View Full Version : Zenith vertical intgrator coplates


wa2ise
10-10-2007, 05:18 PM
Quoted from elsewhere on this board:

I was able to come up with the parts values inside several
of the most commonly found 87-X Zenith integrators.

Remember these are set up as a three-lead package with two of each value resistor
in series, bypassed by three capacitors, with one lead of each cap tied together
making a common lead.

87-4 R= 33K C= 680pf

87-5 R= 47K C= 680pf

87-7 R= 68K C= 680pf

87-8 R= 82K C= 680pf


I measured five samples of each and came up with these figures...
In light of your cap values, I'm wondering about these, plus resistance
varied greatly...

87- ... R= 148-191K... C=.002mf(all five were approx same)

87-1... R= 57-64K... C=.006-.0065

87-10... R=70-83K... C=.0022(again all similar)


I believe the cap values in the 87-1 measuring around .005-.006 might be
about .002 x 3, that's what I had mentioned several posts above and IIRC
that's what I used to make them up with.

Looks like the 87-1 has two resistors each around 30K.

The resistors in the 87-10 must be around 33K-39K each. Cap values
could be 3 x 680 pf, that would give a total around .002



I replaced a 87-5 vertical integrator coplate in a Zenith black and white set,
chassis number partically missing, but starts with "147 ", and uses a 13FM7 vertical tube. Using the above values for 87-5, R=47K C=680pf got the set's vertical working well. The values look to be non-critical, I used one 680pf cap, and 2 caps that measured 720pF. Attached is the diagram of how the caps and resistors are hooked up.

There's another coplate, looks like an 87-4 (has a splotch of yellow paint) that resistance measures consistant with the above list. I didn't try to measure the capacitence, as that might require removing it out of the set, and I didn't want to do that...