| Electronics > Repair |
| Xantrex/Sorensen XHR 40-25 schematic? |
| << < (11/11) |
| ifonlyeverything:
Been trying to understand the CV offset issue for a day or two, kind of stuck. Would appreciate any help. It's a variable offset (see below for examples) and I have discovered two scenarios that will create this problem. At a CV of 36.0V I see a swing up to 36.8V. Delta of 0.8V. At a CV of 22.5V I see a swing up to 23.9V. Delta of 1.4V. At a CV of 12.4V I see a swing up to 13.1V. Delta of 0.7V. Scenario 1: STANDBY enabled. I click V/I and dial in my CV limit of 22.5V. STANDBY disabled. I click V/I and my commanded CV limit has changed to 23.9V. Notice the change from 2.755V to 2.920V, an offset of +0.165V. Scenario 2: STANDBY enabled. I click V/I and dial in my CV limit of 22.5V. STANDYBY remains enabled. REMOTE programming enabled. I click V/I and my commanded CV limit has changed to 23.9V. Notice the change from 2.755V to 2.920V, an offset of +0.165V. R230 measures 10K and the voltage drop across it at all times in all of these scenarios is 0.000V -- it's not a source of current being injected. This is what the 10-turn (R35), V/I check button (SW75A), REMOTE button (SW73), and STANDBY button (SW74) are doing on the front panel. Keep in mind clicking V/I doesn't change the value on the non-inverting pin (as per my measurement), it just does an analog to digital conversion and displays it on the front panel. |
| ifonlyeverything:
Spent some more time playing with this. I've pinpointed it to Q194 causing VCTL to droop when shutdown is enabled i.e., Q194 is pulling the non-inverting pin of U199D (pin 12) to ground. I wonder if this is a "design flaw." The worst delta is at around 22.4V (swings up to 23.9V for a 1.4V error) and is around 6% so it's not too bad. Just annoying that it exists in the first place. :-\ My guess is that increasing R219 would help (and decreasing C220) but I don't particularly feel like finding out what other potential downstream impacts might be... |
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