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 Post subject: Re: 1925 Thompson V-50 Grandette Neutrodyne project...
PostPosted: Jul Mon 13, 2020 5:56 pm 
Member

Joined: Oct Mon 26, 2009 10:02 pm
Posts: 6618
Location: Indianapolis, IN
Hello All,

Finally completed & verified the schematic today from "reverse-engineering" this working radio. Took MANY hours using Microsoft Paint as I don't have any "specialty software"... Am thankful that it turned out so well ! If anyone wants the higher-resolution original, please PM me an e-mail address. It is to be freely shared with anyone who might want it... And yes, did notice the completion date is a day ahead but wasn't worth effort to correct---was up until around 3:00 AM this morning working on it and was "mentally" a day off... Also, not having the original 1st interstage transformer, didn't have the terminal numbers to include on drawing...

Completed a working power supply last night after an almost disastrous "false start". Also, the P-T156 transformers (one spare) just arrived from AES, so hope to have this radio completed, final-tested, and ready to return to owner by this evening. Stay tuned for more details & pics !

John


Attachments:
Thompson V-50 Neutrodyne schematic COMPLETE 7-13-2020.jpg
Thompson V-50 Neutrodyne schematic COMPLETE 7-13-2020.jpg [ 376.8 KiB | Viewed 428 times ]
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 Post subject: Re: 1925 Thompson V-50 Grandette Neutrodyne project...
PostPosted: Jul Mon 13, 2020 7:39 pm 
Member

Joined: Jan Thu 01, 1970 1:00 am
Posts: 642
Location: Bristol TN 37620
John,

Nice job on the schematic. Looks like the jacking system is
slightly different from an NR5. Now if you plug headphoes into
1 and 2, do you get audio?


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 Post subject: Re: 1925 Thompson V-50 Grandette Neutrodyne project...
PostPosted: Jul Tue 14, 2020 4:27 pm 
Member

Joined: May Sat 30, 2015 11:49 pm
Posts: 1422
Location: Keystone Heights, FL, USA 32656
Hornet, the plugs 1 and 2 are not for headphones, they switch 1st or 2nd audio to the speaker.

John, let us know how using the transformer vs the RC bypass compare. My guess is it will be a bit louder but not "better" sounding. Thanks

_________________
Jeff
“Nothin’s worth nothin ‘till somebody wants it.”—Irv Metter


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 Post subject: Re: 1925 Thompson V-50 Grandette Neutrodyne project...
PostPosted: Jul Tue 14, 2020 7:30 pm 
Member

Joined: Jan Thu 01, 1970 1:00 am
Posts: 642
Location: Bristol TN 37620
Jeff,

Thanks for clearing that up, as i was confused. On an NR5, you simply plug into the
stage you want to use.


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 Post subject: Re: 1925 Thompson V-50 Grandette Neutrodyne project...
PostPosted: Jul Thu 16, 2020 6:20 pm 
Member

Joined: Oct Mon 26, 2009 10:02 pm
Posts: 6618
Location: Indianapolis, IN
Thanks Guys (Jeff for answering brnhornet52 question) !

Jeff---the sound is MUCH louder as stated below. Audio quality not bad at all, but does have a somewhat different tone to it----hard to describe...

Installed the P-T156 transformer this afternoon. Was surprised to see that the mounting hole spacing was same as chassis ! When non-original part was installed long ago, stand-offs were added to give clearance to grid-leak resistor/cap assembly beneath, so used them also for new transformer. The holes in chassis were worn larger so that head of screw nearly pulled through. Had some old gray phenolic washers which were used for transistor heatsinks that solved problem neatly. Attached 3 of the 4 wires to ring terminals after removing from connection points. Had to splice the "+45" line as lead wasn't long enough to reach...

Was scrapping out an old Marantz receiver after having problems with first power supply and discovered that it had high enough voltage output on one of the secondary windings that it only had to be rectified and filtered to use for B+. Used a resistive voltage divider for the 45 Volts. Had to make new chassis since transformer larger and wouldn't fit into enclosure on short-lived "early" supply. Kept the 5V 2-amp brick for filament source, but went to 3-"AA" holder for "C" supply... Also installed the audio output transformer for test speaker inside the cabinet of a small, plastic-cased speaker from a cheap stereo system. This will also come in handy for other tube-radio projects...

Assembled chassis into cabinet, installed tubes, applied power, and after playing with knobs awhile radio began working. Audio output MUCH louder with the transformer in place ! Noticed on the connection chart that the B+ center terminal could be attached to junctions of B-batteries to give 22.5, 45, 67.5, or 90 Volts---said to connect as indicated by best results. When reducing B- leg of voltage divider resistance to give approximately 25 Volts, the performance and sound quality noticeably improved---so soldered an additional resistor in parallel to keep this level... Carefully & gently cleaned top of chassis with slightly water-dampened then dry soft cotton cloth pieces.

Returned radio to owner the following day on the way to Kokomo to help Dad with a couple project. Had called him earlier and asked him to measure resistance of horn-speaker driver coil and it had checked okay. When I arrived, we set everything up on the dining room table and strung a temporary antenna from the chandelier across hallway to far side of living room. After warm-up, radio received local station fine. Was amazed on how good that "Music Master" horn-speaker sounded as I'd never heard one before---not as "tinny" as expected ! Both owner and his wife were thrilled to hear it work which made the efforts well worthwhile---but I was also excited since I'd wanted to hear it play ever since they bought it around 50 years ago ! Was so fascinated by this radio as a kid that I used to "draw" pictures of it while in class at school...

Final pics below---Sorry that I forgot to take one with gently cleaned tubes installed, but they don't look much different than they did in "before" pic posted earlier... Also, was afraid to use even water on the knob grooves, so just carefully dusted them out with dry toothbrush which still left dried residue from handling long, long ago... The next to last of my pics show radio alongside 1920 dial candlestick phone which I connected for use on work-table to "celebrate" it's 100th year...

John


Attachments:
ARF TEST SPEAKER.jpg
ARF TEST SPEAKER.jpg [ 474.2 KiB | Viewed 372 times ]
ARF THOMP PWR SPLY.jpg
ARF THOMP PWR SPLY.jpg [ 492.78 KiB | Viewed 372 times ]
ARF THOMP CHS CMPLT BOT.jpg
ARF THOMP CHS CMPLT BOT.jpg [ 329.62 KiB | Viewed 372 times ]
ARF THOMP NEW TRANSFORMER INSTLL DETAIL.jpg
ARF THOMP NEW TRANSFORMER INSTLL DETAIL.jpg [ 654.19 KiB | Viewed 372 times ]
ARF THOMP EMPTY CAB AND OPEN OLD REPLACEMENT TRANSFORMER.jpg
ARF THOMP EMPTY CAB AND OPEN OLD REPLACEMENT TRANSFORMER.jpg [ 332.91 KiB | Viewed 372 times ]
ARF THOMP CHS CMPLT CLN.jpg
ARF THOMP CHS CMPLT CLN.jpg [ 326.47 KiB | Viewed 372 times ]
ARF THOMP INS CLN TUBES OUT.jpg
ARF THOMP INS CLN TUBES OUT.jpg [ 543.81 KiB | Viewed 372 times ]
ARF THOMP FILAMENT PWR ON.jpg
ARF THOMP FILAMENT PWR ON.jpg [ 426.05 KiB | Viewed 372 times ]
ARF THOMP & CANDLESTICK.jpg
ARF THOMP & CANDLESTICK.jpg [ 328.35 KiB | Viewed 372 times ]
ARF THOMP BACK HOME PLAYING.jpg
ARF THOMP BACK HOME PLAYING.jpg [ 481.78 KiB | Viewed 372 times ]
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 Post subject: Re: 1925 Thompson V-50 Grandette Neutrodyne project...
PostPosted: Jul Thu 16, 2020 6:34 pm 
Member

Joined: Jan Tue 07, 2020 1:41 am
Posts: 3073
Location: Fenton, MI 48430
Nice work. Perhaps you may want to find a similar radio to play with.

_________________
NAVY JACK FLAG- 'Don't Tread on Me'


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 Post subject: Re: 1925 Thompson V-50 Grandette Neutrodyne project...
PostPosted: Oct Sun 18, 2020 11:01 pm 
Member

Joined: Oct Mon 26, 2009 10:02 pm
Posts: 6618
Location: Indianapolis, IN
Hello All,

Was visiting this old friend and his wife yesterday evening to show them the '56 Chevy Delco car radio (which he had given me awhile back) that I had refurbished and built a cabinet for recently: https://www.antiqueradios.com/forums/vi ... 1&t=385262 and was told that they had decided to give me this beautiful Thompson ! Was very surprised, but grateful since I've really liked this radio since childhood (have know them 51 years)... His wife mentioned that she wanted me to put a note inside stating that it should go to a museum upon my demise---sure hope I know someone who will at that time ensure that it and many other radios in collection make their way to a place where they're appreciated (if any are still around !)...

He was an Audio Engineer at Delco for many years and is now in process of setting up to perform a detailed analysis of the horn speaker's audio characteristics to satisfy his curiousity and said I could have the speaker when this is complete. Said he'd also give me a copy of his report to share here and with other antique radio groups. Was able to help a bit with this in the early stages and it looks like it will be an interesting endeavor...

Will now need to build the PS into a nice cabinet so radio can be easily used occasionally !

John


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 Post subject: Re: 1925 Thompson V-50 Grandette Neutrodyne project...
PostPosted: Oct Sun 25, 2020 7:19 pm 
Member

Joined: Oct Mon 26, 2009 10:02 pm
Posts: 6618
Location: Indianapolis, IN
Hello All,

After posting request for help in Cabinet Restoration forum and receiving helpful suggestions, remembered having an old bottle of Howard Restor-A-Shine Super-Fine burnishing cream in kitchen cabinet which was left by previous residents many years ago and after reading that it was safe for both shellac and lacquer, gave it a try to remove some white marks on top of cabinet. It worked so well that I did the entire top surface. Man, that wood and original finish is beautiful after removing almost a hundred years of residue !

John


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 Post subject: Re: 1925 Thompson V-50 Grandette Neutrodyne project...
PostPosted: Nov Tue 17, 2020 12:14 am 
Member

Joined: Oct Mon 26, 2009 10:02 pm
Posts: 6618
Location: Indianapolis, IN
Hello All,

Have been a bit concerned about cleaning the knobs on this beautiful antique. Nearly 100 years of crud in the grooves. Today took a chance with a "stubby" (cut-down bristles) toothbrush and water. Tried in a small area first and with a LOT of careful but vigorous brushing grooves came clean and looked fine, so continued. Took several hours of going over & over the grooves on all knobs to complete task and changed "brush dipping" water when dirty. Was very careful to avoid the painted graphics on the skirts and cleaned them (and insides) by gently wiping with water dampened then dry soft cotton cloths. They turned out very well and look MUCH better ! Felt a little uncomfortable at start knowing that I was removing "historical dirt", but was glad after seeing results...

Few pics below---included one of the dirty water that dripped off of one knob since dirt appeared to form an "image" in the small "puddle". Guess I am a bit crazy and have a hyper-active imagination !

Am now looking for a narrow old table or floor cabinet to fit in the only available spot left in family-room for display. Once this is found and radio is in its new, "permanent" location, will post true "final" pics...

Anyone know what to use to clean the front bakelite panel safely ??? Tried water-dampened then dry cloths, but it causes subtle streaking...

John


Attachments:
ARF THOMP KNOBS OLD DUST INSIDE 11-16-20.jpg
ARF THOMP KNOBS OLD DUST INSIDE 11-16-20.jpg [ 233.14 KiB | Viewed 119 times ]
ARF THOMP KNOBS OFF 11-16-20.jpg
ARF THOMP KNOBS OFF 11-16-20.jpg [ 287.96 KiB | Viewed 119 times ]
ARF THOMP DIRTY WATER OFF A KNOB 11-16-20.jpg
ARF THOMP DIRTY WATER OFF A KNOB 11-16-20.jpg [ 271.46 KiB | Viewed 119 times ]
ARF THOMP KNOBS INS CLEAN 11-16-20.jpg
ARF THOMP KNOBS INS CLEAN 11-16-20.jpg [ 600.36 KiB | Viewed 119 times ]
ARF THOMP KNOBS OUT CLEAN 11-16-20.jpg
ARF THOMP KNOBS OUT CLEAN 11-16-20.jpg [ 740.71 KiB | Viewed 119 times ]
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 Post subject: Re: 1925 Thompson V-50 Grandette Neutrodyne project...
PostPosted: Nov Tue 17, 2020 1:13 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 15060
Location: S. Dartmouth MA 02748-1225 USA
The panel can be made of several different materials, of which all can be damaged using most common household cleaners, the most notorious cleaner 409 can strip Bakelite of its gloss the user thinking that years of nicotine are being removed in actuality is the surface is being dulled. Not all Bakelite is the same formula and some do standup with strong cleaners.

I always opt for Murphy's Oil Soap in a weak dilution that seems to work well even on the cabinet, damp cloth only. Some folks like to use grit free Go-Jo hand cleaner. YMMV chas

_________________
List' & I will Enchant Thine Ear


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 Post subject: Re: 1925 Thompson V-50 Grandette Neutrodyne project...
PostPosted: Nov Thu 19, 2020 12:12 am 
Member

Joined: Oct Mon 26, 2009 10:02 pm
Posts: 6618
Location: Indianapolis, IN
Thanks Chas ! Remember using "409" or something similar as a kid many years ago on a bakelite set and ruining the finish as you mentioned. Think I'm going to leave the front panel on this alone for now as it's not too bad and certainly don't want to cause any damage to its finish !

Hello All,

Just phoned the old friend and his wife who gave me this radio the other day to wish them a safe trip to Florida for the winter and he asked if I had tried it yet here with the horn speaker that I recently brought home. Had done more detail cleaning and was going to wait until I could find a table or cabinet to fit within "assigned spot" in family-room to hook it up for operation, but looking at this beautiful antique sitting on bench, decided to try it today...

Used recently disconnected telephone lead-in cable from house to pole as long-wire antenna via a .01 uF capacitor to antenna binding post and the home-made power supply I had built months before.

After power-up, "played" with rheostats and tuning and was actually able to receive several stations including my favorite oldies station, WHBU 1240 in Anderson, IN some 30 miles away ! Selectivity not great initially and could also clearly hear a strong local at 1260 coming in with it. But after being on a long while and with more "tweaking" of controls, it improved significantly and the local could now be tuned out ! Audio quality flat and a bit trebly as expected, but room filling volume. Very impressed with how it performed this time as when I first completed it, it would only receive a couple strong locals. Maybe the tubes are "waking up" as I've read about ??? Actually took my first radio video using i-Phone of it working---not that great, but am thinking of posting it eventually... WHBU was playing "Downtown" by Petula Clark at the time and thought it neat to hear a song that was popular forty years after this radio was new...

Am still amazed at the very good condition (for age) of the Music Master horn speaker---disassembled and took a few pics to show off parts after careful detail cleaning with water-dampened, then dry soft cotton cloths. Used only a dry soft cotton cloth on wood horn itself to avoid risk of damage to finish. The nickel (or chrome ?) plated horn ring appears to have some type of coating (perhaps lacquer ?) which has discolored and worn off in areas. Tried treating a small area with Mother's carnauba wax with mild cleaner and it only shined it up a bit... Am posting several detail pics for those interested...

John


Attachments:
01ARF MM HORN PARTS 11-18-20.jpg
01ARF MM HORN PARTS 11-18-20.jpg [ 368.91 KiB | Viewed 98 times ]
02ARF MM HORN BASE BOT FELT 11-18-20.JPG
02ARF MM HORN BASE BOT FELT 11-18-20.JPG [ 915.36 KiB | Viewed 98 times ]
03ARF MM BASE BOT FELT LABEL 11-18-20.JPG
03ARF MM BASE BOT FELT LABEL 11-18-20.JPG [ 418.2 KiB | Viewed 98 times ]
04ARF MM HORN BASE 11-18-20.jpg
04ARF MM HORN BASE 11-18-20.jpg [ 744.93 KiB | Viewed 98 times ]
05ARF MM HORN INS LABEL 11-18-20.jpg
05ARF MM HORN INS LABEL 11-18-20.jpg [ 794.88 KiB | Viewed 98 times ]
06ARF MM HORN RING 11-18-20.jpg
06ARF MM HORN RING 11-18-20.jpg [ 464.73 KiB | Viewed 98 times ]
07ARF MM RING ON HORN 11-18-20.jpg
07ARF MM RING ON HORN 11-18-20.jpg [ 594.55 KiB | Viewed 98 times ]
08ARF THOMP CMPLT PLAYING INS 11-18-20.jpg
08ARF THOMP CMPLT PLAYING INS 11-18-20.jpg [ 533.73 KiB | Viewed 98 times ]
09ARF THOMP CMPLT PLAYING 11-18-20.jpg
09ARF THOMP CMPLT PLAYING 11-18-20.jpg [ 433.32 KiB | Viewed 98 times ]
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 Post subject: Re: 1925 Thompson V-50 Grandette Neutrodyne project...
PostPosted: Nov Thu 19, 2020 1:23 am 
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Joined: Jul Tue 15, 2008 6:13 pm
Posts: 8484
Location: Gretna, Nebraska
Seldom do you see a set and speaker in such good restored condition.
Nice work.

_________________
http://www.vintagerestorationservices.com
Paul
...... how hard can it be?


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 Post subject: Re: 1925 Thompson V-50 Grandette Neutrodyne project...
PostPosted: Nov Sun 22, 2020 4:06 am 
Member

Joined: Oct Mon 26, 2009 10:02 pm
Posts: 6618
Location: Indianapolis, IN
Thanks much, Paul---but besides performing basic electronic refurb, only needed to very carefully detail clean cosmetics and polish the original finish on top of lid. Both radio and horn-speaker were in amazing original condition otherwise. Mr. Stroud had it for around fifty years and think the guy he got it from may have been a collector as it was in same basic shape back then. Still remember being fascinated by it as a young kid and wanting to hear it play---they had it displayed on top of their antique piano...

John


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 Post subject: Re: 1925 Thompson V-50 Grandette Neutrodyne project...
PostPosted: Nov Tue 24, 2020 7:18 pm 
Member

Joined: Oct Mon 26, 2009 10:02 pm
Posts: 6618
Location: Indianapolis, IN
Just uploaded short video using phone of radio playing to storage site if anyone would like to download and view it: https://app.box.com/s/l3ugndsjvc13lthj1exiw4x3dc646icx

Definitely not professional, but viewable !

John


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