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This scan was made possible by Pete Lancashire.

Hello Fabio

I've taken apart the TG501 and had a closer look. There are only three socketed chips - U310, U300 and U290. U310 is part of the first divide by 5 counter. I think the sockets are the dodgy TI version, so took all three chips out cleaned the pins and replaced them, but no change.

Also checked the 100MHz PLL at its output points (U290D) Both pins 9 (going to U310A in the divide by 5 counter) and 15 (going to U290C in the 5ns section) show exactly 80MHz. So as you suggested, it looks like the divide by 5 counter is the problem and I'll start by replacing U310, once I get hold of another MC 10131.

It also looks like this particular TG501 was originally configured for 10 MHz external reference oscillator, but has been changed back to the internal 1 MHz reference. All the changes seem to have been done according to the manual and I've anyway checked and adjusted the 1 MHz oscillator so that it is correct.

Thanks again for your help on this.

Regards

Kerry

Hi Oliver,

It appears that the 371A will accept one adapter. The 371A is designed with Kelvin connectors for the three transistor leads so it has 6 banana sockets in all.

The adapters for the 575 are not Kelvin so they only have three banana plugs. These three plugs would plug into the left three banana sockets in the 371A and let you measure the device parameter but without the accuracy of Kelvin connectors.

The adapters for the 576 and 577 curve tracers have 5 banana plugs. This is because they use Kelvin connectors for the high current leads of a transistor (emitter and collector, or source and drain) but the Tek engineers decided the base (gate) didn't require the Kelvin connector. These adapters can be used in the 371A and take advantage of the Emitter and Collector Kelvin contacts. The Base contact will not be Kelvin. These 576 and 577 adapters would plug into the first and second vertical row of banana sockets.

The 371A adapters have all six banana plugs and the E, B, and C (S, G, D) connections are Kelvin.

Dennis Tillman W7PF

Here is the November 1988 revision of the Mechanical parts catalog:

I am not sure why i am asking , the tek 371a curve tracer , dose it need the test unit or can you use the same adapter that the 576 uses . Is there something special about test rig or just a clean way to test items with shield ????

Pete and Kurt -

Thank you both for the parts catalogs. Prior to those posts all that I had was the Oct-1982 semiconductors catalog and the knobs section of the mechanical catalog. Your posts will be a great help in keeping vintage Tek instruments working.

Dale H. Cook, GR/HP/Tek Collector, Roanoke/Lynchburg, VA

Hello Mark,

Thousand apologies... I went through the past message replying to one thing you said, but thinking you said something else.
What I meant (about checking whether it was a Tek original transistor or not) was to check Q1486 (the power transistor that's off-board, connected by wires).
This is the one (Q1486) which I got burnt (on my 464) and is the one I learnt is tricky to replace and, therefore the one that, should it not be a original Tek 151-0140-00, might be the cause for your oscillator not working.
About injecting the signal... well, even if you could do it...it wouldn't tell 100% sure that the transformer is OK, but could help give you some hint that it IS NOT.
The generator I used was a very simple one, using one port of an HC Schmitt Trigger (74HC14) as an oscillator (with a resistor and capacitor to set the frequency). This one port driving all the other 5 ports in parallel (to increase current drive) and feeding the signal, through a series resistor into the transformer's primary (having both ends disconnected, from the transistor and from the +V side).

Regarding your question on horizontal drive waveforms...
Yes, should the rest of the scope be working, and assuming that all horizontal controls are set correctly (i.e. Horizontal Display set to "A", Triggering mode set to "AUTO" and A&B sweep dials set to a sweep rate that you can measure, "X10" button out and horizontal position pots at center, and the "NON STORE" button is pressed), you should see opposite voltage ramps on the horizontal plates of the CRT.

Rgrds,

Fabio

i checked Q1484 it is origanal 151-0136-00 is on the trans.i dont have the capability to inject a 30khz signal into hv transformer.besides it is not going neg or starting to run with it out.forgetting about the hv for a minuet, i got to wondering if there is any horz or vert waveformes even without the hv working. i cant find any horz drive waves.even with no inputs shouldnt there still be horz drive waves?

Thank you Pete and Kurt!!!

Vince.

--
Michigan VHF Corp.

Thanks very much indeed - very useful when needed

Try

I can't get to proxy.w140.com as the ISP blocks my VPN provider.

Could you provide another DL location please.

Thanks
David

Thank you Kurt and Pete!
I fretted that I had somehow missed #2, but now it has shown up.
These are excellent scans of excellent information!
tom jobe...

This scan was made possible by Pete Lancashire.

Thanks but priced way too high and too much negative feedback for me

The gems keep coming! My thanks to all concerned who are making this superb reference library
available - hats off!

Craig

This scan was made possible by Pete Lancashire.

Hello Mark,

Regarding Q1484, besides meter check, what is it actually / what's marked on it?
I ask because if this 464 has ever been attempted repair, and if this transistor has been replaced (I.e. by an industry standard stock part), it can very well not oscillate at all.
Mine had a defective transformer that would oscillate and work normally while cold, but would leak H.V. after warmed up so, I had to replace the transformer as one of the first repairs.
After I replaced the transformer and assembled every thing back together, I probably shorted something, when I applied power it didn't work and ultimately I found out that I burned Q1484 (never found the cause).
After I got a Q1484 burnt it started my quest to find a replacement and that was when I learnt this oscillator is very picky about the transistor and that Tek had 3 or 4 different part numbers for this same base transistor (which is a 2N3055 of the old manufacturing process, a MESA transistor), every part number hand picked to meet a specific parameter, for lower gain, or for lower ft.
In this group (you can still find the thread if you search for Tek464), David Hess taught me all that and suggested me to try a 2N3772, which didn't work for me, and then I tried an MJ15015, which did work, but neither me nor David could make sense of this, because the MJ 15015 is a new part, which has an ft much higher than the old MESA 2N3055, which where specifically selected for Tek, for the lowest ft (in the 800kHz range).
Made sense or not, the fact is that selecting a transistor that will work in this circuit is tricky and if yours have been replaced, this may very well the problem at your hand right now.
If, however, it's a Tek part with the correct part number, and if it doesn't seem to be damaged, then I think you may relax in this department and look further.
Another chapter of my quest, when the new transformer arrived and the transistor got burnt, of course that first thing that crossed my mind was that my supposedly N.O.S. transformer I got from Sphere could be bad... So before replacing the transistor I needed to find a way to test the transformer, at least for basic functionality.
I had success in testing the transformer somewhat well feeding its primary from a square wave generator (TTL level, with some resistance in series, like 330R or the like), then, while monitoring the voltage drop on the primary (with a scope), I swept the frequency until it peaked (which happened around 30kHz), and then I was able to measure the output of the feedback winding (Q1484 removed), and of the 600V (peak) winding.
Of course, the obtained voltage outputs were proportional to the actual peak to peak voltage that I was seeing at the primary, knowing that the peak to peak voltage on the primary, on a functional oscilloscope is about 30vpp.

Maybe you can apply the same technique to have a guess about the state of your transformer.

Please let us know,

Rgrds,

Fabio

first thank you for your your help Fabio. i did everything you sugested.she's stuck.i replaced c1487,no change.i checked q1484 out of circuit with my fet analouge meter.checks good,no e to c leakage.i resoldered T1501,no change.when i power unit on,pin 3 goes to + .5 v .i looked at it with my scope,it never went negitive, just clean + .5 v dc. im on a mission to fix this unit.the schematic does not give any resistence checkes on the windings of T1501.cant find the replacement 120-0909-00 any where.any more sugestions on circuit checks ? P.S. YOU DA MAN !

Have one on ebay