View Full Version : Motorola VT-71 (TS4H)
fox_rivers 02-24-2012, 12:59 AM I have restored several radios in the past and I'm finally comfortable enough to dive into this VT-71 I picked up at a funky clothing store in Las Vegas 7 years ago. Its sat at my mothers house until the day came I wanted to restore it.
http://i65.photobucket.com/albums/h238/fox_rivers/Motorola%20VT-71/100_2840.jpg
http://i65.photobucket.com/albums/h238/fox_rivers/Motorola%20VT-71/100_2841.jpg
http://i65.photobucket.com/albums/h238/fox_rivers/Motorola%20VT-71/100_2852.jpg The set is in pretty good shape and is complete aside from it missing the metal back cover and the aluminum bottom plate. I just ordered a set of capacitors for this television from JustRadios last night. http://i65.photobucket.com/albums/h238/fox_rivers/Motorola%20VT-71/100_2862.jpg http://i65.photobucket.com/albums/h238/fox_rivers/Motorola%20VT-71/100_2858-1.jpghttp://i65.photobucket.com/albums/h238/fox_rivers/Motorola%20VT-71/100_2864-1.jpghttp://i65.photobucket.com/albums/h238/fox_rivers/Motorola%20VT-71/100_2860-1.jpghttp://i65.photobucket.com/albums/h238/fox_rivers/Motorola%20VT-71/100_2854.jpg
On top of the capacitors I plan to replace the selenium rectifiers, out of tolerance resistors, any bad micas and I want to replace the ballast with the panasonic capacitor setup posted elsewhere in this forum. I just hope the 7JP4 is still good.
kvflyer 02-24-2012, 09:38 AM You may want to check out these threads when you get a chance.
http://antiqueradios.com/forums/viewtopic.php?t=134239
http://antiqueradios.com/forums/viewtopic.php?t=124246
http://antiqueradios.com/forums/viewtopic.php?t=103616
http://antiqueradios.com/forums/viewtopic.php?t=109379
http://antiqueradios.com/forums/viewtopic.php?t=110760
http://antiqueradios.com/forums/viewtopic.php?f=3&t=155458
miniman82 02-24-2012, 11:37 AM If you need new decals for the front, I have a few sets for the cost of postage.
bandersen 02-24-2012, 11:53 AM Coincidentally, I'm just wrapping up refinishing one of these cabinets. I'll post some pictures in my TS-4H thread soon.
Good luck with the capacitor ballast. I'm curious to hear how they work out. I went with a glass Amperite one and they do get quite hot.
kvflyer 02-24-2012, 01:56 PM If you need new decals for the front, I have a few sets for the cost of postage.
That is a generous offer that you made to fox_rivers. I hope you can send them to him.
Did you make the decals or did you buy them? The reason I ask is because I have 5 of these little guys, one is blonde, and I will eventually need some. But I am not trying to drain your supply. If you make them, I would like to compensate you for some you can. If you bought them please let me know where you got them.
I have restored one of my 5 so far and have not done the cabinet yet. I got the CRT mask from Ed (Blacksmith). If someone has his website, please post a link. I can't find it right now and have to run.
BTW, another reference.
http://antiqueradio.org/motvt73.htm
And two threads that I did.
http://antiqueradios.com/forums/viewtopic.php?t=144209
http://www.videokarma.org/showthread.php?t=248722
And here is Bob's
http://mail.videokarma.org/showthread.php?t=245840
bandersen 02-24-2012, 04:32 PM You can get the gold decals from these places
http://www.radiodaze.com/product/6081.aspx
http://www.radiolaguy.com/MotorolaVT71bk.htm (scroll to bottom)
The blonde set uses dark brown decals rather than gold. No one makes those so I made a custom set myself and could make more if anyone needs some.
kvflyer 02-24-2012, 05:00 PM Here is the gentleman that makes reproduction CRT foam mountings for the 7JP4 in the Motorola VT-71. His name is Ed Schutz and this is his website:
http://www.renovatedradios.com/parts.html
fox_rivers 02-24-2012, 08:28 PM If you need new decals for the front, I have a few sets for the cost of postage.
Thank you miniman82!
fox_rivers 02-24-2012, 08:37 PM You guys are so helpful and kind! Thank you!
miniman82 02-24-2012, 09:50 PM No problem, this is what the community is for!
Coincidentally, I also bought that repro CRT mask for my set and while it is expensive, you can't really do a proper resto without it. I recommend buying one, since the original is always melted to the CRT. I still need knobs for mine, but am holding out for a used set because I refuse to pay $40+ for 4 pieces of plastic.
fox_rivers 02-24-2012, 11:27 PM No problem, this is what the community is for!
Coincidentally, I also bought that repro CRT mask for my set and while it is expensive, you can't really do a proper resto without it. I recommend buying one, since the original is always melted to the CRT. I still need knobs for mine, but am holding out for a used set because I refuse to pay $40+ for 4 pieces of plastic.
I'll hold off on the mask till I can afford it. For the meantime I'll make something temporary out of some sort of foam.
I feel the same way about the mask as you do the knobs. I know the reproduction masks are difficult but still....its just foam to me.
kvflyer 02-25-2012, 08:18 AM You can get the gold decals from these places...
The blonde set uses dark brown decals rather than gold. No one makes those so I made a custom set myself and could make more if anyone needs some.
Thanks for the info Bob. I should just get them and have them "In Stock". I think the blonde cabinet is in the best condition and the markings may be still OK.
fox_rivers 02-26-2012, 01:08 AM I wanna refinish the cabinet at some point in the next couple of days. Whats the best way to strip and refinish it? I've heard in the forum that its best to use a hand rubbed lacquer. What products and methods would you guys recommend to accomplish all this?
bandersen 02-26-2012, 01:29 AM Here's what I used.
Zinsser Magic Strip Citrus-Action Gel follow by Zinsser After Wash to strip off the old finish. CitriStrip works great too.
Minwax Mahogany Gel Stain.
Constantine Mahogany paste grain filler
Deft Sanding Sealer
Mohawk Brown Mahogany Ultra Classic Toner Lacquer. That's to make the top and bottom strips a little darker than the rest of the cabinet. That's how the original finish looked on mine.
Finally, Deft gloss lacquer. After it cures for a few weeks, I like to rub out the finish with #0000 steel wool then pumice and rottenstone abrasive powders. You can just stop with the steel wool for a satin finish or pumice for a semi-gloss.
That probably sounds like a lot of work and stuff to buy, but you'll end up with a great looking authentic finish.
dieseljeep 02-26-2012, 10:31 AM You guys are so helpful and kind! Thank you!
We should rename the website TV SHAMBALA.:D
fox_rivers 02-26-2012, 03:03 PM Here's what I used.
Zinsser Magic Strip Citrus-Action Gel follow by Zinsser After Wash to strip off the old finish. CitriStrip works great too.
Minwax Mahogany Gel Stain.
Constantine Mahogany paste grain filler
Deft Sanding Sealer
Mohawk Brown Mahogany Ultra Classic Toner Lacquer. That's to make the top and bottom strips a little darker than the rest of the cabinet. That's how the original finish looked on mine.
Finally, Deft gloss lacquer. After it cures for a few weeks, I like to rub out the finish with #0000 steel wool then pumice and rottenstone abrasive powders. You can just stop with the steel wool for a satin finish or pumice for a semi-gloss.
That probably sounds like a lot of work and stuff to buy, but you'll end up with a great looking authentic finish.
I really like your method. It may be alot of stuff to get but it will be well worth seeing that cabinet looking like new.
fox_rivers 02-29-2012, 02:35 PM What kinda diodes should I use to replace the rectifiers?
miniman82 02-29-2012, 03:07 PM General purpose silicon rectifiers, even cheap Radio Shack ones are good enough.
bandersen 02-29-2012, 03:50 PM 1N4007 are rated for 1000 volts @ 1 amp and cheap. I keep a bunch on hand for replacing seleniums.
fox_rivers 03-02-2012, 12:34 AM In the meantime while I wait on parts in the mail I thought I'd shine up the chassis. :) http://i65.photobucket.com/albums/h238/fox_rivers/Motorola%20VT-71/100_2878.jpg
bandersen 03-02-2012, 01:43 AM Sweet :thmbsp: Word of warning though. I polished up a section on one of my copper chassis and it tarnished after a couple weeks.
Reece 03-02-2012, 05:55 AM Be sure to get the Brasso out of those tube sockets. Better to mask them. Try some car paste wax on top of the Brasso to retard tarnish.
fox_rivers 03-02-2012, 12:07 PM I'll try some turtle wax then. I figured since I had to clean the tube sockets anyways that I wouldn't bother masking them off but I was still careful about not globbing it in the sockets.
I didn't polish the rear of the chassis because I'm sure I would have took off the labeling for the picture adjustments.
fox_rivers 03-07-2012, 11:02 PM Ok, well got all the parts aside from the electrolytics. My 1B3GT Tested bad so I had ordered a replacement. what I got was a 1B3GT but its much shorter then the original and the placement of the coil around the tube wouldn't be correct. Did I order the wrong tube for this set?
http://i65.photobucket.com/albums/h238/fox_rivers/Motorola%20VT-71/2012-03-07_20-52-17_3831.jpg
bandersen 03-07-2012, 11:06 PM Nope, newer 1B3s are just shorter. When you slide the feedback coil over it, it will need to be a little lower than it was on the taller tube.
fox_rivers 03-07-2012, 11:16 PM Oh good. Well hopefully those electrolytics come in tomorrow so I can get started on this set. Of course the first thing I'd have to replace would be the last to come in the mail. Hah!
miniman82 03-08-2012, 06:29 AM There's a note in the Riders manual and Sams for this set about spring placement between the 2 different styles of tube.
fox_rivers 03-08-2012, 10:58 AM There's a note in the Riders manual and Sams for this set about spring placement between the 2 different styles of tube.
Right. It should show placement of the feedback coil on the older 8016 and then the 1B3GT. I'll just place the coil below the metal band in the tube as it shows for the 1B3.
fox_rivers 03-10-2012, 01:29 AM Still waiting on those pesky electrolytics and how impatient I am I figured I'd rebuild the ballast and replace the HV caps. http://i65.photobucket.com/albums/h238/fox_rivers/Motorola%20VT-71/100_2919.jpghttp://i65.photobucket.com/albums/h238/fox_rivers/Motorola%20VT-71/100_2921.jpghttp://i65.photobucket.com/albums/h238/fox_rivers/Motorola%20VT-71/100_2923.jpg
compucat 03-10-2012, 08:32 AM Please show us how you rebuilt that metal ballast.
fox_rivers 03-10-2012, 12:22 PM I ordered a pair of Panasonic ECQ-E2106KF 10uf 250v film capacitors, a 200 ohm 5w and a 30 ohm 5w resistor from Mouser. http://i65.photobucket.com/albums/h238/fox_rivers/Motorola%20VT-71/2012-03-07_20-38-02_9151.jpghttp://i65.photobucket.com/albums/h238/fox_rivers/Motorola%20VT-71/2012-03-08_00-06-43_957.jpg I removed the innards of the old ballast and desoldered the copper leads from the pins using a solder sucker.http://i65.photobucket.com/albums/h238/fox_rivers/Motorola%20VT-71/100_2916.jpg I placed the resistors on a piece of PCB I cut out of an old power supply and I used this schematic to wire the caps and resistors to the base of the ballast.http://i65.photobucket.com/albums/h238/fox_rivers/Motorola%20VT-71/BallastReplacement2.jpg I spray painted the metal can for the ballast black and installed the newly rebuilt unit into metal can thus looking awesome.
compucat 03-10-2012, 02:01 PM I ordered a pair of Panasonic ECQ-E2106KF 10uf 250v film capacitors, a 200 ohm 5w and a 30 ohm 5w resistor from Mouser. http://i65.photobucket.com/albums/h238/fox_rivers/Motorola%20VT-71/2012-03-07_20-38-02_9151.jpghttp://i65.photobucket.com/albums/h238/fox_rivers/Motorola%20VT-71/2012-03-08_00-06-43_957.jpg I removed the innards of the old ballast and desoldered the copper leads from the pins using a solder sucker.http://i65.photobucket.com/albums/h238/fox_rivers/Motorola%20VT-71/100_2916.jpg I placed the resistors on a piece of PCB I cut out of an old power supply and I used this schematic to wire the caps and resistors to the base of the ballast.http://i65.photobucket.com/albums/h238/fox_rivers/Motorola%20VT-71/BallastReplacement2.jpg I spray painted the metal can for the ballast black and installed the newly rebuilt unit into metal can thus looking awesome.
Does it generate a lot of heat in operation? It looks like a good solution, one of several ways to deal with these old ballast tubes.
fox_rivers 03-10-2012, 02:20 PM This ballast will run 80% cooler and eliminates the current surge when the set is powered so it will prolong the tubes as well as the 7JP4. This thread explains more about how they work. http://videokarma.org/showthread.php?t=249434
miniman82 03-10-2012, 02:33 PM Neat fix, but I prefer the glass ballast.
fox_rivers 03-10-2012, 02:37 PM Neat fix, but I prefer the glass ballast.
I have to admit, the glass ones do look cool.
compucat 03-11-2012, 09:45 AM I have to admit, the glass ones do look cool.
The glass ballasts run just a little cooler than the metal ones and I suspect they are more reliable since they are under vacuum. I am using a glass ballast in my Motorola with good results. I would like to build one of the alternative types as a backup.
polyphase 03-11-2012, 06:59 PM I'm delighted you chose to use the cap balast I described back in Nov 2010 for your project. They are still working great for me.
For best results, it may be necessary to tweak the 30ohm resistor lower to get correct filament voltages. This is due to normal tolerances of the caps.
This is easily done at the socket, by connecting a 2w resistor of between 100 and 300 across pins 1 and 6. You can always change out the ballast R later with the newly established value.
Note: To get stable filament voltage measurements, you need to wait at LEAST 5 minuets from a cold start.
fox_rivers 03-12-2012, 02:23 AM I'm delighted you chose to use the cap balast I described back in Nov 2010 for your project. They are still working great for me.
For best results, it may be necessary to tweak the 30ohm resistor lower to get correct filament voltages. This is due to normal tolerances of the caps.
This is easily done at the socket, by connecting a 2w resistor of between 100 and 300 across pins 1 and 6. You can always change out the ballast R later with the newly established value.
Note: To get stable filament voltage measurements, you need to wait at LEAST 5 minuets from a cold start.
I really liked the idea of the soft start as well as it looking original. I appreciate the tip and the build design. :)
fox_rivers 03-25-2012, 12:08 AM Well I finally got all the electrolytics replaced and the 2 diodes in the power supply. I put a 40watt bulb in line to limit the current to the set. Flipped the switch and nothing, no power. :( I took the bulb out of line and still the same.
I went through all the caps and everything and it all checked out so the only thing I suspected was the ballast and sure enough the ballast schematic i used was incorrect for my tv. Pin 5 which was one side of the ac line wasn't used so I have to figure out which parts in the ballast go to what pins. I'm not exactly sure how I'm gonna figure that out.
Phil Nelson 03-25-2012, 12:13 AM the schematic i used was incorrect for my tv.The VT-71 had more revisions than I've seen in any TV or radio.
Phil Nelson
miniman82 03-25-2012, 12:16 AM The 'H' version is the same one I have, when I put the glass ballast in I remember having to move one pin in the socket over to make it work. Maybe it's the same pin for you?
fox_rivers 03-25-2012, 12:38 AM This ballast was designed to replace the 17A485459 ballast in the vt-71. My ballast is a 17A470303. I didn't realize that that various chassis these sets used also used different ballasts. I have to hit up polyphase and see if he has an alternate method otherwise I have to use the glass ballast.
fox_rivers 03-25-2012, 12:41 AM The 'H' version is the same one I have, when I put the glass ballast in I remember having to move one pin in the socket over to make it work. Maybe it's the same pin for you?
I wouldn't know which pin to move. I also think its more then that since pin 5 and 8 aren't used in the new ballast design. The schematic for my chassis utilizes all the pins.
bandersen 03-25-2012, 01:03 AM You might find this thread on my VT71 with a TS-4H chassis helpful: http://www.videokarma.org/showthread.php?t=233337&page=4
I just had to move one wire to use a 17A485459 in a set design for a 17A470303.
However, if you have a really, really early TS-4, you will need to add an addition resistor between pins 6 and 8 which the 17A485459 does not have.
fox_rivers 03-25-2012, 02:07 AM Cool. Moving the ac line to 6 did the trick but now i only have one tube that illuminates which is the 6201 (12AT7). When i turn the lamp on the bulb glows dim and only the 6201 lights up but after a few seconds after the tube warms up the bulb suddenly brightens and the 6201 tube gets much brighter then its supposed to be. No other tubes light and this issue might explain why the 12AT7 that was originally in the set was dead.
fox_rivers 03-25-2012, 12:26 PM I haven't replaced the non electrolytic caps yet I just expected more then 1 tube to light at this point. I'll start replacing them and see if I have any luck.
bandersen 03-25-2012, 02:04 PM That's a bit odd since the tube filaments are wired in series. If one is glowing, others would have to be as well.
Unless perhaps there's a short somewhere causing the power to bypass some of the tubes and fry the 12AT7.
kvflyer 03-25-2012, 02:34 PM I believe there are two filament strings. If the ballast is not wired correctly, at least one string may not have power.
fox_rivers 03-26-2012, 12:39 AM Yeah I would think that if there was a problem that one string would only light. I don't understand this issue.
polyphase 03-26-2012, 02:48 PM Cool. Moving the ac line to 6 did the trick but now i only have one tube that illuminates which is the 6201 (12AT7). When i turn the lamp on the bulb glows dim and only the 6201 lights up but after a few seconds after the tube warms up the bulb suddenly brightens and the 6201 tube gets much brighter then its supposed to be. No other tubes light and this issue might explain why the 12AT7 that was originally in the set was dead.
Strange behavior indeed. With only a 40W bulb in series with the set, I doubt the tubes would glow visibly at all, although they may get hot enough to function, which would explain the sudden brightening of your bulb. However, the only thing I can think of that would cause a filament to get brighter when DC flows is a defective tube, or perhaps a filament-cathode short at the socket. Dirt in the socket could be an issue as well.
For now it might be useful to disable the DC supply so as to sort out any filament supply issues (If you want to see the tubes glow, you will need a bigger light bulb). The 6201 actally has two filaments, connected in //. Check that pins 4&5 are connected together.
BTW,if you are using the cap based ballast, it will take longer for the tubes to 'light up' in an obvious way, and they will begin to function before fully lit.
polyphase 03-27-2012, 07:59 AM re: Cap based ballast
Earlier in this thread I suggested that the value of the 30h 5w resistor in the ballast be 'tweaked' downward to set ideal string currents.
In fact this resistor is not in the filament circuit at all, it is part of the DC supply. I was writing from memory, and in my arrogance (or senility) I didn't check my notes or the schematic to verify this resistors function.
The correct value for this resistor is 10 to 20h, 5W. The 30h would overheat as originally stated.
My apologies for this lapse.
fox_rivers 03-31-2012, 07:24 PM Damn... No wonder why is set is misbehaving. Turns out there was 6SL7 where there should have been a 25L6. I assumed it was correct but I didn't know for sure since the print was barely legible. Thats pretty frightening.
bandersen 04-01-2012, 12:28 AM Ouch! That'll mess things up. I hope all the tubes in that string survived.
fox_rivers 04-01-2012, 02:59 AM I tested all the tubes and they are fine luckily. A 100 ohm resistor under the incorrect tube had popped in two at some point before I got the set and that wrong tube would explain that failure.
They must have figured since it fit in the socket that it was suitable replacement. Shame on me for not checking in the first place. *shrugs*
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