Re: 2465A +5vd Power Supply Problem
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4.7Kohm resistor in parallel with R1270 no difference in +5d output Still low at 4.55v either way
27kohm resistor in parallel with R1044 no difference either in +5d voltage
Voltage at Pin 7 of T1060 and Ref 2 is 113 volts
Resistance from chassis ground to junction of L1110 and C1110 is 145 ohms (no load on +5d). Reversing the multimeter and it starts at over 140 Mohm and slowly draws down.
Link below is a photo of the ripple output at the junction of L1110 and C1110 with a load on +5d. Looks like the inverter puts out a a fair bit of noise
--- In TekScopes@..., <tekscopes@...> wrote:
Shouldn't it be possible to test this by bridging R1044 with a 27 K resistor? If the +5 Vd supply voltage increases we know its the optocoupler.
From: David <davidwhess@...>
Sent: Tuesday, September 10, 2013 4:28 AM
Subject: Re: [TekScopes] RE: RE: 2465A +5vd Power Supply Problem
1.07 volts indicates that either the optocoupler is bad do to low or no output, R1044 is open, or that there is an open circuit in series with R1044 and the optocoupler output. I was wrong earlier about the possibility of C1048 being shorted.
All of my service manuals so SOC123A which I suspect is a Tektronix house number. My Tektronix parts catalog shows Motorola MOC1005 which is a very close match to the Toshiba TLP631.
Current transfer ratio is the ratio of output to input current which is sort of like gain. 50% means that for every 1mA of input, the output will be 0.5mA. The optocouplers are graded by CTR which is why there is an F and GBF version.
The CTR should not be critical in this circuit so either of the ones you mention should work fine.
If you want another test to confirm where the problem is, then the voltage between pin 7 of T1060 and REF1 with an inverter load should be about 120 volts DC which indicates that the optocoupler output is missing and the pre-regulator is set for the minimum output voltage as determined by R1045 and R1046.
Another thing you could try is halving the value of R1270 on the low voltage regulator board near U1371C by temporarily placing a 3.9 or 4.7 kOhm resistor in parallel with it. That will double the current into the optocoupler so if its CTR has degraded with age, the higher current will allow it to work for now.
On 10 Sep 2013 00:10:39 -0700, you wrote: