R-2001D Display problems...

[2n2222]

Hi all:

I have recently acquired a R-2001D/HS service monitor and it looks like it has two weird display problems.

1. In oscilloscope mode, I can send it a sine wave from a function generator and it draws about the first 1/3 of the waveform, while it gradually gets lighter in intensity - all the way to nothing. When I change either the timebase or vertical switch (can't remember which), I get a flash on the screen of a perfect sine wave, all the way across the screen, but only for about 200mS.

2. In spectrum analyzer mode, I see nothing on the display. If I TX into the service monitor, in the far lower left corner, I see some activity, but it looks like the very peak of the spectrum display trace. I tried the Hor. & Vert. controls and they do nothing....

Seems like there is maybe some problem that could be common to both symptoms?

Help!! I'm eager to start using this piece of equipment, but it's not cooperating!!!!

Regards,
Steve

[DJP126]

First a basic alignment and calibration is needed. Your scope intensity and balance controls are messed up. This MIGHT be the only problem.

Second, if it isn't the only problem, I would suspect the A2 (Scope Amplifier) module, the A7 (Scope/DVM Control) module or the A15 (Front Panel Interface) module.

Third, IF the spectrum analyzer is not sweeping, you 10 MHz reference oscillator might not be working. If the unit generates and receives on frequency, this (the ref osc) would not be the problem with the spectrum analyzer.

[2n2222]

DJP126:

Thank you for the reply. I was fearing that the CRT may have taken a hard hit in shipping, so I hope that is not the case.

The unit will Monitor and Generate fine, and right on freq. It just seems like anything that is not text on the screen (text is fine in all modes) looks screwy and off position.

Also, I tried scope mode again last night and feeding the function generator in to the input, I get a nice sinusoidal trace all across the screen when I turn the timebase knob, but only for about 200mS.

Question: When the unit when it is in scope mode, should it draw a horizontal line across the screen, when there is no input, like a typical o-scope? This one doesn't, and I'd like to know if that's normal.

I am trying to get my hands on a service manual (or even a schematic at minimum) right now so I can dig into it, but it is extremely hard to find...

I can post some pictures of the screen and what it is doing if you think that would be helpful...

Best Regards,
Steve - 2n2222

[DJP126]

DJP126:

Question: When the unit when it is in scope mode, should it draw a horizontal line across the screen, when there is no input, like a typical o-scope? This one doesn't, and I'd like to know if that's normal.

There is a trigger source switch. From what you describe, it sounds like the source switch is in NORMAL. Change it to AUTO.

[2n2222]

If that is the rotary switch on the front panel, I get the same result in either position.

[DJP126]

The front panel has two flex circuits to the mother board. One (or both) connector could be preventing a GOOD ground contact. You can try to CAREFULLY remove the connector and clean it. I stress carefully because the flex circuits (as well as most of the components) are NLA at Motorola.

[2n2222]

OK, I experimented around with it tonight some more..... BTW, thanks for the help so far!

Oscilloscope Mode:
Looks like the 1microsecond/division is working. I get a trace all the way across the screen. On the other modes like 10microseconds, 100microseconds, 1milliseconds, 10milliseconds and 100milliseconds, I don't get a full sweep across the screen.

The 1millisecond range, it draws the input waveform for approximately 1 division and then fades out to nothing. In the 10millisecond range and the 100milisecond range, I see a flash on the far left side of the screen at approximately the selected sweep rate.

If you tease the switch between positions, it defaults to the 1microsecond rate, and seems to work.

The Horizontal and Vertical positions work, but they are very erratic.

The Vertical amp. seems to be ok, but it is necessary to adjust the vertical position and re-trigger if you select a different volts/division.

I did carefully unseat and re-seat the flex cable connectors, and visually they looked good. I want to blow the entire unit out with compressed air this weekend before I start cleaning contacts.

Spectrum Analyzer Mode:
I see nothing on the screen past the first division on the left. No other control on the front panel will change that. Also, the Horizontal/Vertical controls in the OScope group have no effect and I don't know if they should.

The RF Scan dial does change the display and I can sweep and see a peak as I approach the center freq of what's on the input. The Dispr/Sweep control does have an effect on the shape of the peak when there is a peak.

What might also be helpful is if someone has a table of what the pots on the A2 board do. From the inside cover, I figured out that pot R88 controls the trace rotation, which was pretty far off on this unit.

Any help would be GREATLY appreciated!

[DJP126]

What might also be helpful is if someone has a table of what the pots on the A2 board do. From the inside cover, I figured out that pot R88 controls the trace rotation, which was pretty far off on this unit.

Now you are back to the basic alignment and calibration. The procedure (which is in the maintenance manual tells you which pot controls what. Unfortunately I don't remember the designators. Your main concerns are the scope raster, trace balance, pin cushion, vertical center, vertical gain, horizontal center and horizontal gain. You have already found the trace rotation control.

For the basic alignment you will need a good DVM (to check the power supply voltages and to adjust the 5 VDC supply), a calibrated scope and a jumper wire to short out some test points to ground (for vertical and horizontal centering).

[2n2222]

Thanks for the reply.

If there is anyone out there that has a service manual for a R-2001D, that would be willing to share some information, that would be great. Even just a few excerpts from the manual would be most helpful. Until I get some more information, I'm stuck!

I have a nice scan of the R-2001D user manual to trade if anyone is interested....

Best Regards,
Steve Kent - 2n2222

[2n2222]

I got it running last night....

After blowing it out with compressed air, the INT/EXT Reference switch was intermittent. So after cycling the switch about 200 times, it started working.

I eventually got my hands on an Alignment Procedure and ran through it as suggested on this board.

The cause of most of my display problems was the Intensity Bias control. After tweaking that, I was finally able to see a dot on the screen when the Horizontal selector is in Ext mode.

I just thought I'd post it here since it might help someone else out....

Regards,
Steve - 2n2222

[DJP126]

If you can put that alignment procedure into PDF format, I sure would like a copy. Trying to go by memory is a pain.