PG506/Repairs: Difference between revisions

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-If your PG506 Fails to show a display of the Variable Value on the display, check the wave forms at U400 and U470. In case of failure in the "STD. AMPLITUDE_Variable" mode, where the display and HIGH_LOW indicators do not operate; check for these wave forms at U470 and U400.  This assumes that the display momentarily shows "8.8" when the variable switch is pressed "in".  If the display does not show "8.8", then there are other issues related to the display and not the DVM circuit.
+==Replacement front plate==
-U400= SN74LS00N  Link to datasheet here:  https://www.ti.com/lit/gpn/SN74LS00
+* https://www.pcbway.com/project/shareproject/Tektronix_SG504_Front_Plate_a2166d7a.html
-U470= TL710CP or equivalent
+==Repair hints==
+If your PG506 fails to show a display of the Variable Value on the display, check the wave forms at U400 and U470. In case of failure in the "STD. AMPLITUDE_Variable" mode, where the display and HIGH_LOW indicators do not operate; check for these wave forms at U470 and U400.  This assumes that the display momentarily shows "8.8" when the variable switch is pressed "in".  If the display does not show "8.8", then there are other issues related to the display and not the DVM circuit.
+:U400 = SN74LS00N  Link to datasheet here:  https://www.ti.com/lit/gpn/SN74LS00
+:U470 = TL710CP or equivalent
 Here is a link to photos of these wave forms.  There are two photos of a legal pad and hand notations which are an index key to associate the photos to the various pins.  Photos of U400 were taken at each pin and with the variable in Full CCW. ZERO and Full CW positions.  With few exceptions, there are 3 photos per pin.  Exceptions are Vcc, Ground and a few others.  Please refer to the proper PG506 Service Manual for more details.  These photos were taken on the RELAY Equipped Version of PG506 (Not "A")S/N is B040000 and above.
-PG 506 U400 AND U470 Wave forms   https://www.icloud.com/sharedalbum/#B0e532ODWGRrNkO
+:PG 506 U400 AND U470 Wave forms   https://www.icloud.com/sharedalbum/#B0e532ODWGRrNkO
 If you have questions contact me at >mlynch002@gmail.com< or >mlynch003@yahoo.com<.
 PG506 Settings:
+: STD AMPLITUDE: SELECTED
+: AMPLITUDE VARIABLE: OUT
+: AMPLITUDE SWITCH:  1V
+WAVE FORMS Photographed on TDS460A.  See photos for scope settings as these can vary from photo to photo.
-STD AMPLITUDE: SELECTED
+During this repair, I found these parts defective.  The repairs were much more than a non-functional display and some of the components below were related to those additional problems.  The display was the last thing to get working.
-AMPLITUDE VARIABLE: OUT
-AMPLITUDE SWITCH:  1V
-WAVE FORMS Photographed on TDS460A.  See photos for scope settings as these can vary from photo to photo.
+In the course of the repairs, I found these components bad in the unit.
+: Q280 151-0280-00 PNP
+: Q290 151-0280-00 PNP
+: Q745 151-0446-00 NPN
+: Q435  151-0223-00   NPN
+: Q535  151-0223-00   NPN
+: U460   156-0067-00  OP amp  (741CN)
+: U200   156-0067-00  OP amp  (741CN)
+: U240   156-0067-00  OP amp  (741CN)
+: U610   156-0039-00  Dual J-K Flip-Flop
+: U480    156-0399-00 Opto Coupler
+: U255    156-0399-00 Opto Coupler
+: CR290  152-0141-02  (1N4152R)
+: CR291  152-0141-02  (1N4152R)
+[[Category:Instrument repair reports]]