Im sure many of you have run into problems with convergence of the blue horizontal left side adjustment of zenith color sets made between about 1966-1973. It is a wire wound pot with the blue plastic shaft. Sometimes you will watch the set and just simply lose the blue convergence, due to an intermittent shorting 212-72 rectifier. The 212-72 is a selenium and very unreliable, it will develope a high resistance short, sometimes not bad enough to throw off the entire convergence, but will slowly burn up the blue pot. Ive seen this with so many zenith sets. pre 1970 zeniths used part number 63-7076, rated at 180 ohms. Sets from 1970-73 or so used the 63-7620 which was a 130 ohm.
If you attempt to adjust, it will just fall apart, the windings self destruct and or the shaft will simply snap off with minimal turning effort due to heat deteriorating the plastic.
The problem is locating a good substitute. The circuit only uses 2 of the 3 legs of the pot, so you can use a 200 ohm and not effect the characteristics of the circuit as you are not using the fixed resistance of the stator in the circuit.
Any thoughts? Ive looked around the web and found precision potentiometers, they have some good choices and found some that will fit without modification to the board. Anyone know of a vendor or supply house? I don't really want to buy direct from the manufacturer. They probably have an minimal order amount which is beyond what I need.

I need to solve this problem, if so, zenith convergence will never be a problem again.

...

Have you tried Andrews Electronics? They have been known to have OLD OLD OEM parts. I bought a CT-100 pencil box from them in the late 80s or early 90s, new in the box. No promises, but you could call them at (800) 289-0300. If a 16-year-old summer employee can't recognize the old Zenith part number, ask for Joe or C.D. They know how to convert to the new numbering system.

Charles

Doug,

My Zenith "Numerical Parts Price List with Recommended Substitutions" dated February of 1974 states that both of your part numbers were superceded by part number 63-7621X (or as Zenith puts it, 063 07621 X). The YR UD (year updated) is 1970 for the 63-7620 and 1973 for the 63-7076.
Price for the 63-7621X is listed as $1.45.

My June 1974 "Numerical Parts Price List with Recommended Substitutions" shows part number 800-0327 (a kit?) to be a suggested replacement. The 800-0327 is skipped over in the same listing, so it may have been short lived.

If it's a standard convergence pot, they were available in about 6 or 7 resistances - clarostat replacements are the U-39 series (sorry, no knob, just a + slot). Workman sourced about all of the values, but they aren't around anymore either. I wonder if RCA or GE ever used a 130 ohm pot? :scratch2: I'll check my stock. One other possible source - some computer monitors used a convergence-style pot for horizontal centering. I've got a 100 ohm used one in my parts drawers.

Hope this helps -

Doug,

I scrounged my collection of Zenith parts (about 350 or so NOS :D) and found two 800-743 kits! These are the blue convergence pots you've been looking for! :banana:

I took the liberty to open one and take a photo of the instruction sheet and contents:

www.talonix.com/images/100_4930.jpg

It's a HUGE image - wanted to give you good detail on the instruction sheet. I like how they have a part number for a 2 inch long piece of wire!

If you want the two kits, PM me and we'll talk. PS - 2 bucks a kit sound fair?

Cheers!

Thank you!

Once I got that 800-743 part number I decided to look through my stock pile of nos zenith. Luckily I found one of them! Mine is dated 30th week of 1982. Apparently this was a big reliability issue and zenith probably made many of these kits over the years and were probably in demand for some time. They seem to be still out there if you find the right people. Ive found so many late 60's-early 70's zeniths with these burnt up pots. Even if you dont touch them they go bad and burn up. Many times you will see "flash" marks on the convergence board where the wire pot just instantly went up in smoke.

ive PM'd you. thanks again for your help!