Utter novice looking for answers to easy questions:

[Brit01]

I use a light bulb too, but I've never seen it light up.

last night I discharged 2 x 400V 680uF caps. Lit up the whole street for 3 seconds and a few sparks flew when the leads touched the cap!!!

 

[ChrisA]

Some amps have these drain resistors built-in but many do not, so it's a great habit to check the volts on the power supply caps (with one hand) before diving in to work.

If you ever find an amp that does not have these. Stop. Go find a 100K resistor and solder it across the power supply. If you do a little analysis you may find you can use a lower value resistor but the high value one can almost always be used. There is no reason not to have a permanently installed bleeder resistor.

I'd say the same about two prong power cords. If you see one, stop. get the three prong grounded cable wire it in before doing any other work on the amp.

I can go on... Hammon built amps with no fuses on the AC. That was nuts even in the day. If you see one of these amps, fix it.

 

[Wavebourn]

Dumb question- why are standard IFs what they are? For example, most AM broadcast band radios have it at 455kHz, FM at 10.7 MHz. Why not 450kHz and 11 MHz?

There were 456 KHz snandard here, and 465 KHz standard in Europe. Germans used exactly 1 MHz in their Kehln receiver. American BC-348 used 915 KHz. Russian military used 500 KHz. And so on. I don't know why.

 

[Hi_Q]

You should check out the tube arrowed in the picture, it looks a little soft to my me, maybe lost all its vacuum. Whatever you do avoid touching the chassis while taking measurements. The wise words about high voltage and safety already given by other Forum members should be well ingested, like myself, many have learnt the hard way and we just want you to take care.

 

[EC8010]

How about a tube head who is a radio ham and has worked as a radio design engineer for the past 36 years?

Thanks for a more detailed explanation from the horse's mouth.