfish10]

Good to know you replaced bias supply it crackles now. I need to replace my bias supply since i could not make my left speaker crackle even after swapping back plates.

[chungjh]

I replaced the bias supply on one back plate that was blowing fuses and it works very well. But, I noticed that the other panel some times goes quieter than the other and sometimes refuses to crackle no matter the gain. So, I replaced the bias supply for that one too, and now everything is good again.Roger tells me that this is the first failure of the regulated bias that he has been using for the past several years.

[kingdeezie]

Interesting development. I’m wondering if the amp wasn’t the culprit the whole time.

Tubes are wonderful, but in amplifiers they can go nuclear. I used to have Manleys and one time a tube went rogue.

Took out a resistor in the amp when it went. Had to have it repaired.

Hope things stay working well for you! Enjoy.

[John V]

I’m currently in the process of updating my system. For years I’ve used a Crown Macro and Tact 2.2xp. The Crown, not well regarded in the
High End, but worked well for me over the years.
Anyhow, I’m waiting for a pair of Atma Sphere MA-2’s to be returned from AM for some cosmetic upgrades. As to the pre amp, I just received
a used Anthem STR.
CD/Streamer is next, not sure what I’ll get there.
As to vinyl, I have a Goldmund Reference Turntable that I recently refurbed.

[chungjh]

John

What pre and power amp are you using now?

[John V]

Got it, I misread your post. Sorry. It does sound like clipping.
The CLX may be easier to drive than your SL’s. Its also hard to compare your CJ to an OTL amplifier like the MA1.

I ran into a similar situation at one point. I bought a pair of Mac
MK1.2Kw monoblocks, they would not drive my U1’s without clipping.
I guess the Macs couldn’t handle the rising impedance of the SL’s
so I sold them and moved on.

[chungjh]

John

You misunderstood me. Both speakers are distorting. Problem is not in the speakers because SLs work great with a backup class D 300W amp

[yoshi]

The new regulated bias supplies have much more output than the older bias supplies. I could operate the old bias supplies at 70 % (1:30 on the bias dial). The new regulated bias supplies on my new 560 base-focused panels start to pop on heavy bass material at 9:30 on the bias pot. So. Expect there will be a difference in the new bias pot setting. Your Altitude and humidity levels will affect the setting level.

Ken

[John V]

Is the other panel operating properly? If so I would try swapping backplates to try and determine it the issue is with the panel or the backplate.

[chungjh]

I get crackles when the bias is turned up.

[John V]

When you turn up the bias can you get to a point where the panel crackles?

[chungjh]

I replaced the bias supply of the back plate that blew the fuse. However, the Conrad Johnson Premier 12 amp (140W) monoblocks still refused to play. Thinking that there is a problem with the amp, I borrowed Brooklyn Amp, a class D 300 W amp and it played fine. So, I was convinced that something was wrong with Premier 12 and returned it. Because Conrad Johnson is near me, they lent me their LP140M, a newer 140W mono block. This time it made sound. However, I hear distortion at a normal volume. I am either clipping or overdriving, but I played at this volume before with X250.5 Pass Labs amp without problems.With my tiny room (9×11), I thought 140W would be sufficient,especially many SL users drive them with Atma-Sphere MA-1, which is also 140W. I am very puzzled. I know these Conrad Johnsons have no problem with large Mark Logans CLX. Is there something unusual with SL speakers compared to other ESLs?

[kingdeezie]

Nice! Good luck. Hope everything going well!

[chungjh]

I was afraid to put the new fuse in. Dr. West sent me a new bias supply and an electronic service guy is soldering it in. I should have it tomorrow.

[kingdeezie]

Any updates? Did the new fuses blow as well?

[chungjh]

How long after manufacture was the bias supply replaced on your U3?

[grg3939]

Model U3 (the only pair ever made) over 20 yrs old. But I updated the toroids and PX panels and the bias supplies (2011).

[chungjh]

2016 M545

[lotus123]

@grg3939, what vintage was your SL that had a bia supply failure?
What model?

[grg3939]

Hi. Very easy to change it out, assuming you have decent soldering skills. Some years ago I had a bias supply fail and Roger told me that the replacement supply was of reversed polarity vs my original. Since they were a from a new supplier, I decided to order two so both speakers would have the exact same parts. (Audio Nervosa?) Besides, they are not expensive. Since the new ones had reversed the polarity, in order to maintain proper absolute phase, one simply needs to reverse the amp to speaker cable connections. If SL does not mention this, be sure to ask them if the new supply maintains the same polarity as your failed one, or if it is reversed. Depending how old your speakers are, you may already have the newer supplies anyway, which, in that case you do not need to worry about this.

[chungjh]

I am going to have the bias supply shipped to me. I don’t think it is difficult to replace.

[kingdeezie]

Did Dr. West just recommend you send it in for repair?

[chungjh]

I think the fuse blew before I hooked it up to CJ amp, which was playing fine in a friend’s house. This speaker had lower bias for a long time compared to the other one. When I exchanged the fuse with the other speaker, this bias supply must have burned the fuse from the working speaker. I don’t think it is the amp, because the speaker sounded very weak from the get go. Everyone on the SLOG should look out for this possibility if it happens.

[kingdeezie]

Seems odd the bias supply would just go bad to that extent where it’s blowing fuses.

Is the Conrad amp brand new? I would have it checked out.

[chungjh]

Yesterday. So, these regulated bias supply must not have been used in the old SL speakers.

[John V]

Was the response to you from Dr. West within the past few days?

Thx,
John

[chungjh]

I have ordered new fuses. But, Dr. West thinks there is a possibility that the bias supply may be defective. These bias supplies have been in use for the past several years but non have failed yet.

[kingdeezie]

I would get some new fuses to start, obviously.

Then disconnect the amplifier and replace the fuses. Turn on each speaker and see what happens.

If the left speaker blows again, its the plate.

You could then switch backplates to see if the issue follows the plate amp.

If you’ve had the amplifier hooked up during the two blown fuses, I would suspect the amplifier to be the problem.

[chungjh]

I sold my last amp a couple of weeks ago, so I hadn’t been playing any music for a while. Today, I hooked up a new Conrad Johnson tube amp and the left speaker from the get go was very quiet and didn’t respond to turning the bias dial (no crackle). I switched the fuse from right speaker to left and no change. I put the fuse back to the right speaker-now even the right speaker doesn’t respond to bias dial. I check the fuse and both are disconnected. Could it be that my left bias pot is some how burning any fuse that goes in there? Or am I just very unlucky?

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