Stellar CM1 with FOX 460 MOD and PSU update MOD

[Khron]

Slight "oopsie" - i meant the RIGHT-most pin of the LD1084, for step 2).

 

[axlreddy]

Slight "oopsie" - i meant the RIGHT-most pin of the LD1084, for step 2).

That's OK

the value is 11.8v.

 

[Khron]

Hmm... 9.5V AC, rectified and smoothed, should give about 13.3V DC, minus a diode voltage drop across the rectifier. That drop seems to be a bit big, at about 1.5V (with almost no load)...

But either way, 11.8V input should be more than enough for the LD1084 to be able to regulate the 5-6v it's supposed to put out.

What're the odds something's not right in that delayed-turn-on circuitry, i wonder?

 

[ln76d]

It depends Khron
I don't know what sits inside, it is pretty popular to put oversized resistors for higher voltage drop.

 

[axlreddy]

Hmm... 9.5V AC, rectified and smoothed, should give about 13.3V DC, minus a diode voltage drop across the rectifier. That drop seems to be a bit big, at about 1.5V (with almost no load)...

But either way, 11.8V input should be more than enough for the LD1084 to be able to regulate the 5-6v it's supposed to put out.

What're the odds something's not right in that delayed-turn-on circuitry, i wonder?

I can hear almost same noise when I turn on the PSU, and then it disappears.
(In the situation that I turn down the Heat)

 

[Khron]

By the way, did you take those readings with the microphone connected, or not?

 

[axlreddy]

By the way, did you take those readings with the microphone connected, or not?

No,PSU only.

 

[Khron]

... And you hear the noise, from the PSU itself, or..?

 

[axlreddy]

... And you hear the noise, from the PSU itself, or..?

Oh, sorry let me describe more specific

I've heard the noise from headphone with mic connected,

All the reading from multimeter were based on "Heater-turned-down to 5.8v".

I'm sorry for my english

 

[Khron]

Mic connected, and fully assembled?

It would be interesting to see some scope shots of the heater voltage, with the mic connected. And maybe of the B+ as well...

 

[axlreddy]

Mic connected, and fully assembled?

It would be interesting to see some scope shots of the heater voltage, with the mic connected. And maybe of the B+ as well...

Sure, both mic and PSU were assembled

 

[axlreddy]

It depends Khron
I don't know what sits inside, it is pretty popular to put oversized resistors for higher voltage drop.

Which one would you recommend to change?

 

[Khron]

It would be quite useful to take those voltage readings again, WITH the mic connected, since, well... THAT is when the noise happens

No,PSU only.

 

[axlreddy]

It would be quite useful to take those voltage readings again, WITH the mic connected, since, well... THAT is when the noise happens

Thanks again

Should I turn Heater back to 6.3v and test again?

 

[Khron]

It might help to try both - the noiseless(?) 6.3v, and the problematic lower setting.

 

[ln76d]

Which one would you recommend to change?

Draw schematic of heater section (it isn't complicated) and then we all could see if there's problem or not

 

[Khron]

That's kinda my pet-peeve re: "paint by numbers" kits.

Yes, having all the "right" parts in one go is nice, and putting them together (at least in theory) is no big deal, but without knowing what component does what, and/or why it was chosen, it's just a nightmare to troubleshoot... :/

 

[ln76d]

Of course, that's why i really often want to conviece some folks to build microphone from what they have not build just a kit - most microphones can be adapted to any circuit - tube and fet.

Anyway i understand very well, that some people just want to build microphone - because it's cheap, because some circuits aren't available in commercial releases, because it's good to have U47 "clone" in the equipment list, even if it doesn't have nothing to do with the reall U47 (but looks good on the web). These same guys not necessary have a need to learn electronics or anything else.

For me it isn't problem to help with some issues - but! I don't have a time to make all the work for you
If you need help - then give us infromations about the circuit which you build and don't understand. More then better to get solutions.

For example - draw the circuit of the heater (like in this topic) - draw it by hand, even as a "block diagram", just as you can.
I think there's no problem to draw components and check how tracks go, read markings on the parts and write.
I don't see anything complicated here but for me doing the same from blurry pics, where not everything is visible is just a pain in the ***! So!

Help us help you

 

[BudCarroll]

I’ve just built one of these powere supplies with the old style donor power supply,

Powers on ok, but I can’t seem to get a heater voltage at pad B.

B+ reads well 120/120,...LV is 4.6 HV is 115 per side. 

Thanks in advance.