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 Post subject: Collins 212A-1 Restoration Project
PostPosted: Aug Mon 19, 2013 6:10 pm 
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Location: Tampa FLA
Howdy all. Tim here, with a different sort of project that I am getting into. I have been working on setting up a period correct 1950's recording studio...well early 50's. Anyhoo. I picked up a mixing board with two power supplieds and the relay unit.

I'm going to have to replace all of the relays. Does anyone know where I might get suitable relays? I was thinking of installing sockets and using those Ice Cube relays...but I don't know if anyone has other better ideas.

Also I am missing some of the buttons and one knob. I will be needing quite a bit of help I think to get this guy going. The meter selector is confusing to me, even with the schematic.

Anyone out there have one of these or experience with one?


Image

Image

thanks for any help!
Tim
MBL


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 Post subject: Re: Collins 212A-1 Restoration Project
PostPosted: Aug Tue 20, 2013 1:06 pm 
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Can you post a picture of the relays? Do you have a link to the schematic?

Dave


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 Post subject: Re: Collins 212A-1 Restoration Project
PostPosted: Aug Tue 20, 2013 3:46 pm 
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Location: Warner Robins, GA
Looks like you're missing one meter and one control.


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 Post subject: Re: Collins 212A-1 Restoration Project
PostPosted: Aug Tue 20, 2013 5:21 pm 
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I don't know this console specifically, but in general the only relays are for talleys ("on the air") and cutouts for monitors and telephone ringers in the studio. You probably don't need them. But if you want them, the ice cube type is what broadcast stations use for this purpose.

As others have stated you are missing one VU meter.

This console probably has a passive mixing bus which means a loss of about 60 dB. This has to be made up by a program amplifier in the console. There should be two, one for the Program channel and one for the Audition channel. Are they in place or do you have to construct them?

-David


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 Post subject: Re: Collins 212A-1 Restoration Project
PostPosted: Aug Tue 20, 2013 5:46 pm 
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Posts: 527
Location: Tampa FLA
I guess I made a mistake as to where this post should have been.

Here is a link to the manual:

http://www.ianbell.ukfsn.org/EzTubeMixe ... 212A-1.pdf

It seems that the folks that have chimed in are correct. There are two program amplifiers. There is also a monitor amp of about 8 watts.

There are some relays that have a 12vdc coil. And these are 3pdt relays. I think the standard 10A ice cube relays will work for this.

But, there are some relays that need to be able to handle the HV of 325dc. Now I realize that the current would be low, but I am a bit at a loss about what rating might be the best.

Also, there are at least two that have a 200vdc coil, which I don't think I can find. I think perhaps I will need to use one that has a 115vdc coil and use a dropping resistor.

The 12Vdc coil relays that turn on and off the on air/off air lights and redirect the monitor output could likely not be used, but if its not entirely too costly, I'd like to do it.

Here is a pic of the ratty relay unit:


Image

I actually have the switch that is missing, although I am completely at a loss as to how it is hooked up.

The knob is a mystery, but I think the buttons may have also been used on western electric telephone equipment.

VU meters are on the radar for a need for sure.
Thanks for any suggestions!
Tim
MBL


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 Post subject: Re: Collins 212A-1 Restoration Project
PostPosted: Aug Tue 20, 2013 5:49 pm 
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Location: Tampa FLA
Here is a pic of the underside:

Image


and one back some:

Image

The individual amplifers seem to all be in place, though I am sure I will need to at least do a recap.
Tim
MBL


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 Post subject: Re: Collins 212A-1 Restoration Project
PostPosted: Aug Tue 20, 2013 6:04 pm 
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Yes judging by the manual and looking at the picture all the amplifiers are present.


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 Post subject: Re: Collins 212A-1 Restoration Project
PostPosted: Aug Tue 20, 2013 6:56 pm 
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Location: Boston, MA USA
Thanks for posting a link to the manual. Some observations:

1) You don't need the relay unit unless you want to use two redundant power supplies. If you can use only single power supply you can connect it directly to the console.

2) If you want to use two power supplies or the talleys and cutouts, you need the relay unit, and I recommend just cleaning up the old relays rather than trying to replace them. I bet they clean up fine.

3) This is a broadcast console, not a recording console. The main problem is lack of high-level inputs for tape recorders, etc. You will have to use the remote line inputs for those. The transcription inputs are weird by today's standards. They require an external equalizer with a 50-ohm output, not available today. To use these with modern phono preamps your best bet would be to connect them thru a 40-db pad.

-David


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 Post subject: Re: Collins 212A-1 Restoration Project
PostPosted: Aug Tue 20, 2013 8:07 pm 
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This is great info! Thanks! I think perhaps I will try setting it up without the relay unit to start. I can always work on that later. I guess I will need to make sure I have a load on the monitor output.

And I'm going to have to unravel the mystery of how the VU meters are hooked up with the meter switch. That's a tough one!
Tim
MBL


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 Post subject: Re: Collins 212A-1 Restoration Project
PostPosted: Aug Tue 20, 2013 8:38 pm 
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Location: Boston, MA USA
Yes, it's the meter switch that's missing. It's a 4-deck rotary selector switch. It will be hard to find the original but you can get a new one from Mouser without too much difficulty. You will have to specify it carefully to make sure it matches the original.

The meter that's in place just hangs on the Program 1 output with no switching. For now, just make sure that there are no loose leads from the old switch hanging around that could short out. Some of those leads have over 300V on them!

If it were me, I'd find a VU meter (that will be hard enough) and just hang it on the Program 2 output through the same kind of attenuator that the Program 1 meter has. It's really important to be able to set level on a source you are auditioning before you key it live. I've spent many hours operating consoles similar to this one (newer but the same idea).

-David


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 Post subject: Re: Collins 212A-1 Restoration Project
PostPosted: Aug Tue 20, 2013 11:41 pm 
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Location: Tampa FLA
This is great stuff! Here are some more pics. Some of the selector switch.
Image

Image

Image

Now if I can figure out where the cut wires went...ah there'd be a good start.

There is the attenuator board that I believe was mounted in between the VU meters...its somehow used to lower what the meter sees?

Image

Here is a shot of the inerds from the top


Image

So far, I am convinced the way to go would be to get one power supply working and rut it straight to the console. There are some voltages provided by the power supply that may not be needed without the use of the relay. The 12vdc comes to mind.
Thoughts?
Tim
MBL


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 Post subject: Re: Collins 212A-1 Restoration Project
PostPosted: Aug Wed 28, 2013 12:48 am 
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Dual Weston 862 meters found! Now if I can only be sure how to wire the meter switch. Any ideas?


Image

Image


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 Post subject: Re: Collins 212A-1 Restoration Project
PostPosted: Aug Wed 28, 2013 12:51 am 
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Posts: 527
Location: Tampa FLA
Here's the schematic and a pic of the bottom of the switch:

Image

Image

I just don't want to blow up the meter by feeding I
t too much voltage.
Tim
MBL


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 Post subject: Re: Collins 212A-1 Restoration Project
PostPosted: Aug Wed 28, 2013 12:59 am 
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Posts: 4242
Location: Boston, MA USA
You'll have to carefully match up the switch sections with the schematic, and map each terminal to the right lead on the schematic. Label them carefully and wire them up. You can start with the audio feeds, check that out, then do the power supervision leads.

-David


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 Post subject: Re: Collins 212A-1 Restoration Project
PostPosted: Aug Wed 28, 2013 3:16 pm 
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Location: Tampa FLA
Best I can figure from the schematic. The meter is placed in parralell with R108 for the preamps, but for some reason, P1 doesn't have a connection. Not sure why. If I assume that Off/terminal 1 is for the meter itself, I can easily work my way around, but in looking at the switch, it appears that terminal 1 on the switch pictured is just to the right of the post. Then 2 and 3 should follow on the other side of that post, but it almost looks like the Ch1/Ch2 were originally wired to terminals 3 and 4.

I'm just trying not to fry anything at first power up.
Thoughts?
Tim
MBL


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 Post subject: Re: Collins 212A-1 Restoration Project
PostPosted: Aug Wed 28, 2013 5:57 pm 
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Location: Boston, MA USA
It looks like the switch wiper terminals are not numbered on the schematic. That might be the source of your confusion.

-David


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 Post subject: Re: Collins 212A-1 Restoration Project
PostPosted: Aug Wed 28, 2013 10:25 pm 
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Posts: 527
Location: Tampa FLA
Image

In looking around inside I found the knob for the switch?! It was just sitting inside.
I think the wiper is no1 on the schematic...
Tim
MBL


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 Post subject: Re: Collins 212A-1 Restoration Project
PostPosted: Aug Thu 29, 2013 4:51 pm 
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Location: Tampa FLA
Ok I think I have made a decision. Due in part to the feedback/suggetions provided by dberman51. Big Thanks!

I think that I will hook up the meter so that the primary purpose of it will be to measure the ouput of Channel 2. The other one is set up for Channel 1. So this way I have a way to check each. I like the diagnostic puprose of the other settings, but realistically, I don't see myself using them. If I am curious about the voltage at a certain point, I can just rotate the console up and measure it. I thnk this would be a safer way to go.

I'm not sure, but perhaps I can have it so it could be switched between the Ch2 and perhaps the monitor amp and that's it.
Now the trouble with this is that I am not sure how thw attenuators are acually wired. This is not covered in the schematic that I can tell.

Thoughts?
Tim
MBL


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 Post subject: Re: Collins 212A-1 Restoration Project
PostPosted: Aug Thu 29, 2013 5:34 pm 
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Location: Boston, MA USA
You are referring to the meter attenuators, yes? They will be wired differently by different radio stations to set the desired output program level. Common output levels are 0 dBm, +4 dBm, and +8 dBm. For now, just duplicate the wiring for Channel 2 that you see for Channel 1.

-David


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 Post subject: Re: Collins 212A-1 Restoration Project
PostPosted: Aug Fri 30, 2013 10:17 am 
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Location: Tampa FLA
Well the remaining meter in the console has actually disconnected from the attenuator. There are some wires going to earch presumably one set came off the program line one, and the other set came went to the meter itself. I wonder if there is a schematic out there for the attenuators. The other attenuator seems to have some other stuff hooked to it...perhaps this was part of the switching feature.
Tim
MBL


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