Bugera 6260-212 help!

[g1]

I take it you have no power resistors to use? They are pretty cheap. Power resistor something like 100ohm 10watt and a couple alligator clip leads is all you need.
If not and you have the time, turn the standby switch to "play" position and leave it for awhile. Check the voltage on the high voltage caps in half an hour or something. If more than 10V DC, wait longer.
Is there a schematic for this model that you can post?
Exactly which model is it? Infinium?

[frpax]

I take it you have no power resistors to use? They are pretty cheap. Power resistor something like 100ohm 10watt and a couple alligator clip leads is all you need.
I don't have any of those items, but I suppose I could go to Radio Shack and get them.
If not and you have the time, turn the standby switch to "play" position and leave it for awhile. Did that about 5 hours ago when I removed the chassis. Check the voltage on the high voltage caps in half an hour or something. If more than 10V DC, wait longer.
Is there a schematic for this model that you can post? I don't think Bugera makes them public, but maybe they now do.
Exactly which model is it? Infinium? Non-Infinium model. Regular 6260-212.

Answers in BLUE

[frpax]

OK! I'm making progress! After removing all the hot glue on the various connectors, I got the PCB that has the preamp tubes on it mostly out. I could get a good look at the solder side of it and I didn't see anything glaringly bad... it all looked OK to me. I took pics for you. The order that the pics are in are in RIGHT to LEFT order:

[g1]

My understanding is that it is very similar to the 6262 so I have attached that schematic.
Bugera_6262_Schematic.pdf

It's tough to tell about the solder joints without having the board in your hands with a magnifier.
I've pointed at one in your image, but it could be just the picture or a shadow.


Here's another example of some bad joints, but they are not always so obvious.

[frpax]

My understanding is that it is very similar to the 6262 so I have attached that schematic.
[ATTACH]38868[/ATTACH]

It's tough to tell about the solder joints without having the board in your hands with a magnifier.
I've pointed at one in your image, but it could be just the picture or a shadow.
[ATTACH=CONFIG]38869[/ATTACH]

Here's another example of some bad joints, but they are not always so obvious.
[ATTACH=CONFIG]38870[/ATTACH]

g1- I looked at that joint very carefully and it appears to be the same as the others. So perhaps it was just the way it looked in the pic.

All of the solder joints on that board look fine to me. None of them are slightly discolored or duller in appearance than the others and no sign of any arcing.
On the other side of the board, all of the resistors and other stuff look to be brand new. None looked burned or charred in any way.

Now, are we sure that it is something on this board that is failing?
When it did malfunction (before I tore it apart, obviously) and I unplugged the guitar and then plugged it in the the FX Loop IN (as Enzo told me to do) and the volume came back, that test was to isolate whether the failing was on the preamp side or the power side of the amplifier, correct?
And because all the volume DID come back that meant that it indeed was something on the preamp board, correct?

Now, if I've got all that right, then my question is, because of the sudden loss in volume, does that mean that the likely culprit is one of the preamp tube solder joints? It would seem to me that this is so, because it is acting like there is a bad preamp tube, correct?

SOOoo, what if I removed all the preamp tubes and just reflowed the solder on each of the joints for each tube? 5x9=45 solder joints. What do you all think?

[g1]

Now, are we sure that it is something on this board that is failing?
When it did malfunction (before I tore it apart, obviously) and I unplugged the guitar and then plugged it in the the FX Loop IN (as Enzo told me to do) and the volume came back, that test was to isolate whether the failing was on the preamp side or the power side of the amplifier, correct?
And because all the volume DID come back that meant that it indeed was something on the preamp board, correct?

When you plugged your guitar into the FX return and it worked, that verified everything after that jack, which is basically the power amp.
Seeing as you went ahead and removed the preamp board, I figured it prudent to check the solder on the sockets. From the description, they are fine.
This could be as simple as a dirty/oxidized switch in the FX loop switching jack. Running a short patch cord between FX send and return jacks, then playing through the regular input is a good test.

[frpax]

Running a short patch cord between FX send and return jacks, then playing through the regular input is a good test.

Argh! that means putting the whole thing back together just to check that? Not to sound snarky, but the amp is only a little over a year old and has always been kept inside my house. Wouldn't a dirty/oxidized switch in the FX Loop be rather unlikely?

[DrGonz78]

Use your ohm meter to measure across the switching contacts of your effects send/return jacks. That is one way to test them without putting the whole thing back together. You are wanting to measure just under an ohm of resistance across each of the tip and the sleeve contacts while they are latched shut(no cable inserted).

[Enzo]

One advice I give to my trainees is this:
never think up reasons not to check something.

However unlikely something may be, if it is one in 10,000, remember, there are several tens of thousands of the amps, and SOMEONE gets that one in 10,000 unit.

A switch can be dirty electrically without being dirty in a didn't sweep the floor sense. There can be a small bit of debris in the contacts that worked its way into the contact area, there can be a film of some sort from the manufacturing process. If you smoke cigarettes, the tar in the smoke condenses on everything in your home, including the jack contacts.

If you have been operating the amp while taken apart thus far for testing, no reason you cannot poke a cord into those jacks in that condition. Otherwise, to assemble it, you don't need to go all the way, mount the board, put one or two pot nuts back n, and any small machine screws that serve also to ground some part of the board should be installed.

[frpax]

Ok, I'm not sure how I go about checking ohm resistance on those when the jack is an enclosed unit. Like this:

But I did measure the ohm resistance on the top and bottom leads that are sticking out from the board (not the ones on left and right, because those look like anchoring attachments) and both of those measured at .486 ohms each.

[The Dude]

I drew lines on the jacks where the pins SHOULD be shorted together with nothing plugged in. Jacks do vary, so I can't be 100% positive about this, but a good 99%. Hopefully it will help.

[frpax]

I drew lines on the jacks where the pins SHOULD be shorted together with nothing plugged in. Jacks do vary, so I can't be 100% positive about this, but a good 99%. Hopefully it will help.

[ATTACH=CONFIG]38888[/ATTACH]

I'll give it a try!

[frpax]

I'll give it a try!

OK. so I with the ohm meter probes (?), I ran them across touching the leads as you indicated. I got the same readings as just touching the top & bottom of each. 0.486 ohms each one.

[The Dude]

I'm not sure what "touching the top & bottom of each" means? That aside, what do you read if you just touch the two probes together. I'm thinking your meter does not zero.

[frpax]

I'm not sure what "touching the top & bottom of each" means? That aside, what do you read if you just touch the two probes together. I'm thinking your meter does not zero.

When I touch the to probes together, I get ZERO ohms. So I'm thinking it is working correctly.

By "top & bottom" leads, I mean this:



Doesn't matter which probe on which lead, but when I read the resistance between the top and bottom (as pictured), on each one, I get a reading of .486 ohms