I have a pair of BGW GTB's with both having worn out fans, as I intend to use them in a living room the original 120VAC 107CFM fan wasn't useful anyway. I plan to use a 120mm PC fan, something in the likes of a Noctua or Noiseblocker to provide at least some airflow through the case.
I have the schematic of de GTA which is the same except for a second power supply. There is a 12VAC secondary used to power the delay circuits of both channels that I could tap the power from for an AC-DC converter.
Would such thing work without causing damage to the circuit? There is also plenty of space inside the amp.
I have the schematic of de GTA which is the same except for a second power supply. There is a 12VAC secondary used to power the delay circuits of both channels that I could tap the power from for an AC-DC converter.
Would such thing work without causing damage to the circuit? There is also plenty of space inside the amp.
Considering I want the DC voltage to be easily adjustable if needed. What would be the neatest way to do it? The power draw of the fan I plan to use is around 1.7A max.
The delay/display boards both have their own rectifiers built around 1N4004 diodes. In the BGW GTB (with 1 transformer) there are 2 jumper wires that take the 12VAC from Rch to Lch board, omitting the fuse on Lch board, they go straight to the diodes.
Stealing 12VAC and converting it to DC elsewhere using an off the shelf AC-DC board from China sounds like a safer approach rather than taking the DC from one of the boards and using another DC-DC buck converter, what do you guys think?
The delay/display boards both have their own rectifiers built around 1N4004 diodes. In the BGW GTB (with 1 transformer) there are 2 jumper wires that take the 12VAC from Rch to Lch board, omitting the fuse on Lch board, they go straight to the diodes.
Stealing 12VAC and converting it to DC elsewhere using an off the shelf AC-DC board from China sounds like a safer approach rather than taking the DC from one of the boards and using another DC-DC buck converter, what do you guys think?
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Absolutely, however I already have a bunch of high quality PC case fans (Noctua 12x25's).
Since these amps won't ever see any PA duty anymore, it doesn't seem worthwile to put a heavy duty fan in them as even though one could keep the RPM's low, there is still the issue with vibrations, motor and bearing noise. PC fans are also 1/5th the wattage and the bearing noise of the Noctua fans is...zero.
Since these amps won't ever see any PA duty anymore, it doesn't seem worthwile to put a heavy duty fan in them as even though one could keep the RPM's low, there is still the issue with vibrations, motor and bearing noise. PC fans are also 1/5th the wattage and the bearing noise of the Noctua fans is...zero.
If one of the PC case fans in your possession happens to be pwm controlled type, the NA-FC1 pwm controller probably is a better way of fan speed contol, than by adjusting the supply voltage to a fan. As of the 12V DC supply, I would use caution before tapping the 12V AC off the transformer, because A) the fuse F1/F2 rated at 1A hints the winding may not be heavy-duty enough to supply an additonal fan without causing excesive voltage drooping, and B) if the thermal fuse TS1/TS2 trips, the fan would stop, however you may instead want an operating fan when that happens. So, my suggestion is buying an AC/DC China board that works off international voltages, 90-240VAC, and tap off the main windings (BLK-BLK) that produce +/-88.2VDC.
They are PWM types, however I try to avoid PWM or any SMPS to prevent any eventual hum/buzzing getting into the audio chain.
The amplifier runs cold without the fan but I'd like to give it at least some airflow, just to be sure.
The fan is rated at 1.86W only and I've noticed the GTB which I have already has the 12V 1A rail split between the two PCB's and they only use the 1A fuse of the first PCB, right after that the AC wires go straight into the rectifier diodes of the second control PCB - funny enough the second board also has the fuse installed but it's not used.
I haven't seen the thermal fuse so it's probably mean the death of the transformer if it trips.
The amplifier runs cold without the fan but I'd like to give it at least some airflow, just to be sure.
The fan is rated at 1.86W only and I've noticed the GTB which I have already has the 12V 1A rail split between the two PCB's and they only use the 1A fuse of the first PCB, right after that the AC wires go straight into the rectifier diodes of the second control PCB - funny enough the second board also has the fuse installed but it's not used.
I haven't seen the thermal fuse so it's probably mean the death of the transformer if it trips.
Just did the first amp, can confirm this works. The AC voltage was around 13V, I've set up the output to ~6.3VDC by ear but YMMV depending on the fan used.
This is how I've done it: https://ibb.co/album/TM60Ck
These AC-DC regulators from China work surprisingly well and are dirt cheap, as far as I can see they're built from recycled parts. I did a test with 7 various DC fans in total and only the bridge rectifier was getting warm, reaching 50*C with 7 fans at full speed and running just a few degrees above ambient when powering a single fan.
The standoffs will be shorter in the second amp, just had these laying around in the parts bin. Worked surprisingly well with the AC line and the AC inputs being roughly at the same height.
Mind you this solution is most probably not suitable for dusty / filthy environments as this is a very low power computer fan with negligible power draw. (Noctua NF-A12x25). https://noctua.at/en/nf-a12x25-pwm/specification
Even though the transformer is very hefty, I don't know what the maximum power is of the 12VAC secondary.
This is how I've done it: https://ibb.co/album/TM60Ck
These AC-DC regulators from China work surprisingly well and are dirt cheap, as far as I can see they're built from recycled parts. I did a test with 7 various DC fans in total and only the bridge rectifier was getting warm, reaching 50*C with 7 fans at full speed and running just a few degrees above ambient when powering a single fan.
The standoffs will be shorter in the second amp, just had these laying around in the parts bin. Worked surprisingly well with the AC line and the AC inputs being roughly at the same height.
Mind you this solution is most probably not suitable for dusty / filthy environments as this is a very low power computer fan with negligible power draw. (Noctua NF-A12x25). https://noctua.at/en/nf-a12x25-pwm/specification
Even though the transformer is very hefty, I don't know what the maximum power is of the 12VAC secondary.
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