RF T1500-1BD

[brandes.cm]

The two mylar caps in the output filter circuit are completely toast, would anyone know the value? The only number I have for the pcb is 1325-52759-05. RF support is down and can't ask for a schematic, I would guess they won't release it anyway.

Gate resistor value for the PS fets as well?

I have never seen such a mess before, apparently the guy didn't fuse this amp. The PS fets started on fire and actually cooked the paint on the clamp.

 

[Perry Babin]

From photos I have, it appears that the output filter caps are 6.8uf. I can't read the voltage. The gate resistors for the power supply are 60.4 ohms.

At least it's repairable. The following amp wasn't.
IrfanView HTML-Thumbnails

 

[brandes.cm]

Would you have a schematic for anything in that era?
brandes.cm@gmail.com

The current sense resistors Dale WSR .01 ohm, 3W or 5W? They list the same package size for both. The 5W may have the pad on the bottom of the package though.

 

[Perry Babin]

The ones in the amp photos are marked WSR-3 which are 3w resistors.

Sorry, no schematic. They weren't releasing it when I last inquired.

 

[brandes.cm]

The caps are 100V, was able read one once it was removed and cleaned.

 

[brandes.cm]

Still having issues with this amp. If I just apply B+ and gnd or Rem and gnd I have no issues. I can see the gate drive signal in the power supply. One side goes from gnd to B+ and the other is referenced above gnd and switches from here to B+. Looks to be a nice square wave at 50% duty cycle.

Should the sync signal be sawtooth 100Khz? I am basing this off the 1000BD schematic I have.

 

[brandes.cm]

Cancel that, I see the sync signal is suppose to be a low pulse just as it's acting.

I pulled the rectifiers and still the same reaction of my supply going into over current mode. Maybe the transformer is garbage?

 

[Perry Babin]

If the drive signal on the gates doesn't go all of the way to ground, the PNP drivers are likely defective.

I've never seen a sawtooth waveform on the sync pin but I rarely check that pin. The frequency will be twice the frequency of the output frequency on pins 13 and 16.

 

[brandes.cm]

I was getting the 100Khz carrier and sync signal mixed up. The sync looks to be generated from a set of Flip-Flops from the carrier signal. It's divided by 2 first then the sync is generated.

I will just pull that board again and replace the drivers.

 

[brandes.cm]

All working now, thanks again.
Bad drivers causing my grief.

 

[JLH]

From photos I have, it appears that the output filter caps are 6.8uf. I can't read the voltage. The gate resistors for the power supply are 60.4 ohms.

At least it's repairable. The following amp wasn't.
IrfanView HTML-Thumbnails

How does something like that even happen? How did that amp continue to work long enough to cause that much damage? That is some unreal stuff there - wow.

 

[brandes.cm]

Typically not fusing the supply correctly. I'm a person to fuse with a smaller than suggested because a fuse is cheaper than an amp.

 

[Perry Babin]

This can happen with proper fusing. When an FET fails, the source leg fuses open and produces a small arc. If the conditions are right, the arc can grow and you have essentially the same thing you have with a welding machine. If the conditions are right, the arc can be sustained for quite a while. I've seen it happen but the arc never lasted long enough to do this type of damage.