Fender Prosonic Rectifier Question

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benjaturner

New member
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
 
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.
 
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
 
Re: Fender Prosonic Rectifier Question

Bump!

Please help somebody, I think the transformer has just blown as a result of these problems
 
Re: Fender Prosonic Rectifier Question

does it blow the fuse everytime now?
Click to expand...

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
 
Re: Fender Prosonic Rectifier Question

benjaturner said:
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
Click to expand...


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?
 
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.
 
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
 
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
 
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
 
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.
 
Re: Fender Prosonic Rectifier Question

Rich_S said:
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.
Click to expand...

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.
 
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.
 
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.
 
Re: Fender Prosonic Rectifier Question

I couldn't find a schematic - fender.com only has the owner's manual. Go download one, if you don't already have it.

I'd be interested to see if the amp really switches between class A and class A/B, or if it's fixed bias/cathode bias. HTe marketing type get those confused all the time. See "Is the Vox AC-30 really class A? " on the Advanced Tech page at Aiken Amplifcation

Antway, of the three modes on that switch, which one presently work and which don't? That'll help narrow it down, but you're gonna need a tech, or a friend who knows his tube amps.
 
Re: Fender Prosonic Rectifier Question

Thanks for all the posts so far, been really helpful. I've just left it now, I don't really want to do any more damage than I already have. My Dad knows a good tech and I'm going to take it to him, have him look over it and then do whatever he recommends.

Does this mean that I shouldn't worry too much about the possibility of the transformer having blown? I've heard they're really expensive and I'll be gutted after just spending £679.00 on it. If I did attempt to get hold of the components and do the fix up myself how difficult is a 'heat sink' (thanks Rich S!) to get hold of? I guess the cap won't be difficult to find and I can order valves pretty easily as well.

To everyone who's familiar with the amp, how much potential damage have I done by changing the rectifier knob while the amp is on? Could this lead to blowing the transformer or atleast damaging it beyond repair? The amp still powers up and works fine for a while until the fuse blows. Does this show that the transformer, atleast, still works fine?

Thanks for all your help so far,
Benja
 
Re: Fender Prosonic Rectifier Question

I think that if the tranny was blown, the amp wouldn't even have a hint of idle noise......100% dead. You're doing the right thing. Just leave it alone till a qualified amp tech looks at it.
 
Re: Fender Prosonic Rectifier Question

Cheers Gearjoneser,

It pains me to admit, but I think this one is way over my head. I'll have to leave it and let someone who actually knows what they're doing to sort it out. As a matter of princible, I'd like to fix all my gear when something goes wrong, I figure that's how I'll learn about it but I suppose by doing so (in this case atleast) I risk doing damage that I can't afford to get fixed.

I'll let you know what the tech says.

-Benja
 
Re: Fender Prosonic Rectifier Question

Benja, Sorry to not post for 2 weeks here. I avoid switching the class on the back of the amp when it is on. I had done it a few times when I first got it but now i see it could maybe cause a problem.

If I want to switch classes now I turn the amp off. Good luck with the repairs on yours.
 
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