Tripmaster
You wrote, with one channel it is working O.K.
Did you try both boards separately? First the left channel, then the right channel?
Are both working correctly?
Franz
You wrote, with one channel it is working O.K.
Did you try both boards separately? First the left channel, then the right channel?
Are both working correctly?
Franz
Great, thanks!
I will come back to this topic soon.
Actually, I am preparing for camping vacation for one week with my youngest daughter.
Things concerning amps will slow down now for some days...
Franz
Hi Zen
This was yesterdays procedure
Connect one channel to the the psu, light bulb tester lights for a moment and goes out. Removed tester and connected std mains cable, bias to 1.3A - 0.59v for R11/R12
Disconnected the first channel and proceeded to do the same to the other.
I then connected both channels to the power supply and reconnected the bulb tester. This time the bulb glows. Is this just because the amp is drawing a continuous current (class a) or another fault?
Thanks again
Last edited:
@Tripmaster: I don't know if you posted the bulb wattage used? It is actually important - it sounds like the bulb is of too low a rating?
40W has high resistance, resulting in a voltage drop. The more current you draw, the more drop.
As both boards are running correctly you are now on the safe side to remove the bulb or use two in parallel or use a 100W and check the resulting voltages.
Franz
As both boards are running correctly you are now on the safe side to remove the bulb or use two in parallel or use a 100W and check the resulting voltages.
Franz
What happens with the primary AC voltage, measured after the bulb?
I guess: also dropped.
Again: both channels are working correctly.
Dont use a bulb anymore! No big risk now.
Check the voltages.
When you still use a bulb: control the AC voltage on the primary side: it will also be dropped.
Franz
I guess: also dropped.
Again: both channels are working correctly.
Dont use a bulb anymore! No big risk now.
Check the voltages.
When you still use a bulb: control the AC voltage on the primary side: it will also be dropped.
Franz
Look at the math - two F5 channels will be drawing something like 160 watts from the wall, so you need something with higher wattage than that to not light up under normal conditions.
Try this: Bias up one channel and connect the bulb without touching the pots, the 60 watt bulb will stay dimly lit while the amp is connected, as it is placing roughly the same load as the amp.
The bulb tester is only to check for a defective power supply/wiring/amplifier. If you check once, it is fine after that, just bias up and things should be fine.
Try this: Bias up one channel and connect the bulb without touching the pots, the 60 watt bulb will stay dimly lit while the amp is connected, as it is placing roughly the same load as the amp.
The bulb tester is only to check for a defective power supply/wiring/amplifier. If you check once, it is fine after that, just bias up and things should be fine.
The trouble is I replaced all of the bulbs for low energy CFLs in an attempt to reduce my carbon foot print! :joke: 😀
Thanks guys!
Thanks guys!
The bulbs are a good safety measure to power up (and not fire up) the amp the first time when you have no variac.
I did it the same way. Using a 220V 100W bulb.
First the psu only, then one channel after the other.
Thats it, the bulb has done its work.
Never adjust the amp with a bulb in series with the mains! You will always have a voltage drop over the bulb.
Franz
I did it the same way. Using a 220V 100W bulb.
First the psu only, then one channel after the other.
Thats it, the bulb has done its work.
Never adjust the amp with a bulb in series with the mains! You will always have a voltage drop over the bulb.
Franz
Yep.. I did it in that order. But being the simpleton I am 😱, the lit bulb and the low voltage rather foxed me. I couldn't face pulling the amp apart tonight if I had fried a component!
Welcome to the World Wide Whopper, even after a million views old typos are as fresh as ever.
Sorry Jacco, could not understand why that is a typo? The F5 documentation says 180 watts, 160 is close enough with the slightly reduced bias I run during summer.
I used an AC ammeter and the mains voltage to work out the power draw. It seems to be accurate enough in most situations and seemed to be close enough to what the original design specified (of course we have 230V mains so there are minor differences because of the lower current), so I guess I'll leave that as it is.
Some other time, then 🙂
Some other time, then 🙂
at least Zen bothers to read instructions.
You cannot bias a ClassA nor a high bias ClassAB through the bulb tester.
The Tester is there to protect you and the equipment in event of a wiring fault or circuit fault.
It must be removed after checking that working voltages exist at all test points.
Hi Andrew
Everything appears to be in order. The voltages are stable and the offset hovers around 0.01 - 0.08mV. I'll leave the amp on for a couple of hours this afternoon and recheck again before connecting a source and pair of speakers 🙂
Everything appears to be in order. The voltages are stable and the offset hovers around 0.01 - 0.08mV. I'll leave the amp on for a couple of hours this afternoon and recheck again before connecting a source and pair of speakers 🙂