Over the weekend I just rescued a Kenwood CS-4125 20MHz scope that had been thrown out and sitting in the rain. After drying it out and powering it up, it works perfectly aside from the focus and intensity controls. Focus works to a point, but at its sharpest the trace is still about 2-3mm thick. Intensity doesn't affect the trace brightness at all, but will worsen the focus somewhat when adjusted. I checked the control pots with my dmm and getting expected readings throughout their travel. I'm guessing that either an internal adjustment pot for focus needs adjustment, or a resistor etc has gone out of spec/died.

Kenwood: kenwood cs1562a oscilloscope Identifier kenwood_kenwood_cs1562a_oscilloscope. The ARCHIVE.ORG Manual Library. Kenwood: cs 1559.

Popping the case reveals no obviously burnt components. Unfortunately I only have an owners manual with zero useful information, no service manual. Anyone have any experience with one of these units, or maybe the service manual or schematic? After a couple hours of Googling I've only managed to find some sites where you can pay for the manual, but I did find a CS-4025 service manual.

While it's not the same model and some controls are in different locations, the theory behind the power supply unit should be similar I hope. I've emailed Texio and am waiting for a response. The only hint I found in that troubleshooting file for intensity/focus problems is that being unable to reduce the intensity (exactly my problem) may be due to a 'weak DC restorer diode' in the control grid supply. Install Block Version 2.0.7 Crack Load. Unfortunately I don't have a schematic but I suppose I can test all the diodes on the power supply unit board.

In the CS4025 schematic there are 9 in circuit with the intensity control input. I'm guessing here, but would a failed restorer diode cause blanking to not function altogether? I cannot see the beam return so that's not an issue I have.

After a couple hours of Googling I've only managed to find some sites where you can pay for the manual, but I did find a CS-4025 service manual. While it's not the same model and some controls are in different locations, the theory behind the power supply unit should be similar I hope. I've emailed Texio and am waiting for a response.

The only hint I found in that troubleshooting file for intensity/focus problems is that being unable to reduce the intensity (exactly my problem) may be due to a 'weak DC restorer diode' in the control grid supply. Unfortunately I don't have a schematic but I suppose I can test all the diodes on the power supply unit board. In the CS4025 schematic there are 9 in circuit with the intensity control input. I'm guessing here, but would a failed restorer diode cause blanking to not function altogether? I cannot see the beam return so that's not an issue I have. Sorry about the lack of pics so far.

Work suddenly got busy and I haven't had a chance yet. Focus has improved quite a bit after scrubbing some residue from the bottom of the amplifier board with a white eraser. The scope was sitting upside down on the rubbish heap so I guess some rain and dust got in there and created some capacitance or something. I've beeped out some of the circuit path and, after some thought, it seems likely to be a dead component. With the intensity knob on full, it is giving 0V at the wiper, increasing to 5v when intensity is at minimum.

Something must be open or transistor gain weak (resulting in 0v or close to it) and forcing the rest of the circuit to think the knob is at full intensity. The feedback into the autofocus circuit is working as tweaking the intensity knob will change focus slightly but not influence the brightness at all. Sending a signal through the Z-axis input also doesn't do anything to the intensity.

I still haven't gotten a response from Texio, so lacking a schematic with some test points I think over the weekend I'll just start pulling out components in the path and testing them, starting with the transistors. Hopefully I can get this fixed before my Tektronix 2430a shows up and I lose interest. I've replaced 2 diodes (1SS83) in the HV circuit that I found to be leaking (conducting roughly 50% in reverse direction) with same part no., but it has had no effect on the functionality of the intensity knob. I've also checked the large-value resistor (R58 in this diagram). I've attached the circuit diagram for CS-4025, which is similar though does have some differences. Test point 7 seems fine. Test point 8 couldn't be checked as I do not have a 100x probe Test point 9 is correct.