Great night guys,
I finally got my capacitor ballast built for my 9VT1 and powered her up for the first time with a resistor substitute for the CRT. Once she warmed up I got some noise from the speaker (mostly hum from the florescent lights in the TV shop) but some static. After checking a few voltages and not finding to much out of place I worked up the courage to try an untested 7JP4 from my Admiral 19A1 I didn't want to risk my 8BP4 just yet. After a few seconds she lit up, I could see a raster with the lights in the shop off. I then installed my 8BP4 and crossed all my fingers and toes and turned her on. I am happy to say it looks like I have a good 8inch CRT!!!! A bit brighter than the 7JP4. Now time to finish recapping her and see what else pops up in her restoration.
I do have a question though. I used 20watt resistors on the rectifier side of the ballast and they are running warmer than I expected. Not to warm for a 20watt but warmer than I thought it should be. I should ad that I used a CL90 from the ACline to the ballast and she is drawing .8 amps roughly at 115v AC on the line through my sencore variac. My question is is this normal? Thanks in advance.

One more thing to add. I replaced the selenium rectifiers with modern silicon ones.

I finally got my capacitor ballast built . . . . .

I do have a question though. I used 20watt resistors on the rectifier side of the ballast and they are running warmer than I expected. Not to warm for a 20watt but warmer than I thought it should be. I should ad that I used a CL90 from the ACline to the ballast and she is drawing .8 amps roughly at 115v AC on the line

Congratulations! Most 8BP4's went gassy and developed a brown center spot.

Sam's 83-6 says "RATING: .9 Amp at 117 Volts AC" so you are quite close. I'd have estimated a little bigger draw if you have not yet replaced all the small capacitors, especially the plate to grid ones.

Re: Heat from B+ current limiting resistor.

Well, remember the wires in a normal ballast glow red hot and that was the reason for the little square of asbestos that was in side the cabinet over the ballast.

I'd sure keep that resistor above chassis in an old ballast shell and the filament capacitors safely under the chassis away from the hot resistor(s).

Jas.

I'm not sure which resistors you are referring to ? Are these ones you added in series with the silicon diodes ? What value did you use ? I usually leave them out altogether. it really doesn't effect the B+ that much and the sets run cooler. The service info states 0.9 amps @ 117 so your resistors might be too large.

I just read earlyfilm's post and am a little confused. What are you using for a ballast ? One you made yourself with capacitors and resistors or an original one ?

Hi Bob,
I used 2, 10uf AC caps and 2, 33ohm resistors 1 each for the filament strings. I also used a 37ohm before C1 and a 200 after the rectifier M1 both @ 20watts.

You used 33 ohm resistors in series with the 10uF caps ? That really isn't necessary.

So it's the 37 ohm and 200 ohm resistors that are getting hot ? They do normally get pretty toasty.

http://www.videokarma.org/attachment.php?attachmentid=180980&d=1386815210

I also acquired a Motorola 9VT1 a month ago.
Its in the pipeline to be restored.
Your 9VT1, mine, and a 9T1 (similar circuitry) are being
represented here. Have not tested my 8BP4 CRT yet.

Carl

Great to hear that we a restoring at the same time Carl.
I got most of my caps changed last night should finish up tonight accept for a couple of electrolytic s that haven't arrived yet. Hopefully I don't have any mica cap troubles. Mine is the strait TS-18 Chassis, there are a couple of minor production changes that are not reflected in the schematic that are driving me a bit crazy but not to much. C5 off of pin 7 in V4 of the second IF isn't there looks like it never was , and C26 on pin 6 of V3 the 1st IF is a .1 instead of a .5 as shown on the Sams . If anyone knows why please let me know. The .1 looks like it came from the factory, and the set does run with it that way so who knows. So far all the resistors I have checked are within tolerance keeping my fingers crossed on the rest.
Quick question to BAndersen. I know you have restored a few of these Bob. are there any smoking guns I should look out for? I would also appreciate any input on my Cap conundrum.

I've seen some production variations in the IF circuits too. If it looks like it's original, I'd just go with that value and see how it plays. I'm surprised you haven't found any out of tolerance resistors though. I've had to replace a bunch in every set I've worked on. Especially the low valued ones ( < 1000 ohms) in the IF circuits. As for smoking guns there's the ballast, selenium, electrolytics stuff you've already been working on. Also you may have some issues with linearity and height that swapping the 6SL7 can cure.

Thanks Bob,
I did have linearity problems swamped the tube tonight and cured it thanks for the hint. The good news is I have a picture and sound tonight after replacing the remainder or the paper caps. I do have some horizontal tearing until she warms up and a hum bar in the picture. I have 2 electrolitics that haven't been replaced yet that I'm sure are causing that problem. So far I've been very fortunate , the 8bp4 CRT looks like new. I'm a happy camper so far thanks so much for all the help. At this point im sure this is a low time set, although she has no origanal tubes in her she only had one or 2 caps replaced. I will post pictures soon.

Hi, what value resistor did you use to replace the crt for testing, and what pin #s should be connected?

C5 off of pin 7 in V4 of the second IF isn't there looks like it never was , and C26 on pin 6 of V3 the 1st IF is a .1 instead of a .5 as shown on the Sams . If anyone knows why please let me know. The .1 looks like it came from the factory, and the set does run with it that way so who knows.

If you check the factory schematic also on the ETF website, you will notice the electrolytic called C-5 by Sams is not present and there are some other changes in the 1st & 2nd IF circuit.

Remember when using two sources, that the component C, R and V numbers probably won't be the same and they are not the same here.

James.

Moto had so many production changes on their electrostatic sets that finding a matched TV set/schematic pair can be a challenge. If it looks original underneath use the schematic as more of a conceptual tool for how it works / signal flow, and replace parts based on what is actually installed in the chassis.

Jon f , if I remember correctly I used a 10 ohm resistor on pins 1 and 14.

Got her running guys, finished replacing the last caps and the few resistors that were out of tolerance. The first 2 pics are of the set with the 7inch CRT. BTW she has sound but can't get sound clear when pic is fine tuned. I am using a hd converter box. Question? I don't have a sweep generator that will go down low enough to align her. Do you think I can get by with only an audio alignment?
Also , if you look at the last pic you will notice the dark stain on the right. This is after stripping the cabinet. Any idea what I can use to bleach it out so I can give her a proper finish?

Great picture! My 9T1 is getting close to that also.

Also , if you look at the last pic you will notice the dark stain on the right. This is after stripping the cabinet. Any idea what I can use to bleach it out so I can give her a proper finish?

I have literally used Bleach to remove stains from cabinets before.
dilute it with some water, maybe 50-50, brush it on and let it soak but watch it closely so you don't overdo it.

Just a quick update on the set guys. I didn't have a sweep generator that covered the frequencies used to align this set so I ordered one from eBay. As of today I have received 3 that got destroyed by UPS and Fed-ex. Welcome to the wonderful world of shipping. Most of these were packaged very well but the shipping companies just kicked them around like a football.
I am pretty sure that an alignment is all I need to finish her electronically, then on to the cabinet restoration. I am looking for a back and knobs. If anyone has any that are willing to part with please let me know. I have had a lot of fun working on this old piece of history, looking forward to finishing and moving on to my next project.

It's been months since I finished the electronics restoration on my 9VT1. Yesterday I finally finished my cabinet restoration. I only need a back and knobs to complete the job. If anyone knows of anywhere I can find them please let me know.
I don't think she turned out to bad at all. If you look closely you can see the set is playing in the pictures, not to bad considering the flash was on on the camera. She actually has a viewable picture even with 4 sets of 8ft florescent lights on in the shop.

Nice job :thmbsp: I think I can dig up a full set of the proper red knobs for ya :)

Bob, that would be great! Thanks
Just let me know how much you want for them and where to send the money.
I was also thinking I could make a back if I can find a supplier for honeycomb metal panels.

The back on my recently-bought 9VT1A is made of 1/8" or 5/32" hardboard.

Looks great!

Ya Done GOOD !

I finally found the knobs :) PM sent.
https://farm6.staticflickr.com/5071/14211759026_8b6f39cc10.jpg (https://flic.kr/p/nDQYQ3)

Here's a picture of a back (click for a larger version).
https://farm3.staticflickr.com/2903/14048316290_6c936589b2.jpg (https://flic.kr/p/npphZQ)

Thanks for the info and the pic. I think I can reproduce it now. Bob, I got your pm and sent a reply thanks so much. I'm really looking forward to finishing this set.

I have had my 9VT1 restored since 1999 and I can say it is a great performing set for what was surely considered a budget model in its day. The only gripe about mine that I have is that for the first 15 minutes or so, the vertical hold has to be readjusted. Other than that it is a great daily watcher.

I've been lucky with mine compucat. The only real trouble I had was figuring out a new ballast and alignment. The alignment still isn't perfect but i will get around to fixing that soon enough. BTW your 9VT1 is the reason I chose to restore mine. Until I saw it I didn't think one could look good at all.

I've been lucky with mine compucat. The only real trouble I had was figuring out a new ballast and alignment. The alignment still isn't perfect but i will get around to fixing that soon enough. BTW your 9VT1 is the reason I chose to restore mine. Until I saw it I didn't think one could look good at all.

Wow, thanks. The finish on your's turned out nice as well. I ended up painting my chassis, ordering some correct repro knobs for the volume and contrast controls. My metal Nichrome wire ballast eventually burned out, set turned off without warning in the middle of a program. i am using a glass Amperite ballast but will probably build one of the capacitor based ones for improved reliability. I could not salvage my original grille cloth nor find a matching replacement so I had to use what I had which is a piece of upholstery fabric but it works and looks unique. The only alignment adjustment I made on mine was to synchronize the sound and video for the fine tuning. Before that I could only optimize one or the other, not both. It has been a very reliable set and I love the round screen. In fact, I was watching Kojak on it about an hour ago.

Thanks to Bob Anderson for a set of knobs. Got them installed this morning. Now I'm done with this one, on to the next.

Nice job. I'm glad those knobs found a good home :)

Set looks nice!!!