Bugera 1960 Classic Head Bias went horribly wrong NEED HELP

[plushgarden]

I tried biasing my Bugera 1960 amp with regular bias probes. I put the lead probe in the rca bias outlet and held the ground probe to the outside of the rca outlet. Immediately after, I heard a sizzle sound and a small pop coming from the amp speakers.
And, now, no sound. All tubes work fine, checked the guitar cables, and fuses. What did I mess up?

[oc disorder]

It's possible one of the tubes was faulty.
When you say "All tubes work fine" have you tried them in another amp or do they just light up as usual? Even though the heaters/filaments may light up it doesn't mean the tube/s is/are ok.
Did you have a speaker load connected? If not, that may have blown the HT fuse which is probably inside. Worth checking anyhow.
Also it would appear that Bugera intend for the bias supply voltage to be measured rather than the voltage drop across a 1 ohm resister. Therefore if you were measuring with a current meter it would have shorted out the bias supply which inturn would have blown an internal fuse at best...at worst caused some damage to the power supply and possibly the tubes.

Here are some of the instructions from a Bugera biasing doc.
***WARNING***
These amps carry a very large, potentially lethal dosage of electrical charge,
EVEN WHEN THE * AMP IS TURNED OFF AND UNPLUGGED! Those not familiar with electrical safety precautions should not attempt to perform these instructions.
It is important to purchase and install a matched quad set of power valves to ensure that the valves all draw the same amount of current.
Most BUGERA amps are equipped to change freely between 6L6 or EL34 style valves. Users may elect the modern west coast sound of 6L6 valves (Rectifer, SLO) or the classic British grind of EL34s (JCM) by changing the output valves, fipping a switch and adjusting the bias knob. BUGERA has also developed a line of valves that are specifcally matched with these amps to give optimum balance and compatibility. With a matched quad set of BUGERA power valves, coupled with the simple setup procedure, the biasing process becomes so easy it can be done by virtually anyone with a volt meter.
By setting the bias on your amp, you are determining how much idle current is running through the valves. The current is adjusted by measuring and adjusting the voltage at the Bias Test point inside the amplifer. Follow these instructions to change the output valves and adjust the bias.
Instructions
CAUTION: WE HIGHLY RECOMMEND THAT BIAS ADJUSTMENTS BE CARRIED OUT BY QUALIFIED ! PERSONNEL!

1.Turn the STANDBY and POWER switches to the “Off” position. DISCONNECT the power cord from the mains outlet!

2.Unscrew the 2 screws on each side of the amp to remove the back plate.

3.Remove the 4 old power valves from their sockets. These are the larger valves and can be removed by pulling directly upward while gently rocking them back and forth (DO NOT twist).

4.Insert the new set of matched BUGERA power valves into the empty sockets.
Make sure that the keying pin on the bottom center of the valve is properly aligned with its respective hole.

5.Flip the BIAS SELECT switch to the appropriate valve type (6L6 or EL34). .Turn the Master Volume control down to 0.
If biasing an amp head, make sure it is plugged into a cab.

7.Plug in the power cord and turn the POWER switch on. Before setting the bias, verify that the mains voltage actually matches your country version according to the table on top of the following page.

8.Turn the STANDBY switch on. The voltage of the power valves must now be measured by plugging a volt meter into the BIAS TEST RCA jack. Make sure the meter is set to 100V DC (direct current) measuring range, and beware not to short the RCA contacts.

9.While reading the measurement on your volt meter, turn the BIAS ADJUST control so that the bias is set for optimal performance for the type of valve. The chart on the following page will display the desired voltage for your new valves. Biasing a valve “too hot” (too much idle current) can reduce valve life and potentially put strain on the amp’s output transformer. Biasing “too cold” (too little idle current) may cause the tone to sound gritty and
distorted. Deviating from the recommended bias settings should only be done by a qualifed professional.

10.The bias tends to drift slightly after the amp has had a chance to warm up for a few minutes. We recommend fine-tuning the bias voltage after 10 minutes of operation.

11.Once the bias is set, play through the amp to ensure that the tone sounds right.

12.Replace the back plate with the original screws.

13.It is a good idea to check the bias again after six months to ensure that the bias knob has not moved on its own due to vibration. If you decide to change back to the original valve type, you must repeat the entire bias process again.

Bias Voltage at BIAS TEST RCA terminal
Tube Grade --6L6-GC (5881)-- EL34 (6550A)
A --------------44.3 V------------38.7 V
B --------------45.8 V ------------39.7 V
C --------------47.2 V ------------40.7 V
D --------------48.7 V ------------41.7 V
E --------------50.2 V ------------42.7 V
F --------------51.6 V ------------43.7 V
G --------------53.1 V ------------44.7 V
H --------------54.6 V ------------N/A

[plushgarden]

Thank you OC Disorder. Great information. You hit the nail on the head. I think I shorted the bias with the wrong equipment. The head was plugged into the cab with the correct ohm setting. But, your right that I did not check the tubes other than seeing they were glowing as usual with no discoloration. When you say the power supply are you speaking of the power transformer? I looked inside and checked all fuses (ceramic) and didn't see discoloration, so I THINK they look fine.

[oc disorder]

The fuse could still be blown .. the ceramic ones are impossible to tell without measuring them with an ohm meter.
It will be a light weight one like half an amp or 500mA.
The transformer is part of the power supply then there are diodes (to convert ac to dc) and capacitors and resistors.
With a fault like that start with the fuse (they never seem to blow when you want them to) then check the diodes with a multimeter pref one with a diode test.
I havn't got a schematic of that one Behringer only hand them out to their service agents whom have to sign an agreement not to disclose them.However Enzo can advise you without disclosing should you need more accurate detail.
A multimeter would soon find what went bust.. from the fuse to the voltages present on the socket.
If the bias was not present any more the tubes woud be "red Plating" a bad sign ie the main greyish plate inside the tube glows a dull red and the amp would start humming like crazy !
This makes me think the HT (high voltage) fuse has blown .
The standby switch is usually in line with the HT fuse so with the fuse blown it's kinda like permanently on standby.
The other fuses are most probably heater fuses and would be high current ones at least 6.3A. If you haven't a meter get some fuses of the same rating as the ceramic ones and swap them.
Thats about all you can do without knowledge and test gear.

[plushgarden]

OC Disorder, it was an internal fuse! Thank you very much! That was so much better than spending $$$ on a diagnostic. I was about to just return it and I incur the shipping costs. You are awesome!

[powertuber]

thanks oc got my 1990 back up