Tektronix PG-506 Calibration Generator info

[mskobier]

All,
 As many if you are aware, I have three 2400 series scopes that will be needing calibration touchups. After weighing the options available to me, I decided to locate a PG-506 Calibration Generator, a SG-503 Leveled Sine Wave Generator, and appropriate TM-503 series main frame to put them in. I located the PG-506 and SG-503 from a surplus company on the east coast for a reasonable price (way less than -bay prices), and the TM-503 from -bay. I have been traveling the past 10 days, arriving home late last night. The PG-506, SG-503 and TM-503 mainframe arrived while I was away. I had a chance to check them over today. Physically they appear to be in good shape. After a through visual inspection of the internal circuit boards looking for obvious damage, I installed the plug-ins in the mainframe and applied power. No smoke, and everything seemed to be working. There is a question with the PG-506 and the reason for this post.

 I am not familiar with the PG-506, and am currently using a PDF of the late version manual to figure it all out. The correct manual has been ordered. I checked the standard outputs, and they seemed to be as expected. The question I have is in regards to the Amplitude Variable output knob. In reading the manual, it is not clear if the amplitude variable knob is a latching push button or not. It leads one to think it is, but It is not clear. Anyway, the variable output knob on my PG-506 arrived almost flush with the amplitude nob, which did not look right to me. I loosened the Allen screws on the knob and positioned it the way I thought it should be. I can push the knob, and it does depress, then returns to its original position. When I push the amplitude variable knob, the led display shows 88 as specified in the manual. When I release the knob, the display goes dark.

 I am thinking the Amplitude Variable knob is supposed to be a latching push button, that has two positions, out and latched in. Is this correct? Some of the pictures I have seen on the net show the LED display lit up with various numbers displayed. My PG-506 is an early model SN B016XX. The pictures I have seen of the unit in operation are of later models or A versions. My PG-506 display is dark unless I push the Amplitude Variable knob.

 Other than the question in regards to the Amplitude Variable knob, the plug-in appears to be working and generates a nice clean square wave in the STD position, and the Period and Amplitude in High Ampl seem to work fine. I have not yet tested the Fast Rise mode of the unit yet.

 The SG-503 Leveled Sine Wave plug-in seems to work fine, but I have not fully tested it yet.

 Thanks
 Mitch

[mskobier]

All,
     I received a number of responses over on the Tek scope yahoo group in regards to the switch. Yes, it is a latching switch, which in my case was stuck in the "in" position. I was able to get the switch mechanism unstuck, however, it still did not appear to be working as it should. I took it back apart and found that the plastic cover that guides the switch plate was held in position by three stubs that stick through the circuit board and hold the switch slider in place. These stubs are held in place by three little blobs of glue. In my case, the glue had broken and allowed the switch slider cover to lift up a small amount. This caused the slider to not press down enough on the spring contacts to make contact with the pads. I dismantled this switch cover and slider, cleaned everything with IPA and put it back together. I used a type of superglue designed specifically for plastics to hold the stubs through the circuit board. This glue is thick, slow curing, and does not leave the haze around the glue joint that normal super glues do.

Mitch

[Stray Electron]

Mitch,

   FYI.  When I use super glue to glue around electronics I set up a fan to blow the fumes away from the electronics. If I didn't,  sometimes the fumes would form an insulating coating on the key board contacts on the circuit board and the keys would not make contact.

   Police down here noticed that super glue fumes would stick to things around it but not oil on the ridges in finger prints. They now use gently heated super glue under a fume hood to highlight fingerprints!

[mian2zi3]

I located the PG-506 and SG-503 from a surplus company on the east coast for a reasonable price (way less than -bay prices), and the TM-503 from -bay.

Mind sharing where you got them?  I got a 2400 series scope to refurbish recently, and I've been thinking about acquiring the necessary equipment to calibrate it.

[mskobier]

mian2z13,
      I found my PG-506 and SG503 at a surplus company in the US called BMI Surplus out of Massachusetts. I do not know if they have any more. I purchased them in as is condition, and fortunately they work. Once I got the switch freed up, everything worked as it should.

I have since picked up from -bay a TM504, PS503A, and a TG501, that appears to work properly, though I have not tested it completely. The few ranges I have tested work as they should.  Just a few day ago, I acquired a TG501A, So I will soon have a verified working TM503, TG501 and PS503 (dual supply with one side dead, no time to repair) available to go to a new home. Probably put the units up on the big auction site in the coming weeks. If anyone is interested, let me know via Message.

Mitch

[Orpheus]

I'm glad your courage has been rewarded. I live in MA, and have one step more to do on my series 24xx refurb, but could never bring myself to buy those "as is" units, afraid I'd be buying myself into ANOTHER long term debug/old parts projects instead of finishing the one I have.

[mskobier]

Orpheus,
      I too am glad they worked. However, as with any of this old equipment, we take our chances. The one thing I did do before I placed the orders was to make sure I could get the service manuals either electronically or my preferred method, hard copy with the fold out schematics. I figured that if I could troubleshoot the scope using the Tek manuals, how hard could it be to trouble shoot a non working plug in module. I also found a supplier of an extension cable kit to plug into the mainframe and then plug into the module for troubleshooting purposes. Pretty good price too. Way cheaper than the Tek made expansion cables. I did purchase on of the extension cable kits, but have not needed to assemble it yet.

Mitch