Lerok

Full Helios Pre Schematic
« on: February 12, 2019, 05:58:32 PM »
Hello! After a six month break from my tiny side project (switching jobs and houses), I'm back, and I just wanted to run this schematic by the helpful people here before I went and began making a PCB for it.

Anyways, I've combined the 15C1 and 22113 schematics on this website, made a few adjustments (125uf caps are hard to come by around where I live), and cleaned up the wiring mess as best I could.

Warning: It isn't the prettiest schematic you'll ever see (I'm more suited to graph paper and a good old pencil), but it gets the job done.

I'll probably use Cinemag in and out transformers, though I might look into some other ones (maybe a 1:2 10k Jensen for the output?) after the basic build is done.

Anyways, any thoughts/concerns are always welcome! I'm fairly new to electrical work, apart from basic console repair.

Schematics I used:

15C1: https://groupdiy.com/index.php?action=dlattach;topic=58393.0;attach=32789;image
22113: https://imgur.com/lzT8SKf


gyraf

Re: Full Helios Pre Schematic
« Reply #1 on: February 13, 2019, 02:14:10 AM »
You don't need 125 or 200uF, they are for psu filtering and decoupling, not for time constant. Use 220uF, that'll do.

Your 3707 (first transistor in preamp) is drawn wrong or oriented wrong? Or is it the other two? Something dosen't compute for running off a -24V supply  (we almost only use negative supply for pnp-germanium technology)...

Jakob E.



..note to self: don't let Harman run your company..

ruffrecords

Re: Full Helios Pre Schematic
« Reply #2 on: February 13, 2019, 03:06:08 AM »
I agree with Jakob, use the nearest next larger available cap size for the electrolytics.

I think the first stage is drawn correctly but the power supply is the wrong way round. It should be +24 like the output stage. I think they only made a few of the -24V versions in the very early days.

Edit: don't forget to turn the appropriate electrolytics round as well. Also, you do not need the 600 ohm resistor across the output. It is only there to make sure the output cap gets charged up. Change it to 10K. And lastly don't use a 1:2 10K transformer for the output; you need a 1:2 with a 600 ohm secondary i,e, 150:600

Cheers

Ian
« Last Edit: February 13, 2019, 03:11:27 AM by ruffrecords »
www.customtubeconsoles.com
https://mark3vtm.blogspot.co.uk/
www.eztubemixer.blogspot.co.uk


'The only people not making mistakes are the people doing nothing'

moamps

Re: Full Helios Pre Schematic
« Reply #3 on: February 13, 2019, 03:27:18 AM »
I think the first stage is drawn correctly ....

Hmm.
2N4058 is PNP, so it can't be used for second and third transistor if +24V is used for PS.  Also, there is lower 50uF string which shunts output to gnd.  And R13 and C9 are questionable, upper 50uF string can be smaller.

ruffrecords

Re: Full Helios Pre Schematic
« Reply #4 on: February 13, 2019, 03:32:39 AM »
Hmm.
2N4058 is PNP, so it can't be used for second and third transistor if +24V is used for PS.  Also, there is lower 50uF string which shunts output to gnd.  And R13 and C9 are questionable, upper 50uF string can be smaller.

Nice catch. The schematic is still correct but drawn as for the +24V version with  the transistors are labelled from the -24V version. So use the 2N4058 for the first stage and something like the modern equivalent of the BC184L for the  two NPNs.

Cheers

Ian
www.customtubeconsoles.com
https://mark3vtm.blogspot.co.uk/
www.eztubemixer.blogspot.co.uk


'The only people not making mistakes are the people doing nothing'

Re: Full Helios Pre Schematic
« Reply #5 on: July 13, 2020, 03:19:47 PM »
So, How did this turn out for you Lerok?
If succeeded, I am Very interested to see your final schematic, as I am eager to try this as well.

Thank you.
//Ted

Re: Full Helios Pre Schematic
« Reply #6 on: August 10, 2020, 12:07:10 PM »
As Q9 is MJE182, Q10 should be MJE 172.

Rocinante

Re: Full Helios Pre Schematic
« Reply #7 on: August 11, 2020, 11:23:03 AM »
As Q9 is MJE182, Q10 should be MJE 172.
Yep.
If there's a harder way to do this, I haven't found it yet.


 

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