Flea Market Checkout
From mgarvi–(at)–anix.com Sat Oct 25 22:17:44 CDT 1997
From: mgarvi–(at)–anix.com (Mark Garvin)
Newsgroups: rec.music.makers.guitar,alt.guitar
Subject: How to check amps at flea markets and pawn-shops
Date: 25 Oct 1997 17:25:59 -0400
Xref: geraldo.cc.utexas.edu rec.music.makers.guitar:164644 alt.guitar:204618
(Prev thread was “Fender Vibro Champ”):
> Puma
>I saw a used one of these in a pawn shop. They were
>asking 175.00. It is missing one of the tubes.
>Is this a good amp? Is this a good price?
A couple things occurred to me while reading the post above. It’s not
always possible to listen to a flea market or pawn shop amp, so there
are some things you should be aware of:
The most important thing in an old amp is the transformers. If they
are toasted, you’re in trouble. Speakers are next, but those can be
replaced more easily.
The very least you should do when buying an amp is to (first) check
the fuse to make sure it’s the right value, and then make sure that
the tubes light up, etc. Sometimes not possible to plug a guitar in,
but listen for normal background hiss. This is some indication (but
NOT a guarantee) that the transformers are OK.
NOTE!: Very old amps that have not been powered up for a while may
have bad electrolytic (filter) caps. In that case, I recommend
NOT powering the amp up. Having a good repair shop do the testing.
Do not pound power chords thru an amp that is not making any sound!!!
Three !!!’s warranted. This often means that the speaker has been
blown or disconnected. On some Marshall amps, the impedance selector
comes loose. Players who crank the amp and play loud to see if they
can get any sound will often fry the output tubes, the output
transformer, or even tube sockets (Really!). This happens due to
high voltage spikes that can occur when no load is connected (flyback
effect like high voltage generators in TV sets). Arcs occur and
carbonize anything in the path (hence socket replacement, etc).
This seems like common sense, but I’ve had amps come to my shop that
were supposedly checked by pro service men–they’ve had 30 amp fuses,
aluminum foil, pieces of wire, etc. in the fuse holder. This
sometimes means that the owner couldn’t find the right fuse and the
service shop didn’t check. Other times it means that the amp kept
blowing fuses of the correct value, and the owner ‘corrected’ the
problem with a short circuit.
Ex: I saw an old BF bassman that had developed a short in one of the
output tubes. When it started blowing fuses, the owner put in a 20
amp fuse. So instead of blowing the fuse, the amp melted down the
filament windings on the power transformer. A bit more expensive than
a fuse. (The inside of that Bassman also looked like a giant roach
motel! They had Barco Loungers and a shuffle-board court set up in
there!…But that is a revolting subject.)
The original post mentioned that one of the amp’s tubes was missing:
Some tube amps (like the Champ) have tube rectifiers. Service shops
occasionally install internal solid state rectifiers and pull out the
rectifier tube. When this is done, the socket should at least be
taped over, and marked with a warning not to install the tube rect.
Watch for this. Fender tube charts show which is the rectifier socket.
It’s usually a tube that starts with a ‘5’ (like 5AR4 or 5U4), but not
always (not in the Champ).
The down side of the solid state rectifier substitution is that s.s.rects
do not drop as much voltage as tube rectifiers. Wall socket AC voltages
have been getting higher over the years (often 127 vac in NYC), so
old amps’ power supplies will usually run high to begin with. Most
modern output tubes are not as tolerant of high voltages as the older
American or European brands, so many flame out from over-voltages–
esp 6V6’s (Champs, Deluxe Reverbs). Swapping in solid state rects
compounds the situation cause they drop less voltage. That mod can
usually be reversed easily by a competent repair shop. Amps that still
run high can sometimes be helped a bit by using a different rectifier
tube (see old alt.guitar.amps articles for info).
I recommended listening to make sure the amp was at least making normal
background noise (hiss). Well, that’s not always possible at flea markets
that have no AC. Keep in mind that those amps may be toasted, so the
value will be hard to determine. If the amp makes *some* sound, at
least there is a chance that the transformers and speaker are good.
Those are the most expensive components. Old transformers are often
impossible to find, so replacements can require cutting larger holes
in the chassis and other ugly mods.
Very old amps have two-conductor AC cords. I have some reverence for
vintage amps, but unless the amp is for display only, I never flinch
at replacing those with new 3-wire grounding plugs. Have a competent
tech do this. Better consider the shock hazard if the amp is not
properly grounded. In fact, make sure that ALL your gear is grounded
correctly–it only takes one badly wired device! Yes, guitarists have
gone out in a blaze of glory because of wiring problems (supposedly
incl Keith Relf from the Yardbirds).
One last trivial thing, since the original thread was about Champs…
Many have blown speakers. Tube Champs used 4 ohm speakers and had
no screen resistors. The technical reason for this is beyond current
scope, but I recommend finding 4 ohm replacement speakers. Using 8-ohm
speakers in a Champ cranked to 10 will often fry the output tubes.
I’ve also posted about this in old alt.guitar.amps articles, so I won’t
elaborate here.
I hope that helps to make buying decisions a bit easier. The little
old lady who only overdrove her Tweed Bassman at church on Sunday is a
myth, but I’ve found some nice old Fenders, Ampegs, etc at flea markets–
even in NYC! It helps to look for a couple of those things to make sure
repairs won’t exceed the value of the amp.
MGarvin
Mr. Moron improves his signal to noise ratio by 12.6%
From jesPAmile–(at)–adtel.net Sat Oct 25 22:17:51 CDT 1997
From: jesmiley
Newsgroups: rec.music.makers.guitar,alt.guitar
Subject: Re: How to check amps at flea markets and pawn-shops
Date: Sat, 25 Oct 1997 18:05:13 -0400
Mime-Version: 1.0
Content-Transfer-Encoding: 7bit
Xref: geraldo.cc.utexas.edu rec.music.makers.guitar:164687 alt.guitar:204661
Mark Garvin wrote:
> (Prev thread was “Fender Vibro Champ”):
>
> > Puma
> >I saw a used one of these in a pawn shop. They were
> >asking 175.00. It is missing one of the tubes.
> >Is this a good amp? Is this a good price?
>
> A couple things occurred to me while reading the post above. It’s not
> always possible to listen to a flea market or pawn shop amp, so there
> are some things you should be aware of:
>
> The most important thing in an old amp is the transformers. If they
> are toasted, you’re in trouble. Speakers are next, but those can be
> replaced more easily.
>
> 8< snip a lot of good advise >8
>
> MGarvin
>
> Mr. Moron improves his signal to noise ratio by 12.6%
I would also advise smelling the thing. Burnt electronics has a distinctive
odor. So give it a sniff, look at the fuse, turn it on, give it another sniff
and listen.
J. remove the PA to reply
From mgarvi–(at)–anix.com Sat Oct 25 22:18:12 CDT 1997
From: mgarvi–(at)–anix.com (Mark Garvin)
Newsgroups: rec.music.makers.guitar,alt.guitar
Subject: Re: How to check amps at flea markets and pawn-shops
Date: 25 Oct 1997 20:23:39 -0400
Xref: geraldo.cc.utexas.edu rec.music.makers.guitar:164676 alt.guitar:204649
>Mark Garvin wrote:
>> …not always possible to listen to a flea market or pawn shop amp, so there
>> are some things you should be aware of:
>>
>> The most important thing in an old amp is the transformers. If they
>> are toasted, you’re in trouble. Speakers are next, but those can be
>> replaced more easily.
> jesmiley
> I would also advise smelling the thing. Burnt electronics has a distinctive
> odor. So give it a sniff, look at the fuse, turn it on, give it another sniff
> and listen.
Good addition, J.
I’ve also run into a lot of old Fenders with toasted screen resistors.
Less pungent odor than (more serious) burnt transformers.
MGarvin
Please excuse possible multiple post. Server problems I think.
