TV IF alignment
 

I have a B&k 415 and doing a google search I found a thead "B&W alignment almost too easy" but it was back when we had video in the audiokarma forums, nothing comes up when I try that link.

Needless to say it caugh my attention. Looking for some pointers on how to use my new toy, esp after I goofed up an IF alignment on an old B&W tv.

I Have the 415 and a HP 10mhz scope, just dont know how to use it. I am chasing down a manual, trying to get one from a guy that posted in ARF, just sent him a PM, waiting to hear back.

If anybody has heard of a video link that goes thru the process of an IF alignment on a TV I sure would like to see it.

If you lay your hands on a 1950s TV servicing book, it will usually have a chapter on alignment. Those books are cheap on the used market.

The first sentence is invariably a warning. "Do not attempt alignment unless you are absolutely sure there is no other cause for the symptoms."

I have read the procedures a few times and never been tempted to try it myself, although I have aligned many AM radios and a few FM sets.

Phil

well I popped for an eico sweep gen so that will be coming in a couple weeks.

If i understand this right, you pic a med point like 44mhz, then sweep that with a 10mhz sweep (34-54) and watch the detected signal on the scope.

Looking for the correct IF shape, using markers to see where the curve is.

At least that is the way I understand it. I have attempted alignments on FM receivers using sweep gens and scope.

I have had a hard time getting results to look right, dont know if its me or my equipment or both.

Anyway I will press on and post my results.

You can see my attempt at alignment, and the RCA alignment equipment in my thread in the b/w forum. For the older sets, you'll need a unit that'll sweep down around 25Mhz. It is interesting to see the different equipment they made. There's that thread about the Sencore units now in the rectangular set forum too. And I remember a post a while ago about an older all-in-one unit that even had the scope built in. I think it was a Philco? I'd like to see a discussion comparing the different alignment equipment that was made, I came down here to start a thread on that but figured I'd post in this thread already here.

I did a quick search on here for threads discussing IF alignment:

Philco unit with the scope built in: http://www.videokarma.org/showthread...ight=alignment
Sencore speed-aligner: http://www.videokarma.org/showthread.php?t=246891
my RCA KCS47 alignment with RCA equipment: http://www.videokarma.org/showthread.php?t=246398
what sweep generators do the older IF frequencies: http://www.videokarma.org/showthread...ight=alignment
aligning a DuMont RA103: http://www.videokarma.org/showthread...ight=alignment
alignment of 1963 Philco color set: http://www.videokarma.org/showthread...ight=alignment
ctc-16 alignment: http://www.videokarma.org/showthread...ight=alignment
sweep generators: http://www.videokarma.org/showthread...ight=alignment
630ts sound alignment: http://www.videokarma.org/showthread...ight=alignment
630 sound part#2: http://www.videokarma.org/showthread...ight=alignment
ctc-15 IF alignment: http://www.videokarma.org/showthread...ight=alignment

Great collection of post.

I had some luck with my B&K 415, but I need to review all those others 1st.

I managed to get a trace that looked like it should (well close anyway) and the markers from the 415 are neat as it allows mutilples.

I did check the marker freq 1st since I had no idea of the calibration of the unit, they all tested right on the nose.

the odd thing is the scope had a mirror image with the lower freq markers on the right side and the higer ones on the left.

I had to play with the amplitude some and the AGC bias a lot to get the shape right. Guess that is where the real experiece comes into play.

you can see the markers are a little off from where they should be on the left side (hi side) like the slope is too vertical, and there in no visual hump between the 1st two markers where there should be. This is from a working B&W set that looks fine, so I will not mess with it. I have 3 of these particular chassis, all working fine, so the idea is to compare the setups and see how they look. I need to get some confidence that I am on the right track. Then I will try my hand at an actual alignment of a goofed IF (I was the idiot with the diddle sticks) to see if I can make an IF curve look right.

It's reversed from left to right for me too. Mine was also upside down, but I just flipped the vertical polarity switch on the scope.

I can't produce all those markers at once with the equipment I have. It's either 1 marker at a time, or markers spaced 4.5, or 2.5mhz apart. Actually, it says you can take an additional signal generator, and connect it up to the marker generator, setting it to the difference in frequencies between the 2 markers you want, to get 2 different markers at the same time.

well I just realized my 415 has a horz seep norm/reverse for the trigger, so I just need to get a cable to hook it up to the external sweep and I should be able to reverse that image.

did the hookup of the to horz on scope, rev and normal did not reverse the image, just moved it over, oh well, not a big deal I just wanted it to look like the display on the the 415.... guess I could look at the scope or the 415 in a mirror...

will be hooking it up to another tomorrow, again same chassis just anohter TV so hopefully I can make a pretty much direct comparison, I will leave all the settings alone (bias,sweep,amplitude) and just compare IF strip to IF strip. I hope the next tv has a slightly better curve/marker profile, that way I will know I am getting the correct results. If they match this one, then I have to wonder if I am setting it up right, since a match to the same wrong profile may mean I am detuning something with the hook ups.

another set, this time with the injection point being the Osc tube with a ungrounded shield. I added a 44mhz marker, shown in the center of the two main humps

The second from the right is the picture marker, the far right are the two audio markers, there is supposed to be a small hump there, but you cant see it at the bias setting I am using to keep from flattening out the two main humps.

I am learning about this OJT, the TP was right next to a IF coil, actually INSIDE the can (removable shield). the shield alone would drasticly effect the tuned response as would the TP leads etc (this is for the demodulated IF signal). Anyway care must be taken for lead dress when hooking up to these TP's.

here is the Emerson, the 1st pic is the B&K 415 setup with various markers set, the second is the IF curve.

note due to the sweep direction of my scope the IF curve is a mirror image of the curve plottted out on the B&K.

The picture marker on the B&K (middle of slope on right side) is present on the IF curve (middle of slope left side) its just not easy to see.

after consulting with a bud from another forum, I may try touching up the traps to get the bottoms a little closer to the markers. I hooked up the set to the cable and I get a bit of interference. I am guessing its ajacent channel noise that was not an issue with the DVD player. I am able to tune the VHF band ok, but the interference looks sorta like herringbone patterns (like it needs fine tuning but the fine tuning only gets it so far).

oh and subing out IF tubes can make big changes in the size of the humps, I could swap 2 IF tube and reverse those gain diff indicated by the size of the two humps.