Re: Tek 4654M; No Trace, No +5V, No +95V; Help


Harrison
 

Thanks Chuck. I have taken your advice and concentrated on the +5V circuit. Current conditions +32 TP reads 34.1, +5 TP 3.8, -5 TP -4.7 and 95 TP reads 8.8. I have read out all components in the +5 circuit from the +32 feed through R741 and R742 to the jumper before the +5V TP. If I got a good reading in circuit, I went with that. If I did not, I pulled the item from the circuit or lifted one lead and tested it that way. Everything seemed to check out OK except for pin 6 of U722B (FO-10) should read +5 but was reading 0.660, pin 7 should read 6.0 but read 14.71. Because the “power on” LED is not lit when the unit is turned on, I decided to jump over there a bit and read out U2280 on the Trigger board (Figure FO-5). All seemed well there except pin 6 reads -.38 instead of -3.6 and pin & reads -.25 instead of +5V. Now trying to figure if I need to back up more in the system or is the issue coming from somewhere else in the unit. I have no background on this unit. There appears by magic marker markings that some work or alignment has taken place, which is not surprising given the age of the unit. However, I do not see any real hack jobs or obvious internal damage or signs of non pro lab work. I have been trying to raise my electronic theory knowledge and troubleshooting skill on this unit. It came from a Ham fest, was labeled “working” which it clearly was not. Bottom line, while I found a couple of bad readings, I am no closer to solving the issue and getting this unit back online. I did replace CR 582 (Figure FO-9) and Q742 (FO-10) I am not convinced either was bad. My initial TP readings were +32 read +32, -5 read -5.07, +5 read -.752, and 95 read 5.74. My current set of readings is different. I do not know if that is because of the two part replacements, something else or just variation in collection. I did use the same Beckman HD110 meter to take the readings. Because the TP reading are now out of spec should adjustments be made for the respective pots for each circuit? At a loss as to where to go from here. Don’t like throwing in the towel but not sure I am making any meaningful progress at this point. Any advice and ideas, anybody, would be appreciated? Harrison N1FAM

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