Need help with repair

[Bogeytomd]

Hi guys and gals, I'm new to the forum and looking for some help. First of all i can solder but know very little about tube amps so I'll guaranteed ask some stupid questions. I bought a home built tube amp years ago and it has developed a constant hum which I'm assuming are bad filter cap(s). I'm going to just replace all of them. The amp is about 20 years old after all. Its a single ended el84 amp I'm assuming putting out about 5 watts. My question is that I'm having trouble finding caps of the same values that are in there now. How much leeway do i have on that? What will the effects if any be? Also I'm open to any general observations you have about the amp on general. i know very little about what it is.

Its not letting me upload photos or even one photo. says file is too large. Any tips?

[Papa Jim]

What you are taking pics with you need to set for lowest pixel count, least resolution, least quality, or else somehow use a program or app to reduce the file size of the photos you have. This way the files will be small enough to then attach. Does the amp have a name on it which may be used to search for a schematic? Is it a copy of a known amp? Do you have a schematic? Worse case give the value and voltage rating of the filter caps and someone more knowledgeable than me can help you I'm sure.

[shooter]

How much leeway do i have

my "Ecap rule", go to the next higher "common" value.  Keep volts the same or more
coupling cap need more thought 

[sluckey]

Electrolytic filter caps typically have a +20% value tolerance but you need to get the same or higher voltage rating. As for uploading files, pay attention to the file size limit or the upload police will get you. 

[vampwizzard]

Bogey,

Welcome! Use a resizing program to make the images a bit smaller. 1600x1200 is good enough for most of us on the web.

Sourcing hum is a challenge. If it were me, Id listen for ticking or other splattering going on while the amp is turned on and up to see if its filter cap noise. After that, id chopstick the amp to see if there were any weird spots. Depending on the quality of the build (which we will probably see in the pictures) a few of the wise elders can make some suggestions about potential layout issues, etc.

Welcome to the journey. Love tube amps. cant get enough!

[Bogeytomd]

Any observations or suggestiona are welcome

[tubenit]

Have you tried replacing the tubes first?

[Bogeytomd]

Yes ive replaced them all. Its a constant loud hum unlessthe volume is all the way off

[vampwizzard]

Is there no grounded center tap for the heater circuit? What are those wire nutted yellow leads from the PT?

[Bogeytomd]

I have no idea. I haven't done anything to it. This is how i got it

[st]

Is there no grounded center tap for the heater circuit? What are those wire nutted yellow leads from the PT?

Two wires are grounded at the pt (red and dark green). I'm guessing one of them is heater ct. The tapes off yellows are probably 5v rect heater.

Just to be sure, the amp has developed this hum while you had it? It didn't have it before? Did it come gradually?

[Bogeytomd]

It did not have it when i first got it but it sat for long periods without me playing it. At one point it probably sat 5 years with no play. Got it out recently and the hum was there. It definitely sounds like video clips ive seen of bad filter caps and seeing as how its 20 years old i figured replacing them couldn't hurt at the least.

[Jennings]

My little tips from one novice to another:
1) Don't Panic!  Relax and have a coffee, think everything through before acting, ask loads of questions!

As you've not touched anything and it played fine before, my money is on grounding or contact points...so..

2)  Check that all grounds are either soldered well (haven't cracked etc), or are screwed down OK.  Sometime screwed ground connections get small amounts of dirt of grime or metal corrosion which prevent proper contact...resulting in hum.
3)  Take all the tubes out of their sockets and pop them back in several times...you're doing this to try and rub off any grime or surface corrosion which may be making contact bad between the little tube pins and their sockets.  If you spot any visibly dirty or black ones, try and clean them off gently.  Also check that the sockets are gripping the pins well...loose sockets will give potential contact issues.
4) Clean the jack sockets (including any grounding tabs), and if you have some isopropanol or similar, a little squirt-and-turn in the pots can only help.

That's all good cleaning practice, and can clear up a lot of hum, crackle and pop when you come back to an amp you haven't used in a while.  If it doesn't work then you'll be confident before moving on to replacing or changing components etc.

[sluckey]

I would replace the caps with commonly available 47µF and 22µF.

[ALBATROS1234]

I was about to say exactly what sluckey just said about the caps. After you replace those if it's still there +1 on the chopstick method. This means use a non conductive stick, chopsticks are common. And are a good size, and then probe around and touch components and connections trying to see if it increases or decreases the hum. This can help you trace out bad components or bad connections. Recently I converted a 50s Silvertone r2r to a nice se amp. After a while it developed a intermittent hum. It turned out one of my filter cap connections was just slightly faulty. It worked great for months but then would periodically hum and stop. I thought a microphonic tube at first but the chopstick method proved I had a bad solder joint. Easy fix now I'm golden. Good luck

[Bogeytomd]

Anybody know what circuit this is modelled after? Controls are volume, tone, master volume, reverb. I'm curious

[shooter]

Anybody know what circuit this is modelled after?

 a schematic would help here, looking at chassis' is like lookin at Mandarin, kinda cool, just not worth hours figuring it out 

I built an SE about 5yrs ago, it was based off my imagination, was a well liked build though