RCA 9TC240 Alignment...The start of my education (I hope!)

[Chris K]

Originally Posted by bandersen

1077 is not an alignment generator or fixed frequency RF generator - it only outputs test patterns. Composite or RF modulated video.

Yes yes yes yes yes....I shouldn't talk about these things without them in front of me...I meant the 415...I have them both.

[Electronic M]

Originally Posted by bandersen

1077 is not an alignment generator or fixed frequency RF generator - it only outputs test patterns. Composite or RF modulated video.

+1 the 1077 is for figuring out WHY your IF is dead, not for alignment....It's also good for signal injection troubleshooting on every other circuit in a TV (which is why I like mine it helps me fix dead sets faster).

[Penthode]

I bought my HP 606B locally thru Facebook Marketplace for $35. It required some repair. But to obtain the accuracy with it or any other marker source, you will require a frequency counter.

Decent sweep generators are easy to find cheaply. Coupling the equipment should be straight forward if you follow the procedure outlined.

You will be able to get the responses depicted only if you have the proper equipment and you can trust your frequency source.

And I only ended up with the HP606B because it was cheap and available. I have have three different HP frequency counters which I obtained over time because they happened to be cheap and were readily available. I believe we live in a fortunate time where so much 1960s and 1970s test equipment which we once could only dream of are now available for next to nothing.

What have you to measure the frequency source accurately?

[Penthode]

I want to reluctantly add that I have not be averse to dumpster diving. A local community college was throwing away Wavetek sweep marker generators. The cords were cut off and a few toggle switches were faulty. All easily fixed and it was free. I earlier used an old Precision generator made in Elmhurst NY which I got for free. It needed a few repairs but it worked well. The venerable HP5245L I bought for $25 with a few minor faults. The best addition I made to it was to replace the noisy original fan with a quiet modern computer fan.

I would suggest you first present here your equipment choices and we can provide advice.

[Chris K]

Hi all...just a couple of things and questions.

I did the first two steps in the alignment that required the use of the VTVM and I think I was successful.

So yes Penthode, I will detail a list of the equipment I have. Below is what I bought, restored and thought would provide the entire package for doing these alignments.



The way I understood this worked was the RF frequency out is selected using the dial on the right. You select signal strength with the attenuator dials. Sweep width is selected using the sweep dial. Maximum range on this is 10 megacycles. The signal is fed into the desired point(s) on the chassis. If the signal out requires demodulation, it comes back in from the desired point in the circuit using the demodulation cable back into the 369. At that point, a marker is added to the trace selected by the dial on the left and the marker size is adjustable. The processed signal comes out and goes to the scope by the scope out jack which is a funky, special jack that essentially provides a horizontal, vertical and ground signal interpreted on a scope using X-Y mode.

Here are my oscilloscopes...an HP 54600B and a Chinese scope...works well and cost a little over $200 (not that it indicates anything. It was well reviewed)





That's what I got! I don't have a frequency counter or a separate RF generator and sweep generator. I think I have a shelf full of equipment that needs to be scrapped and I'll have to start from scratch!


Some of this has already been done but if my friends can provide some shopping lists and maybe some information on how all of them work together it would be appreciated. I think, at this point, I don't have what I need to dive into the more detailed and intricate steps in this process.

[Penthode]

I see the Eico sweeper marker generator has a crystal in it. What is it's resonant frequency?

The marker frequencies for the traps were 19.75, 21.25 and 27.25MHz. The bandpass markers that are most important are 22.1, 24.5 and 25.75MHz. The Eico could use the one or perhaps two or three crystals to calibrate it's variable frequency generator.

A cheap shortwave receiver with digital readout could be used to calibrate the marker. The marker accuracy needs to be roughly +/-10kHz particularly with the sound IF and sound traps vs the video carrier 45% position on the slope of the video IF response. The 27.25MHz traps must be fairly accurately set as they will affect the overall IF response. The 19.75MHz traps accuracy is least important.

Historical sidenote affecting the design of the 1948 thru 1952 receivers. This was the time of the TV station construction freeze. 1948 coincided with the sunspot peak and it played havoc with RF reception. Co-channel and adjacent channel interference between stations beyond the RF horizon created headaches for FCC planners. The double upper and lower adjacent channel traps were RCA's answer to alleviate the problem at the time. I recall the summer of 1972 the interference with another sunspot peak. From Toronto Canada reception, KMOX channel 4 in St Louis totally obliterated WBEN channel 4 Buffalo. KDKA channel 2 Pittsburgh would override EGR channel 2 Buffalo. I had an RCA 8T243 (the same chassis as yours which I still have more than 50 years later) and it worked better in these summers than many newer sets. Having more traps was a brilliant idea but it makes alignment more difficult.

[Chris K]

It’s a 4.5 mc. I have some pictures of pages from the user manual I can post in a bit

[Chris K]

For your reading enjoyment... Actually, I don't expect anyone to read all of this. My only hope is I can somehow use this piece of equipment to do some of the things, starting with the audio IF, I can do to optimize it's function.





























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[Penthode]

I skimmed through the instructions and it is pretty standard stuff. The 4.5MHz crystal was intended mainly for later intercarrier sets which this is not. It has little use in this alignment other than perhaps using a harmonic as a reference to set the variable marker frequency. I have to emphasize that a split sound set alignment, especially this chassis, is somewhat more complicated than the average intercarrier set and an accurate marker is essential.

The 4.5MHz crystal oscillator has a useful 5th harmonic at 22.5MHz and 6th harmonic at 27.0 MHz. These would be useful as a reference for calibrating the variable marker.

The bottom line is that you can use the Eico but it is going to be more difficult to use that a more modern set up. Good equipment is relatively cheap. My first suggestion would be try the Eico sweeper and find a separate RF generator and a frequency counter to obtain an accurate marker. A separate marker oscillator can be loosely coupled. You can also use the separate accurate marker to calibrate the Eico marker.

For my IF alignment the HP 8600a Digital Marker with the HP 8601a Sweeper is one of the best setups. The equipment dates from the 60's and 70's and provides five accurate bandpass markers. I bought them twenty years ago for about $40 each on eBay. The HP8601a is common: there are about six on eBay at the moment but the lowest price is about $165. The HP8600a was it's companion and is to integrated with the HP8601a for accurate markers and spot frequencies.

The pair of HP devices essentially is an RF Network Analyser. I do not know how much you are into electronics but a more modern and efficient approach (and cheaper too) is to you to use a modern RF network analysis tool. I see Chinese built ones on eBay for under $50 and with client software on a computer I would see this as a very accurate and spiffy way to align your set. I have for the last decade seen the cost drop and performance improve. I haven't tried this solution out myself but you should be able to see the trap notches and IF and tuner RF responses very clearly and accurately with this device. This thread has kindled my interest to finally buy one these things to try out in the application.
https://www.ebay.com/itm/126284122318

[Penthode]

Here is another nifty one with a display. You should be able to see the IF response and accurately set the traps with one of these. I haven't tried it yet. But rather than using old clunky equipment, this may be the most efficient and yet least costly way to go.

https://www.amazon.com/Portable-Tiny...s%2C241&sr=8-4

[Chris K]

Originally Posted by Penthode

Here is another nifty one with a display. You should be able to see the IF response and accurately set the traps with one of these. I haven't tried it yet. But rather than using old clunky equipment, this may be the most efficient and yet least costly way to go.

https://www.amazon.com/Portable-Tiny...s%2C241&sr=8-4

I bought it. Maybe when it gets here we can take a shot at doing this together?

[Penthode]

The second one, does it have a tracking generator? The first one which was cheaper has a tracking generator. The tracking generator feeds the network under test ( in this case the RF/IF section of the TV).
The second unit has also two connectors. But is one the tracking generator output?

What is required is a network analyser and not just the spectrum analyser. Need to find more information on the product.

[bandersen]

I made a video on using the TinySA as a sweep gen for TV alignment. I think you'll find it useful.
https://youtu.be/BQJjgpHyWRs

[Chris K]

Looks like it can be used in conjunction with a separate tracking generator

[bandersen]

It is the tracking generator. I think you mean marker generator. Yes, you can loosely couple a second generator to create a marker blip