Tubes do not warm up. No sound out of amp.

[mexidan]

I have a Bugera 333 and recently i have been able to turn on the amp but cannot get to the tubes to warm up at all. i have checked the fuse and it seems fine. i dont want to go out and buy new tubes until i know for sure that i need to. can anyone help me figure this out?

also i was having problems with my cab getting sound out of all 4 speakers. i solved this by connecting the wires from the mono/right side to the stereo/left side. could this be harmful to my amp??

[bry melvin]

Have a few questions

1 what impedance are the two sides of your speaker cabinet originally?
2 How did you connect the two sides...series...parallel ?
3 What was your impedance switch on the head set at?

Short answer is yes you can damage your amp with the wrong impedance Rule of thumb is the impedance can double for a short time without damage Very short time.It will run a LITTLE happier on half the impedance set. This is why most good amp setups (tube ones anyway) have two speakers per cabinet in series and the sets then paralleled if you blow one series pair the amp will survive for a little while running on the other.
If they are all series and something goes open the amp will shortly self destruct. Tubes  tolerate shorts better than open. Open usually doesn' t hurt Solid State but they don't tolerate shorts. Your 333 is tubes.

whether you damaged it or not with the speakers is a guess at this point.

For grins plug a cord into the speaker and measure how many ohms you read across the speakers.
(plug it in just like you had done with the amp) This won't give exact ohms of impedance  just DC resistance but it will help figure things out.

Then look to see what your speaker impedance switch was set at.

Let us know the values.

I can't find a schematic ...but you possibly have other fuses inside. It COULD be a fuse on the 6.3 volt heater circuit.
BUT BUT BUT!!!
DON'T stick you hands inside that thing unless you know what you're doing. There are ~500 volts possible in there even if it has been shut off for days.

Actually don't even slide the chassis out you could get bit doing that with a finger in the wrong place/

It can kill you very quickly.

To be honest if you aren't sure about speaker wiring. You are not safe to be opening up a tube amp.

Don't mean to sound harsh but we'd rather you stay alive.

Oh by the way...this is a Solid State forum...but someone here probably can help you.

[mexidan]

1. Stereo is 8ohm and Mono is 16ohm
2. im honestly not sure which. i had my neighbor do the connection since he was more knowledgeable on electronics so i will ask him.
3. i had my head set at 8ohms

Could wrong impedance be the cause for my tubes going out? ive checked the tubes and they look fine. my tone was not suffering the days before they went out. do i need to change the tubes??

[Enzo]

No, impedance at the speaker will not make the tube heaters go dark.   And no, all your tubes did not burn out at the same time.

Does the power light come on, or is that dead too?

Fuses are inside and could be at issue.

If your Bugera is somewhat older, your power connector inside could be bad.  There is a 6-wire connector (or 5, I forget) from the power transformer to the circuit board.  The pins in it for tube heaters fail.  The factory bulletin tells us to solder the wires directly to the connector  male pins.


And the 4x12 speaker?  It is normal to get soun d from all 4 when plugged into the mono jack.  If you plug into the stereo jack, then only half will sound unless you connect two speaker cords.

[mexidan]

the power light does still come on. how should i check the fuses? my Bugera is only a year or so old. and where can i find the heater pins??

[Enzo]

They are the colored wires coming from the transformer.   Fuses must be pulled from their holders and checked with a meter.

[mexidan]

i solder the wires to the pins and still my tubes dont warm up. i checked and replaced all the fuses just to be sure. any other suggestions??

[J M Fahey]

In your power tubes, the heater pins are 2 and 7; on preamp tubes they use 4+5 together as one pin and th other is pin 9.
Set your meter to 20VAC and measure across pins 2 and 7 of power tubes, you should get around 6.3V AC across them.
Most preamp tubes should get 6.3 VAC across pins (4+5) and 9.
Probably one or two preamp tubes (the ones closest to the guitar input)  are fed 6.3 volts DC so just in case use the meter on 20V DC scale if you have no AC measurement.
Follow the filament tracks (it's easy because they are thicker than most) up to the connector mentioned by Enzo; you may not get voltage on the board solder side, yet have it coming from the transformer= bad contact.
Good luck and post a couple pictures, specially the connector area.
BE VERY CAREFUL BECAUSE OTHER PINS CARRY DEADLY VOLTAGES , ONLY A COUPLE MM AWAY, measuring probes and hands slip easily.

[rowdy_riemer]

BE VERY CAREFUL BECAUSE OTHER PINS CARRY DEADLY VOLTAGES , ONLY A COUPLE MM AWAY, measuring probes and hands slip easily.

Yeah, don't forget the one-hand-in-your-pocket rule. xP

[JacksenC]

hi...sorry to bump the old thread
but i have this same problem
here is the pic


does anyone know which one is the heater fuse for the power tubes???

[J M Fahey]

No, but pull them one by one and check continuity across them.
Then replace them, being careful not to misplace them.
If some of them is open, buy a few, cost is nil and you may probably blow the first one you replace.
*Something* killed it in the first place, and you have repaired nothing yet.

[rowdy_riemer]

Without pulling them, you should be able to see if you can measure a voltage across them with the power on. If you do, you've got an open, since there should be no voltage drop  across a good fuse (actually, there will be a super small drop across a good fuse).

[bry melvin]

also see if voltage is GETTING to the fuse....these type of amps have problems with the header  (multiwire connector to left of fuses)

Good time to practice SAFETY meter lead clipped to earth...one hand on meter lead...other in your pocket..feet insulated

[JacksenC]

No, but pull them one by one and check continuity across them.
Then replace them, being careful not to misplace them.
If some of them is open, buy a few, cost is nil and you may probably blow the first one you replace.
*Something* killed it in the first place, and you have repaired nothing yet.

I did check them,but without pulling them out and power OFF
Is my procedure correct??
I'm new for this kind of amp
and this is my first problem 

[Jack1962]

always turn off power and remove fuse's and check with a ohm meter, to address a the impedance question , if the impedance of your speakers drops below 2 ohms on a tube amp yes it will damage your amp (the output transformer) . Now back to the tubes not warming up , after you have good fuse's installed and you have voltage on the fuse's on the preamp tubes check pins 4, 5, 9 , these are the pin's that connect to the heaters on the tubes if you don't have a heater voltage your amp will not work.

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