Re: Helios thread
« Reply #260 on: October 08, 2019, 09:24:41 AM »
Do you have idea of what circuit was that?
Any schematic available for that circuit?

thank you so much


I went looking and found the info in an old email.   I was incorrect in remembering it being push-pull, it's an emitter follower with a constant current source.   Anyway, I think this was made public by Dave Amels over 10 years ago so I'm hoping it's OK to post here.

PDF is attached to this and pertinent info written by Dave is:

"These were for the silvers which ran on -24V.  The schematic shows two which
were both on a pcb.  You can rearrange the circuit for +24V if needed.  The
output transformer is a Cinemag CMOQ-3L wired for a 1:2 stepup."


Re: Helios thread
« Reply #261 on: October 08, 2019, 11:30:19 AM »
Internal pic of  Manor mobile or Strawberry desk module, not sure which, it's been a long time:

Re: Helios thread
« Reply #262 on: October 08, 2019, 11:32:16 AM »
Likewise, it's a Manor or Strawberry, probably whichever the other pic isn't.

Re: Helios thread
« Reply #263 on: October 08, 2019, 11:34:47 AM »
No idea!

Re: Helios thread
« Reply #264 on: October 08, 2019, 11:36:54 AM »
Has this particular drawing of the 69 been posted?

Squeaky

Re: Helios thread
« Reply #265 on: October 08, 2019, 03:17:09 PM »
Thanks for posting the photos and schematic John, they are all appreciated.

I have never seen the version 3 schematic you posted (there is version 2 schematic available that is drawn in the same style). Interesting to see that the 22113 makeup following the eq employs the same sort of filter and bypass attenuation configuration (27k and 5k1) as modules that use the 2128 as the eq makeup. Rightly or wrongly, I did the same with my diy versions. The 22113 is running on 24V (early example of use?). I have seen a snapshot of the 22113 part of that version 3 schematic somewhere.

The module in the first photo has the high level line amp (22113) with an extra HPF buffer transistor (8 transistor) on the board. Looks like a little Beyer input tranfo?

The second has the high line level amp without the the filter buffer (seven transistor) but with an output transformer?  I presume the output transformer was a mod and not original? I wonder if it was a step-up or 1:1? Looks like there is a Carnhill inductor added as well (on its side). Also looks like it might be using a little Beyer transformer?

The boards on the third photo do not look like original Helios boards at all, at least not like I have seen in photos. However, unlike yourself and others, I have no first hand experience. Everything else looks as it should. Looks like a  three transistor amp with the filter buffer (makes 4 transistors) and looks like a Lustraphone transformer. This one reminds me of the version 2 (Musicland) channel module. Unfortunately, the makeup amp is obscured.

Cool.

Whoops

Re: Helios thread
« Reply #266 on: October 08, 2019, 05:03:22 PM »

I went looking and found the info in an old email.   I was incorrect in remembering it being push-pull, it's an emitter follower with a constant current source.   Anyway, I think this was made public by Dave Amels over 10 years ago so I'm hoping it's OK to post here.

PDF is attached to this and pertinent info written by Dave is:

"These were for the silvers which ran on -24V.  The schematic shows two which
were both on a pcb.  You can rearrange the circuit for +24V if needed.  The
output transformer is a Cinemag CMOQ-3L wired for a 1:2 stepup."


Thank you so much for the schematic and info Winston, I will try that circuit out.
Some fellow members were using the 22113  circuit after the mic pre to be able to drive a transformer, but it seems maybe too much circuit just for that.
This simple 4 transistor buffer from Dave Amels seems elegant and simple enough.

Byt the way, do you know what output transformers were used on the Kravitz's console?

Thank you

Re: Helios thread
« Reply #267 on: October 09, 2019, 08:37:08 AM »
This simple 4 transistor buffer from Dave Amels seems elegant and simple enough.

Byt the way, do you know what output transformers were used on the Kravitz's console?

The buffer is even simpler than it looks, the schematic shows buffers for 2 channels since it was laid out in pairs on a PCB.
It's a simple class A emitter follower with the other transistor as a  constant current source.  There's a healthy amount of quiescent current - 100mA - and a heatsink will be required for both transistors.
As for transformers used in the modded Kravitz modules, Dave indicates they used Cinemag CMOQ-3L strapped as 1:2.

Remember, this was for the older silver Helios modules which ran on negative 24v so, for other schemes running on a positive rail, you'll need to switch polarities.





Re: Helios thread
« Reply #268 on: October 09, 2019, 08:47:14 AM »
Thanks for posting the photos and schematic John, they are all appreciated...

Hey, thanks for the analysis of the modules, you know your Helios that's for sure 👍

I'm pretty certain the amp card in the last picture is original as the owner of it is a big collector of Helios and originality would be VERY important to him.
I think it just looks different because it's an older module, an earlier iteration of the amp.

Re: Helios thread
« Reply #269 on: October 12, 2019, 11:12:03 AM »
Some fellow members were using the 22113  circuit after the mic pre to be able to drive a transformer, but it seems maybe too much circuit just for that.

I missed this part of your reply, sorry  :o
Yes I think you're right regarding the 22113.  If the card was run on 36V like some desks were, then the headroom is "just about" OK for pro levels in my opinion.  But running on 24V, we need help via other means to get headroom up.
Having a beefy class A follower driving a 1:2 step-up gives us around 6dB extra output before the amp clips.
Even if you're running on 36V, I don't think it hurts to have an output able to source enough current to the outside world.

By the way, thank you for your uploads to the Helios docs section, I'm late to the party and only just saw them.
Cheers 👍


Whoops

Re: Helios thread
« Reply #270 on: October 12, 2019, 07:07:28 PM »
By the way, thank you for your uploads to the Helios docs section, I'm late to the party and only just saw them.
Cheers 👍

Thank you also for your knowledge Winston

rooster

Re: Helios thread
« Reply #271 on: November 06, 2019, 08:11:48 AM »
I am in touch with one of the original designers of the Helios circuits. He told me that the 10H inductor did not have a spec as we would think of it today. The first units were made from a bunch of inductors purchased from a surplus store in the Edgeware Road.

Cheers

Ian
Maybe you can me help out.
I got from a customer 2 Helios 69 for repair. One is working well now. The second shows no output. Up to the input section the signal is there. Any ideas to help me out with this issue????

ruffrecords

Re: Helios thread New
« Reply #272 on: November 06, 2019, 01:30:21 PM »
Maybe you can me help out.
I got from a customer 2 Helios 69 for repair. One is working well now. The second shows no output. Up to the input section the signal is there. Any ideas to help me out with this issue????
Divide and conquer is the best approach. Check for output from the mic pre stage. If that is OK then check for output in wiper of bass cut switch - if this is not working then no signal gets to the rest of the EQ.

Next check for lower level signal at EQ output (across the 5K1 resistor (should be about 14dB down). If it is there then check output of HPF then the output stage.

You do need a schematic to trouble shoot these but there are many variants so they are not always accurate.

Cheers

Ian
« Last Edit: November 08, 2019, 03:17:25 AM by ruffrecords »
www.customtubeconsoles.com
https://mark3vtm.blogspot.co.uk/
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'The only people not making mistakes are the people doing nothing'

Whoops

Re: Helios thread
« Reply #273 on: November 07, 2019, 07:56:43 PM »
Maybe you can me help out.
I got from a customer 2 Helios 69 for repair. One is working well now. The second shows no output. Up to the input section the signal is there. Any ideas to help me out with this issue????

Post some pics of the modules and circuit board, then we can know which circuit you have and help out with the proper schematic.

Like Ian said there's a few variants of the 69


 

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