We have reached post 15000
Imagine the poor soul who has just started reading page one.
Lord Of The Rings by JRR Tolkien is not even this long.
Hahahahaha
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Da Pub is having almost 20K
but it's more like Herbert's Dune serial ......
Whoever starts reading Pub from page one today and completes it is one special individual
gain is 6times (NFB =50r/10r) and maximum output is 25W into 8ohms which is equivalent to 14.142Vac.
This gives an input sensitivity of 2.35Vac if there is no attenuation at the input.
But typical input attenuation is 1k into 47k or 0.979times giving an effective sensitivity of around 2.4Vac.
The numbers to arrive at this value are all over this Thread and in the Pass documentation.
Seems you arrived at the same answer and that is obviously not a coincidence.
This gives an input sensitivity of 2.35Vac if there is no attenuation at the input.
But typical input attenuation is 1k into 47k or 0.979times giving an effective sensitivity of around 2.4Vac.
The numbers to arrive at this value are all over this Thread and in the Pass documentation.
Seems you arrived at the same answer and that is obviously not a coincidence.
Where ever this problem is hiding it is hiding well....
So I pulled the out the PS and removed the rectifiers. They all tested good but I replaced them anyway. Without load the PS comes up to ~ 25 on both sides. Under the load of one board I get uneven voltage and mechanical hum from the transformer.
Moving up from the rectifiers, here is what I am thinking
- I would think that if the problem was too high of uF in the power supply, I would get a mechanical hum that would go away once the caps came up. Is that correct?
- Could I possibly have a bad cap? They all look fine to me and I can't see why one would be bad.
- I am not sure there is anything else that could be wrong with the PS, it is pretty simple
Moving on to the amplifier
- Could something on the amp boards be pulling extra current while still allowing the amplifiers to play without a problem?
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If you can get a big low ohm resistor and stick it between psu and amp you can verify current draw by measuring voltage drop over the resistor.
Are you using old caps? I dont think they would draw extra current and they try to charge up in one cycle so that means 1/60th of a second. A lightbulb can be your resistor by the way.
Are you using old caps? I dont think they would draw extra current and they try to charge up in one cycle so that means 1/60th of a second. A lightbulb can be your resistor by the way.
I do not believe I have DC on the mains and I am not seeing on when I measure. I do not get any mechanical buzz while the tranny is unloaded. Progress update. I have now pulled all the caps off to test them and they all seem fine. I soldered on a pair of 10,000uf caps to make a CR PS and even though the input voltage is the same for both secondaries I am still getting a difference. What are the chances that something is wrong with the PCB?
Not sure if this was suggested or tried. Have you checked that both secondaries are in sync? Amplimo uses different colours for the secondary wires to make sure you avoid that issue.
Have you tried changing the secondaries, i.e. if you now use sec.a for + and sec.b for -, what happens when you swap a and b? If the problem is in the secondaries it will move from + to - (or v.v.). If the problem is in the psu or amp it will stay in the + or -.
Hope you can figure it out. Good luck,
Albert
Have you tried changing the secondaries, i.e. if you now use sec.a for + and sec.b for -, what happens when you swap a and b? If the problem is in the secondaries it will move from + to - (or v.v.). If the problem is in the psu or amp it will stay in the + or -.
Hope you can figure it out. Good luck,
Albert
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Update - After trying everything I could think of I ended up damaging a trace on my power supply PCB. I ordered a new PCB and some parts from chipamp.com but they haven't arrived yet. In the mean time I ended up replacing the linear supply with a SMPS500R running @ +/-24V from Connexelectronic. I have noticed a difference in sound between the SMPS and the linear power supply. However, with my linear power supply not working correctly in the first place, I am not sure it is fair to attribute the difference to the SMPS. My scope is in storage right now so I don't have any way to measure to find out what is going on. I'm going to let it play for a few more days before I decide what I am going to do next.
Those Connex power supplies are pretty good units, IMO, but they do indeed provide a rather different sound with the F5 amp - amp is quite dependent on power supply components and systems - I didn't know that these supplies could go below 32volts but ...
You could replace the power supply output Nichicon cap (as per web photo) that will change the sound a bit or even add a series Cmultiplier with low drop out power device that only reduces rails about a volt for better isolation
Amp is a bit sensitive to pretty much any change in components particularly if you have revealing type speakers
... hope this helps
You could replace the power supply output Nichicon cap (as per web photo) that will change the sound a bit or even add a series Cmultiplier with low drop out power device that only reduces rails about a volt for better isolation
Amp is a bit sensitive to pretty much any change in components particularly if you have revealing type speakers
... hope this helps
Ah, I see says the blind man!
I looked up the site and indeed they do offer a +/- 24 volt version (about U$90, I think) This is the 'R' type with the auxiliary winding and all the goodies - I think it does come with the Nichicon caps and possibly, you could get them built with different o/p caps but I would imagine some extra costs
I looked up the site and indeed they do offer a +/- 24 volt version (about U$90, I think) This is the 'R' type with the auxiliary winding and all the goodies - I think it does come with the Nichicon caps and possibly, you could get them built with different o/p caps but I would imagine some extra costs
Can someone let me know the lead spacing/turns on the Pots (variable resistors) that are used in the current V3 board available on the store.
From looking at the build guide this seems to be a good choice from Mouser:
3296Y-1-502LF Bourns | Mouser
Thanks for the help.
Dave
From looking at the build guide this seems to be a good choice from Mouser:
3296Y-1-502LF Bourns | Mouser
Thanks for the help.
Dave