Blackstar HT VENUE MkII MK2 Bias Instructions (For the New Amps)

Discussion - HT Venue amplifiers. Inspiration from Studio to Stage.
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brianwrym
Posts: 15
Joined: Wed Sep 23, 2015 5:24 pm

Wed Feb 05, 2020 3:45 pm

Blackstar HT VENUE MkII BIASING

LED method: (No Need to remove Chassis, located in rear next to tubes)

1) From rear of amp/chassis, locate the two round BIAS and BALANCE trim pot holes and
four small rectangle slots near to the power valves.
2) Identify each: The set of holes nearest the power valves are for the BALANCE trim pot
and LED’s. The other set of holes are for the BIAS trim pot and LED’s. Round hole for
trim pots, rectangle slots for LED’s.
3) Set the BALANCE and BIAS pots to minimum/anti-clockwise.
4) Install valves, if not already done.
5) Connect amp to load (speaker) and put dummy jack or guitar lead into INPUT.
6) Set all Volumes including Master to minimum.
7) Turn amp On and in Standby. Let it warm up for a minute or two.
8) Switch to fully On, still with Master at minimum. Both Green LED’s should be lit.
9) Turn the BIAS trim pot until the corresponding green LED goes out and before the red
LED comes on.
10)Now adjust the BALANCE trim pot until the corresponding green LED goes out and
before the red LED comes on.
11)Re-adjust BIAS trim pot if necessary to keep both corresponding LED’s off.
12)Re-adjust the BALANCE trim pot if necessary to keep both corresponding LED’s off.


Internal voltage measurement method: (Requires chassis removal - only for the experienced)

1) From rear of amp/chassis, locate the two round bias/balance trim pot holes and
identify each as above.
2) Set the BALANCE pot approx. in the middle. Set the BIAS pot to minimum/anticlockwise.
3) Locate the main bias test point, TP13, on the main PCB.
4) Connect a Digital Volt Meter (DVM) set to 200mV range as follows: Black lead to
chassis, Red lead to TP13. (It can be clipped to the leg of D7 that is connected to TP13.)
5) Connect amp to load (speaker) and put dummy jack or guitar lead into INPUT.
6) Set all Volumes including Master to minimum.
7) Turn amp On and in Standby. Let it warm up for a minute or two.
8) Switch to fully on, still with Master at minimum.
9) Turn the BIAS trim pot while observing the DVM reading:-
10)For 40/50/60 watt models set the BIAS trim pot for a DVM reading of 50mV (+/- 2mV)
11)For 100 watt models set the BIAS trim pot for a DVM reading of 100mV (+/- 5mV)
12)Now adjust the BALANCE trim pot to make both corresponding LED’s go out as
described in LED method above. Alternatively this can be tuned by ear by connecting
the output to a speaker and adjusting the BALANCE for the lowest hum.
13) Repeat points 10 to 12 until both the BIAS and BALANCE are optimised.

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