Bias amp 2 only 1 side output
![bias amp 2 only 1 side output bias amp 2 only 1 side output](https://robrobinette.com/images/Guitar/Fixed_Bias/Measure_Bias_5F6A.png)
Now I am able to get the bias current to -57mA for both sides, and the voltage at C9 is -47.7V and at C44 -49.05V. The rest of the procedure outlined above is the same.)Īfter flipping the bias switches to the 6L6 position and verifying that the switches had an effect, I then I switched them back and the levels significantly improved. The voltage across each resistor should read 50mV corresponding to 50mA. (If only volt meters are available, an alternate method of biasing can be used by substituting 1, ½ watt resistors where the milliamp meters would be as described above. CAUTION: The power supply capacitors will remain “charged” for a period of time after the amp has been turned off with voltages near 500 volts. Remove the milliamp meters from the series connection and re-attach the red wires directly to QC2 and QC16 again.
![bias amp 2 only 1 side output bias amp 2 only 1 side output](https://d1aeri3ty3izns.cloudfront.net/media/39/391630/1200/preview.jpg)
![bias amp 2 only 1 side output bias amp 2 only 1 side output](https://d29rinwu2hi5i3.cloudfront.net/article_media/0d5d8109-116c-410e-a8cc-1a62b839a021/headline-bias-amp-2-review.jpg)
Turn the amp off, leaving the standby switch on and let the residual high voltage bleed down. Leave the amp on for a few minutes making sure the readings don’t change. Adjust the bias pots accordingly to obtain a 50mA reading on each of the milliamp meters. Power up the amplifier – switch the stand-by switch on.Make sure the bias select switch is in the correct position for the tube type and the meters are set to “mA” or milliamps.Make sure the leads don’t touch anything such as the chassis, each other or you- VERY HIGH VOLTAGES ARE PRESENT! Current can now be measured through both output transformers while no input signal is present. Insert a milliamp meter in series with each of the red wires to the printed circuit board. Remove from the printed circuit board the red wires connected from the output transformers to QC2 and QC16.Each side of the amplifier must be biased with ALL four power tubes installed. Bias potentiometers are also near those switches for fine-tuning. Above those switches are markings that indicate the different tube types. Inside the amplifier, on the component side of the power tube printed circuit card, are switches to select the tube type for each channel. If different tube types are used in each channel, the amp should only be used in STEREO mode. The TS100 can be set up to use either E元4’s or 5881’s (6L6GC) in each channel. (Note: Biasing should be left to a qualified technician due to the fact that lethal voltages near 500 volts are present inside the amplifier).
![bias amp 2 only 1 side output bias amp 2 only 1 side output](https://i.stack.imgur.com/ow8UH.png)
Here is the excerpt from the manual for the biasing procedure (I did the series current reading method): The C9 and C44 voltages are at the most positive direction, in other words I can adjust the voltage more negative only. Sorry I get a little confused when asked about max voltage when talking negative voltages. OK, so heater voltage from pin 2 to 7 is 6.4V. I'm sure if I switched the bias more switches to 6L6 more and put 5881s in it I could get the current down but Carvin only gived 1 value for all tube configurations. I got the same results as the first time I worked on it which was about 93 mA on each side for the lowest I could set the current. Then proceeded to retest and the output was back and working fine (I hate intermittent issues). I did find that R76 value had gotten out of spec, so it was probably what the customer was smelling. I tested the power supply and both OT and found no problems. When I powered it up there was indeed no output (I used an 8 load for each channel). When I opened it up, nothing was actually burnt. The amp just came back to me, the complaint was that audio stopped working in 1 channel and then he switched it to bridge more and shortly after no sound at all. Biased it but could not get it down to the 50mA that is recommended but is sounded clean and looked good on the scope. I put in E元4's in it and new tubes for the phase inverter about 6 months ago. I am working on a customer's Carvin TS100. I am wondering if 93 mA (per side) is an acceptable bias current for this amp, recommended is 50mA.