Gabriel,
I was able to get to the backside of the mainboard without removing it. I removed the switch/potentiometer board and an RF plate covering that area, and hit all the solder joints for channel 2 including the K112 relay. It took care of the trace height problem It now goes to the correct level for the voltage under test; or at least it matches channel 1 which functions correctly. It was a solder joint somewhere in there. I didn't know which (X10, X100, etc) was for what voltage setting (2V, .5V, 20mV, etc.)
The volt meter function was off, I thought, as a result. Channel 1 would function correctly, but channel 2 would read quite high compared the CH. 1. After the resoldering, I ran the calibration routine on the scope right after I powered it up (cold). The voltmeter did indicate the voltage correctly. I left it powered on for some time, and did a factory default run on it which recal'd the voltmeter again. The voltmeter function for channel 2 went high again, like 14 volts for a .5VDC actual level, but the trace was at correct height for the given voltage. I shut it down overnight and this morning I powered it up and ran the voltage calibration routine again thinking the problem was due to heat now. It correctly calibrated this time again. So, I see now there is separate problem. I also notice the voltmeter cursor will not appear in the correct location on the trace like it does on channel 1. It will display the voltage correctly, but the voltage trace gets a little lost on the display. So, I will dig into that. Anybody run into this type of a problem?
Nick
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--- In TekScopes@..., "iglesia_cristiana_arpas_eternas" <iglesia_cristiana_arpas_eternas@...> wrote:
Hi Nick!.
The 2246 input channel has a X10 & X100 att controlled by K102 & K103 at the front end of U112.
At the back end of U112 you have an other att X1,X2,X5 controlled by K104 & K105 .
There may be the place for your problem.
Gabriel.
--- In TekScopes@..., "nielsentelecom@" <nielsentelecom@> wrote:
Thanks for the replies. iglesia_cristiana_arpas_eternas, I am not sure what you mean by the "back attenuator works with the front one" I do see where there is a cascading arrangement, meaning, the attenuators do work together for certain vertical settings. Is that what you refer to?
Nick
--- In TekScopes@..., "jtjewell83" <jtjewell83@> wrote:
Nick,
About 3 years ago I fixed a 2246A with a dead channel per one of the relays was not operating. Problem was a CD4094 IC. It was an easy troubleshoot, but I don't remeber the details right now. I didn't remove the main board to replace the IC, but simply clipped the leads from the bad one, trimmed the leads of the new one a little, and soldered it to the pads on the bottom of the board. The scope still works great.
Jimmy
--- In TekScopes@..., "iglesia_cristiana_arpas_eternas" <iglesia_cristiana_arpas_eternas@> wrote:
By definition, a relay is the strongest device in the input channel path, great probability that bad solder or bad resistor is the guilty one..not the relay..but who know?.
Check the manual, if I remember right, this scope, At back end vertical amplifier has a low impedance attenuator which works with the front end one .
PM.
--- In TekScopes@..., "nielsentelecom@" <nielsentelecom@> wrote:
Can anyone shed any light on this problem? If the relay is bad, is there a source for it?
--- In TekScopes@..., "nielsentelecom@" <nielsentelecom@> wrote:
I picked up a Govliquidation Tek 2246 mod A. I am having an issue with channel 2 vertical deflection. It is off when compared to any other channel. When I have it on the calibrator terminal (1KHZ @.5VDC)it will indicate higher than normal about half the time I roll it thru the voltage range. I have done the bump test, and it will pop down to where it should be when it gets a smack on the side. I did remove the cover, and when I poked around the channel 2 vertical attenuator area, I found when I pull/push/tap on the K112 relay, I will get the level that is expected/manipulate the problem. I suspect a bad solder joint. I did get the service manual and read how the attenuator cascades. Below are the affected voltage settings. .1V and and 10 mV are not affected. 5mV and 2mv are tough to get on the scale so I did not test those reliably.
.1V and 10mV not affected.
.2V, .5V, 20mV, and 50mV are all affected.
5mV and 2mv not reliable enough for conclusion.
I did do the self calibration on the voltage section, and now the voltmeter is indicating a much higher than normal reading, where before the self calibration, it was measuring the correct voltage even if the waveform was higher than normal.
Is there any way to get to the backside of the main board where the vertical section is at without removing it? I see in the svc man that It involves gutting the machine for removal. I would prefer to leave the board in place and move around any solder joints and resolder it. Are these relays reliable? Since I was able to tap the relay as it was the most sensitive to the tap, I suspect that relay is either bad or not soldered in properly.
Nick
