Demco demon 150

[Staybolt]

I just got ome but blows the interal fuse and some of the bride diodes check shorted. Anyone know what type they are as I cannot find a schematic on this amp? I come up with the demon 250.

 

[nomadradio]

Here's all I can find. No parts list, just the schemo. The tubes have no fixed bias, so turning down the radio's carrier may overheat the tubes once you get it running. But that's a moot point until you can get it to key up and show power.

73

 

[Staybolt]

Here's all I can find. No parts list, just the schemo. The tubes have no fixed bias, so turning down the radio's carrier may overheat the tubes once you get it running. But that's a moot point until you can get it to key up and show power.

73

It

 

[Staybolt]

Here's all I can find. No parts list, just the schemo. The tubes have no fixed bias, so turning down the radio's carrier may overheat the tubes once you get it running. But that's a moot point until you can get it to key up and show power.

73

It would help me if I knew what the diodes were and I haven't even hooked anything to this amp, and yes I know a high powered radio will damage these old amps. I've rebuild a few in my time, trust me...

 

[nomadradio]

knew what the diodes were

The rectifier diodes? The schematic shows four diodes. This is the generic full-wave bridge circuit. To use just four single diodes they would need to have a voltage rating around 1500. Highest you'll see that are easy to get are 1000 Volt. Not quite enough for this circuit. Putting a pair of diodes in series to each replace one diode as you see in the schematic is the safe way to go. Varmint and D&A both did it this way. Takes eight parts this way. I would go with the 3-Amp 1000 Volt part 1N4508. It's pretty generic, and should be reliable. Rectifiers with a lower current rating might work, but the price difference is too small to take the risk, IMHO.

73