the Radio Geek thread

Stoves, Fridges, Radiograms and more
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Al F. Furnituremaker
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Re: You Might Be an Old Home Owner if...

Post by Al F. Furnituremaker »

The McIntosh factory is in my hometown, Binghamton,NY. Here is a link to a segment CBS did at the factory.

McIntosh Factory

I also work with another business that restores old radios. They gut the cases/cabinets and I repair/refinish them, while they are repairing the electrics/electronics. Right now I have 5 in my shop, all in various stages of progress.

My first year of college they taught us tube theory (oops showing my age). I never really worked with tubes since solid state was coming into play (discrete components - transistors, resistors, caps, etc.)

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jharkin
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Re: You Might Be an Old Home Owner if...

Post by jharkin »

Mick_VT wrote::text-threadjacked:

Do you guys want me to move the above to a Radio Geeks thread?


You might want to. I feel like this could go on .......... :lol:
-Jeremy

1790~1800ish Center Chimney Cape

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Re: You Might Be an Old Home Owner if...

Post by jharkin »

phil wrote:New silicone rectifiers (with added resistance to compensate for the old selenium)

one thing that selenium rectifiers did was that they didn't power up instantly. I have read about some who have a method of using some capacitors and resistors to somehow cause the power to ramp up. I don't know if that matters a lot, the theory was that the instant on power might shock the filaments but I have no idea if that holds water. It sounds like you did a great job of restoring it and glad to hear there is still one that didnt' get bought up by one of the rich collectors. I commonly see radios from about 1929 with '45 tubes and the price of the radio, so they end up either getting junked or with some other output tubes used. Does the Mac use 6L6? If it were mine I wouldn't sell it either ! it's an investment now

"drooling on my keyboard ;-) "

Phil


Yeah selenium is a bit slower than silicone, but still not as slow as tube rectifiers where. The danger was in hitting the plates with full B+ voltage before the filaments warm up, trying to forcibly rip electrons form the still cold cathode. But the mac designers where smart and they thought of that...

The Mac is an unusual design, even for its time. There did some really different stuff in the output stage, using special transformers with dual output winding's, in a setup that provides neg. feedback within the output stage. They also had the output tube grid and plates cross coupled and setup to be self biasing.... supposedly all of this made the thing twice as power efficient as any other contemporary design. Driving all this is a power supply that is interesting as well. On the B+ side they used a full wave rectifier with silicone diodes and a whole bunch of caps. the B- supply used a simple half wave rectifier with a selenium. I replaced all of them with new silicone, fast switching hexfreds on the B+ side and a basic 1n4007 on the B-. On the B- side i added a resistor to compensate for the selenium and get the voltages to factory spec.

The best part, is that the mac engineers used and inrush current limiter (aka "ICL" which is basically a thermistor) on the line side of the input transformer to give the whole thing a slow warm up. I think that was fairly common as my H.H. Scott receiver has one too. The 80s vintage CJ tube preamp I use with the Mac accomplishes the same effect using a timer relay to block the high voltage supplies altogether for 30 seconds to let the filaments warm.

In any case when I rebuilt it I replaced the ICL with a new one of the same spec :)

mc240.gif
mc240.gif (18.62 KiB) Viewed 995 times


To answer your other question - the amp does use 6L6s. Nice since those are such a popular guitar amp tube there are millions of options in new production. When I found it there was a set of worn out RCA's, I put a matched quad of Svetlana 6L6GC in it (this is the Svetlana of the 90s that was made at Reflektor in Russia, not the new Svetlana brand owned by NewSensor)

They made a whole series of stereo (MC225, 240, 275) and monoblock (MC30, 40, 60, 75) amps based on this general design. The 225 used 7591s and is what real purists go after. The 275 and 75 used the high power 6550 and is what the Japanese collectors buy up and is the one that Mac reissued in the $$$$ anniversary editions. The 40/240 sits right in the middle and gets overlooked somewhat so is a bit more approachable, but like you pointed out collectors have ruined the market for its average folks so I am just plain damn lucky I got a cheap one in the 90s. No way I could afford to buy one now, even in barely functional condition they are worth a couple grand.
-Jeremy

1790~1800ish Center Chimney Cape

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jharkin
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Re: the Radio Geek thread

Post by jharkin »

Does this mean we have been forgiven for clogging the other thread, and may continue?
-Jeremy

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Mick_VT
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Re: the Radio Geek thread

Post by Mick_VT »

jharkin wrote:Does this mean we have been forgiven for clogging the other thread, and may continue?


Nothing to forgive! Please do :thumbup:
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Re: the Radio Geek thread

Post by phil »

Yes we should have moved the radio discussion to the antiques Emporium as the details won't interest others so much but oh well, if we find it moved , no issue. I keep meaning to take some pictures of some of the radios in my collection. and can start a new thread in the appropriate place. Many , mostly the project cases reside in boxes but I have enough out to give others a glimpse and I think most here are interested in antiques of other sorts as well as houses.

I find that to myself and many others , the real interest is in the restoration and then after a time even though the radios are restored and able to be used daily they get shuffled aside. AM radio gets hard to listen to for long periods as there are a lot that are talk radio and such. When I had a bigger antenna I was amazed how much I can get on am and even shortwave. lots have gone to rebroadcasting from their I Phones or computer and through one of these
http://www.sstran.com/pages/AMT3000/overview.html

I bought up a few 45's and a few more rare tubes that I need for restorations like eye tubes and 01A tubes even some of the older 1 volt tubes used in early radios like the WD11 They are becoming harder to get. along the way I have aquired a few 6L6 and other output tubes not often used in radio and some used in communications equipment, and of course a lot of TV tubes which are useless. I have some pretty rare tubes that aren't much use other than a historical display. Rogers made their own spray shield tubes and I got on to a nice collection of those. it's hard to organize them all and they don't display well but it ocurred to me that it might be wise to latch on to some of the ones that would become difficult to get and prevent my restorations.

at one point I decided I wanted an Atwater Kent breadboard and I just saw lots on Ebay but never wanted to drop upwards of a thousand bucks on one so I began buying parts with the intention of building my own breadboard. I aquired almost every part but there is one part I can't seem to find one part, the 2 tube island on the far right.. anyway sometimes collecting all the bits is fun and here is what the 12C will lok like when complete
http://www.nixie.dk/~jthomas/4910.html

one of the ones that I have and just want to get into is a grunow teledial 12 , it is quite a big radio with 12 tubes and often people refer to it as a shirley temple radio because of this ad
https://www.flickr.com/photos/22283683@N07/4250722639/

other personal favorites are the D25 crosley.. this one was manufactured in pretty high numbers so some others might recognize it. it was a refrigerator radio or a bedside radio and came fitted with a plug so it will turn on a lamp or whatever you plug in. it seems reminiscent of a car dashboard of the era
http://web.eecs.umich.edu/~srs/Antiques ... hp?pid=370

westinghouse columair radios always caught my eye. these are from about 1929 and look like a grandfather clock. the speaker faces upward from the top. the clock has a synchronous motor and to start it you have to plug it in then open the face and there is a little lever that gives it a push to get it started. they didn't want ot pay the patent rights for the self starting motor. I restored one WD12 and I have a couple of WD10's that are a bit rough but restorable. I love seeing radios that are also clocks and there weren't many made at that era. so one of the first clock radios.

the one shown also has the optional "remote control" which was actually wired to the radio but enabled the listener to tune it without getting up from their chair.
http://www.radioatticarchives.com/image ... Potter.jpg

I have one like this , a philco chairside radio. It doesn't have a remote control , instead the radio is built into a table. a few manufacturers including zenith made chairside radios.
http://www.johnjeanantiqueradio.com/philcochairside.htm

It's just fun to collect them. Most of my examples are ones that I obtained without spending more than 100 or so as Im not a rich collector. One of the great things is it really isn't alll that expensive to get into restoring them I have had as much fun restoring some typical table radios that were in horrible shape and it is fun to see some of these old barn relics turn back into something beautiful.

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Mick_VT
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Re: the Radio Geek thread

Post by Mick_VT »

phil wrote:Yes we should have moved the radio discussion to the antiques Emporium as the details won't interest others so much but oh well, if we find it moved , no issue.


If you guys want it moved you can either just let me know or report the post to the moderators as being in the wrong forum. :thumbup:
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jharkin
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Re: the Radio Geek thread

Post by jharkin »

Or maybe we need an off topic forum for discussions like this. Im sure members here have lots of other interests to discuss. it can be interesting learning bout what the members are into besides houses.
-Jeremy

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Re: the Radio Geek thread

Post by phil »

I just watched a neat documentary called I Dream of Wires It goes into a lot of detail about Moog and the development of early synthesizers. I enjoyed it, here is the trailer
http://www.idreamofwires.org/

one thing that got me into old radio was in researching an old tape machine I got ahold of . it was made by Bradmatic in 1952 in Birmingham. It came with a documentary on tape that was recorded after the war in birmingham , during rebuilding the city.
I joked with my brother that this thing had with it spare tapes , from england, made in 1952 and it was studio equipment. I joked that it had lost beatles recordings worth millions, but when we actually played the old cellulite tapes , to our surprise it did have some beetles recordings! I think they are recorded from some other source like a record though. But it was fascinating none the less. It had a song "every little thing she does" which was an early beetles recording.


Bradmatic was one of the first making tape machines, earlier than that they used wire recorders. the company was approached by becuase they wanted to buy lots of tape heads. the mellotron was subsequently developed. The mellotron wasn't mentioned in the video but I was fascinated by the tape machine, it is quite unique with 10 inch reels and all the studio recording controls, it is mono and about the size of a dishwasher.
a mellotron is like a keyboard but each key, when pressed. activates it's own tape reel so the mellotron could sound like any instrument, the owner just had to fit tapes to make it sound like whatever instrument the set of tapes mimicked.
The changes in equipment created a lot of sounds in music. I found the connection to the machine I discovered quite fascinating.
i even got to call John Bradly in England and spoke to him about the machien I had aquired, it just got more fascinating the more I dug into the whole story of the mellotron. John must have had a really fascinating career keeping the mellotrons going and working with a lot of big names. You can read up on streetly electronics here
http://www.mellotronics.com/about%20us.htm


here is an article that talks about the connection between the bradmatic tape machien company and the development of the first Mellotrons.
http://www.normleete.co.uk/?page_id=19



and yes we got way off topic didn't we? but oh well I dont' mind if the post is moved. Fun to talk about other stuff beside houses too..

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Jamie
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Re: the Radio Geek thread

Post by Jamie »

You guys really started something! I used to post on the Old House Web going back to the days before you had to register. Gave up when the spam took over. I never joined the Wavy Glass site but would "troll" there occasionally to see what was was going on. Checking in this morning I linked over to this new site. What a nice surprise. I want to add I'm having my Edison R-2 Radio restored as this is being typed. Thomas A Edison Inc. only produced radios for a few years in the late 1920's. The serial number on the chassis is: 10055 which indicates is was made early in production. I have a "tape mitter" which is a low power transmitter sold back in the day to allow portable tape players to broadcast through car radios. I'll use that to provide a source of decent vintage music and programming. Looking forward to hearing my favourite Jack Benny broadcasts over the old set!

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