Tube amp question

[tehfunk]

Okay, this isn't exactly a stompbox question, but it involves the same kind of knowledge and I need some prompt answers.. I might be buying a vintage tube amp in a couple of days, (early 1980s Marshall), I am just worried that because it doesn't have a warranty that it is going to break on me and I am going to be screwed, as in having to pay a lot of money to fix it. I am going to play it first, but I just wanted to know, how often do vintage amps break? Is there a good chance of capacitors going out, transformers? If there was a problem with a part that would break down within a month, would I be able to notice that in the amp when playing it? Lastly when I go to try it out tomorrow, anything I should look for in particular as bad signs, or even good signs?
Thanks you for your help!

[zachomega]

Make sure the bias cap has been recently changed.  While you are in there, you might as well replace the filter caps. 

Retube regularly (more often with el34's)...You might get 3 to 6 months with regular play...more if you play the amp less.

With some preventative maintenance, vintage amps are probably less prone to going down than modern amps. 

-Zach

[tehfunk]

What if it's all original, except for the tubes? I was saying that if I bought it and took it home without doing anything to it, ignoring the tubes, is it likely something will break? I noticed that the transformers are very expensive, so how do you break one, and how long do they last? BTW, I don't gig, and I won't be pushing the amp hard.

[ACS]

Afaik, about the only way you'll kill a transformer is if you get the ohmage wrong and don't have enough load on there - it'll over heat real quick, and yes, this will be pretty obvious when you test it.  There will be bugger all (if any) output!!  Have a sniff inside too - any acrid burnt smell is bad news, just don't confuse this with the nice hot smell of the tubes

Good luck!
Aidan

[ambulancevoice]

if the amp has standby, use it, it helps pro long the life of the tubes, doesnt matter to much for the pre amp tubes but it helps with the power tubes
turn the power and standby on (so the power is technically off but the heater supply is running, and use indicators for both power and standby, so you know) and give the amp 30 seconds to 5 mins (longer the better i think ive heard) for the tubes the heat up to there efficient running temperature, instead of shoving over 100v to 300v's on them instantly even though they havnt heated up enough for the electrons to pass effectively across the electrodes (they are electrodes right? plate grid cathode etc)

although, if this thing has a tube rectifier and no standby, it shouldnt matter tooo much but it couldnt hurt to install one

also, if you travel with the amp, take out the tubes and put them in a box or something with lots of foam (they enjoy being comfortable when there on holiday from the grueling work they endure in the amp gives them a longer life too!)
not right after youve played the amp for like an hour, cause the tubes will be to damn hot to handle!
but yeah

also, id replace the filter caps (discharge the old ones first before you desolder/replace them!) because there probably old and weak, and put them in a nice place to retire too! put some new ones of the SAME TYPE (if there 600v caps, replace them with 600v caps, unless the power is like 350v or something, then 450v will do)
if any component looks old and worn out or damaged or just plain  then replace them
also, if the sockets are plastic or whatever, replace them with ceramic sockets, i think R.G. said there the best ones to use.
yeah

check this out too, has alot of stuff on tubes
http://www.geofex.com/gtramps.htm (g tramps??? ok R.G.)

[tehfunk]

Okay, interesting, I appreciate the help? Any more answers to my questions???

also, id replace the filter caps (discharge the old ones first before you desolder/replace them!) because there probably old and weak, and put them in a nice place to retire too! put some new ones of the SAME TYPE (if there 600v caps, replace them with 600v caps, unless the power is like 350v or something, then 450v will do)

How much do you think this will cost me if I bring it to an amp techinician?

[MarcoMike]

what is a technician?!?! just kidding....
but it's not a difficoult thing to do, you just need to be careful as everyone told you.
which kind of amp is it? for a 50W a full set of caps will cost you less than 20$, (the technician will probably say they were 40$ and then charge you for his work... lets say 100$ would be ok ... )

as usual, I suggest the DIY way, this way you are also learning something new!

if it is a 100W I have a theory which I could never verify... 100watters have the first filtercaps which are in series, with voltage divider resistors (please correct the term if it is awfully wrong) across them. these resistor are actually connected from B+ to ground, so they should act as discharge-resistors when the amp is off. this makes me think that 100Watters should not retain voltage when off. any idea?

[ambulancevoice]

Okay, interesting, I appreciate the help? Any more answers to my questions???

also, id replace the filter caps (discharge the old ones first before you desolder/replace them!) because there probably old and weak, and put them in a nice place to retire too! put some new ones of the SAME TYPE (if there 600v caps, replace them with 600v caps, unless the power is like 350v or something, then 450v will do)

How much do you think this will cost me if I bring it to an amp technician?

i have no idea
didnt even know there was such a job, amp tech
i just thought the tech's people described where just regular electrician people...
but, it would probably cost more if you took it to a technician than if you did it yourself
and its not hard replacing stuff, just gotta be REAL careful and pay full attention to everything since your working on a vintage tube amp (high voltages!!!)

...now i look back at your questions...
well, depending on the condition of the parts in the amp (tubes, caps, transformers, sockets, pretty much everything), the amp could last 5 mins after using it or it could last 6 months, but like i said, replace anything that looks old and worn out and just plain bbbblllleeaaauuuggghhhh

if a part was to start to @#$% up, you will be able to notice it
either the amp wont sound ...right
or, there will be no sound!

bad signs would be things like weird smells or fumes/smoke emitting from the amp
red heaters instead of orange (they glow red instead of orange, which is BADDDD, means the heater is MELTING)
weird noises and stuff (could indicate bad components and whatnot, dirt and dust causing problems etc)
thats all i cant think of

good signs? well, if it sounds good, thats a good sign
if it runs smoothly in various settings, another good sign
if the components still look good, thats well, good
you get the idea

[drewl]

Which model, 2203?
These amps are very easy to work on and parts are readily available.

I've fixed dozens as well as built a few.

[tehfunk]

actually it's a 2204.. I really like all the tips, I am going to the store in a couple of hours.

[petemoore]

  I'm 1/2 inclined to recommend what I did:
  Bought used SLP 100w, used it very often for ~12 years, tested new tubes against the old tubes, put the new tubes in only because they were new/ perhaps because such a big amp not distorting, the sonic subtleties were not perceptible, but I believe the old tubes were doing what the new tubes did at that time, +/- tube construction differences [small, they looked very similar] old tubes got swapped into other amps...
  Get it and run it, if it acts wierd [loss of tone, clicks, noises, excessive hum, static...rebeef the output section.
  But the other side of that coin is that new tires is new tires...if you're going on a long trip, and you don't have a second 'vehicle'...yer screwed if the first one breaks. It might not tell you anything except 'I don't light anymore, and now I'm blowing fuses'...{Long OT about 90's Marshall 50w choke..early tests on amp under warranty]. Warranties provide little entertainment at a gig...good for a good 10 seconds of chuckle.
  That amp has almost certainly been 'tested', so the tranny's, if working, will pass most tests.
  Having spare tubes is just part of the equation..eventually, having the new ones w/old spares is a +.
  Caps aren't that expensive, if can verify to your satisfaction they Are Discharged and draining, changing them isn't that hard..
  For my limited exp., I've always been able to notice when capacitors tell the tale of demise, [and twice, I refused to listen, resulting in..start from scratch with new tubes and caps, one got rebuilt into an 18w  ] amp acts funny one way or makes some kind of unusual behavior or noises, I've seen amps operated with faulty capacitors and tubes, catastrophic failure caused by capacitor neglect also.
  Anyway you get to working with tubes and transformers and gigs and kinda want the output section to be able to pass muster..probably does = usually does IME, I've seen amps run with extreme neglect on stages...also I've seen the backup amps make fill-in appearances too ...just plug in...here.
  ya never really know what that cap has seen unless you just put it in there..could have been cryogenically dehydrated for all we know...confidence inspiring.
  if it works and passes the initial tests [plays for a couple hours] it'll probably do that for a good long while.
   

[tehfunk]

Let me get this straight, you guys are saying that when I get the amp home (if its from the early 80s), that even if it's sounding good, that I should have the caps changed? I am also wondering, for someone who plays on quiet settings and does not gig, how often will I have to repair the amp, say if the tubes and caps are new? Like when will it need to be fixed again? How often do you guys have to fix your amps? I am starting to become a little hesitant...

[frequencycentral]

Just buy it - it'll be fine. Trust me on this.

[Mick Bailey]

I have a tube tester and even with plenty of hours use tubes don't tend to fail. I tend to leave them alone if the amp sounds ok.

I've found that most amp faults are either hum due to electrolytic failure, or are intermittent faults due to connection problems, either with solder joints or connections such as sockets.

If there are no obvious problems, leave it be.

'Servicing' an amp is a misguided concept and at it worse amounts to nothing. What is there to do? Oil change, tappets, transmission flush, air filter, air-con recharge, new pads and disks? It isn't a car. If it ain't broke, don't fix it.

The early 80's amps used LRC electolytics in the PSU and and the tops bulge before they eventually fail. Early indications are above average hum levels. Marshall sell Ruby caps as a replacement (they need wrapping with masking tape as they're slightly smaller). Also, the pots get a little noisy, but this is a nuisance rather than a fault you need to rush out to fix.

[signalpaths]

I would buy the amp

with the amp i would also buy:

1. several good books on troubleshooting and repair of vintage tube amps

2. filtercaps

3. extra tube quads

join ampage forum
become your own tech

if you want an amp with a warranty buy a new one

if you want a amp that sounds good buy the Marshall

[ambulancevoice]

Let me get this straight, you guys are saying that when I get the amp home (if its from the early 80s), that even if it's sounding good, that I should have the caps changed? I am also wondering, for someone who plays on quiet settings and does not gig, how often will I have to repair the amp, say if the tubes and caps are new? Like when will it need to be fixed again? How often do you guys have to fix your amps? I am starting to become a little hesitant...

maybe, if the caps look old, worn etc, or if there cheap paper ones, replace them
also, look at this on filter cap replacing http://www.diyguitarist.com/GuitarAmps/filter_caps.htm

also, did you read r.g.'s tube amp page i linked you to?
cause that may answer some of your questions
including stuff about repairs and shit

[kurtlives]

I think you are over analzing this purchase way too much. Just buy the amp!

For the transformers always connect a load...Thats really all you have to worry about.

Look inside, whats the lead dress like. Might want to reflow a few joints and maybe neaten things up a bit.

Yes I would change the filters. Tube amps filter caps should be changed every 10yrs. Not a big task just be careful to discharge the caps. You could even add bleeder resistors in there so if you ever want to work on/service the amp again you don't have to worry about discharging the caps.

Other than that you should be fine. Of course if you see a really "dodgy" component it would probably be a god idea to replace it but you should be fine. Vintage amps are always fun.

[ambulancevoice]

Vintage amps are always fun.

[mac]

Vintage amp are, in most cases, more reliable than modern ones, remember how hard Pete Townshend had to hit their amps before they stop working! A fly stopping over your new Bassman reissue and it is dead.

If you are paying a fair price for it, do not hesitate and take it to a good technician, or have it inspected by a someone. If PS, OT iare ok, and there is no sign of a fire, the extra bucks you pay will worth it in the long run.
After all, vintage gear is becoming a good retirement plan.

mac

[m-theory]

Take it to a good tech and have it gone through.  That's the only way to be certain that it's going to be reliable.  At the very least, the filter caps need to be replaced.  If one fails while the amp is under load, it could very well take out the tubes and output transformer along with it.  You cannot tell by looking at caps whether or not they're any good, unless they're physically deformed and/or leaking.  If they're older than 15 years, they should be replaced. 

Once you've had a tech check each component for tolerance drift, tightened up anything loose, reflowed connections, completely tested the tubes, you'll have a solid, dependable amp.