#1
|
||||
|
||||
EICO 368 Sweep Gen (1959)
I have a number of roundies that need IF alignment, am recapping this EICO 368 sweep generator. Marker crystal is 4500 kc.
Are these a good model? Will it work? Do I need an external AGC supply? |
#2
|
||||
|
||||
I think you are asking for trouble if you use Eico stuff for alignment. It was poor quality when it was made, and it can only be worse now.
Alignment is difficult anyway, and modern test equipment makes the job much easier. |
#3
|
||||
|
||||
Ditto on Steve's comments - get yourself a VA48 or VA62 and never look back. No manual? no problem - the VA48 PDF manuals are available for free from Wiscojim, and others have the VA62 PDF manuals, online, for free. Cabling is simple as well, with maybe a pad or two to build. My VA48 from 1976 is still using it's original caps, so no recapping necessary.
You'll still need a 20MHz scope or better. Have one? I worked in my Dad's TV shop for nearly 25 years, and we only aligned the IFs on TWO TVs, among the 10,000 or so he serviced. One (a Sanyo) had an IFT open, and the other was a Heathkit that someone bodged the pre-aligned IFs on. There are only three reasons to align - if something (other than the paper/film caps)has been replaced, if someone has been tweaking the cans, or if a massive shift in tolerances has pushed the response curve off. My 1964/5 CTC16 is spot on, original factory alignment. So unless it needs alignment, I'd stay away - most alignments are painful, with lots of oscope interpretation needed, perhaps a bias supply, and a set of decent probes for the aforementioned oscope. Just my 2 cents.
__________________
Brian USN RET (Avionics / Cal) CET- Consumer Repair and Avionics ('88) "Capacitor Cosmetologist since '79" When fuses go to work, they quit! |
#4
|
|||
|
|||
I have one of those, used it to align a split chassis early Admiral (mainly due to the 22mhz IF used).
it took a while to learn how to use it, and I used a modern day freq counter to confrim the markers. As to why it needed alignment, well it had a been "restored" before I got it, (no it did not work, long story about why people should not shot gun recap and then lots of diddle stick drift). Anyway I agree with the others, a more modern rig would be the way to go IF you really need to do an alignment. I have a BK 415 which I have used. as mentioned its rare to really need to do an alignment. If you go that route just be sure to learn on something that is not the precious to you. |
#5
|
||||
|
||||
I agree. If you must get a Sencore VA48 or 62.
Besides alignment they do almost anything you want. At one point we had 3 VA48's on crash carts along with a power right & scope. You cant beat them for usefulness. I also agree alignment is rarely needed. In almost 40 yrs I saw 2 sets that were tampered with & one GE that a xfrmer got smashed. We did that one by eye. Thats tens of thousands of sets I did, not including the other guys. What may help more than anything is fresh NEW tubes in the tuner, 3 IF's and 1st video amp. Do note believe a checker here. They can make a HUGE improvement especially on cheap sets & early all tube jap sets. There are also a few traps especially the 4.5 you can eyeball. Just my 2 cents, I know there are many that dont agree. 73 Zeno |
Audiokarma |
#6
|
||||
|
||||
Neither a VA 48 or 62 is a sweep generator though. Also you don't need a scope with a high bandwidth. What you need is one that can do X-Y mode.
I like the Wavetek 1002 or 1080/1 for a sweep gen and an HP 8657 RF gen for peaking coils and marker generation. |
#7
|
||||
|
||||
Quote:
I agree it's not a dedicated sweep gen - I used plenty of them in the Navy - HP, Century and Wavetek, but it's the best-all-around for TV use. As to the scope and X-Y mode, I dunno - the VA62 was paired with the 60MHz SC61, but a common 20MHz scope does fine. Trying to resolve on a cheapo 5MHz scope will drive you nuts. And what do you use for calibrated markers? VA48 can be had for less than 50 bucks, and will do a lot more for a tech than a sweep gen. I have the HP 8601 and a Wavetek 185, but would never reach for them in servicing a set - see my prior comments on IF alignment necessity. In 25+ years of fixing sets, I've never had a set that needed alignment. 1 exception - APC alignment, easy with the VA48. Not saying that others haven't had such luck, but too many folks (newbies?) see a problem, and without troubleshooting, opt to align, when the problem is an open peaking coil, a shady cap, a missing bias voltage, AGC gone wonky, or a defective IF amp tube or transistor. Blade track an ARC-51, align a APX-72 lid with a perfect bell curve, or align a 1030MHz preselector in a UPM-137, well, yes-I'd grab a sweep gen first. Of course, offer me an HP 8656B, and I'd probably sing it's praise - loved those sig gens I used in the Navy!
__________________
Brian USN RET (Avionics / Cal) CET- Consumer Repair and Avionics ('88) "Capacitor Cosmetologist since '79" When fuses go to work, they quit! |
#8
|
||||
|
||||
Yes, agree, should eliminate doubt on IF/tuner mixer tubes first as a low gain stage on a stagger tuned IF strip would seriously alter shape of broad passband! One RCA has symptom of shifting ghosting when fine tuning (a common symptom of misalignment?)
|
#9
|
||||
|
||||
Quote:
http://www.videokarma.org/showthread.php?t=259995 I don't have the equipment or skills to align in the conventional way. Maybe this could be used instead? I do have a 30MHz B&K 1474 scope which I've used to observe lots of TV signals. That scope supports X-Y mode. Phil Nelson Phil's Old Radios http://antiqueradio.org/index.html |
#10
|
||||
|
||||
If you use a VA62, you won't need a scope with X-Y mode. That's only needed if you use a sweep gen and want to see the actual IF response curve.
The VA62 uses something called "bar sweep alignment" which makes use of the multi-burst function. Rather than a continuous sweep of frequencies it uses 10 bursts of increasing frequency. Basically you connect the output of the IF to a scope and tweak the IF while observing the peaks of those bursts. So rather than a response curve, you get a bar graph. Here's an image taken from the manual. Last edited by bandersen; 07-17-2015 at 02:27 PM. |
Audiokarma |
#11
|
|||
|
|||
That is an interesting approach. Bob have you got any videos on using one of those to do an alignment?
|
#12
|
||||
|
||||
Would love to see a video of someone doing a complete visual alignment using a VA-48 or 62. I think those units were primarily marketed as a visual tool for verifying a sets frequency response, however there's quite a bit of mystique surrounding how one would actually proceed to do a full alignment. I'm not suggesting that it cannot be done, but I don't believe it ever caught on as a standard that was suggested in servicing literature of that period? And from a strictly educational point of view, it's not really very applicable to ones better understanding the operation of a set's video response curve. But I can certainly see how these were attractive to a very busy service shop, and even as a tool to show the uneducated customer that their set was in fact performing within spec.
|
#13
|
|||
|
|||
I'm 110% certain that once Phil gets into doing sweep alignment, he'll ace it with the same aplomb he's displayed in all his restorations.
Maybe a practice run on a BW first, and with a known good genny. He's already got a nice scope. |
#14
|
||||
|
||||
IMHO IF alignment at the pro level became a dead issue in the
early 70's. If one worked on both tube & SS after 6 months getting used to the new ways you saw how stable things became. I believe Sams did start referring to Sencore in later years. Also remember Sams couldnt afford to re-invent alignment for the hundreds of sets it covered. Just use the OEM manual instructions. As far as eye candy goes we had a shelf above the bench. It had a row of test eq that included at least 2 generators for alignment. Had RCA, Hickok, B&K, Eico & others. Only ever used a yoke/FTB tester. I asked the owner why it was all there when space was very valuable he said " its to impress the customers, I couldnt use most of it myself". 73 Zeno BTW the owner never did an alignment & started in the early 50's. He opened his shop in 1957 & lasted till abt 2010, he knew his shit. He made $$ til the end but bowed out on the up-side. When I started with him he told me within a few days " touch an IF coil & you WILL be fired !". Quote:
|
#15
|
||||
|
||||
Quote:
In the military, we aligned IF strips and pre-selectors all the time, as a catapult shot would knock stuff wonky, or the vibration in a helo would wreak havoc in a mechanically tuned radio. We couldn't seal them in place with wax, paint or Loctite - just had to live with it. My Setchell Carlson 21" b/w schoolroom set has a label indicating the IF module is sealed - with wax - to prevent misalignment during shipment. Go figure.....
__________________
Brian USN RET (Avionics / Cal) CET- Consumer Repair and Avionics ('88) "Capacitor Cosmetologist since '79" When fuses go to work, they quit! |
Audiokarma |
Thread Tools | |
Display Modes | |
|
|