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 Post subject: Re: Collins 212A-1 Restoration Project
PostPosted: Aug Sat 31, 2013 10:39 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 527
Location: Tampa FLA
I think I have found the source of at least one point of confusion. On the metering circuit schematic, the resistor that is listed as R657 is actually attenuator R649...and R654 is actually attenuator R652. So I think I can get the VU meters hooked up right by following what is still hooked up on the attenuators.
Tim
MBL


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 Post subject: Re: Collins 212A-1 Restoration Project
PostPosted: Sep Sun 01, 2013 4:01 am 
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Joined: Jul Sat 23, 2011 9:33 pm
Posts: 919
Location: Long Beach Ms. USA 39560
One model of the Collins board had the audio controlled by a light-sensitive resistor in each amp. The panel knob actually changed the bulb brightness (DC) , If it failed, that channel was always on.
If you did not know that failure mode it was almost impossible to troubleshoot it.
If you find a lot of hum, the DC supply may be the culprit.
Enjoy the rebuild, you will really have accomplished something when you are finished.

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Pat W5THT
Unhappy tubes blush while unhappy power FETs scatter plastic


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 Post subject: Re: Collins 212A-1 Restoration Project
PostPosted: Mar Mon 03, 2014 9:02 pm 
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Joined: Mar Thu 24, 2011 6:23 am
Posts: 412
Location: New Jersey 07755
I guess this is a bit off topic, but this seems like a good place to mention it.

I would love to have a console like this or similar. I am not very concerned about the condition; I used to do a lot of work on gear like this.
When I was young and energetic I refurbished a console like this for our college radio station. It came from the scrap pile at a local station.
Now that I'm old somewhat burned out, I'd like to have one.
If you get bored with your project or if anyone knows where I can find a similar console, I'd sure like to hear about it!


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 Post subject: Re: Collins 212A-1 Restoration Project
PostPosted: Apr Wed 09, 2014 2:28 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 527
Location: Tampa FLA
Ok, semi update. I pulled two of the mic preamps, and I am going to recap them. Interesting little things. The plat supply caps are "paper" and not electrolytic. Since I am going to be using this as a recording mixing console, the goal will be to get all preamps working proper and set up so that mics and line level inputs can be mixed...then have a line out to a recorder.

All the circuitry related to the relays and such, I'm not gonna be too concerned with that.
Tim
MBL


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 Post subject: Re: Collins 212A-1 Restoration Project
PostPosted: Apr Wed 09, 2014 10:19 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 4232
Location: Boston, MA USA
In the 1950s and 60s there was an attempt to minimize the usage of electrolytic capacitors in high-quality broadcast equipment, for reasons of reliability.

-David


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 Post subject: Re: Collins 212A-1 Restoration Project
PostPosted: Apr Thu 10, 2014 11:59 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 527
Location: Tampa FLA
I'm finding that. In the monitor amp, there are some 4uf@600v caps. Of all the things that was messed with, the monitor amp was most messed with. I'm gonna need to redo the whole thing. The other stuff seems to be mostly left alone. In the monitor amp though, I can see using electrolytics, mostly because it shouldn't have any effect on the sound that gets recorded...that will come from the line level outs. or at least I think.

Tim
ML


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 Post subject: Re: Collins 212A-1 Restoration Project
PostPosted: Apr Thu 10, 2014 2:27 pm 
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Posts: 20037
Location: Warner Robins, GA
All that would affect is the sound of the monitor amp and if you use it to monitor the recording you might wind up adjusting any EQ (if used) based on what you hear from the monitor amp output which could affect the final recording.

That said I've never really done an A/B test between film capacitors and electrolytic capacitors in the same circuit so I cannot say for certain that there is indeed any difference other than that film capacitors will last a lot longer than electrolytic capacitors.


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 Post subject: Re: Collins 212A-1 Restoration Project
PostPosted: Apr Thu 10, 2014 5:41 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 527
Location: Tampa FLA
Well, I will keep film type caps in the signal path for everything for sure. It was odd to see film caps as the source of the plate voltage. In either case, I would probably use headphones to review any levels rather than the monitor amp. We'll see.
Tim
MBL


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 Post subject: Re: Collins 212A-1 Restoration Project
PostPosted: Apr Fri 11, 2014 2:16 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 20359
Location: Utica, NY 13502 (USA)
These consoles were often used in high RF environments when the station's transmitting tower(s) were very near or sometimes even on the roof of the studio. The need for good RF bypassing on B+ lines and other circuits in radio station audio consoles is essential. Electrolytics are notoriously bad at bypassing RF. Film caps are much better at this.

Dave


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 Post subject: Re: Collins 212A-1 Restoration Project
PostPosted: Apr Sun 13, 2014 3:17 am 
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Posts: 8803
Location: Beaver Falls, PA. USA
Pat, I have one of those LDR-controlled consoles; it's a 212T-1. They were in production in the late 1960s through the 1970s, and had slide faders. I'm planning to use it for my basement studio, when I get around to putting things together.

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Tim KA3JRT


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 Post subject: Re: Collins 212A-1 Restoration Project
PostPosted: Oct Sun 21, 2018 7:15 pm 
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Joined: Oct Sun 21, 2018 7:05 pm
Posts: 1
Hi:
I own one of these consoles and may be able to help with parts. I had aspired to restoring it someday or use the preamps etc. as I am a recording artist and sound engineer. However, it looks unlikely at this point that I’ll get the thing going. In other words I am willing to sell all or part for reasonable price. Let me know if I can help. I also have a Collins 12-Z, a 212Y mixer w/meter and a couple nice 50s Gates preamp-mixers I’d be willing to sell or trade. I’m in Sedona AZ. Thanks,

Richard


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