Tektronix 494AP service manual O o o o O o o o o, Ai kHr, OotHi

b,

-

O

O

o

I

o

Io

I

o

I

O

o o

I

o

to

o o o o o o o o o

I

O

a a o o o o

I

o o o o o o o

		ro.a	attr				TT
							-ll
							a
							a
							.A
							-t
							-t
							{
							{
							*
	f" Rrynm ot tqOE filtrr.
	(Ex	re.&ra					n
							-ta
					t l		a
				.
					ilqdr		-a
				EFILTER
	_1a r r l			\t		I	-ar
							-a
	/
	F,>Ai kHr				\		.,
							{
			r l
/
			lOtHz				-e
		G I . E	D{T		lqlfl		{
		fEo	B		EL[rn
					lrrccDil
	B. Rorpolrrc oil lolrlls			fft	r.
E -loil	q	lo.dtla					TI
							- tl
					I		€
					lilllz	-	-4.
				\	FILTER		-ca
		E U I					€
	I	>!oot(Hi-{					-a
					I		{
					\
	I	-Jn"J			\		d
ut		,.T"*r					-t.
rlrngt
08tr
	C. Rcrpoor	ot tnz		fihcr.		55@-29

Flgurc 5-19.10 kHz, 100 kH:" and 1 MHz lilter response.

Adjurtment Procedure- 494A1494ApSeMce Vot. I

e.p693

Disconnect (Figure5-17)and activateMtN

NOISE.Applya 10 MH4 -25dBm signat,from the sig- nal generator, through a bnc-to-sealsctro adapter to J693: Set the genoratorfrequencyto peak the signal amplitude. (Signalamplitudeshould be between 3.5 and 6.5 divisions.tf signalamptitudeis not withinthese limitsit indicatesa gainproblemin the VariableResolu- tion module.)

f.lf the signalamplitudeis over 5 divisions,adjust the Post VR Gain R1030(Figure5-15)for a 5 diviiion signalamplitude.

g.Resetthe front panelAMPL CALfor a 7 division signal.

h.Switch MIN NOISEoff, decreasethe g€nerator outputto -35dBm, leavethe REFLEVELat -20 dBm, and adjustthe 10dB Gain R303S,on the 10dB Gain board (Figure5-17)so the signal amptitudeis 7 divi- sions.

i.Change the generator output to -4SdBm, the REF LEVELto -40dBm, and adjust the 20 dB Gain R2023on the 20 dB Gain Step board (Figure5-17)for a 7 divisionsignalamplitude.

j.change the generatoroutput to -65dBm, the REF LEVELto -60dBm,and adjustthe t0dB Gain R2060on the 20 dB Gain Step board (Figure5-1Tltor a 7 divisionsignalamplitude.

k.set the REFLEVELto -30dBm and the genera- tor output to -35dBm. Check lor a 7 divisionsignal amplitude. Repeat this check for -45,-55, and -65dBm input levels. Note that each maintainsthe Z division signal to verify that the gain of the Variable Resolutiongain stages are correct. Readjustgain il necessary.

l.Removethe 10 MHz signalto J680and reconnect P680. The final band level adjustmentsar€ described after calibratingthe PreselectorTrackingand checking flatness. The mean level for each band is set to th€ levelof Band1.

m, Removethe extenderboardsand re-installthe VariableResolutionmodulein the SpectrumAnalyzer.

n.Press <Blue-SHIFT>CAL to reruna calibration routineand re-establishprocessorcorrectionfactors.

5-19