Calcell HF500.2 repair

[Stream]

Hello. Have Calcell HF500.2 amp (2*500Wt@2Ohm).

Worked nice about 2 years (1*alpine SWR12, then 2*Alpine SWR12 bridged) but then suddenly "fried". I replace 8 transistors in PS (irfp044) and then amp reborn and worked well for one week...
Then strange thing started. Shaking amp (when driving) caused loud BUMP from subs. We tried to kick amp slightly - it work as drum
But it works well, when it's is in "normal" conditions (not shaking\ striking).

Ok. Opened this again and noticed some strange things:

1. One of secondarie's wire is torn and there arent about 2cm of this... I'm afraid it can short to others, yes? What to do? Repair with piece of wire and isolate? Just isolate? Or It's so serios, tht only tranformer rewiring will help?

2. When I replace transistors, the area about this was black dust, like after fire, but all part were ok, so I just cleaned them. But I also noticed, that transformer's wires were "filled with laque\dielectric" (I thougt...). But maybe it is just MELTED laque\dielectriс from wires?

3. I checked resistance between secondaries and main - it seems ok (not shorted). But who knows ok this or not when amp is

Hope You will give usefull advices and comments, thank You.
Here are some photos:

http://radikal.ru/F/i024.radikal.ru/...d5313c6c63.jpg

http://radikal.ru/F/i057.radikal.ru/...f553028279.jpg

http://radikal.ru/F/s52.radikal.ru/i...e4e52264e0.jpg

[Perry Babin]

With one meter probe on the B+ terminal of the amp and the other probe on the secondary center tap (or a non-bridging speaker terminal) can you twist, push, pull on the transformer and make the meter read near 0 ohms intermittently?

[Stream]

Perry Babin,
After I twist, push, pull it, resistance drop to 0 or 100-200 ohms and then rising slowly (???).

Here is my short video with measuring results:
YouTube - Calcell hf500.2 repair issue

It's shorted trafo, right?

[Perry Babin]

When it shorts, it goes to (near) 0 ohms. After the short is broken, the meter is likely seeing a charging capacitor. It is discharged every time the windings short again.

If you pull the two red windings well away from the core, can you still make it short by pushing/twisting?

[Stream]

Do You mean something like this?
http://radikal.ru/F/s55.radikal.ru/i...584354a137.jpg


Now I see only "1" on DMM !
Do you think, I can fix toroid and windings with hot glue, isolate those wire pieces and use this?

[Perry Babin]

Yes, like that.

If you cannot get it to go to near 0 ohms now, it may be good enough to use as it is. I wouldn't worry about the single open conductor. It's not ideal but it shouldn't cause any problems. If you have epoxy, brush a thin layer over the windings in that area. I wouldn't use hot glue. Make absolutely sure that you cannot make it short again before applying the epoxy.

If it fails again and a replacement isn't available, then you can re-wind it.

If it has four 25 amp fuses (or whatever it has), you may want to reduce them to four 10 amp fuses and drive around with it a day or so (listening at low to moderate volume) to make sure that there are no other problems. This will help protect the power supply FETs if there is another short. If it's OK for a day or two, you can go back to the original fuses.

[Stream]

Just Imagine - this amp HAS not fuses! I realized this today...
Thank You!