Newbie Question

[keefriff]

I have an old Gibson Falcon amp. Last time I played it, it sounded good, but had a habit of shocking me through the guitar. Anyone have any ideas what I'd be looking to correct/adjust?

[Chuck H]

You probably have a leaky capacitor. I would replace the filter capacitors (they go bad with age). Test the film caps for leakage and replace any that are leaking. Change the power cord to a three prong type with a proper chassis ground.

Chuck

[keefriff]

Thanks for the advice

I think i could find and replace the capacitors, but what are film caps and how are they tested? if you could dumb this down for me, i'd be in your debt.

[keefriff]

I forgot to mention

it had a habit of blowing fuses. would this still point back to the parts you suggested looking at?

[GibsonLover]

Change the power cord and filter caps first and the fuse problem may go away. For the film capacitors, you can measure DC voltage on each side to determine if they are leaking at all. There is usually a high voltage on one side, so don't be alarmed, but the other side should ideally be zero. Make sure your meter is on a range to measure something close to zero accurately. If they measure very low DC voltage, and are about the same from cap to cap, leave them alone. If one ot two have oddball readings or you judge them as 'high', change what you need. If you need to depend on this amp, change them all. It's more expensive, but if go through it once, it'll last for your grandchildren. If you sell, it's a good selling point that the new owner won't have to spend money on.

[keefriff]

took the panel apart

a couple of questions.
1) i don't know a filter cap from my ass or a hole in the ground i guess. I've attached some pics going from right to left, showing the guts. Which are the caps or other pertinent parts I'm looking for
2) Replacing the power cord with a 3 wire (ground ) unit makes lots of sense, but what would I ground the extra ground to on this chassis?

Thanks in advance for any advice.

[txstrat]

No offense, but if you don't know a filter cap from your a.. or a hole in the ground, you might better bring the amp to a qualified tech.
Inside tube amps are lethal voltages which can store up for a loooooong time. These can KILL YOU.

[keefriff]

No Offense taken

times being what they are, i can't really afford/justify having someone else look at it. and being curious as I am, i'd like the opportunity to learn something new. At this rate, the amp hasn't been plugged in for likely 6 or 7 years, if thats long enough for any charge to dissipate.

[txstrat]

OK I assumed you've played it recently when you've been shocked. Anyway, pluggin' it in for a second can be enough to charge up the caps with lethal voltages. Keep that in mind and keep one hand in your pocket while you work inside the amps chassis (use a chopstick to move things around).
Filter caps for instance should look similar to this: Atom Electrolytic Capacitor 20µF / 500V
or this: Illinois Electrolytics Capacitor 22µF / 500V
Find them and replace them with the proper value. BTW the pics you uploaded are too small to identify anything.
Put the ground of the three prong cord to one of the power transformers bolts (and therefore to the chassis). There might be a ground connection already.

[stokes]

The shock is probably from a leaky "death cap",the cap connected to ground from one side of your ac line.Changing to a 3 prong cord will elliminate this cap and the resulting shock.As txstrat says,if you dont know a filtercap from..... you shouldnt dive in and start monkeying with the amp,at worst you could get dead,at best you could foul up a good amp,sure the caps may be discharged now,but at some point you have to fire it up to do any diagnostics,get some books,learn some basics first.Jack Darrs book is a good start,you can down load it free at Jack Darr Book, chapters 1 - 8

[Chuck H]

Keefriff

Doing your own amp repair is no better a way to save $$$ than taking out your own kidney. By my guestimate unexperienced individuals doing their own repairs end up with new problems that they created (by not knowing what they're doing) about fifty percent of the time. Sure, it seems easy to do something rote if you can only get good info. But in practice it's impossible to cover every single variable you may encounter so that we may prepare you for this work. An understanding of the circuitry becomes invaluable when little questions pop up. And we here have all experienced someone asking questions 'the wrong way' because they don't really know what they're doing. In other words, it's easy to misunderstand an answer or advice when you didn't even know how to ask the question.

That said... These are not boom boxes or tape decks. There are indeed potentially lethal voltages inside your amp. Whats more is that they are stored charges and can remain in the amp even when it is turned off and unplugged. No kidding. Heed the warnings. And if you can't tell one explative from another inside your amp no one here is getting in line to send you in there. Because none of us could blithely disregard your death having been personally involved.

If you have read and understand explicit safety instructions for working on tube amps (they are available all over the web) and studied enough about the project to relate a schematic to your amps innards (schematic here):

http://www.schematicheaven.com/gibsonamps/falcon.pdf

Then maybe someone here will try to guide you through changing to a proper grounded cord and replacing the filter caps.

Again, this kind of repair on this kind of equipement is NOT the kind of thing you do to save $$$ (like doing your own tune up or painting your own house). It's the kind of thing you do because you are an inquisitive self motivated person. Not that you aren't... But right now you don't know a filter cap from... Well, you know.

Chuck

P.S. If your still set on repairing your own amp I'll need some better photo's too. That way I can draw on them and present them back to you with info.