| Electronics > Repair |
| Understanding and Repairing Clock Generator on Adret 742A UHF Generator |
| << < (10/10) |
| PerArdua:
Hi George, thanks for your message. It's quite interesting to see the difference material science has made in shrinking the volume of capacitors. The connections between boards appeared good. I had soldered the ribbon cables between boards and bent the cables so as to not strain the soldered joints. All the same, I desoldered these and disconnected the connector to the OCXO PCB - essential leaving the PSU on its own. I powered it up and measured the following: 5Vfloating: 0.0V (measured from bottom) +15Vpilot: 11.2V (measured from bottom) +5V: 0.0V (measured from PSU Control PCB) +15V: 1.3V (measured from PSU Control PCB) -15V: -3.4V (measured from PSU Control PCB) I've attached a picture of my test setup - just to ensure I've not done anything completely stupid. In this disconnected state the fan still turns on - but not sure what to make of that given the floating state of the PSU enable now that is separated from the CPU PCB. However, the lack of 5Vfloat and 15Vpilot leave me concerned that something isn't quite right. The AC input voltages are all correct, though I did notice that my meter (Fluke 15B+ captured some high startup transients for one measurement period - around 20VAC on the 10VAC rails, and 35VAC on the 20VAC), however I'm not sure whether to trust these readings - could they be some measurement artifact or something that could've caused damage? The capacitors I used were: 6800uF: https://www.digikey.co.uk/en/products/detail/nichicon/UVR1H682MRD6/588859 10000uF: https://www.digikey.co.uk/en/products/detail/nichicon/UVR1V103MRD6/588834 I also noticed a repair on the PSU control PCB, It appears D22 has been resoldered, and C28 (next to it) resoldered or replaced. Circled in the attached image. I'm thinking the next step is to get the 5Vfloat supply working again. I'm unsure the best way to do this given the difficulty in accessing the power transistor and the control PCB, all I can think to do is to solder wires to useful points and measure with everything in the instrument. Any times/suggestions would be very welcome. |
| vehiculeselectriques:
Hi, do you finaly repaired your ADRET ? |
| PerArdua:
Sorry, I'm afraid I did not. Work posted me away for some time, and the unit had to be left in storage. It is on my revisit list, I will probably pick it up again in the next few months. Do you have a unit yourself? |
| vehiculeselectriques:
Hello, yes i'm repairing a 740A which power on and seems to have all buttons and functions working but... no output signal |
| Navigation |
| Message Index |
| Previous page |