Hi, what about this approach. To the left you add up 3 admittances and to the right you have one admittance. To the left you adjust for any values you like. To the right you adjust for balance which o

Perhaps it should be Yngve? That is the way I would spell it. Göran Den lör 4 jan. 2020 23:29Dennis Tillman W7PF <dennis@...> skrev:

Hi, quite possible that you have an oscillation here. If so something is broken. What you can do is to measure all DC voltages in this amplifier and compare with the schematic. If you find unexpected

Hi, there is a peculiar property with emitter followers and FET source followers. Under some circumstances they will provide a negative input impedance. This with a certain source impedance will start

More. You can check diodes by making differential measurements across the diode. I found two bad power diodes this way. You can do this measurement while the unit is in tic mode. I found the diodes co

You need a load of about 50W, possibly equally shared between positive and negative outputs. Either on the raw voltages or after the regulator board. You need to check all caps and diodes on the recti

In the archive there is another document "7k_PS_currents" describing typical loads, also scanned by Zenith. In my case the total load was 50W. I connected a number of power resistors to the various LV

In the archive there is a document scanned by Zenith, a specification 155-0067-02, pdf. For pin 13 there shall be two conditions: Logic "0": 0.0 - 0.05 V Logic "1": 0.85 - 10 V Well, if you dare you c

Hi, I worked on this PS in a 7904 some years ago. There are two overload conditions, over/under voltage and over current. Either shall turn the supply off. However, I think there is a third condition

No, I don´t think so. I got the impression that the problem occurs when and only when the mainframe is connected and not the dummy load. Try to lift one voltage to the mainframe at a time if this is d

Hi Dave, do you have a voltage across that resistor R10? Can you discharge and make a new measurement? Göran

Hi, The over-current signal path is T1235 - CR1290 – U1275, pin 13. Pins 4, 6 and 2 are also interesting. And why not check all pins on U1275 and report back. Göran

Hi, you may check the file "7k_PS_currents" in the archive. I built my own dummy load from it. It worked fine. Göran

Hi Dennis, The dummy load seems to be ok I think and also the connections. The total sum power in the load should be about 50 W in order for the supply to operate normally. What is your predicted tota

A good laugh is no waste of time! Still the block diagram of this instrument is quite interesting. Göran

Or support for board? Den tors 9 aug. 2018 18:40Jeff Urban <JURB6006@...> skrev:

I once read somewhere that one of the major relay vendors, don’t remember which, suggests that a 10 V zener diode is inserted in series with the fly back diode. The purpose is to make certain that the

Hi, can anyone explain why this calibrator needs transformer T1255. Such a component should be expensive. Would it not be possible to have an oscillator/Schmitt trigger design and still get the same p

Hi Tony, Your measurements: -50V 100 ohm 50W ---------- 0.76V -15V 4.7 ohm 50W ---------- -5.57V +5V 2.2 ohm 50W ---------- 5.047V OK +15V 4.7 ohm 50W ---------- 18.24V +130V 2.2K 50W ----------- 128.

Hi John, what about checking R1459 (150 ohm) and the other corresponding resistors for the other regulators as well? Göran