BOGNER ALCHEMIST/ Thermal PT Fuse

[plexi50]

I have a Bogner amp that has no secondary voltages. I see that the PT says it has a thermal protection fuse in it

Where would this fuse be?

[sluckey]

Probably underneath the paper. Locate the primary wires then start peeling paper back until you find it. It may not look like a regular fuse.

I'd make darn sure that I could measure line voltage across the primary leads before I started peeling.

[LooseChange]

I had a Crate with the fused tranny blown. I dug down one wrap found it. I bypassed it and all was good.

[plexi50]

This is a strange one. I had removed the PT from the chassis to get the bell ends off the PT. I looked at it a while and peeled back the primary side paper to get a look at the primary lead connections right at the bobbin itself. I put my DVM clips right at the bobbin solder points and checked for any loss of continuity from each primary lead and found no open circuit. I then connected a small breaker i have along with a clipped AC cord to fire up the PT at that point. The PT showed secondary voltages all as they should be for a good PT. I put the bell ends back on the PT and remounted it on the chassis. I hooked up all previously exhisting wires and flipped the ON switch. I now have a working amp except that i have a screwy tone cycle that runs up and then down and starts all over again. Tommorow i will use my DVM to see weather there is a fluxuation in AC voltage. The plates VDC is solid at 400 VDC. There is a small transformer or filter on the PS board that i dont understand what it's function is. Thats all i can think of right now

[eleventeen]

Sure looks to me like the type of inductor found in a low voltage switching power supply. [google images, "switching power supply' if you're not familiar] And then you have a 68000 ufd 10 volt cap..? How many terminals does that little inductor have? Are there any power semiconductors in TO-220 or TO-3 case in that area? Any ultra-low value resistors (eg; .1 ohm, .3 ohm, something like that?)

[FYL]

There is a small transformer or filter on the PS board that i dont understand what it's function is.

Could be part of a PS dedicated to channel switching etc.

[plexi50]

I fixin to check to see if that is dedicated to the channel switching. Man it's funny to hear all those relays trickle when you switch the amp on

[FYL]

I'm pretty sure that's the case. Check the "Digital board" marking next to a board socket and what looks like analog/digital boundaries. This is standard mixed-mode board design minimizing digital-induced noise.

[plexi50]

Ok i found the up and down swirling  problem. The Digital board is wacked and making all kinds of noise and funky sounds. Out of control. Gone with all pots on the DB CCW. I unplugged the board feeding at the DSP pots so i would not loose the clean channel. I find it hard to believe that this is made by BOGNER.  Sounds good but just looks like another chinese board with a ton of problems waiting to happen.  What was the main PT issue? None that i can figure. Maybe i just had a bad PT main plug on the board and unplugging it and putting it back on solved it. I dont know. Maybe the main fuse was not making a good contact in the IEC recepticle.  It looks tight. Anyway!