How to troubleshoot an amp before buying

[samato]

I might go check out and possibly buy a silverface Twin Reverb someone is selling.  All I know about it right now is that it's "not working" and one speaker is "not wired".

If you were planning to go evaluate something like this what would you take with you and how would you start troubleshooting it? 

[Dave]

Hmm, wierd situation.
Let's say you do some quick troubleshooting and you determine what the problem is. Or worse yet, it turns out to be a fuse. Then all of a sudden the owner decides to back out because now its a working amp.

I wouldn't do anything more than a quick once over and maybe have a look at the fuse.

Word is getting out. More and more I am noticing that people are quick to overprice an amplifier if it has tubes in it.

Pawn shop guys are the worst. If its a tube amp, its got to be worth $999.

Dave

[samato]

Good point.  If I fix it or do anything that makes it seem like it could be an easy fix I could be screwed.

Okay, so new question: what's a good price to pay for a silverface Twin Reverb that's "not working".  Let's assume it's worst case scenario.  What would be the worst case scenario by the way?  Blown PT or OT?  Let's also assume it's all there - tubes, speakers, etc. and cosmetically average.

[Willabe]

Yes, most of the time, PT, OT, and choke (altho most chokes that MI amps use are less then speakers/and some/most tubes) cost the most, then speakers/tubes, then cab and then chassis. Then tube sockets, next R's and C's but, as long as your not going to use anything fancy, mojo hoodoo'y stuff, not much $. Same for wire, cheap.

Sometimes if a trany is bad you can smell that it burned out, even see it. Look at the tube sockets, both sides (top/bottom) and see if they look burnt. Look at the speaker cone for ripes or tears, make sure the basket frame and magnet look good and not banged up or distorted/bent /warped. Make sure the magnet is not loose. You can take a small 9v batt. and touch it to the speaker (but just for a second, don't leave it on there. Speakers don't like DCv but will tolerate this for a short little blip of juice.) to see if the cone moves. If it moves than the voice coil is most likely good. If you've never done this before try it on a known good speaker to get a feel for how it should respond.

Hope this helps you.
         
               Brad         
       


   

[phsyconoodler]

Depends.A master volume Twin Reverb is not a good buy.If it's a non-master and doesn't have any hum-balance and tube-matching nonsense on the rear panel then there is not a whole lot that is hard to fix on that amp.
  Get a price that reflects the fact that it's 'not working'. Groan a lot and make a low-ball offer.Then up it a little bit if the guy balks at it.
anyway,the idea is to not get too excited in front of the seller and test him to see where his lower limit is.
  If it's a pawn shop,have no mercy.If it's an elderly guy who looks like his next meal comes from the shelter down the street,be merciful.

[G._Hoffman]

I'm not sure how it goes for amps, but for guitars the general rule of thumb is that a guitar that needs work can be valued by the equation;

V_c = V_pr-C_pr-F

Where:

V_c = value in current condition
V_pr = value after professional repair
C_pr = cost of professional repair
F = Fudge factor (a little extra for the bother)  

For instance, I was looking at a D35 yesterday that needed about $400-500 worth of work, and after all the work was done would be worth $1400-$1600.  Before the work, we told the customer a retail value of about $800-$1000, so about $600 less.  (He wasn't looking to have us buy it, but was simply looking for a rough estimate of the value, so I had no financial stake in what I was telling him.)  

I would assume that for amp, it is not much different, except for the issue of the relative difficulty of finding the problem with an amp.  With a guitar, I can come up with a reasonable estimate in just a couple minutes of looking at the guitar.  With a guitar, the work takes longer than the estimate.  Amps seem to be just the opposite, most of the time.


Gabriel

[Ritchie200]

Gabriel,

Sorry a little off topic for a sec...  You mentioned that the D35 needed about 4-5 hundred of work to make it worth more.  I'm trying to think what you would have to do to it (or any guitar) - that would not affect original finish, construction, etc.?  Sorry for the noob question, I've just always heard hands off on vintage stuff.  I realize a D35 is not vintage!  I guess it depends on the guitar?  Like a 70's LP that is not a collector, but needs a fret job to make it playable?  Maybe I just answered my own question!  Hijack over!

THanks,
Jim

[jojokeo]

Hi Jim,
Hijack back on - Did you just come accross a 70's LP?! Either way, re-fret that baby & get to shreddin'! I really don't like it when people buy stuff and hoard it away to never play or use it. Many collectors can't even really play anyway. Same when people come accross some good ol' amplifier and you see the thing parted out on eBay for the almighty extra dollars they hope they can get. Hijack off.
Keep following that cathode  - J

[samato]

I'm not sure how it goes for amps, but for guitars the general rule of thumb is that a guitar that needs work can be valued by the equation;

V_c = V_pr-C_pr-F

Where:

V_c = value in current condition
V_pr = value after professional repair
C_pr = cost of professional repair
F = Fudge factor (a little extra for the bother)  

For instance, I was looking at a D35 yesterday that needed about $400-500 worth of work, and after all the work was done would be worth $1400-$1600.  Before the work, we told the customer a retail value of about $800-$1000, so about $600 less.  (He wasn't looking to have us buy it, but was simply looking for a rough estimate of the value, so I had no financial stake in what I was telling him.)  

I would assume that for amp, it is not much different, except for the issue of the relative difficulty of finding the problem with an amp.  With a guitar, I can come up with a reasonable estimate in just a couple minutes of looking at the guitar.  With a guitar, the work takes longer than the estimate.  Amps seem to be just the opposite, most of the time.


Gabriel

I think that equation makes sense for amps too.  By that equation the amp might be worth about $0!  Or maybe he needs to pay me to take it!

Anyway, he didn't get back to me so it doesn't matter this time I guess.

[jjasilli]

Ditto to Gabriel.  I would assume for bargaining purposes that the amp needs new iron, tubes and filter caps (Unless you get a money back guarantee for dead iron, e.g.)  Figure the cost for those repairs in that model amp.  Go to eBay and try to find Completed Listings for a repaired (not pristine amp of that type).  Use Gabriel's formula to determine if you could re-sell the amp and recoup your total outlay & labor value.  If barely, it's a marginal deal unless you really want such an amp. 

[samato]

I really don't want such an amp.  In fact, I can't believe I was considering it.  

Well, let me clarify.  I love the sound of a Twin Reverb.  I might even say there is nothing better for the sound I want...

BUT....

... There is no way I'm lugging one of those things around to gigs.  Plus, it's too darn loud!  (though I think they still sound good turned down.)

[TIMBO]

Hi guys, I found a valve junior in a secondhand shop in mint condition (very rare to find a valve amp anywhere in australia thats CHEEP )i know that here the s/hand shops sell a lot of their stuff for about a 1/3-1/2 of what they are new. I bought it for $170 US ( about the same in Australian dollars)  . Had a quick play, sounded CRAP but worked. I even got the guy to take off 20 bucks, paid cash  . When i looked at it and did a quick math and worked out what the parts would cost me to buy, Cab $40, Speaker $40, Valves $30,Iron $80 and other bits $20 as well as a lot of the hard work was done :laugh:i had to buy it.I had a look on ebay here and did not find one VJ for sale. Lots and lots of SS stuff and any of the Valve amps were near new and cost big $$$$.I modded the VJ to a hot rod and now have a great little amp, total cost of amp and mod $280(new about $500) :grin:So if it was me GO FOR IT,I've got to believe that here in australia when the SS stuff hit our shores all the valve gear was thrown in the dump You guys seem to have an endless supply of old amps to be tempted by, and so have you asked yourself "DO I REALLY NEED ANOTHER AMP". Thanks

[samato]

I guess things are a lot different in the US because I would consider that too much for a Valve Jr. here. I got a Fender Pro Jr. used, mint, for $200.  I guess if it does what you want that's what really matters though.

[Willabe]

Timbo,

I still have a hard time understanding what you and others around the (I'm in Chgo. Il. US) world have to go through/pay just to get the parts you need. I need to be more thankfull and stop complaining as much as I sometimes do.



           Brad            


              

[samato]

Me too, I always think everything is too expensive but I guess we've got it pretty good in the US compared to many other countries when it comes to musical equipment prices.  Are salaries higher on average in Australia?

[rafe]

I always figure if it isn't working and the owner didn't bother to fix it. I'm going to low ball it. you really never know what the issues are until you get into it. If they are asking $400.00 and It's only worth a hundred to me I don't insult them by offering $100.00 I'll usually pass.

[samato]

I don't consider low ball offers insulting.  If other people do that's their problem and they can tell me no.

I used to buy and sell a lot of motorcycles and if I was afraid of low balling I wouldn't have done nearly as well as I did.  Things are only worth what a person is willing to pay and cash talks.

I've never understood why people get insulted by low offers.  I never did.  Actually I find it offensive that people get insulted!  

Seriously, let's say you think your amp is worth $1200 and I offer you $550.  You are insulted by my offer.  Well, sorry but $550 is still a lot of money in my world.  If that's not acceptable to you just refuse it.  No need for emotions, just move on. 

You'd be surprised how many bikes I bought like that and I don't feel bad about it; not one bit.

[rafe]

I guess the equation was off. I'm real good at making a deal too, and can read a seller pretty well. I answered an ad for a couple guitars and amps one of which was a supro thunderbolt (that's why I called)
The owner was interested in selling the more modern equipment and had pretty high prices on them but I was interested in the TB it was covered in dirt had a mouse nest behind the chassis and it was rusty and out in a shed in the backyard. I had brought $400.00 in cash and my checkbook. I asked what she wanted for it. She said she didn't know, I kept pressing her and she said make an offer.....I offered $60.00
and she took it. It cleaned up well needed electrolytics and is now a STELLAR amp has original RCA's including rectfyer..so it's an early one.If she had asked for a grand, I would not have offered $60.00 and if she had looked on E-bay at that time she would have been asking that....the were going for more than that. I have met more than a few people who got real upset(nasty) at a low-ball offer, so I guess what I was trying to convey was that it's thinking on your feet that counts. I agree with you that I would never be insulted by a low offer.

[Dave]

Was she a single mother on food stamps? If so, you really got one over on her, good! 60 bucks buys a lot of ramen noodles and a bottle of flintstones vitamens for her 10 snot nosed little losers.

I'm just kidding of course, but I thought I'd make my comment a little over the top to illustrate a different side of the low ball process.

Dave

[rafe]

Not at all if she was I'd of offered $30.00  She inherited it all from a deceased husband (boyfriend)
and to be honest I was afraid the mice were in the chassis and ate it up and pissed all over the speaker so I bid on it as a learning project. It just turned out way better than I hoped or ever imagined...I am sure the dead steel player is smiling on me and is glad it was me that got it .....