Difference between Tektronix TG501 early version, later version and TG501A

[mskobier]

All,
 I have been working on getting my 2400 series scope calibration equipment together and operational. I have acquired two TG501 modules, the first one has the small led display window (early) and the second has the large red plastic cover over the display. The first one is a B034xxx and the second is a B049xxx. I have a service manual for theTG501, but is appears to be for the earlier version. Other than cosmetics, can anyone tell me the differences between these models? In examining the circuit boards, the first thing I noticed was the absence of the adjustment capacitor C102 for the 1mhz time reference adjustment on the later version. Other than that, the circuit boards are almost identical, with the circuit board numbers being version 02 versus 03. I have also seen some manuals for sale for the TG501A, but have not been able to find a picture of the A model. Is the version with the large red plastic piece the A version?


 The later version appears to work properly and the earlier version works, but the marker frequency is off by a factor of 10 low. So when setting the unit to 1 micro sec (1mhz), the actual output frequency is 0.1mhz or 100khz. At this point, I do not know if the knob position is not installed properly, or there is a problem with one of the multiplier/divider circuits. I'll get it figured out eventually.


 Mitch

[SoundTech-LG]

Hi,

Also have both versions here. I have been working on the early version. Replaced about 90%, or more, of the 7400 series socketed IC's (the later version only has a few sockets) there was a major problem. All is fine now, EXCEPT, one of the 2 BCD to 7 segment Display Driver ICs, are bad. Problem is they chose a Signetics 8T06 (part of the 8000 series Signetics line) as their driver IC. Totally non-standard pin out. Unlike the DM44 DVM's  (of the same era) that used 4511 type pin-out. Very hard, and expensive to source the 8T06. I may try to dead bug a 4511 and rewire to make it work. While I trouble shot all the dead 7400 series, I found some differences from the schematic. So the early series are different, for sure.