I hate the RCA 630 chassis
 

I am working on an 8TS30 for a friend. The set was recapped by Kamakiri and was working but the contrast was terrible. I picked up the set a few months back while in Buffalo visiting. Owner of the set is close to me in VA. Kamakiri suggested replacing the four 270 pf mica coupling caps in the video IF, as these can sometimes be a problem and cause this issue. So I did. Took all of 15 minutes to replace those four caps. The originals all tested a bit high, but no higher than 320 pf. I also found a resistor that had broke free of the contrast (AGC) pot. It was going to the audio amp tube. Fired it up and I do get audio but ZERO sign of a picture. Nothing even close. Mostly just a gray raster. AGC alters that a bit, and alters audio too. All the other controls seem to work as they should. Set is putting out 9 kV to the CRT and running solid otherwise.

Could replacing these 4 micas in the video IF throw the set that much out of alignment that I would not get even a hint of a picture?

I do not have the equipment and have never done an alignment of a set. So if it is the alignment I am kinda out of luck.

I did all the easy troubleshooting items, checked/swapped tubes. Cleaned tuner, etc.

Any other suggestions?

This is the second RCA 630 chassis I have had my hands on and both have given me fits! :tears:

Double check you wired in the caps correctly, and that they are the correct value.

Try disconnecting that resistor and see if it goes back to some semblance of previous operation.

Do you have a B&K 1075/76/77 analyst?...If so try using it's IF output to inject into the IF system. You could also inject video past the detector to check if a video stage failed.

I double checked that the caps were all 270pf (like originals) and that they were wired in the correct spots. I also ran the set with that resistor connected and disconnected to the contrast (AGC) pot. Without it connected, no audio and contrast pot has zero affect on raster. With it connected, audio returns and raster is affected by adjusting the control. Just no picture. I do not have an analyst. Only thing I have for injecting a direct signal would be a VCR. Guess I could pass that video signal through a cap into the grids of each video stage, right?

The VCR method should work. If the cap is rated high enough voltage, and placed in series with the injection probe you should be able to do both grids and plates. It will probably not be enough amplitude to drive the final video output.

You will at least know if it is the IF if video injection works.

The analyst may have allowed you to isolate the issue down to a single stage or component...If you plan to have more than 10 TVs cross your bench I highly recommend getting a cheap B&K analyst. They do almost everything....I dare say I could get by %99 of TV repairs with just a DMM with an HV probe and an Analyst...They are that useful (if you understand signal injection/substitution based troubleshooting).

Some of those 270pF micas are rated at 1000 volts, IIRC.

Make sure you didn't solder in a 500 volt replacement. You might of fried one.

I love 630TS/8TS30 chassis. Never let me down.

M3-STR8 beat ne to it. Those micas should be 1000 volt rated caps.

Not sure where you guys are getting the 1000 volt rating for video IF coupling caps. There's no potential for those to short and the value is not that critical.

My Sam's folder 54 shows 500 volt 270 pf caps for I.F. coupling.

500 volt ought to be plenty. Since the picture completely disappeared when something was changed around the contrast control, I think I'd be looking at the DC bias on the grids of those IF tubes. The contrast control should change the voltage on those grids. If you have the Sams compare your voltages to what they list.

Both the SAMS and original service material call for 500 volt micas for the 4 coupling caps in the video IF stages.

I just scored a B&K 1075 Analyst. Thanks Kamakiri!!!! Just need to recap it when it arrives. Then I can start properly injecting signals to diagnose these types of issues. Now to figure out how to use it. Have to find the manual.

Hmm. I think you'd find the 1077 easier to use and has a lot more features. The 1075 is pretty ancient.

I was introduced to the 1077B, a most-helpful piece of equipment in high school vo-tech. This along with about eight 21" color TV's (RCA, Philco, GE) donated years before. Of course, the Zenith roundies were easily fixed and then sent on to the truly needy.

The older students got bored with them, yet but sets continued to be freely given to the "shop class" and I used the Analyst to locate dead tuners, IF stages, video 1-2 amps and most importantly, determine if H-oscillators were dead or flybacks shorted when HOT's red-plated.
Good times during the school day, payback for the daily crap I endured until 10th grade:)

I have a 1076 but have not fired it up, opting instead to use a Sencore VA-48 for the color sets Ive been doing.
I will say though, the 1075-77 series is great for older sets like that RCA ,Al.

The 75 ought to be sufficient for a set like this. The newer 76 and 77 were better (especially for later hybrid/SS sets) but the 75s appear to have all the bare essentials of an analyst.

This set was a problem child from wayyyy back:

http://www.videokarma.org/showthread.php?t=265546

It did work fine when I posted last, but before Al showed up to pick it up the contrast was really weak. But, that was its ride home.....

The 1075 was

F R E E

It is in great shape too. Gotta start somewhere. Unless someone wants to donate a 1076 or 1077 to Big Al's charity?? :yes:

I'd have to blow the dust off of my 1077. Used it all of once....to make sure it worked :)

Of course the moment I need it......

That's b/c for some strange reason your sets never seem to have signal issues. You get hot plating HOTs!!! :boxing:

Yeah, I got a hat trick of those....one down two to go.

There's a fellow over on ARF that swears by his 1075. I think as long as it's serviced and up to spec it will do well. But do yourself a favor and test it out on a more modern CRT TV first.

We used a 1075 in the TV shop I worked in in the early 80's. It was a good piece of equipment and never let us down.

I had an 1076 that I had back in '88 that used to belong to where I was working at the time, sadly it no longer exists. :(

Replacing the interstage micas is a no no unless you want to do a full IF realignment. I have restored a number of RCA sets from 46 thru 52 (before RCA succumbed to cost cutting) and have never found a bad interstage mica.

The realignment is more complicated on these sets and you'll need a good sweep generator and accurate marker to do it right. Split sound sets like the 630 require the job to be done right because of the audio video tracking when tuning. Split sound sets are tuned for best sound and not picture.

When aligned correctly the picture quality is the best on RCA sets. No expense was spared. But patience and perseverance will now be required to bring the alignment back.

An oscilloscope is your friend.

Get one and learn how to use it, and this problem will be solved in 5 minutes or less.

A sweep generator, a marker generator and of course an oscilloscope. All three are required to properly realign the IF strip.

Could probably recruit help at ETF......

Any chance the original mica's were kept so you can revert back to square one?

I think it's unlikely that replacing those inter-stage mica's would completely blow the picture off frequency.

Do I need to bring my alignment rig to the meet and do some teaching?

That's a good idea Nick, I'd like to be there for that as well but am stuck in Wisconsin this year. :(

RCA didn't succumb to cost cutting! It was high time, they incorporated intercarrier audio. Everyone else was using it!
Good old Davey, didn't want to pay Motorola the royalties. He just liked collecting them.
I have to get back to my 621TS, haven't touched it in months! :sigh:

My experiences with the KCS-47 chassis tell me otherwise. :puke: RCA did succumb to cost cutting, and how!

I could advise you to check the IF transformers with an ohmmeter, you might disturb their pins while recapping. If even one of the windings gets opened, you loose the signal completely.
BTW, I've never seen a bad interstage mica.

I wasn't referring to just the move to intercarrier. RCA reduced the number of IF stages and cheapened the sync circuitry and dropped DC restoration.

The loss of the video IF stage means that about 1MHz of video response was lost. I suppose the loss of picture detail was worth the cost saving.

There was a couple of RCA B&W models with four VIF stages in 1953 but I believe they were gone in 1954.

I believe the best RCA B&W sets were built between 1948 and 1952. (The cheapened kcs47 chassis is an exception). The kcs66 (Million Proof) sets were the epitome: they employed intercarrier sound, four video IF stages, DC video coupling and keyed AGC. They went downhill from here.

Assuming the wiring to each stage is correct and the tubes are conducting and the tube dc voltages are present, then evaluating the IF alignment can begin. Replacing the capacitors and altering the wiring dressing, will dramatically affect the staggered tuning. There is a lot of gain in the VIF strip and if the tuning of two stages coincide, the strip will likely oscillate resulting in a total loss of picture.

To determine if the VIF is oscillating, measure the dc voltage across the detector load resistor with no signal input. There should be no DC (less than one volt DC). You need to test this first. Reducing the contrast control will increase the bias on the first stages (there is no AGC in the ts630). If the IF is indeed oscillating, you will reach a point the dc across the detector load will dramatically drop. It is important that the IF strip is not in oscillation before proceeding.

Next, rough alignment is first achieved by injecting a signal stage by stage and tuning each of the staggered stages to what is recommended. Then as each stage is tune to its recommended frequency, you would use the sweep generator to review the combined stagger tuned response.

Follow the RCA published data for the ts630 and it will say essentially the same thing.

I have a 17T150 in the collection, chassis KCS-66, the 'Colby'. If it doesn't have a better picture than my 630, then it is a very, very close second.

Could it be that the size of the picture compared to the 630 distracts from the resolution?

I once saw a Colby and it had a very good picture. Have you put a resolution chart up to check the frequency response?

I haven't checked with a resolution chart. I aligned it though; I'm nearly positive it's making it out to 4.0 MHz. It's probably just the larger jug and the more visible scan lines that make the image look a bit softer. The mind can play tricks on you; never trust your eyes. Also note, I said the image was nearly as good as the 630. That's a pretty solid standard to measure up against.

Has anyone with an RCA 8TS30 had to order those wire wound power resistors and the riveted in voltage divider? I'm having problems finding replacements and just what to order for a work around.

Ohhhh yes. In fact, I do that every time I rebuild an 8TS30. This may help :)

http://i452.photobucket.com/albums/q...pszxc1jyev.jpg

Generally, I use 1.5 K and 250 ohm 25W Ohmite 210 series adjustable wirewounds to replace the 2 sections of R185. Both resistors will stack perfectly end to end on the original mounting hardware. Set the adjustable tap bands to get the odd values of resistance needed. Order the mounting washer kits (p/n 7PA25) with the resistors, as the OD of the new resistors is smaller than the original.

The riveted in "candohm" resistor (R186) can be replaced with a pair of chassis mount 10W power resistors (Ohmite HS10 series or similar). I use 6.8K and 100 ohms, as the closest standard values, with no problems. You will need to drill new mounting holes, after removing the original resistor.