Use X10 scope probe to look here.

! "$#%'&)(+*-,/.102-3425(+,/,)67*839.;: <1:)6),=.?>A@ B;:)(+#C:).1DFEG.1HI3KJMLN@ OP1OBK25&)(+DF&QD<I#%'.1(/#)*. R<1,+%F.?HI3KLS<I#%8>8<I,+,/3TVUK*WD(+,/,=.G%'<I>NXYR4LZU\[].1#)TQ%$2-<^%$_`: 3a*Z<1bc:)&.1*W3KD<Id:.1>8.?%'<I>W*e "$#f.1t)t)(g%'(/<1#h%'&73>83i(/*j.k&)(/h1&l(/d:m3t.1#7d3mn<i6)>wd3o<i,+,/<p2s3a>qxn7or[s25&)(/df&t.?,/,/<p25* <1#)3s%'<Vd<I#)(g%'<I>A%'&)3^(+#):)67%9%8<V%'&)3sR4LZUu25(+%'&7<I67%KT)(+*W%86)>80)(+#)HQ%'&73v.1Da%8(/<I#<1b-.1#_ :7>83Da3T)(+#)Hvw,+%83>]25(+%8&x3zyD3a*8*8(g{I3,/<.1T7(/#)H)e }Z&)3 DF&)(/:~(/*4LZJqU\n emn,g%'&)<16)hi&~&)(/hi&73>z{i<i,g%f.1h13*a.1>83;:m<i*8*w(/0),+3.?*at73a%f.?(/,/3ati0_ %8&)3 *W: 3aD(gwD.?%8(/<I#i*8&)3a3a% 2S3;25(/,+,c<1: 3a>'.?%83 <I6)>ADF&)(+:MbY>8<Id.Qƒ; ^R<I,+%A*W6):):),g_q.1#7T 0m3D.1>W3abY6),r%'<~dC.1(/#%F.?(/#}Z}5,/<IH1(/Ds,+3a{I3a,/*jXPG GR\[K.?%\%8&)3C(+#):)67%eVJM.?E13jDa3>ˆ%F.1(+# %8&)3; sešlne<? *W3a%A<I#V%'&)3KŒk. {I3a%83Ex(/*Z*W3a%4.?%5 a3>8<vr<i,g%'*e }Z&)34*83a#)*8(g%'(+{139o Žr}H.G%'3*-.1>W3N.1T73 6.?%83,+_:)>W<1%'3aDa%83TQ*W< %'&).?%-_1<I6Q*W&)<I6),+Tj#)<1% #733T %'<~<I0)*W3>W{13j*W6)DF& :)>W3D.?67%'(+<I#)*.1*;.~HI>W<I6)#)T *W%8>'.1: <I# _1<I6)>\25>8(+*W%\%'<i. {I<I(+T *ˆ%F.?%8(/DT)(/*WDF&.1>WHI31ex" %;2S<I67,/Tk0m3Q.~HI<`<T (/T)3.i#)<?% %8<q.1:):7,+_ (/#7:)67%;*8(+HI#.1,+*;25&)3a# %8&)3>W3(/*Q#7<h \L :m<2-3>v<1#t%8&)3df&)(+: 4&7<2-3a{13>x%'&)(+*QDF&)(+: (+*Q:)>W<I0.10),g_f>W6)HIHI3aT 3a#)<I6)H1&i#)<?%Z%'<0 3KT)3aHI>'.?T)3Ti0 _Q*86)DF&~%'>83.?%'d3#%e LS<I#7#)3Dz% _1<I6)>rDF&)(+:^(/#v.9*ˆ%F.1#)T).1>8Tvšr&.1*W3A <`DFEs <`<I:sDa<I#7wHI67>'.?%8(/<I#v.1* *8&)<p25# (+#CwH16)>83 @Ier"$#)(+%8(=.1,+,+_ 6)*83A%'&)3Nœ4UK td<id:.1>8.?%'<1> <167%':)6%SbY>8<1dž:7(/#VŸ`er"$#V.sšr&.1*W3 <`DFE <<1:q%'&)3v e LNe <I67%8:)67%;<1b %'&)3^Da<Id:.1>'.G%'<I>9(+*\.1,+2S. _`*\by3at (+#%'<x.qw,+%83>9%8< :7>8<p{`(/T)3^.j sešlnemd<i#%8>8<i,c{i<i,g%f.1hi3\by<i>a%'&)3 %8&)3 R4LZUse }Z&73s<I67%8:)67%K<1b %'&)3 R4LZUu(/* %8&)3#>W3a%86)>8#)3aT%'<j%8&)3sD<1dC:.?>'.?%8<I>4%8<Q0 3 dj.?%8df&)3t.?h.1(/#7*w%n%8&)3s(+#):)67%4by>8<id %'&73 Œk. {I3z%'3Ee "$# HI3a#)3>8.1,S<1#)3V&.1*s%8<0 3QD.1>83zbY6),S%8<HI3a%^%8&)3Q:m<I,=.1>W(+%$_ <1b5bY33aT)0.1DFE Da<I>8>W3Dz% 0)67%A(+#x%8&)(/*ZD.1*83\%'&73>83\(+*Z<I#),+_j<I#)3\:m<I*8*W(/0),+3KD<I#)#73Da%8(/<I# e 56)# %'&)3QŒk. {I3z%'3E (+#k%'&73~lzu\ A}Z" N NU\ NnhJ~<T)3?e A*83~.q*8 6.1>W3V2]. {I3~.?%.?0 <I6%j@CE A 1 <1*8D(+,/,/.?%'(+#)HV0 3z%$2S3a3# P?R.1#)T ƒ; Rse} >W(/HIH13>K%'&)3C*8Da<I: 325(+%8& %'&73 (+#):)67%KŒk. {I3z%'3E*W(/HI#).1, exxy]%kby>83a `673#)Da(/3*\%'&7(/*K,/<p2 (+%\dc. _q*83a3dªd<i>83s.1t7{?.1#%f.g H13<I6)*%'<;{`(/3a2l%'&)3A*83aD<I#)Tj*8D<1: 34DF&.1#)#)3a,m25(g%'&%'&)3NL] 9UKššŽ «>8.?%'&73>r%'&.?#C%'&73 N }5Ž A 4r}5Žfd<T)3K<1#~*WD<I:m3*A6)*W(/#)H^%'&73*83\bY3.G%'6)>W3*e [ R.1>ˆ_s%'&735Œk. {I3z%'3E^bY>W3 6)3#7Da_<p{I3>-.925(/T)35>8.1#)HI3A.1#)T<I0)*W3>ˆ{I3A&)<p2f%'&)3ZR4LZU 25(+,/,*W<IdC3z%'(+dC3a*-,+<DFE^(+#j*W_`#)DF&7>8<I#)(+.?%8(/<I#25(+%8&j%'&)3AŒ. {13a%'3aEj.?#)TQ*8<1dC3z%'(/d3*>W6)# by>w33a,+_ <I67%C<1bK:7&.1*83?ẽ 4<1%8(/D3x%'&).?%j(+# %8&)3M,+<DFE?3TfDa<I#)T)(g%'(+<I# %'&)3a>83M(+*j. *W%'.10),/3 {1<I,+%'.1HI3K(+#):)67%Z%8<v%8&)3KR4LZU.1*Z>83.1T~0 _~.^T)(+HI(+%'.1,{I<I,g%'d3a%'3a>5.?%5%'&)3 n7o <I6%':)67%e o (+>8*ˆ%T)(/*ˆ%'(/#7HI6)(/*W&v `6).1,/(g%F.?%8(+{I3a,+_ 0 3z%$2S3a3#j%8&)3A,/<`DFE (/#^>8.1#)HI35<1b by>83 6)3a#)Da_C.1#7T @

Use X10 scope probe to look here. Comparator 3 13 2 WAVETEK 8 5 16 10 K 1 K 9 VCO 11 12 6 7 V dd = +5 V 0.1 uf 500 pf 27 K 820 K o (/HI6)>W3^@ %8&)3xD.1:%'6)>W3~>8.1#)HI3V<?b4bY>W3 6)3#7Da_Ieh}Z&)3x,/<`DFEI $(/# >8.1#)HI3V(+*^6)*86).1,/,g_ HI>W3.?%83>^%'&.?# %8&)39D.1:7%'67>839>8.1#)HI3?e UK#7D39,+<DFE?3TV(/# %'&739(/#):767%SbY>W3 6)3#7Da_QD.1#V0m39dC<p{13TV*8,+<p25,+_ <p{13>v.i25(+t)3q>'.?#)hi3v.1#7t %'&)3jR4LZU 25(/,+, *ˆ%F. _,+<DFE?3T (+# :)&.1*W31e 4<p2-3a{I3a> <I#)Da3 %8&)3K,/<`DFE13aTiDa<I#)T)(g%'(+<I#Q(/*Z,+<I*W% %8&)3\(/#):)6%]bY>83a `673#)Dz_idC. _j#733tx%'<v0m3\.1t W6)*ˆ%'3aT~%8< >W3D.1:7%'67>83K%'&)3\,+<DFE?3TMDa<I#)T)(g%'(+<I# e JM.?E13x.i#7<1%'3C<1bZ%'&)3C&)(/H1&.1#)T,+<p2 by>83a `673#)Da(/3*^<?bZ_I<I6)>,/<`DFEI $(/# >'.1#7HI3Q.1#7T %8&)3C sešlne,+3a{i3a,-<?bs%'&73c(+#):)67%\%'<x%'&73r4lzu.?%\%8&)3*w3j,/(+dc(g%'*aesr.1>w_%8&)3œk. {I3z%'3E by>w3 6)3a#)Da_ *8<.?*;%8<q.1:):7>8<.1DF& %'&)3C,/<`DFE (/# >'.?#)HI3CbY>W<Idª<I67%8*8(+T)3%8&)3j>8.1#)HI3?.1#7T %8>W_v%'< w#)tq*w(/d(/,=.?>r&)(/hi&j.1#)tq,+<p2t,/(/d(+%8* by<i>,/<`dfe (/#CD.1:7%86)>83?e Œt&)(/,+3A%8&)3NR4LZU«(/*,+<DFE?3TV(+# :7,/<1%-%'&)3NR4LZU (/#7:)67%Z \Ll,+3a{13, by<1>s*83z{i3a>'.1, by>w3 6)3#7D(/3a*5.1#)TQDa<IddC3a# % <1#x%8&)3\,/(+#)3.1>W(+%$_C<1bc%'&)3; \L,+3a{13,.1*A.sbY6)#)Dz%'(/<1#~<?b by>w3 6)3#7Da_Ie Œt&)(+,/3Q*ˆ%'(+,/,S67*8(/#7H %8&)3Vœ4UK <I67%':767%v<1bA%'&)3xD<1dC:.?>'.?%8<I>xX :7(/# ŸI[ {?.1>ˆ_k%'&73 Œk. {I3z%'3E^bY>W3 6)3#7Da_<p{I3>r%8&)34,+<DFEI (/#^>'.?#)HI3A.1#)T<I0)*W3>W{134&7<2l%'&)35>83a,=.?%8(+{13Z:)&.1*W3 0m3a%$2-33a#%'&)3~R4LZU.1#7TlŒ. {13a%'3aElT)3a: 3a#)T)*V<I#hbY>83 6)3a#)Da_1e Ž y7:7,=.1(+#h25&_h%8&)(/* :7&.1*83v{?.1>8(/.?%'(+<I#q(+*;#73D3a*8*8.1>W_ (+b %'&73vœ4UK Da<IdC:).1>'.?%8<I>9(+*\%8<x(/# 673#)Da3%8&)3^bY>83z 6)3a#)Da_~<1bc%'&73\R4LZUse A<1%'3V%'&73>83i.1>W3xbY>W3 6)3a#)D(+3*<I67%'*W(/T)3x<1bA%'&73~#7<I>8dC.1,],+<DFE >'.1#)H13x25&73>83x%'&73 R4LZU.1#7T Œ. {13a%'3aE 25(+,/,,/<`DFEK(/# :)&.1*W31 I0767% 25&)3a>83S%8&)3-%$2-<9<I*WD(+,/,=.G%'<I> by>w3 6)3#7D(/3a* Ÿ

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