[BUILD] STA LEVEL PCB OFFICIAL BUILD & HELP THREAD

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bernbrue

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Oh, then it needs to be replaced. The TL783 is fine here. What is the max voltage of the caps in your psu and on the mainboard? Check the (wiring of the) resistors for dropping down the voltages as well. The psu needs to be under load, otherwise the voltage can go up quite high.
Bernd
 

zero

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bernbrue said:
Oh, then it needs to be replaced. The TL783 is fine here. What is the max voltage of the caps in your psu and on the mainboard? Check the (wiring of the) resistors for dropping down the voltages as well. The psu needs to be under load, otherwise the voltage can go up quite high.
Bernd

The caps voltage is 450v,
Ill replace the TL783 and check the wiring, what bugs me is that it was working fine.
I see! the voltage under load , when it worked fine, 290v, now it´s 385V, with no load 440v ( normal? )

So there is no other way of dropping the voltage from the xformer other than the 3 resistors i have in series after the diode bridge? just a proper transformer?

The only thing i did, before starting to blow fuses, was replacing the R32s with a 18k resistor so i could get more compression with lower input.
Thank  you.
Kind regards,
Pedro.
 

zero

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Hi Bernd,
Sorry for being such a pain but i´m a little noob at psu design and i am trying to understand  how this circuit works.

i want to calm down the beast as it produces excessive heat, even the front panel gets hot from the 3 resistors in series i have to tame down the dc after the rectifier.

My thinking (maybe wrong), from what i get from the schematic:

-The trafo from don audio outputs 337Vac.
-After the rectifier, from the math Vac*1,414, the 337Vac goes to 476,518Vdc.

What i gathered in my head from the  TL783 , it needs a little over voltage to regulate, like 25V and it´s not easy to read with no load.

I really want to cool the thing down so my idea is to put there a 230Vac/200MAh trafo so it outputs 325Vdc ( 230Vac*1,414=325,22Vdc)

Am i thinking ok?

Will a 230Vac trafo be ok or will the voltage drop under load and something like 275Vac be better?

I still didn´t replace the TL783 to see what´s burning fuses but before i do that i wanna sort this out.

Sorry for any hassle or stupidity.

Cheers,
Pedro.
 

Kid Squid

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Hi Chaps,
Hope you are all doing well in these crazy times  :)

Just wondering, if any people need cases etc, I'll be doing another run ( order dependant), with a different mains transformer option. If any of you are interested, or know anyone that was missed the first time..

https://groupdiy.com/index.php?topic=74776.0

Be safe

Steve
 

IanB

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Apr 16, 2018
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Just plugged in and it works perfectly! I am SO stoked! Using 6386 with 1k R after the rectifier bridge (had to use a huge chassis mount jobby as they were previously actually cooking!!!) & Carnhill input tranny (the 4:1 Colin had made for LA2A builds....I wired it backwards - compresses really nicely and sounds typical Carnhill: great).  Also using Hairball Bournes output attenuator (works a treat!). Using Steve’s beautiful case, power tranny & bypass switch - thank you man!!! (Tempted to get another but not sure I’d use a pair....drums?!).
Thanks B & Z for the boards & wiring diagram & the boys who helped with the bypass and output wiring etc. What a great project.
It’s such a cool feeling! Cheers!
 

Kid Squid

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Hi Bernd,

Hope you are well in these crazy times !!

I'm looking into getting another batch of the power transformers for my case design, and I'm curious about the overvoltage that some people are reporting with the v.1 transformer. Is this on the secondary HV windings, or the LV windings ?

Jens, it looks like the 5V winding - Should I increase it to 10V ?


jensenmann said:
I didn´t read the entire thread, so maybe this has been addressed before. In case not here´s a problem I found:
I´m using Steve´s transformer with 5V AC for V+ and 5V relays. Without regulator installed I get 6,5V DC at the regulator input pin. With regulator installed the voltage drops to 4V at it´s input and I get 3,3V at the output. Several others have mentioned this before, but nobody did care.
The reason for this is that if we want to get 5V out of the LM317 regulator it needs to see at least 3V more at it´s input. But we only have 6,5V instead of necessary 8V. So it shuts down.


Lads, lovely to see the cases being used  ;D, Having a little catchup on posts and they look bloody wonderful !

Best,
Steve
 

bernbrue

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Hi Steve,
the 5V relay voltage should be 9V to get the 3V difference for the LM317 to regulate. I can’t verify if the other voltages were fine or too high, since I haven’t used your poorer tx.
Bernd
 

Kid Squid

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Hi Bernd,
No problem, I'll get that seen too.

I'll have a read over the whole thread, but I'm pretty sure that some people have been 'choking' back the HT with dropping resistors ?

Not sure if this was for my 'poorer'  ;) transformer, or the one from Don audio..  I'll look into it.

Hope you are doing well in these mad times !

Best,
Steve
 
Joined
Dec 10, 2017
Messages
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Hey guys, maybe I'm just missing something here but I can't find any details about the HTTRIM resistor/trimmer on the PSU board? Any idea where I can find more info on that?

Cheers
Badger Brian
 

FarisElek

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Oct 26, 2019
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443
Does anyone have the Simpson 27 scale image that was posted at the beginning of this thread? I see someone posted a hoyt one. Is it the same? It doesn't look quite the right shape but I may be wrong.

Ryan
 

fallout

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Jun 3, 2004
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Caldwell, NJ
Hi folks. I'm getting ready to put one of these together and was wondering what were the current options for power transformers? I understand Don Audio makes a 'somewhat' suitable power transformer but it's output is a bit too high for the B+ and bit too low for V+.

Thanks!
 

Jim50hertz

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Jan 18, 2005
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Glasgow, UK
Also interested, I have the Kid Squid transformer.  I just need to add a 9v transformer for the relays right?  Or is there a dropping resistor required for HT?
 

fallout

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Caldwell, NJ
Jim50hertz said:
Also interested, I have the Kid Squid transformer.  I just need to add a 9v transformer for the relays right?  Or is there a dropping resistor required for HT?

From what I understand Kid Squid's transformer was spec'd @

Dual Primaries - 100,110,115,120V
Electrostatic screen
Sec 1 - 300v @ 250mA
Sec 2 - 9V @ 4A
Sec 3 - 5V @ 1A

It seems like you'd need to drop the voltage with some high wattage resistors (x2 470ohm 25w resistors in series) for the B+ and also do something with the 5V secondary to raise the voltage a bit for the V+ PSU, it seems like 5V is too low. In reply #397 in this thread jensenmann suggested a few ways to remedy the problem. I personally would try his 3rd suggestion of using a voltage doubler. Should be easy enough to try.

https://groupdiy.com/index.php?topic=59017.msg902527#msg902527

Kid Squid was toying with the idea of doing a 2nd run of cases and a proper transformer but hasn't confirmed as far as I know. I might just go with a custom power transformer as it seems there's nothing currently available that's suitable for this project.
 

FarisElek

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Messages
443
fallout said:
Does anyone have the meter scale PDF file for Simpson 27 meter? If anyone has it, please shoot me a PM. Thanks!

I poorly photoshopped one for myself and it's working out fine on my Drip build. If anyone has a better one you should probably use theres but in the meantime.

 

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