A couple weeks ago I found another Predicta Tandem set locally for a reasonable price :banana:

Unlike my other Tandem set (http://videokarma.org/showthread.php?t=253856), this one has a good cable. Also all the knobs, back and the antenna!

Now for the bad. When the sets former owner moved back to Chicago from Texas, a fire broke out inside the moving truck :tears: Some of his other sets were a total loss, but this one didn't look too bad. I think it's all superficial.

Also he said it had been restored and working back in Texas, but it wasn't anymore :scratch2:
http://farm6.staticflickr.com/5276/7423175712_a31dcdaf5a_c.jpg (http://www.flickr.com/photos/70039806@N00/7423175712/)

http://farm8.staticflickr.com/7127/7423176058_73331a3cd2_z.jpg (http://www.flickr.com/photos/70039806@N00/7423176058/) http://farm6.staticflickr.com/5339/7423178622_854da14eb6_z.jpg (http://www.flickr.com/photos/70039806@N00/7423178622/)

I hope this gunk will buff out.
http://farm8.staticflickr.com/7247/7423178972_fe27b80ba2_z.jpg (http://www.flickr.com/photos/70039806@N00/7423178972/)

The chassis is all sticky and stinky, but looks to be in good shape.
A few caps have been replaced from the topside. I found more repairs underneath.
Both the fusible resistor and thermistor are intact. They have both exploded in my other Predicta sets.

http://farm9.staticflickr.com/8003/7423179462_f78beb2db7_b.jpg (http://www.flickr.com/photos/70039806@N00/7423179462/)

http://farm8.staticflickr.com/7266/7429667608_de03c8c4bd_b.jpg (http://www.flickr.com/photos/70039806@N00/7429667608/)

http://farm8.staticflickr.com/7257/7423180712_325e9915b3_z.jpg (http://www.flickr.com/photos/70039806@N00/7423180712/) http://farm8.staticflickr.com/7268/7424166294_d2c2bc1f3c_z.jpg (http://www.flickr.com/photos/70039806@N00/7424166294/)

Wow, 2 of those! They are rare enough. That cable looks better than your other one before you cleaned it. Can't wait for the video! Hope the CRT tests good.

It sure does :banana: Good life test too.
Better yet it's a 21FDP4A aftermarket replacement that's superior to the failure prone original.
http://farm9.staticflickr.com/8002/7429667102_c8b18b7e01_z.jpg (http://www.flickr.com/photos/70039806@N00/7429667102/) http://farm8.staticflickr.com/7138/7429666680_9b188de4a3_z.jpg (http://www.flickr.com/photos/70039806@N00/7429666680/)

The chassis is cleaning up well with naptha paint thinner.
On top of the goo from the fire the sets former owner is a heavy smoker. It has quite a delightful aroma :yuck:
http://farm6.staticflickr.com/5117/7424167210_d6a72a62db_b.jpg (http://www.flickr.com/photos/70039806@N00/7424167210/)

I found a loose wire and broken resistor lead on the contrast control. I wonder if that's what caused the set to stop working ?

http://farm6.staticflickr.com/5236/7429668174_3171217e08_z.jpg (http://www.flickr.com/photos/70039806@N00/7429668174/) http://farm9.staticflickr.com/8148/7424166758_9b717713fb_z.jpg (http://www.flickr.com/photos/70039806@N00/7424166758/)

Only one way to find out :D
http://farm9.staticflickr.com/8008/7424165920_8fc4d1c98b_b.jpg (http://www.flickr.com/photos/70039806@N00/7424165920/)

I used a 150W bulb in series and slowly brought it up on a variac. Just a little crackle from the speaker.
http://farm9.staticflickr.com/8158/7424165628_be198e18b5_z.jpg (http://www.flickr.com/photos/70039806@N00/7424165628/)


I plugged the set directly in and was treated to some sporadic flashes of light on the CRT accompanied by arcing sounds. I checked inside the flyback cage but didn't see any arcing.
Next, I wiggled the tubes and the arcing clear up.
Here's the first stable raster.
http://farm8.staticflickr.com/7270/7424165320_926e318c9a_z.jpg (http://www.flickr.com/photos/70039806@N00/7424165320/)

I hooked up an antenna and was able to pick up a local LP station on channel six but no sound.
http://farm8.staticflickr.com/7264/7424164942_d075da76a2_z.jpg (http://www.flickr.com/photos/70039806@N00/7424164942/)

Then I hooked it up to cable. More tube wiggling and I have sound :music:
It's weak though and I have a lot of horizontal tearing.
Not bad for a first power up :yes:
http://farm8.staticflickr.com/7130/7424167642_86d1fbdb64_z.jpg (http://www.flickr.com/photos/70039806@N00/7424167642/)

Ah that lovely smokey barbeque flavor :D

SR

Hi Bob, I corrected your typo in the title. :yes:

I saw your video on this set and I can only imagine how it smells!

I think I would take the 409 and a garden hose to this chassis, otherwise you're going to have to live with it every time it gets warm!

Hi Bob, I corrected your typo in the title. :yes:

Thanks! I was going to ask, but you beat me to it ;)


I saw your video on this set and I can only imagine how it smells!

I think I would take the 409 and a garden hose to this chassis, otherwise you're going to have to live with it every time it gets warm!

Good idea. Yes, it sure does stink when the set warms up.

Here's a link to the video I shot while working on the set: http://youtu.be/qQLT7X1erbg

The screen is funky - especially at the bottom left. Perhaps it's from the fire ?
It also has a faint aroma of vomit so typical of this type of plastic (tenite?) :yuck:
http://farm9.staticflickr.com/8020/7430646644_2f7bacd678_z.jpg (http://www.flickr.com/photos/70039806@N00/7430646644/) http://farm6.staticflickr.com/5316/7430645604_8a6ae157f5_z.jpg (http://www.flickr.com/photos/70039806@N00/7430645604/)

Novus #2 had no effect on the haze, but #3 plus a lot of rubbing did the trick.
http://farm8.staticflickr.com/7268/7430645024_0d35e85b16_z.jpg (http://www.flickr.com/photos/70039806@N00/7430645024/) http://farm6.staticflickr.com/5200/7430646090_38de03c5be_z.jpg (http://www.flickr.com/photos/70039806@N00/7430646090/)

There are a few scratches that perhaps could be wet sanded out.
http://farm9.staticflickr.com/8010/7430647688_7247d408e2_z.jpg (http://www.flickr.com/photos/70039806@N00/7430647688/) http://farm6.staticflickr.com/5337/7430647138_f18a0f4200_z.jpg (http://www.flickr.com/photos/70039806@N00/7430647138/)

The screens seem to be very receptive to buffing out.
I stole the one from my Holiday to put on the Pedestal set, I had to do a bit of buffing on it too. I used a headlight buffing kit, started at 800 grit and went to 3000 followed by rubbing compound and then polish. It looks good but it seems impossible to get all of the fine swirl marks out, they aren't visible when watching it so I guess it doesn't matter.

My biggest complaint is the green-ness of the screen cover, almost Hoffman like.
I like the picture when viewed directly off the tube but putting the cover on muddies it up.

I agree about the greenish tint. The later Sietsa and Princess sets have clear covers. I think it's a different type of plastic as there's no stink
http://farm3.staticflickr.com/2669/4168230384_b941468ff8_z.jpg (http://www.flickr.com/photos/70039806@N00/4168230384/)

I feel the same way with the color roundies, the shaded non glare safety glass has the same effect. The early ones have clear plate glass and some of the later ones have a clear non bonded lens. The clear ones seem more bright and you tend to keep the brightness a little lower.

Now as for the cabinet, it has some damage from the fire. It's darkened in areas and there's a big stain on top. Also one side seems to have gotten wet which caused the masonite bottom to swell and push the veneer out a bit.
http://farm8.staticflickr.com/7247/7430771192_37d5565dab_z.jpg (http://www.flickr.com/photos/70039806@N00/7430771192/) http://farm6.staticflickr.com/5453/7430771736_47e8ef9caf_z.jpg (http://www.flickr.com/photos/70039806@N00/7430771736/)

I started out with some Howards RAF mahogany and 0000 steel wool. Later I switch to GoJo hand cleaner.
I really should have gone with the Gojo from the beginning to try dissolving the crud off rather than steel wool.
http://farm9.staticflickr.com/8010/7430772776_9a2bd6e707_z.jpg (http://www.flickr.com/photos/70039806@N00/7430772776/) http://farm8.staticflickr.com/7271/7430772164_6598c287f7_z.jpg (http://www.flickr.com/photos/70039806@N00/7430772164/)

I fixed some veneer separation too.
Next, I used some 400 grit sandpaper to smooth out the worst of the aligatoring and applied a couple coats of lacquer sanding sealer.
http://farm8.staticflickr.com/7131/7430769506_ca66d6e431_z.jpg (http://www.flickr.com/photos/70039806@N00/7430769506/)

Despite the superficial fire damage, it looks like you got a very nice restorable Predicta.... I know exactly how that thing will be smelling right now! :yes: When ever you 'fire' it up in future it will fill your apartment with the aroma of charcoaled BBQ cigarette smoke! Maybe stick it out on your back porch for a month! :D LOL Cheers Glen

Can't wait to see this done. Not sure if there is much need to have it perfect. I'm sorta fond of that "survivor" look if it's not really "broken" looking. Some sets are just BEGGING to tell you a story. It's nice that you DO have the story behind this set's survival.

Found this AD for the Predicta Tandem.

Matt

Cool, thanks. I'll be diving into this chassis soon now that my Holiday is working.

So there was success with the remade K Networks?

Now that I've gained some experience from restoring a Holiday set, I've begun work in earnest on this set.

Here are some closeups of the old repairs.
http://farm9.staticflickr.com/8460/8061831536_98e3578f51_c.jpg (http://www.flickr.com/photos/70039806@N00/8061831536/)

I would have clipped out the old resistor.
http://farm9.staticflickr.com/8174/8061832162_29f3b15624_c.jpg (http://www.flickr.com/photos/70039806@N00/8061832162/)

The thermistor has been replaced. I'd better check it.
http://farm9.staticflickr.com/8320/8061832462_cbf883ece6_c.jpg (http://www.flickr.com/photos/70039806@N00/8061832462/)

The schematic calls for a 30-6519-1 network, but I found a 30-6519-2. The difference being the value of resistance between points 2 and 6.
Maybe they ran out back at the factory and added the external resistor to compensate :scratch2:
http://farm9.staticflickr.com/8177/8061830127_bb6d19ecef_c.jpg (http://www.flickr.com/photos/70039806@N00/8061830127/)

I though I'd use my other, all original, tandem chassis to guide me in the restoration but it turns out they are slightly different.
http://farm8.staticflickr.com/7132/8167128676_28d92725c7_c.jpg (http://www.flickr.com/photos/70039806@N00/8167128676/)

http://farm9.staticflickr.com/8199/8167098887_92377a0f13_c.jpg (http://www.flickr.com/photos/70039806@N00/8167098887/)

One obvious difference is the height of the flyback cage and color of the big socket. More importantly, I've found some component and wiring differences so I'll have to be careful.
http://farm9.staticflickr.com/8347/8167097081_1196889b49_c.jpg (http://www.flickr.com/photos/70039806@N00/8167097081/)

I wasn't really happy with the cabinet so I decided to strip it. That will also give me the opportunity to fix a few issues like the swollen side and bottom.

The cabinet is held together by screws and comes apart fairly easily.
http://farm8.staticflickr.com/7130/8170081424_7a93f10b17_c.jpg (http://www.flickr.com/photos/70039806@N00/8170081424/)

I stripped the legs and used Mohawk red mahogany toner on them followed by semi-gloss lacquer. I think they turned out real nice.
http://farm8.staticflickr.com/7277/8170047491_e857bfdac2_c.jpg (http://www.flickr.com/photos/70039806@N00/8170047491/)

I've stripped the main body and managed to steam out most of the dings :)
http://farm9.staticflickr.com/8210/8170079916_3aae4c5b23_c.jpg (http://www.flickr.com/photos/70039806@N00/8170079916/)

If the cabinet turns out as well as the legs, you've got it made! :))

Thanks, we shall see.

I wasn't able to steam out all the marks. I think because it's more of a scratch or gouge and the wood is just gone. So I'm trying an old trick I learned on "This Old House".
I made some mahogany sawdust using scrap veneer and a little saw. Then dabbed a little glue into the scratch and sprinkled the sawdust on. Once the glue sets up, I'll sand it smooth.
http://farm9.staticflickr.com/8204/8180722019_a1eac84352_c.jpg (http://www.flickr.com/photos/70039806@N00/8180722019/)

Good luck, I must remember that trick myself!

Will the scratch still stand out against the photofinish when it's done? Even if it does, I suppose it's a lot better than nothing. (Or perhaps you could use a very light veneer as your source of shavings then fill in the grain with a selection of brown textas to recreate the photofinish)

I'll be interested to see the final result! :)

Oh, this isn't a photofinish like on the Holiday. This is all real solid and veneer mahogany. If the damage had been really bad, I would have just re-veneered the whole top. Next, I'll seal the wood, fill the grain and use the same red mahogany toner lacquer I used on the legs.

I'm making steady progress on the chassis despite the dubious old repairs and production run differences.
Currently, I'm down in the horizontal output tube corner where I encountered some corrosion.
http://farm9.staticflickr.com/8065/8187454884_dc7220fd4f_z.jpg (http://www.flickr.com/photos/70039806@N00/8187454884/)

The rust was easy enough to dissolve, but the socket has seen better days. It's an octal and snaps into the chassis with no fasteners.
Does anyone know where I can get a replacement :scratch2:
http://farm9.staticflickr.com/8068/8187456482_757f616513_z.jpg (http://www.flickr.com/photos/70039806@N00/8187456482/) http://farm9.staticflickr.com/8202/8187456780_1dff272f05_z.jpg (http://www.flickr.com/photos/70039806@N00/8187456780/)

I'd be going after that smoke damaged chassis with some 409 and hot water.

I've washed quite a few chassis now with soap and water and so far it hasn't hurt any of them, things like paper Filter covers and labels have to be removed first but most everything else is metal, plastic or coated with Shellac.

This place has some self-mount sockets like that but I've noticed in the past that there are several different chassis hole sizes so you'd have to check that well.

http://www.vacuumtubesinc.com/Products/SocketsAdaptersParts/NewManufactureTubeSockets.aspx

I'd be going after that smoke damaged chassis with some 409 and hot water.

I've washed quite a few chassis now with soap and water and so far it hasn't hurt any of them, things like paper Filter covers and labels have to be removed first but most everything else is metal, plastic or coated with Shellac.

Thanks for the tip. I've been using a similar product called Spray 9. It works as well or better than 409 and smells nicer :) Just like in my Holiday, the wires have gone all gooey from age. The Spray 9 works OK on that but paint thinner is even better.

This place has some self-mount sockets like that but I've noticed in the past that there are several different chassis hole sizes so you'd have to check that well.

http://www.vacuumtubesinc.com/Products/SocketsAdaptersParts/NewManufactureTubeSockets.aspx

Thanks. I see they have a few other items I need for other projects too :thmbsp:

Thanks for the tip. I've been using a similar product called Spray 9. It works as well or better than 409 and smells nicer :) Just like in my Holiday, the wires have gone all gooey from age. The Spray 9 works OK on that but paint thinner is even better.



I suggested 409 because it was the only commonly available cleaner I could think of that's worth a darn.
We use something at work from Ascot Supply called Purple Cleaner, similar to 409 in that it's Purple, but in undiluted form it'll dissolve Bakelite and strip paint! (don't ask how I know that :sigh:) Anyway it's great for cleaning chassis, Chassi, Chassis's... (what is the plural of chassis BTW?)

I'd seen Lee (M3-SRT8) touting the virtues of Spray 9 in his restoration threads, but it seemed to only be available on the East coast. Until a few months ago that is when I found it selling in 1 Gal. bulk containers for just a few bucks at a local Home Depot.

Apparently chassis is the plural of chassis ;) http://www.merriam-webster.com/dictionary/chassis

The topside was pretty grungy too, but I'm slowly making progress cleaning it.
http://farm9.staticflickr.com/8482/8189134207_ffacd4748e_z.jpg (http://www.flickr.com/photos/70039806@N00/8189134207/) http://farm9.staticflickr.com/8490/8190737547_9c8576d628_z.jpg (http://www.flickr.com/photos/70039806@N00/8190737547/)

Also, the cabinet is ready for some grain filler.
http://farm9.staticflickr.com/8485/8191822162_15ecbb115f_z.jpg (http://www.flickr.com/photos/70039806@N00/8191822162/)

I filled the grain with some Constantines red mahogany grain filler. After it dried, I lightly sanded the cabinet and sealed with Deft lacquer sanding sealer.
I managed to get a couple light coats of Mohawk cherry/red mahogany toner lacquer on the cabinet before the temperature dropped 40F Thursday night :sigh:
It might be a while before I can put on some coats of clear and rub out the finish.
http://farm9.staticflickr.com/8059/8212026833_455d5f8c05_c.jpg (http://www.flickr.com/photos/70039806@N00/8212026833/)

I'll keep plugging away at the electronics in the meantime.
http://farm9.staticflickr.com/8348/8192689672_e3dfa8e164_c.jpg (http://www.flickr.com/photos/70039806@N00/8192689672/)

I filled the grain with some Constantines...

I'll keep plugging away at the electronics in the meantime.
http://farm9.staticflickr.com/8348/8192689672_e3dfa8e164_c.jpg (http://www.flickr.com/photos/70039806@N00/8192689672/)

Looking good as usual! I think that there are very few original components on that PC board! Should work like new or even better.

Thanks for sharing the progress.

Fantastic job so far! That cabinet is really looking the part.

It's interesting to see the board, I notice that all the components are either parallel or perpendicular to each other. One thing I generally notice about vintage boards is that components just seem to be randomly scattered at crazy angles. Even my Princess and Debutante boards (same thing) are not neatly arranged like your board shown here, yet they were produced by the same company at much the same time. Weird...

Right you are. Funny, I never noticed that before. Here's the main board from my Princess set with the crazy angles (and plenty of dust).
http://farm4.staticflickr.com/3659/3364446932_586e5250bf_b.jpg (http://www.flickr.com/photos/70039806@N00/3364446932/)

Bob: I'm finishing up my restore of a tandem and I'm trying to figure out how to remove the back of the case from the crt so I can replace the caps, etc. I haven't found any info on a strategy. Have you worked out what to do on this yet?

Sure. I'll take the case apart like I did with my Holiday set. http://www.videokarma.org/showthread.php?t=255328&page=10

The procedure is outlined in the Sams service info. Basically, remove the decorative brass plate, unhook the spring holding the plastic trim and remove the steel strip holding the case halves together.

Thanks for the info. I thought it would be a different procedure than the princess, etc., but you're right, it's the same. Came apart very easily and all old caps are gone. Best regards.

I just got this mahogany base unit from a fellow collector. No legs, no cable, no CRT.

I think I'll use this chassis too as it's relatively rust free. Looks to be 100% original components except for the tubes.

http://farm9.staticflickr.com/8536/8647764746_870d4b0f6d_c.jpg (http://www.flickr.com/photos/70039806@N00/8647764746/)

Assuming the paint comes off, all it needs is a little touching up :)
http://farm9.staticflickr.com/8399/8647764438_4d852023c7_c.jpg (http://www.flickr.com/photos/70039806@N00/8647764438/)

Unfortunately, the antenna was bent and just barely hanging on. One little flex and it just broke off :(
http://farm9.staticflickr.com/8519/8647765598_e738e26dba_c.jpg (http://www.flickr.com/photos/70039806@N00/8647765598/)

http://farm9.staticflickr.com/8522/8647765252_bf7bce07bb_c.jpg (http://www.flickr.com/photos/70039806@N00/8647765252/)

A little 0000 steel wool and 600 grit sandpaper took care of the paint splatters easily :) After a little more sanding, I'll fill in the dings and clearcoat it with lacquer.

While working on it, I convinced myself that this is actually a photofinish. Odd considering the other Tandem cabinet is really mahogany veneer.
http://farm9.staticflickr.com/8122/8649702454_9e599fbc5f_c.jpg (http://www.flickr.com/photos/70039806@N00/8649702454/)

With another Tandem fresh on my mind, I decided to dive right into finishing this one off.

Rather than continuing with the original corroded, fire damaged chassis, I'll be using the "new" chassis.

The previous owner said it had been stored in a dank, damp basement for many years, but it looks pretty good to me. Minimal corrosion and no repairs. Just a few tubes have been replaced.

First, I tackled the main board.
http://farm4.staticflickr.com/3731/11957103013_d2b83bee09_c.jpg (http://www.flickr.com/photos/70039806@N00/11957103013/)

Here are my replica networks. I used 630v C0G ceramic for most. A couple micas only because Mouser didn't have those ceramic values in stock.

Also, one HV disc cap in the vertical feedback network. It's the yellow cap in the middle.
http://farm3.staticflickr.com/2863/11989032485_acdb55e247_c.jpg (http://www.flickr.com/photos/70039806@N00/11989032485/)

Here they are after painting, ready to be installed.
http://farm8.staticflickr.com/7390/11989570244_25d2f03157_c.jpg (http://www.flickr.com/photos/70039806@N00/11989570244/)

Great job on those K-nets! (and everything else as well)

Thanks! Before I reinstalled the main board, I removed a bit of corrosion.
http://farm8.staticflickr.com/7318/12059821003_c7e300d71d_c.jpg (http://www.flickr.com/photos/70039806@N00/12059821003/)

Here's a closer look at that flyback. Some material has melted out the bottom but otherwise it's in OK condition.
http://farm6.staticflickr.com/5529/12060404636_322b0db8a3_c.jpg (http://www.flickr.com/photos/70039806@N00/12060404636/)

Now, I've moved on to working underneath the chassis. It appears to be 100% original. Even the filament dropper and thermistor test OK.
That sand coated dropper is showing green corrosion though so I'm inclined to replace it.
http://farm6.staticflickr.com/5521/11957099563_961df9351d_c.jpg (http://www.flickr.com/photos/70039806@N00/11957099563/)


This big multi-section cap is crusty and bulging :eek:
http://farm4.staticflickr.com/3833/12059826033_1f6fc419b4_c.jpg (http://www.flickr.com/photos/70039806@N00/12059826033/)

Very nice work on those couplates!

Thanks! Finally time for the first power up.
http://farm8.staticflickr.com/7334/12112871686_98da2acf30_c.jpg (http://www.flickr.com/photos/70039806@N00/12112871686/)

First a test with the fusistor pulled so no B+. After a little cable wiggling, they lit up.
http://farm3.staticflickr.com/2808/12112608234_75dfe869eb_c.jpg (http://www.flickr.com/photos/70039806@N00/12112608234/)

Now with B+ and a raster appeared :)
http://farm6.staticflickr.com/5523/12112881486_5757ef57ba_c.jpg (http://www.flickr.com/photos/70039806@N00/12112881486/)

Next with a signal applied. Horizontal sync is impossible to achieve.
http://farm4.staticflickr.com/3705/12112219395_337349bc58_c.jpg (http://www.flickr.com/photos/70039806@N00/12112219395/)

Rotating the coarse hold control to one extreme, tweaking the hor. osc. and twiddling the hor. sync finally resulted in a somewhat stable image.
http://farm3.staticflickr.com/2815/12112220185_a2d972b4f2_c.jpg (http://www.flickr.com/photos/70039806@N00/12112220185/)

Swapping out a few IF tubes helped, but it still doesn't feel right. The sound is clean but not loud enough, the contrast is poor and the sync touchy. I suspect there's not enough gain somewhere.
http://farm4.staticflickr.com/3823/12112882776_85d904769b_c.jpg (http://www.flickr.com/photos/70039806@N00/12112882776/)

I switched to a different head unit with a good 21FDP4 in it and was surprised that it didn't look any better. The set takes about 5 minutes to fully warm up and stabilize and the picture isn't very sharp.
B+ is about 10% low which might account for these issues. First I think I'll try swapping out the ancient silicon rectifiers with some 1N4007s.
http://farm6.staticflickr.com/5548/12143403744_d5b26d937a_c.jpg (http://www.flickr.com/photos/70039806@N00/12143403744/)

Just tested the original diodes and they're OK, but I'll try replacing them anyways. Something else odd. The total current draw is only 1.15A. It should be around 1.6A :scratch2:

Hi Bob and all,

I find these sets very appealing, mostly because of my engineering nature. But I wonder how these sets were used and how it was marketed.

What would the consumer do other than just put the CRT on top of the cabinet? One could have kept the cabinet near a viewing chair and used the cabinet as a remote control - and not have to get up to change channels. One could have kept the cabinet inside the house and brought the CRT outside on the patio for watching TV outside. Is the speaker inside the cabinet of the CRT using? Any ideas why these sets were/are populate other than the novelty of it?

-Steve

The speaker is inside the cabinet but there is an audio jack in the CRT base. I've never seen an actual external Philco speaker. They're much less common that than Holiday model that came out at the same time so I don't think they sold all that well.
http://farm9.staticflickr.com/8333/8077668965_09098e2804_z.jpg (http://www.flickr.com/photos/70039806@N00/8077668965/)

I believe this is what the speaker looks. I suppose that could just be any old generic speaker plugged into the base though.
http://www.antiqueradios.com/forums/download/file.php?id=32595

I bit the bullet tonight and dissasembled the CRT housing so I can service the 2nd video amp. It's been partially recapped, but I can see an original electolytic in there.

http://farm3.staticflickr.com/2874/12165787285_18c67e9561_c.jpg (http://www.flickr.com/photos/70039806@N00/12165787285/)

It actually was a lot easier because of a great tip posted recently (sorry can't remember the author). Instead of fighting to undo the stiff spring on the decorative gold band, leave it attached and slide the band over the plastic housing.

http://farm4.staticflickr.com/3746/12166018933_4951343035_c.jpg (http://www.flickr.com/photos/70039806@N00/12166018933/)

That needs a good cleaning :yuck:
http://farm8.staticflickr.com/7289/12166192434_7b11d566c8_c.jpg (http://www.flickr.com/photos/70039806@N00/12166192434/)

So does the inside of the rear cover.
http://farm8.staticflickr.com/7311/12165785365_8a80762c23_c.jpg (http://www.flickr.com/photos/70039806@N00/12165785365/)

There's an odd, faint "starburst" pattern on the CRT face :scratch2:
http://farm4.staticflickr.com/3733/12166436916_9d049020b4_c.jpg (http://www.flickr.com/photos/70039806@N00/12166436916/)

Finally, I can get at that little circuit.
http://farm3.staticflickr.com/2828/12166015373_b26a9e4ff2_c.jpg (http://www.flickr.com/photos/70039806@N00/12166015373/)

http://farm6.staticflickr.com/5531/12166432666_79b7e23538_c.jpg (http://www.flickr.com/photos/70039806@N00/12166432666/)

Looks like the CRT was replaced in 1965 in LA.
http://farm8.staticflickr.com/7346/12166195194_e1d7332dd3_c.jpg (http://www.flickr.com/photos/70039806@N00/12166195194/)

The small 'lytic, should have been changed, as well.
I like that shielded H.V. anode lead and the line interlock.

I tested that 4uF 'lytic and it's not leaky, but the power factor is around 20% so I'll replace it.

The plastic CRT cover is polishing up nicely with Novus #2. Here you can really see how dark the tint is.
http://farm6.staticflickr.com/5492/12177874715_2d1b4b154f_c.jpg (http://www.flickr.com/photos/70039806@N00/12177874715/)
001 (http://www.flickr.com/photos/70039806@N00/12177874715/) by bandersen (http://www.flickr.com/people/70039806@N00/), on Flickr

Here's a side view showing how short the CRT is.
http://farm8.staticflickr.com/7349/12201276216_1365362ec9_c.jpg (http://www.flickr.com/photos/70039806@N00/12201276216/)

I noticed some corrosion on the plug and the cable is loose.
http://farm4.staticflickr.com/3736/12227075394_57363b4afc_c.jpg (http://www.flickr.com/photos/70039806@N00/12227075394/)

So I opened it up and found it's much worse than I realized. The pins are corroded, screws are very rusty and it's been poorly rewired.

Here's a nice, neat factory original for comparison. Now I can the see the rewired one is so loose because it should have a section of the vinyl outer jacket inside the plug.
http://farm4.staticflickr.com/3741/12227077224_3a461f0404_z.jpg (http://www.flickr.com/photos/70039806@N00/12227077224/) http://farm4.staticflickr.com/3790/12226855073_7155edbf6e_z.jpg (http://www.flickr.com/photos/70039806@N00/12226855073/)

After more examination, i decided to rewire it myself.
http://farm6.staticflickr.com/5477/12238660284_1e245a86c4_c.jpg (http://www.flickr.com/photos/70039806@N00/12238660284/)

The point of no return :eek:
http://farm6.staticflickr.com/5496/12238658274_3a446eb2ae_c.jpg (http://www.flickr.com/photos/70039806@N00/12238658274/)

Here are the wires for AC line interlock, tube filament, audio, horizontal & vertical yoke, HV and video.
http://farm4.staticflickr.com/3682/12238820296_e3f52c2ca7_c.jpg (http://www.flickr.com/photos/70039806@N00/12238820296/)

That must have taken a few minutes to wire each one of those plugs at the factory.

Here it is cleaned up and ready for rewiring.
http://farm4.staticflickr.com/3812/12277066546_7247471c62_c.jpg (http://www.flickr.com/photos/70039806@N00/12277066546/)

Unfortunately, I discovered one of the pins had broken off and been replaced with a bit of bent wire. Not sure what to do about it.
http://farm3.staticflickr.com/2861/12276662353_b692d05992_c.jpg (http://www.flickr.com/photos/70039806@N00/12276662353/)


Also spent some time troubleshooting the chassis. It takes several minutes for the horizontal to stabilize and even then it's very touchy.

Also the 410 boost voltage is less than 300.
http://farm6.staticflickr.com/5500/12277231093_efd2e553b2_c.jpg (http://www.flickr.com/photos/70039806@N00/12277231093/)

The horizontal is so touchy just bringing my hand near the tube has an effect.
http://farm3.staticflickr.com/2824/12277499574_e5c60ca087_c.jpg (http://www.flickr.com/photos/70039806@N00/12277499574/)

That got me thinking one of the pins might be floating. Sure enough - pin 2 is open.

There should be a 1Meg resistor between it and pin 7 of the AFC tube. It's buried inside one of the networks so I must have made a mistake somewhere :(

I tried tacking an external resistor between the tube sockets. It had a definite effect, but now I can't get hold lock at all.
So much as I hate to do it, I'll have to pull the board again.

That looks like a 1.5 ohm resistor...

The last band should be green for a 1 meg, looks gold here...

Brown, Black, Green is 1 meg but my eyes are quite bad...

Have a good one...

rrrhre2s

Ditto here, it sure looks gold to me too.

You're both correct - it is a 1.5 ohm resistor. I wonder how that got mixed in with my 1 Megs ? Installing a correct 1M took care of my hold stability issue, but the boost is still 100 volts low.

I left the original boost filter cap in because it tested OK, but it seems like a good place to start troubleshooting.
http://farm6.staticflickr.com/5508/12282210986_767507e2df_c.jpg (http://www.flickr.com/photos/70039806@N00/12282210986/)

Luckily, I was able to pinpoint and repair the replica network. A little paint will hide the repair.

Note to self - do some basic tests before installing these!
http://farm3.staticflickr.com/2811/12328354485_69f24d4ea3_c.jpg (http://www.flickr.com/photos/70039806@N00/12328354485/)

Replacing the boost filter cap got the voltage up to the correct level. I often read about others able to run sets on original electrolytic caps, but I never have any luck.

Picture and sound are pretty good now. This original very weak 21EAP4, has those telltale bright white areas on faces.
http://farm4.staticflickr.com/3667/12328352815_ff0930a85c_c.jpg (http://www.flickr.com/photos/70039806@N00/12328352815/)

I pulled out an unrestored, nearly 100% original tandem chassis and hooked it up to an unrestored head unit to check the current draw.

About 1.25 Amps or 145 watts. That's the same as my restored chassis.

So why Sams states 1.65 Amps and the back of the set has 180 watts stamped on it remains a mystery :scratch2:
http://farm8.staticflickr.com/7381/12487851664_c39503d878_z.jpg (http://www.flickr.com/photos/70039806@N00/12487851664/) https://ycpi-farm8.staticflickr.com/7320/12487388535_fd6296049b_z.jpg (http://www.flickr.com/photos/70039806@N00/12487388535/)

I just received this 21EVP4 and will attempt to replace the nearly dead 21EAP4.

It appears to be physically identical. As for the CRT data, all I have is what's at the radiomuseum.
http://www.radiomuseum.org/tubes/tube_21evp4.html

2.68 volts at 0.45 Amps. So I figure I can add a current shunt across the filament to handle the 600mA string.

Does anyone have data on the G1, G2, G4 and anode voltages ? Is it identical to the 21EAP4 ?

http://farm8.staticflickr.com/7430/12621476383_0ba643b0aa_c.jpg (http://www.flickr.com/photos/70039806@N00/12621476383/)

It tests like new so I proceeded with the transplant.
http://farm6.staticflickr.com/5472/12627794485_bbdd697aa3_c.jpg (http://www.flickr.com/photos/70039806@N00/12627794485/)

http://farm8.staticflickr.com/7331/12627795875_9e16fb32c1_c.jpg (http://www.flickr.com/photos/70039806@N00/12627795875/)

Time for a little math to figure out the appropriate filament shunt resistor then I'll fire it up.
https://ycpi-farm4.staticflickr.com/3789/12627797195_3f0ba44431_c.jpg (http://www.flickr.com/photos/70039806@N00/12627797195/)

18 ohms was the right value to shunt 150 mA across the 2.68 volt filament.

The picture is bright and crisp now. It just needs to little tweak to the centering.

https://farm6.staticflickr.com/5483/12629005263_c6f2f02dde_c.jpg (http://www.flickr.com/photos/70039806@N00/12629005263/)

What's the actual voltage you're getting across the heater?

Wow, nice improvement!!!!!

Wow, nice improvement!!!!!

Using a dark Night Gallery episode probably wasn't the best example though ;) Now I can crank the brightness all the way up without losing focus or contrast.
Replacing a Predicta CRT with their goofy metal strap mounting system is not the easiest of tasks :no:

What's the actual voltage you're getting across the heater?

2.71 volts with 117 on the ac line. Ideally I want 0.15 amps flowing through that shunt. 2.68 volts / 0.15 amps = 17.87 ohms. I rounded it up to 18.

I plan on added a little more resistance in series with the filament string so the set can be run on a high line voltage of 125 without stressing the tubes.

I'm curious as to how they could make an electron gun that runs on only 1.2 W (2.68 volts * 0.45 amps) that works as well as one that runs on 3.8 W (6.3 volts * 0.6 amps) ?

Did they use improved cathode material or is there some downside like shortened life ?

..2.71 volts with 117 on the ac line. Ideally I want 0.15 amps flowing through that shunt.
I'm gonna stick my neck out a little bit here. :nerd:
Ideally, and for longevity's sake, i would run the CRT heater voltage as low as possible consistent with a nice bright picture (irrespective of what current is flowing thru the shunt resistor.
The logic behind this is that the 2V Predicta guns were notorious for going flat prematurely.
Other discussions have mentioned voltages ranging from about 2.25V to 2.5V as being appropriate.
I would experiment with adding a little more shunt resistance, say a hundred ohms at a time, across the 18 ohms you've already got there. And see how low the heater can be run and still give a bright pic.
The name of the game is preserving emission in a CRT that's probably irreplaceable.

I'm curious as to how they could make an electron gun that runs on only 1.2 W (2.68 volts * 0.45 amps) that works as well as one that runs on 3.8 W (6.3 volts * 0.6 amps) ?

Did they use improved cathode material or is there some downside like shortened life ?
2V Predicta CRTs generally had drastically short life, even when bought new.

Does anybody know for sure the logic behind the 2V guns?:screwy::saywhat::saywhat:

I'm gonna stick my neck out a little bit here. :nerd:
Ideally, and for longevity's sake, i would run the CRT heater voltage as low as possible consistent with a nice bright picture (irrespective of what current is flowing thru the shunt resistor.
The logic behind this is that the 2V Predicta guns were notorious for going flat prematurely.
Other discussions have mentioned voltages ranging from about 2.25V to 2.5V as being appropriate.
I would experiment with adding a little more shunt resistance, say a hundred ohms at a time, across the 18 ohms you've already got there. And see how low the heater can be run and still give a bright pic.
The name of the game is preserving emission in a CRT that's probably irreplaceable.


2V Predicta CRTs generally had drastically short life, even when bought new.

Does anybody know for sure the logic behind the 2V guns?:screwy::saywhat::saywhat:

I wouldn't exactly call them irreplaceable, since I just replaced one ;) I'll be using a 21FAP4 in another Predicta that will also require a little modification to work properly.

Perhaps I should add a zener diode clamp across the filament like some guys do with 3KP4s for extra protection ?

As far as I know, only the only the original 21EAP4 CRTs had the short life. This is a rebuilt non-Philco 21EVP4. Other brands used the low voltage heaters not just Philco. I assume it has something to do with reducing the heat / power consumption.

Ah, nuts. The transient suppression devices suggested for 3KP4s only go down to about 6.8 volts.

http://www.littelfuse.com/data/en/data_sheets/littelfuse_tvs-diode_1.5ke.pdf

There is some geometry distortion. Primarily the vertical lines bend on the right side.
I don't think there's much I can do about it. I suppose it won't be noticeable when viewing actual programming.
https://farm8.staticflickr.com/7409/12642629645_b0ac961fae_z.jpg (http://www.flickr.com/photos/70039806@N00/12642629645/)

Ah, nuts. The transient suppression devices suggested for 3KP4s only go down to about 6.8 volts.

http://www.littelfuse.com/data/en/data_sheets/littelfuse_tvs-diode_1.5ke.pdf

IIRC form a class I took a couple of years ago those AC transient suppressors are just two Zener diodes diodes in series with either the anodes or cathodes connected together....You could probably make your own with two Zeners each of the max voltage you want across the heater and a suitable current rating.

There is some geometry distortion. Primarily the vertical lines bend on the right side.
I don't think there's much I can do about it. I suppose it won't be noticeable when viewing actual programming.

That almost looks like stray magnetic field interference. Did you try moving it around in the room?

That almost looks like stray magnetic field interference. Did you try moving it around in the room?

What about the adjustments on the yoke cover? I don't remember if they're just for centering. The "T" shaped magnet, on the side of the yoke should have an effect on the pincushioning.

That almost looks like stray magnetic field interference. Did you try moving it around in the room?

Yeah, that has no effect. This is a rebuilt CRT and the neck is a little crooked which may be throwing things off.

What about the adjustments on the yoke cover? I don't remember if they're just for centering. The "T" shaped magnet, on the side of the yoke should have an effect on the pincushioning.

A little. Mostly it effects the horizontal linearity.

OK, I didn't realize you could not only bent the "T" but also twist it.

It's still a little warped in the upper-right, but not too bad I think.
http://farm4.staticflickr.com/3712/12643120174_ca49b51dc2.jpg (http://www.flickr.com/photos/70039806@N00/12643120174/) https://v4s.yimg.com/so/7370/12658691365_627214820b.jpg (http://www.flickr.com/photos/70039806@N00/12658691365/)

That looks pretty darn good to me. Seems to have improved the focus, too.