Fender Prosonic Rectifier Question

[benjaturner]

Got a new amp today! Yay! It has this cool feature where I can select the the operating class of the rectifier. However, when I turned it on the amp was in Class A and after a while, I wanted to compare it to Class A/B. When I did this the power fuse failed immediately. I replaced the fuse and tried again, samething happened. This time I figured maybe I'm not supposed to change the rectifier settings while the amp is on. But I can't find any mention of that in the manual I downloaded.

Anyone got any ideas?

-Benja

[FenderBoy]

Re: Fender Prosonic Rectifier Question

Benjaturner- I wish I could answer your question :-(


I bought a Prosonic a few months ago. I didn't want to get one for a while do the the channel change "pop" issue but I'm happy enough with it, but I end up using it as a single channel amp. best of luck with the issue.

[benjaturner]

Re: Fender Prosonic Rectifier Question

Hi FenderBoy,

So I guess this hasn't happened to you? That means there's probably something wrong with my amp. Do you switch between Class A/B and A much? If so could you please tell me what experience you've had with it. Do you find it to be as sensitive as mine seems to be? I've literally only had the amp a few hours and this happens! I've still got a lot of figuring out with this one.

Any hep is greatly appreciated.
Thanks,
Benja

[benjaturner]

Re: Fender Prosonic Rectifier Question

Bump!

Please help somebody, I think the transformer has just blown as a result of these problems

[the guy who invented fire]

Re: Fender Prosonic Rectifier Question

does it blow the fuse everytime now?

[benjaturner]

Re: Fender Prosonic Rectifier Question

does it blow the fuse everytime now?

Worse! A capacitor has blown up completely and a Ceramic thingy has cracked it half. I daren't put a new fuse in to try again incase I do any more damage. Before this happened it blew about 4 mains fuses. Do you know what this means?

-Benja

[the guy who invented fire]

Re: Fender Prosonic Rectifier Question

Worse! A capacitor has blown up completely and a Ceramic thingy has cracked it half. I daren't put a new fuse in to try again incase I do any more damage. Before this happened it blew about 4 mains fuses. Do you know what this means?

-Benja

what kind of cap has "blown up" and what do you mean by blown up? Also, what ceramic "thingy" has cracked? Did yo put the amp on standby before you switched rectifiers?

[Gearjoneser]

Re: Fender Prosonic Rectifier Question

Is the ceramic thing the female socket underneath the Rectifier tube? The Rectifier tube is the mid-size tube, smaller than the 6L6's. If it were mine, I wouldn't switch between the SS and tube Rec without turning the amp off, or very least on standby.

If your tube socket is broken, you'll need to replace it with the same Fender part.
Before you turn the amp back on, go buy the exact same rectifier tube and exact fuse.
It sounds to me like the Rec tube was fried. I doubt you fried the Transformer, but if the amp makes no sound on the Rec side, a small component burned up. If the amp makes no sound on the SS side, I'd take the amp to a tech, along with new tubes, so they don't charge you retail on new tubes at their shop.

[benjaturner]

Re: Fender Prosonic Rectifier Question

I'm not sure what the ceramic thing is, it's on the mains PCB board and looks to be fairly early on in the electrical route. My Dad thinks it might be some sort of case around a component that gets very hot. It has readings for 220 ohms and a 10% figure. I've no idea what this means.

The capacitor has literally blown up! It's got a big lump on the side and has split with some sort of goo-y 'glue like' stuff seeping out but has dried now. It's right next to the ceramic thing that has also blown up.

This has all happened on the mains PCB board after repeatedly blowing mains fuses. I figured because of this there has to be something wrong with the power supply and jumped to the conclusion that the transformer is at fault. It's a relief to hear you say it's probably not the transformer, I've heard they're really expensive to replace.

I always put amps on standby for at least 30 seconds before turning them on, is that long enough? As this was new to me I was extra careful and the standby mode was on for over a minute. Can you put an amp on standby mode for too long?

The amp still works, infact it works better than before all the smoke came out. I've had it on for quite a while and the mains fuse has lasted longer than it has done before with no signs of it failing. I've tried the amp in all rectifier settings and it goes in them all. I'm tempted to just say 'If it ain't broke...' but I'm scared of doing any more damage, and I'm pretty sure if smoke has been bellowing out then I should get someone to look at it. An amp tech guy who's friends with my Dad said he'll have a look when he's not busy at work (He's PAing a festival somewhere this week) so I'm not sure if I should leave it off until he's had a look, it works fine as it is. What do you think?

Thanks,
Benja

[jeremy]

Re: Fender Prosonic Rectifier Question

DO NOT change the recto switch while the amp is on. you are just asking for problems by causing the voltages to jump up like that. like joneser said, at least put it on standby. you cant really leave the amp on standby too long.

a friend of mine has a pair of those amps, cool stuff

[benjaturner]

Re: Fender Prosonic Rectifier Question

Thanks Jeremy. I guess I should have known that from the start really. Any idea how much damage I've done to the amp by messing with the rectifier settings while it's on?

Can I just get direct replacements for the components that have blown.

Cheers,
-Benja

[Rich_S]

Re: Fender Prosonic Rectifier Question

I'm confused - does this switch change the rectifier type (tube or SS) or the operating class (A or A/B)? The "operating class of the rectifier" doesn't make any sense.

[Gearjoneser]

Re: Fender Prosonic Rectifier Question

I'm confused - does this switch change the rectifier type (tube or SS) or the operating class (A or A/B)? The "operating class of the rectifier" doesn't make any sense.

That amp has both those options on the back panel. I'm assuming that you need to have the amp on standby before switching either of them.

My guess is that the Rectifier tube is just about completely shot. They get really hot, so it'd be no surprise if it's on it's last leg.

The best solution is to change every tube in the amp, get the leaky capacitor swapped out either by a pro, or you if you're capable. I have a feeling that ceramic thing was the heatsink around a large transistor, possibly the SS Rec.
I'd replace that too, although it's not an urgent necessity. The cap should be replaced ASAP though.

[Rich_S]

Re: Fender Prosonic Rectifier Question

Come on, guys. He said the ceramic thingy said "220 ohms 10%" on it - IT'S A POWER RESISITOR. Possibly one of the decoupling resistors in the power supply. I'm going to look for a schematic, then post again.

[Gearjoneser]

Re: Fender Prosonic Rectifier Question

Did you buy this amp locally, or off Ebay? Nobody should be selling you an amp that's got those kinds of issues. Rich is right about it being a resistor, so if it's damaged, there's too much current flow somewhere, which is what would cause fuses to blow.

Take it to a tech. It needs a full checkup. Kinda unfortunate for a new aquisition, but I'm sure you'll like the amp, once it's healthy again.