1970 Fender Bassman 100 went pop

[StuarDaddy]

I’m clueless when it comes to stuff like this but I have a reunion gig coming up next week after 12 years doing nothing. I got my old Bassman head out of the cupboard to see if it still powered up and the valves still lit up. Switched it on for 10 min, then flicked the standby on l, it hummed a bit then went pop inside on the part circled on the attached photo, smoke came out of the hole in the casing but the valves all still worked. Now that’s not the transformer or valve is it so what’s inside that casing??? Any helpers? 

[Bill Fitzmaurice]

The power supply caps. They were about 20 years overdue for replacement.

Edited February 6, 2019 by Bill Fitzmaurice

[StuarDaddy]

I’m assuming these aren’t a bad fix? I only had it for a couple of years before it went into hiding 12 years ago so I don’t know if they had been done before that?

[BreadBin]

Did you have a speaker connected? Apparently it's bad if you don't. 

[StuarDaddy]

Nope schoolboy error if that’s the case. It was literally to see if it powered up 🙈

[Bill Fitzmaurice]

Firing the amp up without a speaker wouldn't bother a Fender, the speaker jack is switched to short the output transformer secondary when there's no plug inserted. Electrolytic power supply caps dry out, whether the amp is used or not. 25 years is the usual life span.

[BreadBin]

Ah, I see 

[3below]

If you are ok with a soldering iron this is an easy DIY job on a vintage amp like this (usual caveats about safety etc, possible damage to other components caused by the failure).  If there is minimal damage other than the capacitors it should not be expensive if taken to an amp tech. The capacitors are inexpensive, components.

[LukeFRC]

1 hour ago, 3below said:

If you are ok with a soldering iron this is an easy DIY job on a vintage amp like this (usual caveats about safety etc, possible damage to other components caused by the failure).  If there is minimal damage other than the capacitors it should not be expensive if taken to an amp tech. The capacitors are inexpensive, components.

Given that the OP started with “what’s under here” I suggest a good amp tech may be a more pleasant experience for everyone involved. 

[3below]

On 06/02/2019 at 22:12, LukeFRC said:

Given that the OP started with “what’s under here” I suggest a good amp tech may be a more pleasant experience for everyone involved. 

An eminently sensible suggestion

[Bill Fitzmaurice]

Oh come on, you don't know what fun is until you've had 470 volts make their way through your body. 🙄

[StuarDaddy]

Bought a cheap rig to make do with while the Bassman gets fixed now. Ashdown Abm evo II with an abm 410h cab. Only £180 and it’s immaculate. So I can’t moan. Bassman goin away next week. To be fair I never liked gigging the Bassman anyway and especially not the 412 cab with it. Too delicate to be dragging round. If I don’t end up slipping back in to retirement I’ll probably keep this Ashdown until I start getting amp fever and start looking at them the way I should look at my wife

[3below]

3 hours ago, Bill Fitzmaurice said:

Oh come on, you don't know what fun is until you've had 470 volts make their way through your body. 🙄

Unfortunately Bill I have done this one  once was enough...

[Bill Fitzmaurice]

I only took a full 470 once, exploring my '65 Bassman, discovering that capacitors store charge for a long time. Working on AC outlets I probably got hit a hundred times over the years, too lazy to make my way to the breaker box to turn the circuit off. That's common with electricians here working with 110v. I suspect on your side of the pond with 220v they tend to be more careful.

[ezbass]

37 minutes ago, Bill Fitzmaurice said:

I only took a full 470 once, exploring my '65 Bassman, discovering that capacitors store charge for a long time. Working on AC outlets I probably got hit a hundred times over the years, too lazy to make my way to the breaker box to turn the circuit off. That's common with electricians here working with 110v. I suspect on your side of the pond with 220v they tend to be more careful.

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

[LukeFRC]

1 hour ago, StuarDaddy said:

Bought a cheap rig to make do with while the Bassman gets fixed now. Ashdown Abm evo II with an abm 410h cab. Only £180 and it’s immaculate. So I can’t moan. Bassman goin away next week. To be fair I never liked gigging the Bassman anyway and especially not the 412 cab with it. Too delicate to be dragging round. If I don’t end up slipping back in to retirement I’ll probably keep this Ashdown until I start getting amp fever and start looking at them the way I should look at my wife

Not a bad cheap rig. If you didn’t like gigging the bassman then it’s probsbly an upgrade.

I only gigged a bassman once when I shared a rig with the bass player from Glasvagas - to my ears it sounded amazing 

[TheGreek]

Is it this one?

https://www.ebay.co.uk/itm/Fender-Bassman-100-Amp-Head-and-Cab-4x12-Valve-Tube-Guitar-Bass-Speaker/163532155251?hash=item261346a973:g:hbEAAOSwVNNcVBVb

[goingdownslow]

1 hour ago, Bill Fitzmaurice said:

I only took a full 470 once, exploring my '65 Bassman,

Was it enough to expose your skeleton?

 

[StuarDaddy]

Yes that’s the same model as mine. Amp and cab. Mine is a 1970 one. The sound amazing, but u can’t gig that cab at bigger venues even with a DI and just using it for stage monitoring. Got to push it to much, brilliant for recording tho. Sounded great mic’d up. Used to have an old 2x15 rotec with an Acoustic B120 for gigs, didn’t look much but it was a trouser swinger!  Idiot for selling it

[BreadBin]

My first amp was the very same Bassman stack - it was bloody hard work wheeling the cab 2 miles through town on foot for band practice. 

[Unknown_User]

On 10/02/2019 at 18:28, Bill Fitzmaurice said:

I only took a full 470 once, exploring my '65 Bassman, discovering that capacitors store charge for a long time.

Roughly how long would a capacitor in an amp store charge for?  Do you have to do anything in particular to help them lose charge or just unplug the thing and wait?

Edited February 12, 2019 by Unknown_User

[3below]

11 hours ago, Unknown_User said:

Roughly how long would a capacitor in an amp store charge for?  Do you have to do anything in particular to help them lose charge or just unplug the thing and wait?

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 ...

Edited February 12, 2019 by 3below

[Unknown_User]

11 hours ago, 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 ...

Thanks for the reply.  I try not to mess around with anything that would plug into 240V!  How long is longer than I might think though?  Are we talking in hours or days?

[bartelby]

On 10/02/2019 at 14:09, Bill Fitzmaurice said:

Oh come on, you don't know what fun is until you've had 470 volts make their way through your body. 🙄

 

On 10/02/2019 at 17:36, 3below said:

Unfortunately Bill I have done this one  once was enough...

I managed to hit myself with 550v from a flashgun once. 

[3below]

18 minutes ago, Unknown_User said:

Thanks for the reply.  I try not to mess around with anything that would plug into 240V!  How long is longer than I might think though?  Are we talking in hours or days?

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.