1970 Fender Bassman 100 went pop

[fleabag]

On 10/02/2019 at 19:06, ezbass said:

Yep, you,know when you’ve had a full 240v, 13amp belt 😬.

Got the T-shirt.

I had a 2 bar fire , remember them ?  ( we're back to the early 70's now ) and i switched it on and the elements didnt glow red as per normal. So i thought i'd tap the elements to see if it was bad connection. I used a dinner fork.  I realised this was a bad idea when i ended up sliding upside down,  on the opposite wall , after being hurled at it

[EliasMooseblaster]

On 12/02/2019 at 21:02, 3below said:

a. Longer than you think.... well designed kit will have a 'bleed' resistor to discharge the capacitor on power down to aid safety.  Resistor failure and/or dielectric absorption may give you a nasty surprise

b. Discharge through a resistor and led or the 'proper tool'  e.g. https://www.amazon.co.uk/ANRIS-Discharger-Protection-Electrician-Discharging/dp/B074PQF6GC  - you can make your own.

c. or, as my colleague took great joy in demonstrating, put a screwdriver across the terminals with a direct short circuit (he was/is braver than me, even assembled a bank of capacitors for extra effect ).

Let's be careful out there ...

A computer tech once advised me I could drain the (admittedly much smaller) caps in a PC by unplugging and then pushing the power buttom - if there's enough juice left in them, you may even see some of the LEDs on the casing light up briefly. Could you do the same with an amp, or would that be inadvisable?

[cattytown]

On 13/02/2019 at 09:21, 3below said:

I would always use a discharge tool or at the very least check what (if any) voltage they are showing with a multimeter set to highest range voltage.

You mean checking with your tongue isn’t an appropriate method?

[3below]

18 hours ago, cattytown said:

You mean checking with your tongue isn’t an appropriate method?

Depends on what result you are hoping to gain

[fleabag]

Deep fried bassist ?

[Cathode_Follower]

On 10/04/2019 at 16:29, EliasMooseblaster said:

A computer tech once advised me I could drain the (admittedly much smaller) caps in a PC by unplugging and then pushing the power buttom - if there's enough juice left in them, you may even see some of the LEDs on the casing light up briefly. Could you do the same with an amp, or would that be inadvisable?

Not advisable. The tubes will only suck the capacitors dry while they have the ability to draw current, which depends on the cathode heaters still being warm, and they tend to cool-off pretty sharpish after power is removed - within about 5 seconds. Even if you just straight-up unplugged the amp from the mains while leaving your power and standby switches on, you could still easily wind up with a few hundred volts sitting on the power rail.

@Unknown_User - Capacitor self-discharge varies wildly depending on the design, anything from minutes to hours to maybe days.

Always ALWAYS check your voltages before poking around. Multimeters are inexpensive and really if you're opening up anything electrical you should own one regardless.
 

Edited April 23, 2019 by Cathode_Follower

[Billy Apple]

I got told off by Marshal for pulling my Super Bass out the sleeve to have a gander.