开云体育

-------- Original message --------From: nielsentelecom@... Date: 3/14/19 7:16 PM (GMT-08:00) To: [email protected] Subject: Re: [TekScopes] 2247A PSU Troubleshooting Nick,I have a 2246A that I had to get the ripple on the various DC busses knocked down. Replacing the ZS diodes was done, most of the secondary DC busses caps, a number of those were bad, I could not get all the voltages into spec with the single voltage adjuster. And I replaced those hot resistors near the HV section that scorch the board, they sit right in front of the air intake, and I replaced them with a higher wattage R and elevated them above the board. they were OK, but its a pain getting that power supply out! There is a HV cap in that section that will need constant discharging after powering up. It holds a lot of juice! I also blew the regulator chip in mine when I was probing around that tall heat sink, I forget which semi conductor, I had hit it with the ground ring on my scope probe on it. Pop, it went. I believe it has 150VDC on it. From your symptoms, it's similar to mine with the popped chip. Read about the delayed start feature, make sure it's doing what it's supposed to. There is also a crowbar circuit. I sourced that chip at DigiKey. I also created a resistive load to test the power supply voltages outside of the scope. I have lineman's gloves, and I put that HV CRT cable inside of that glove. I also elevated the board above a cardboard box with a box fan inside to cool those load resistors. It was a pain, but it worked very well. I have those resistor values if you need them. And I know all, doing it this way was not very safe! And I did use an isolation xformer.Nielsen TelecomTom Jobe helped me a few years ago get thru the repair. He has good advice. Search my handle and you will see what I did.