2. amps-preamps
  3. 1235884396

Strange amplifier problem

Dear mates,
I started to experience a strange problem with my amplifier. Here is the description.

1. I'm listening to the music, everything is OK. Then I make a break for about on hour or two. Want to listen again, but there is no sound, though all tubes are glowing.

2. I check the CD player (change tracks, switch off and on, etc.), it is OK.

3. After some time I see a spark near the IEC inlet and check the fuse - it is blown.

This problem occurs for the second time during the last week. It is obvious that something inside the amp makes the fuse blow.

Some time ago I noticed another problem - when the amp is running, the left output transformer runs warmer than the right one. I wrote the dealer and the manufacturer, but company's president answered that this was normal because the left transformer is closer to the tubes (!!!), though this is not the case - they are symmetrical. The company's president either does not know what his company makes or deliberately ignors my problem in order to rule out any attempts to bring the amp back to him.

My numerous questions about the transformers and fuse remain unanswered.

Before bringing the amp to the dealer, I will appreciate any opinions of those who encountered similar problem and to whom such symptoms are familiar.
transl

Showing 7 responses by transl

transl OP
156 posts
 
Newbee: The amp does not show tube plates glowing red, and there is no strange sound. I will try to insert the stock output tubes (KT-66) to see what will happen next.

Cyclonicman: I use aftermarket power cords (VH Audio Flavor Four and AirSine).
transl OP
156 posts
 
Good idea!

...Inserted the stock KT-66 tubes... So far, so good. The X'formers are barely warm - but the left one is still a bit warmer than the right one.
transl OP
156 posts
 
Swampwalker:

My observation: the connection at the IEC is often poor because the position of the IEC socket at the back of the amplifier is often very awkward and inconvenient - e.g., at the side and not in the middle of the amp's back, which causes excessive tension of the power cord.
transl OP
156 posts
 
Ther amp has an autobias feature.
transl OP
156 posts
 
This is not a Danish, but an Italian amp.
transl OP
156 posts
 
Yes, exactly. One side still runs cooler.
transl OP
156 posts
 
The stock output tubes are Golden Dragon Retro KT66 (Shuguang?). Good tubes, slightly warm.
I also tried vintage grey glass GEC KT-66 tubes. As they are very old, I admit that though they were sold to me as NOS/NIB, some of them may have lost some vacuum or might have undergone other deterioration due to old age. They sound marvellous, more airy, deep and intimate than the stock tubes.
I also have clear glass GEC KT-66 tubes. Unlike the grey glass variety, they sound very dynamic, fast and articulate, if a bit harsh and clinical. Quite unexpected for GEC tubes (unless they are faked).
The stock tubes don't have such air and depth as the grey glass GEC KT-66 tubes, but sound very deep and consistent,

The amp also uses two 5687 driver tubes (in came with NOS Raytheion "orange paint" tubes which I replaced with NOS TungSol tubes) and one 6922 tube (I use Amperex JAN 7308 "green paint").

I did not have an opportunity to listen much with the stock tubes, but so far it does not blow the fuse.
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