An illustrated guide to building an F5

[bnorrish]

Thanks. Those are LEDs. Nice part, a little pricey:

Q14F1BXXB24E Apem | Mouser

I live outside Boston - major snow storm today. Working from home, listening to music for the last 8-9 hours. Sounds awesome.

 

[KWS1]

F5 R11 & R12

I am seeing 20 volts at R11 & R12....What is wrong? No smoke....

 

[Marra]

Is that at or across the resistor? Are the trimmers set to zero?

 

[KWS1]

One probe..gnd the other at the resistor.

 

[6L6]

Do you have the pots turned all the way down? Are you sure which way they turn? You might have one all the way up...

Also, Check all your solder connections. Especially around the P channel output Fet

 

[KWS1]

I am unable to get behind the pot to zero .... I think clockwise increase.. I will check the solder connections... Thanks

 

[6L6]

Clockwise or counter-clock increaseis a function of how the PCB attached to the pot, so it's not necessarily logical.

Twist for minimum resistance across R5 and R6

 

[Marra]

I would recommend connecting your Dmm across R5[2k2] powered down of course and turn the trimmers which ever way gets you to zero.You might only get down to about 3/4 ohms which is as far down as mine went.
6L6 beat me to it.

 

[KWS1]

There is no change ......both trimmers have no effect. I checked the solder connections....everything looks ok

 

[6L6]

Do you have your DMM set to ohms ?

 

[KWS1]

Yes. Ohms

 

[Itsmee]

I am seeing 20 volts at R11 & R12....What is wrong? No smoke....

Could be nothing, depends what your voltage rails are.

One probe..gnd the other at the resistor.

Measure the voltage across R11 & R12.

Red probe connected to +V, black probe to Q3 source/ R11 junction.
Black probe connected to -V, red probe to Q4 source/ R12 junction.

Marra pointed to this earlier.

 

[KWS1]

The voltage ...R11 & R12 20 volts. I hooked it to speakers and drive and it sounds great....I do not understand. I built the Amp Camp.....worked right away.

 

[6L6]

What's the DC voltage on the speaker jack?

 

[KWS1]

1.3 volts right .95 volts left

 

[AudioSan]

you have not measured correct. measure across the Source resistors(R11/R12) one probe on each side of the resistor. and do NOT hook up any speakers until bias and DC offsett is adjusted. you are lucky you did not blow up your speakers.

 

[KWS1]

On one side I have 4.85 & 0.80 on the other....the speaker output is...1.3 volts. I was using old speakers....I have been trying to get this going for along time.

 

[AudioSan]

4.85V????? 4.85V/0.47ohm=10.3A. 10.85A*23V=250W dissipation. no way.
to get around 1.3A bias, you will want to see about 0.6V across the Source resistors. and close to 0mV offsett.

 

[Russellc]

On one side I have 4.85 & 0.80 on the other....the speaker output is...1.3 volts. I was using old speakers....I have been trying to get this going for along time.

Perhaps this is mV?

Russellc

 

[bnorrish]

What about taking pictures of the DMM and the location of the DMM probes?