I hate the RCA 630 chassis

[dieseljeep]

Originally Posted by Penthode

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.

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!

[benman94]

Originally Posted by dieseljeep

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!

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

[Penthode]

Originally Posted by dieseljeep

RCA didn't succumb to cost cutting! It was high time, they incorporated intercarrier audio.

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.

[Penthode]

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.

[benman94]

Originally Posted by Penthode

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.

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.

[Penthode]

Originally Posted by benman94

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?

[benman94]

Originally Posted by Penthode

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.